The incidence of invasive infection of Klebsiella pneumoniae (Kp) in the community is increasing every year, and the high disability and mortality rates associated with them pose great challenges in clinical practice. This study aimed to explore the clinical and microbiological characteristics of Kp invasive infection in the community.

This study investigated the data of 291 patients with Kp infection in the community in three hospitals (Zhongshan City, Guangdong Province) from January 2020 to August 2023. The risk factors for invasive infection and death due to Kp infection were determined through multivariate logistic regression models and Cox models.

The mortality rate of community-acquired Klebsiella pneumoniae (cKp) invasive infections markedly exceeded that for non-invasive infections (47.6% vs 25.9%) (p = 0.001). Multivariate logistic regression analysis identified high viscosity type (OR:2.26, p = 0.031) and shock (OR:3.42, p = 0.001) as significant risk factors for invasive infection. Among patients who succumbed to invasive infections, multivariate Cox regression analysis revealed that elevated CK-MB (OR: 1.01, p = 0.040), increased IL-6 levels (OR: 1.00, p = 0.023), and high SOFA scores (OR: 1.16, p = 0.017) were linked to increased mortality risk. This study found that co-infection of the liver, lungs, and bloodstream was most prevalent in invasive infections. Notably, co-infection involving the lungs, bloodstream, and brain was associated with the highest mortality rate (100%, 6/6). No significant differences were found between patients with or without invasive infections, as well as between surviving and non-surviving patients (all p ≥ 0.05).

Patients with cKp invasive infections exhibit more severe inflammatory responses and a poorer prognosis, necessitating vigilant attention from clinicians. The treatment of cKp invasive infections remains inconclusive between "heavy-handed strikes" and "sensitivity is sufficient". Focusing solely on the liver and lungs while neglecting infection sites outside of these organs can lead to catastrophic results, which should be avoided during treatment.

The gram-negative bacteria Klebsiella pneumoniae are genetically heterogeneous and a common cause of sepsis and bacteremia in humans. The complement system is the first line of defence against bacteria when they invade the body. We previously investigated K. pneumoniae isolates from sepsis patients. We found that complement factor (C) 3 is deposited on all isolates independent of serum sensitivity, but the membrane attack complex (MAC) was only formed on the serum-sensitive isolates. To investigate the mechanism for serum resistance, we incubated one serum-sensitive and one serum-resistant isolate in human serum and identified bound complement factors by mass spectrometry. The serum-sensitive isolate had all expected complement factors bound, including C4, while the serum-resistant isolate had only C3 bound. The serum resistance was caused by a fast cleavage of C3b to iC3b. Thereby, the C5 convertase, and thus MAC, cannot be formed. To confirm the role of C4 in serum sensitivity, C4 was inhibited by the nanobody hC4Nb8, resulting in the survival of the serum-sensitive isolate. This suggests that C4 is indispensable for MAC formation through the classical and lectin pathways. In contrast, when activated selectively, the alternative pathway primarily leads to the generation of iC3b, thereby enabling serum resistance by bypassing MAC assembly.

Klebsiella pneumoniae is primarily an opportunistic pathogen known for causing healthcare-associated infections in individuals with significant risk factors and comorbidities. These bacteria are typically multidrug-resistant (MDR), a phenotype conferred in part by the production of extended-spectrum beta-lactamases and/or carbapenemases. By comparison, so-called hypervirulent K. pneumoniae (hvKp) are defined by their ability to cause severe community-acquired infections in otherwise healthy individuals. Although hvKp lineages have historically not been MDR, there has been a recent emergence of strains with both hypervirulence and multidrug resistance phenotypes. Treatment of infections caused by MDR K. pneumoniae can be difficult, and new preventative measures are needed. As a step toward the development of a vaccine directed to prevent or moderate infections caused by these pathogens, we tested the ability of capsule polysaccharide (CPS) derived from eight selected K. pneumoniae capsule types (KLs) to elicit rabbit antibodies that recognize important KLs isolated from human infections. Seventy-one out of 84 (84.5%) contemporary K. pneumoniae clinical isolates tested were recognized by CPS-specific rabbit antisera. There was the unexpected binding of the antibodies to some isolates with KLs not included in the CPS-antigen cocktails. Notably, rabbit IgG purified from CPS-specific antisera promoted and/or enhanced human PMN bactericidal activity toward all but one of the selected clinical isolates that were not killed by PMNs outright (in the absence of specific antibody). These data provide support to the idea that a CPS-antigen cocktail could be developed to protect against the K. pneumoniae KLs that are the most frequent cause of human infections.IMPORTANCEKlebsiella pneumoniae is among the leading causes of death by infectious agents. Many of the prominent K. pneumoniae lineages are resistant to multiple classes of antibiotics, and options for treatment are limited. New countermeasures that prevent infections are needed. Here we tested the ability of capsule polysaccharide (CPS) antigen mixtures (or cocktails) to elicit rabbit antibodies that recognize K. pneumoniae from a large collection of extended-spectrum beta-lactamase-producing clinical isolates. Importantly, these antibodies had the ability to promote opsonophagocytic killing by human PMNs. Our results provide proof-of-concept for a CPS vaccine cocktail approach that could be developed to prevent infections caused by the most important K. pneumoniae lineages.

Community-acquired infections caused by Klebsiella pneumoniae (K. pneumoniae) have become a significant global health concern, particularly with the emergence of hypervirulent strains (hvKP). These strains are associated with severe infections, such as pyogenic liver abscesses, even in otherwise healthy individuals. Initially reported in Taiwan in the 1980s, hvKP has now spread worldwide. The pathogenicity of hvKP is attributed to an array of virulence factors that enhance its ability to colonize and evade host immune defenses. Additionally, the convergence of hypervirulence with antibiotic resistance has further complicated treatment strategies. As a member of the ESKAPE group of pathogens, K. pneumoniae exhibits high resistance to multiple antibiotics, posing a challenge for healthcare settings. This review provides a comprehensive overview of hvKP, highlighting its structural and pathogenic differences from classical K. pneumoniae strains, key virulence factors, mechanisms of antibiotic resistance, and the increasing threat of multidrug-resistant hvKP. Lastly, we discuss current treatment guidelines and emerging therapeutic strategies to combat this formidable pathogen.

This study aimed to determine the antibiofilm properties of Klebsiella pneumoniae phages previously isolated from Thai hospital sewage water. Furthermore, we aimed to develop a phage-embedded and coated alginate hydrogel, suitable as a wound dressing or surface coating to prevent K. pneumoniae proliferation and biofilm formation.

The biofilm forming capacity of six clinical K. pneumoniae isolates was determined by means of the crystal violet assay and four strains which exhibited strong adherence were selected for further characterization. Two phages (vB_KpnA_GBH014 and vB_KpnM_GBH019) were found to both significantly prevent (P = <0.0005) and disrupt (P = <0.05) biofilms produced by their K. pneumoniae hosts as determined by optical density readings using the crystal violet assay. Furthermore, alginate layers embedded and coated with phages vB_KpnA_GBH014 and vB_KpnM_GBH019 produced antibiofilm surfaces. Viable counts of recovered biofilms showed that alginate hydrogels containing phage vB_KpnA_GBH014 or vB_KpnM_GBH019 were associated with significantly fewer K. pneumoniae vs. no-phage controls (1.61 × 108 cfu ml-1 vs. 1.67 × 104 cfu ml-1, P = <0.005 and 1.78 × 108 cfu ml-1 vs. 6.11 × 102 cfu ml-1, P = <0.00005, respectively). Confocal microscopy further revealed a significant reduction in the biovolume of biofilms formed on phage embedded and coated alginate hydrogels compared to no-phage controls.

Phages vB_KpnA_GBH014 and vB_KpnM_GBH019 can both prevent and disrupt biofilms produced by clinical isolates of K. pneumoniae. Embedding and coating these phages into alginate produces an antibiofilm matrix which may have promise for coating medical devices or as a wound dressing.

Background: The prevalence of Klebsiella pneumoniae in surgical site infections (SSIs) has increased recently. This study aimed to evaluate the antimicrobial resistance patterns and biofilm formation capacity of K. pneumoniae strains isolated from SSIs. Methods: A total of 63 K. pneumoniae isolates were obtained from patients with SSIs. Antimicrobial susceptibility testing was determined using the Kirby-Bauer method. Molecular analyses were performed to confirm the presence of virulence and antibiotic resistance genes. Biofilm formation was determined using a semiquantified microtiter plate assay, and optical density measurements were used to classify the isolates into weak, moderate, and strong biofilm producers. Biofilm structure was observed using field-emission scanning electron microscopy. Statistical analyses were performed using SPSS software version 16 (SPSS Inc., Chicago, IL, USA), and data were analyzed and presented in terms of frequency and percentage. Results: The frequencies of fimH, mrkD, mrkA, wcaG, and magA were 98.4%, 96.8%, 77.7%, 61.9%, and 7.9%, respectively. The highest rates of antibiotic resistance were observed for cefazolin, cefuroxime, and piperacillin/tazobactam and 98.4% of the isolates were resistant to at least one antibiotic agent. The most prevalent resistance genes were blaSHV (42.8%), blaCTX-M (31.7%), blaTEM (28.5%), and blaOXA48 (22.2%). All the tested isolates were able to produce biofilms, and 76.2% were classified as strong biofilm producers. Conclusions: Klebsiella pneumoniae is one of the common pathogens in SSIs, and due to its antibiotic resistance and the presence of multiple virulence factors, proper controlling strategies need to be carried out.

Klebsiella variicola is an emerging pathogen within the Klebsiella pneumoniae species complex, and its clinical and microbiological characteristics remain poorly understood. This retrospective case-control study analyzed 252 patients with bloodstream infections caused by K. pneumoniae species complex, including 60 with K. variicola infection, to elucidate these characteristics. Our study showed no significant differences in clinical outcomes, such as 30-day mortality, between K. variicola and K. pneumoniae. However, a significant difference was found in the rate of harboring [peg-344, iucA, and rmpA] genes, which are associated with virulence in K. pneumoniae, suggesting that K. variicola may be generally less virulent. Notably, we identified two patients with community-acquired liver abscess caused by hypervirulent K. variicola, representing the first genetically analyzed case of this phenomenon in Japan and highlighting the potential virulence of this species. While there have been several reports on K. variicola carrying hypervirulence genes, this is the first report in Japan, to our knowledge, to genetically characterize a hypervirulent K. variicola isolated from a patient with disseminated liver abscesses using whole-genome sequencing. Multilocus sequence typing revealed high diversity among K. variicola isolates, with 49 distinct sequence types identified, 30 of which were newly registered, highlighting the genetic heterogeneity of this pathogen. No significant clinical differences were observed between K. variicola and other Klebsiella spp. The emergence of hypervirulent K. variicola strains with the potential to cause severe complications warrants further surveillance and research.

Klebsiella variicola is increasingly recognized as an emerging pathogen commonly found in the environment and human gut. However, its clinical and microbiological characteristics remain poorly understood. This study provides a comprehensive analysis of K. variicola bloodstream infections (BSIs), comparing clinical and genetic features with the closely related K. pneumoniae. We identified significant differences in the prevalence of virulence genes between the two species. Notably, we observed K. variicola causing disseminated liver abscesses, similar to hypervirulent K. pneumoniae strains. These findings have important implications for accurate species identification, informing treatment strategies, and improving patient outcomes in the face of this emerging infectious threat.

Klebsiella pneumoniae, a Gram-negative bacterium, comprises strains with diverse virulence potentials, ranging from classical to hypervirulent variants. Understanding the genetic basis underlying the virulence disparities between hypervirulent (hvKp) and classical K. pneumoniae (cKp) strains is crucial. hvKp strains are characterized by hypermucoviscosity, attributed to the presence of specific virulence genes and the production of molecules that aid in their ability to survive, evade host immune defenses, and cause infection. In contrast, classical strains exhibit a broader array of antimicrobial resistance determinants, conferring resistance to multiple antibiotics. Although current definitions of hvKp incorporate clinical features, phenotypes, and genotypes, identifying hvKp strains in clinical settings remains challenging. Genomic studies have been pivotal and have helped to identify distinct genetic profiles in hvKp strains, including unique virulence plasmids and chromosomal variations, underscoring the genetic diversity within K. pneumoniae populations. This review examines the virulence and genetic determinants associated with hvKp. The presence of genes defining hypervirulence, alongside considerations of their utility as biomarkers and targets for therapeutic strategies, is discussed, while also providing insight into biofilm formation by hvKp and key questions that need urgent responses in understanding hvKp.

Hypervirulent Klebsiella pneumoniae (HvKp) is a virulent strain associated with invasive infections. While initially community-acquired, hospital-acquired HvKp (HA-HvKp) and carbapenem-resistant HvKp (CR-HvKp) are increasingly reported. This meta-analysis evaluates the prevalence, risk factors, and clinical outcomes associated with HvKp, including CR-HvKp and HA-HvKp, among Kp infections.

A systematic search of PubMed, Scopus, Embase, and Cochrane Library was conducted until December 2024. Observational studies comparing HvKp vs classical Kp (cKp), CR-HvKp vs carbapenem-sensitive HvKp (CS-HvKp), and HA-HvKp vs community-acquired HvKp (CA-HvKp) were included. Quality was assessed using the Joanna Briggs Critical Appraisal Tool, and pooled prevalence and odds ratios (ORs) with 95% confidence intervals (CIs) were calculated.

Fifty studies with 6,663 participants were included. The HvKp prevalence was 33.0%, with most studies from Asia, predominantly China. Temporal analysis revealed an increase in HvKp prevalence (27.7% in 2006-2018 to 38.5% in 2019-2024). The CR-HvKp prevalence rose from 9.5% to 16.5% (2016-2024). The HA-HvKp prevalence increased from 25.9 to 47.1%. Key risk factors included diabetes mellitus (OR = 1.56), CA-Kp (OR = 2.59), and hypermucoviscous (HM)-phenotype (OR = 29.79). Complications included liver abscess (OR = 6.35), metastatic spread (OR = 4.74), meningitis (OR = 11.14), and septic shock (OR = 1.30). Mortality was higher in HvKp infections but not statistically significant (p = 0.219). HA-HvKp and immunosuppression were significant CR-HvKp risk factors, with CR-HvKp showing higher mortality.

Diabetes mellitus, CA-Kp infections, and HM-phenotype are significant risk factors for HvKp. The rising prevalence of CR-HvKp and HA-HvKp highlights the need for early detection, infection control, and targeted treatment strategies.

Nagendra D, Chaudhuri S, Gupta N, Shanbhag V, Eshwara VK, Rao S, et al. Prevalence, Risk Factors, and Clinical Outcomes of Hypervirulent Klebsiella pneumoniae Strains among Klebsiella pneumoniae Infections: A Systematic Review and Meta-analysis. Indian J Crit Care Med 2025;29(4):370-393.

Bacteria continually evolve. Previous studies have evaluated bacterial evolution in retrospect, but this approach is based on only speculation. Cohort studies are reliable but require a long duration. Additionally, identifying which genetic mutations that have emerged during bacterial evolution possess functions of interest to researchers is an exceptionally challenging task. Here, we establish a Rapid and Integrated Bacterial Evolution Analysis (RIBEA) based on serial passaging experiments using hypermutable strains, whole-genome and transposon-directed sequencing, and in vivo evaluations to monitor bacterial evolution in a cohort for one month. RIBEA reveals bacterial factors contributing to serum and antimicrobial resistance by identifying gene mutations that occurred during evolution in the major respiratory pathogen Klebsiella pneumoniae. RIBEA also enables the evaluation of the risk for the progression and the development of invasive ability from the lung to blood and antimicrobial resistance. Our results demonstrate that RIBEA enables the observation of bacterial evolution and the prediction and identification of clinically relevant high-risk bacterial strains, clarifying the associated pathogenicity and the development of antimicrobial resistance at genetic mutation level.

Klebsiella pneumoniae is one of the main pathogens of nosocomial infection, among which carbapenems can be used for multidrug-resistant Klebsiella pneumoniae. However, in the past decade, the resistance rate of carbapenem-resistant Klebsiella pneumoniae has increased yearly. Tigecycline has good antibacterial activity in treating severe bacterial infections, but the reports of tigecycline resistance are increasing. This study aimed to investigate the mechanism of drug resistance and epidemiological characteristics of tigecycline-resistant Klebsiella pneumoniae (TRKP) in a large teaching hospital in southwest China, Chongqing.

We isolated 30 TRKP strains from this hospital between August 2021 and December 2023. By PCR and sequencing, we examined the presence and mutation rates of genes associated with tigecycline resistance, including acrR, oqxR, ramR, tmexC, tet(x), tet(A), tet(L), and rpsj, and performed efflux pump inhibition experiments to verify efflux pump activity. At the same time, real-time RT-PCR was used to detect the expression levels of efflux pump genes (acrB and oqxB) and ramA. To investigate the prevalence trend of TRKP in our hospital, we performed multi-site sequence typing (MLST) analysis.

The mutation rates of ramR (73.3%) and tet(A) (63.3%) were significant. In efflux pump inhibition experiments, PaβN could reverse the resistance of 29 TRKP strains (96.7%) to tigecycline. Real-time RT-PCR results showed that acrB and ramA genes were up-regulated in 22 strains, while oqxB genes were overexpressed in only 4 strains. MLST analysis showed that these strains could be divided into 25 different ST subtypes, indicating that no outbreak of TRKP occurred in our hospital. In addition, two tmexCD-torpj positive strains, ST661 and ST1561, were identified for the first time.

The efflux pump acrB and tet(A) mutations are the primary mechanisms of resistance to tigecycline-resistant Klebsiella pneumoniae at our hospital. The ramR mutation can mediate efflux pump activity of acrB by up-regulating ramA overexpression.

Extreme environments significantly impact the metabolic profiles of plants, leading to variations in chemical composition and bioactivity. This study investigates the effects of altitude, plant part age, and light exposure on the chemical composition and antimicrobial properties of Moringa peregrina. Based on our results, mineral contents were plant location dependent; while dry matter, ash, total digestible nutrients (TDN), fibre, protein, and tannins, were greater in the samples from the mountain. Vitamin E was more concentrated in the wadi. Vitamin A, selenium, phenols, and heavy metals were undetectable in both environments. Antimicrobial assays revealed stronger activity in mountain samples than the other locations. Age-dependent analyses showed that nitrogen, protein, ash, and electrolyte leakage were higher in young plant parts, whereas chlorophyll a and b levels were elevated in mature leaves and younger branches, particularly in lower elevations. Interestingly, young leaves from mountain regions had higher chlorophyll concentrations compared to mature leaves, contrasting with trends at other elevations. Photosynthetic photon flux density (PPFD) measurements were also highest in the mountain region. These findings suggest that M. peregrina employs diverse metabolic adaptations for survival in challenging environments, potentially offering socioeconomic value to indigenous communities through its bioactive properties.

The aim of this study was to isolate Klebsiella spp. from clinically healthy animals fed diets with or without antimicrobial growth promoters (AGP). Additionally, the study evaluated whether the inclusion of growth promoters affected the recovery of multi-drug-resistant isolates.

A total of 144 isolates were obtained from rectal swabs on Simmons citrate agar supplemented with 1% inositol. Of these, 45 non-replicative isolates underwent extensive characterization, including molecular and phenotypic analyses. Sequencing identified that 77% were Klebsiella pneumoniae, 14.5% K. aerogenes, and 8.5% K. variicola. Isolates exhibiting the same polymorphic profiles were detected across different animals and treatments, with and without AGP. Seventy-one percent were multidrug-resistant, as determined by disk diffusion testing. The isolates harbored genes such as mcr-1, blaCTX-M-2, sul2, tetB, qnrS, and dfrA, among others. Additionally, genes encoding siderophores like enterobactin, aerobactin, and yersiniabactin were detected via Polymerase Chain Reaction (PCR). Thirty-nine isolates were strong biofilm producers, 45% moderate, and 16% weak in vitro tests. The predominant genetic profiles included single, double, or triple-locus variants of ST25, ST147, and ST4691. Two novel sequence types were identified: ST7694 (K. pneumoniae) and ST7699 (K. variicola). Survival and persistence analyses in Galleria mellonella showed that these isolates exhibited a virulent phenotype and an enhanced capacity for multiplication in the early hours of infection.

Clinically healthy swine act as reservoirs for multidrug-resistant Klebsiella spp. exhibiting significant virulence phenotypes. The identification of novel sequence types contributes to epidemiological surveillance and the One Health framework.

The hospital setting serves as a critical conduit for pathogen dissemination, particularly amid the escalating concern of nosocomial infections in China. Currently, most studies use metagenomics to investigate microbial communities in hospital settings, with less focus on the transmission strategies of individual bacteria. In our study, we identified two Klebsiella pneumoniae strains exhibiting different mucoid characteristics. The strain designated as KPE was obtained from a well sanitized ward, while the strain KPH was isolated from the sputum samples of patients within the identical ward. We characterized the KPE strain as not lethal to mice and showed a distinct hypomuciod phenotype, strikingly different from the virulent KPH isolate. Two strains harbored the single nucleotide polymorphism (SNP) mutations in the virulence-related gene rmpA and wcaJ promoter regions, resulting in the downregulation of mucoid regulatory gene rmpA and capsule synthesis genes. Consequently, this led to diminished production of capsular polysaccharides and weakened virulence in the KPE strain. Furthermore, the KPE strain exhibited an elevated capacity for acquiring antibiotic-resistant plasmids and greater material survival ability. These findings indicated that mucoid changes enable K. pneumoniae strains to survive better on inanimate surfaces, promoting their persistence ward environment and further transmission in patients.

Hypervirulent Klebsiella pneumoniae (hvKp) poses a serious public health threat. Gas gangrene caused by hvKp is rarely reported and potentially results in a poor prognosis. This study describes the case of a hospitalised patient with gas gangrene and sepsis caused by hvKP. Carbapenem-susceptible hypervirulent Klebsiella pneumoniae (CS-hvKp) strains KPLSN and KPLSX were isolated from the knee joint pus and blood specimens of the patient for further investigations. Whole genome sequencing revealed that KPLSN and KPLSX were highly homologous (single nucleotide polymorphisms [SNPs]<10) and belonged to ST412/K57. The minimum inhibitory concentration and minimum bactericidal concentration under biofilm values of meropenem in KPLSN and KPLSX were significantly higher than in the planktonic state (>128 mg/L vs. 0.25 mg/L, P<0.0001). These two strains had high biofilm formation ability, and the results from fluorescence staining experiments showed that they were not easily killed by meropenem in the biofilm state. KPLSN and KPLSX showed high capsule production and were confirmed to have high virulence through experiments with the Galleria mellonella infection model and the BALB/c mice abdominal infection model. The persistent symptoms may be due to enhanced biofilm and capsule formation. Phylogenetic analysis of global ST412 strains showed their evolution towards higher virulence and resistance. These results emphasise the critical need for judicious antibiotic use and novel therapeutic approaches to combat special infections caused by these pathogens.

Due to the strong pathogenicity of hypervirulent Klebsiella pneumoniae (hvKP), its performance against disinfectants in water should be understood to protect public health and ecological environment. Unfortunately, the disinfectant tolerance of hvKP with a hypermucoviscosity (HMV) phenotype is a critical underexplored area. Here, the tolerance of K. pneumoniae isolates to common disinfectants was evaluated, and its underlying mechanisms were clarified. Results showed that hvKP strains with HMV exhibited remarkable tolerance to triclosan (TCS), sodium hypochlorite (NaClO), and benzalkonium bromide (BB), surpassing that of low-virulent K. pneumoniae (lvKP) and Escherichia coli, which is the microbial indicator of drinking water quality. Ct value of NaClO reached 4.41 mg/L·min to kill 4-log hvKP, while the values were 2.52 and 2.28 mg/L·min to achieve 4-log killing of lvKP and E. coli, respectively. The curing of the virulence plasmid from hvKP strain K2044 revealed that capsular polysaccharide (CPS) synthesis, driven by the virulence plasmids, helped mitigate cell membrane injury and bacterial inactivation under NaClO stress; consequently, it provided a protective advantage to hvKP. Enhancing the antioxidative stress system to reduce ROS production and mitigate oxidative stress caused by NaClO further improved the disinfectant resistance of hvKP strains with HMV. This study emphasized that hvKP strains with HMV posed a considerable challenge to disinfection procedure of water treatment. It also revealed that an improved dosage of NaClO ensures bacteria killing, indicating the optimization of the design of water treatment processes involving disinfection strategies and technical parameters should be considered.

Klebsiella pneumoniae is well recognized as a serious cause of infection in healthcare-associated settings and immunocompromised individuals; however, accumulating evidence from resource-limited nations documents an alarming rise in community-acquired K. pneumoniae infections, manifesting as bacteremia and pneumonia as well as neonatal sepsis. The emergence of hypervirulent and antibiotic-resistant K. pneumoniae strains threatens treatment options for clinicians. Effective vaccination strategies could represent a viable alternative that would both preempt the need for antibiotics to treat K. pneumoniae infections and reduce the burden of K. pneumoniae disease globally. There are currently no approved K. pneumoniae vaccines. We review the evidence for K. pneumoniae lipopolysaccharide (LPS) as a vaccine and immunotherapeutic target and discuss the role of antibodies specific for the core or O-antigen determinants within LPS in protection against Klebsiella spp. disease. We expand on the known role of the Klebsiella spp. capsule and O-antigen modifications in antibody surface accessibility to LPS as well as the in vitro and in vivo effector functions reported for LPS-specific antibodies. We summarize key hypotheses stemming from these studies, review the role of humoral immunity against K. pneumoniae O-antigen for protection, and identify areas requiring further research.

Bloodstream infections (BSIs) caused by Klebsiella pneumoniae (K. pneumoniae) are associated with high morbidity and mortality rates. This study presents a sequence type 25 (ST25) strain of hypermucoid K. pneumoniae A1 isolated from the blood of a patient with liver cirrhosis (LC) who succumbed to severe infections. We performed whole-genome sequencing of K. pneumoniae A1, which revealed virulence factors and antibiotic resistance genes. The strain harbors virulence genes encoding aerobactin, salmochelin, yersiniabactin, enterobactin, and rmpA. Additionally, the strain possessed five drug resistance genes: blaSHV-110, blaSHV-81, fosA6, OqxA, and OqxB. We further constructed a phylogenetic tree using 98 ST25 K. pneumoniae strains downloaded from NCBI together with K. pneumoniae A1. Phylogenetic analysis revealed that our isolated strain was closely related to a highly virulent strain isolated from a neonate in our region, differing by only 123 single nucleotide polymorphisms (SNPs). K. pneumoniae A1 is highly suspected to be Hypervirulent Klebsiella pneumoniae (hvKp). This study provided the first in-depth genomic analysis of ST25 K. pneumoniae in a patient with LC in China, highlighting the urgent need for early identification and diagnosis to combat this emerging threat.

The string test is a screening method for detecting hypervirulent Klebsiella pneumoniae (hvKp). Agar media are used for string tests; however, the effect of the type of media on the test results remains unclear. We aimed to determine the optimal agar medium and cutoff value for the string test. We performed the string test on 99 Klebsiella strains using different agar media: sheep blood, chocolate, Drigalski's and MacConkey. The diagnostic accuracy was calculated in concordance with the rmpA, rmpA2 or iucA gene levels. The diagnostic accuracy rates for sheep blood, chocolate, Drigalski's and MacConkey agar were 0.79, 0.75, 0.73 and 0.64, respectively. When the cutoff was changed from 5 to 10 mm, the diagnostic accuracy rate for sheep blood agar decreased from 0.79 to 0.65. Our findings suggest that the type of agar medium impacts the string test results and sheep blood agar with a 5-mm cutoff is the optimal condition for detecting hvKp.

Pylephlebitis is an infective, suppurative thrombosis of the portal vein that is often a complication of intra-abdominal infections. Herein, we report a rare case of hypermucoviscous Klebsiella pneumoniae pneumonia complicated by pylephlebitis. The patient was administered antibiotics and anticoagulants. His pneumonia improved; however, the thrombus in the portal vein did not shrink, and the patient ultimately died of liver failure. Furthermore, hypermucoviscous K. pneumoniae is involved in the formation of portal vein thrombosis, and if bacteremia persists even after pneumonia has improved, investigating possible complications, including portal vein inflammation, is necessary.

We report a case of Klebsiella pneumoniae bacteraemia in an 80-year-old man in France with no history of travel to Asia, complicated by endogenous endophthalmitis, multiple cerebral microbleeds and hepatic microabscesses, associated with a Bentall endocarditis. Hypervirulence pathotype was suggested based on clinical picture, bacterial isolate genomic sequence and hypermucoidy. Interestingly, the isolate had the non-K1/K2-capsular serotype locus KL113-like, carried a KpVP-1-like virulence plasmid, and belonged to the emerging sublineage SL660 (comprising the sequence type ST660).

Hypermucoviscous Klebsiella pneumoniae (hmKP) is a bacterium known to cause lesions, including abscesses, in various organs. Unlike typical Klebsiella pneumoniae, hmKP can yield a positive string test in culture specimens. Infections caused by hmKP often become severe and are associated with a poor prognosis. In this report, we describe a case of iliopsoas abscess, spondylodiscitis, septic pulmonary embolism, and symmetrical peripheral gangrene (SPG) caused by hmKP. The patient received non-invasive positive-pressure ventilation, hemodialysis, platelet transfusions, fresh frozen plasma, thrombomodulin, and intensive antibiotic therapy including rifampicin. The patient underwent 148 days of antibiotic therapy and achieved a good outcome.

We report a case of a patient with distal bile duct cancer who presented with ocular pain and eye redness due to a liver abscess. The patient developed a liver abscess while waiting for surgery. Since Klebsiella pneumoniae with high viscosity was identified and imaging studies showed systemic infection, a diagnosis of klebsiella invasive syndrome was made. In addition, infectious intraocular inflammation was also observed at the same time. In addition to antibiotic therapy, vitrectomy and percutaneous transhepatic abscess drainage successfully normalized the inflammatory response and negative blood cultures were obtained. Thirty-four days after the start of treatment, surgery was performed and the postoperative course was uneventful, and the patient was discharged from the hospital on the 39th postoperative day. Forty-six months after that surgery, there has been no evidence of recurrence of cholangiocarcinoma or recurrence of infection, but unfortunately, vision loss in the right eye remains. Some Klebsiella pneumoniae are highly pathogenic and are often reported from Southeast Asia, and ocular pain and hyperemic symptoms are important physical findings.

Klebsiella pneumoniae is a Gram-negative pathogen that has become a threat to public health worldwide due to the emergence of hypervirulent and multidrug-resistant strains. Cell-surface components, such as polysaccharide capsules, fimbriae, and lipopolysaccharides (LPS), are among the major virulence factors for K. pneumoniae. One of the genes involved in LPS biosynthesis is the uge gene, which encodes the uridine diphosphate galacturonate 4-epimerase enzyme. Although essential for the LPS formation in K. pneumoniae, little is known about the mechanisms that regulate the expression of uge. Ferric uptake regulator (Fur) is an iron-responsive transcription factor that modulates the expression of capsular and fimbrial genes, but its role in LPS expression has not yet been identified. This work aimed to investigate the role of the Fur regulator in the expression of the K. pneumoniae uge gene and to determine whether the production of LPS by K. pneumoniae is modulated by the iron levels available to the bacterium.

Using bioinformatic analyses, a Fur-binding site was identified on the promoter region of the uge gene; this binding site was validated experimentally through Fur Titration Assay (FURTA) and DNA Electrophoretic Mobility Shift Assay (EMSA) techniques. RT-qPCR analyses were used to evaluate the expression of uge according to the iron levels available to the bacterium. The iron-rich condition led to a down-regulation of uge, while the iron-restricted condition resulted in up-regulation. In addition, LPS was extracted and quantified on K. pneumoniae cells subjected to iron-replete and iron-limited conditions. The iron-limited condition increased the amount of LPS produced by K. pneumoniae. Finally, the expression levels of uge and the amount of the LPS were evaluated on a K. pneumoniae strain mutant for the fur gene. Compared to the wild-type, the strain with the fur gene knocked out presented a lower LPS amount and an unchanged expression of uge, regardless of the iron levels.

Here, we show that iron deprivation led the K. pneumoniae cells to produce higher amount of LPS and that the Fur regulator modulates the expression of uge, a gene essential for LPS biosynthesis. Thus, our results indicate that iron availability modulates the LPS biosynthesis in K. pneumoniae through a Fur-dependent mechanism.

Convergence of Klebsiella pneumoniae (KP) pathotypes has been increasingly reported in recent years. These pathogens combine features of both multidrug-resistant and hypervirulent KP. However, clinically used indicators for hypervirulent KP identification, such as hypermucoviscosity, appear to be differentially expressed in convergent KP, potential outbreak clones are difficult to identify. We aimed to fill such knowledge gaps by investigating the temperature dependence of hypermucoviscosity and virulence in a convergent KP strain isolated during a clonal outbreak and belonging to the high-risk sequence type (ST)307.

Hypermucoviscosity, biofilm formation, and mortality rates in Galleria mellonella larvae were examined at different temperatures (room temperature, 28°C, 37°C, 40°C and 42°C) and with various phenotypic experiments including electron microscopy. The underlying mechanisms of the phenotypic changes were explored via qPCR analysis to evaluate plasmid copy numbers, and transcriptomics.

Our results show a temperature-dependent switch above 37°C towards a hypermucoviscous phenotype, consistent with increased biofilm formation and in vivo mortality, possibly reflecting a bacterial response to fever-like conditions. Furthermore, we observed an increase in plasmid copy number for a hybrid plasmid harboring carbapenemase and rmpA genes. However, transcriptomic analysis revealed no changes in rmpA expression at higher temperatures, suggesting alternative regulatory pathways.

This study not only elucidates the impact of elevated temperatures on hypermucoviscosity and virulence in convergent KP but also sheds light on previously unrecognized aspects of its adaptive behavior, underscoring its resilience to changing environments.

Hypervirulent Klebsiella pneumoniae (hvKP) has emerged as a novel variant of K. pneumoniae, exhibiting distinct phenotypic and genotypic characteristics that confer increased virulence and pathogenicity. It is not only responsible for nosocomial infections but also community-acquired infections, including liver abscesses, endophthalmitis, and meningitis, leading to significant morbidity and mortality. HvKP has been reported all over the world, but it is mainly prevalent in Asia Pacific, especially China. Moreover, hvKP can acquire carbapenemase genes resulting in the emergence of carbapenem-resistant hypervirulent K. pneumoniae (CR-hvKP), which possesses both high virulence and drug resistance capabilities. Consequently, CR-hvKP poses substantial challenges to infection control and presents serious threats to global public health. In this paper, we provide a comprehensive summary of the epidemiological characteristics, virulence factors, and mechanisms underlying carbapenem resistance in hvKP strains with the aim of offering valuable insights for practical prevention strategies as well as future research.

The World Health Organization (WHO)'s list of neglected tropical diseases (NTDs) highlights conditions that are responsible for devastating health, social and economic consequences, and yet, they are overlooked and poorly resourced. The NTD list does not include conditions caused by Gram-negative bacilli (GNB). Infections due to GNB cause significant morbidity and mortality and are prevalent worldwide. Southeast Asia is a WHO region of low- and middle-income countries carrying the largest burden of NTDs. Two significant health threats in Southeast Asia are Burkholderia pseudomallei (causing melioidosis) and hypervirulent Klebsiella pneumoniae (HvKp). Both diseases have high mortality and increasing prevalence, yet both suffer from a lack of awareness, significant under-resourcing, incomplete epidemiological data, limited diagnostics, and a lack of evidence-based treatment. Emerging evidence shows that both melioidosis and HvKp are spreading globally, including in high-income countries, highlighting the potential future global threat they pose. In this article, we review both conditions, identifying current trends and challenges in Southeast Asia and areas for future research. We also argue that melioidosis and HvKp merit inclusion as NTDs, and that mandatory global surveillance and reporting systems should be established, and we make an urgent call for research to better understand, detect, and treat these neglected diseases.

Introduction Hypermucoviscous Klebsiella pneumoniae (hvKP) is related to invasive infections; however, there have been very few comprehensive reports on the clinical features and prognosis of critically ill patients with the infection. Methods We conducted a retrospective case series in a general intensive care unit in Japan. Patients with positive blood cultures for KP between January 1, 2020 and December 31, 2022 were included. hvKP was defined by the positivity in the string test. We analyzed the patient's characteristics at baseline, including comorbidities, abscess formation, Sequential Organ Failure Assessment (SOFA) score, Acute Physiology and Chronic Health Evaluation (APACHE) II score, septic shock, duration of hospitalization, 30-day mortality, and infection site. Results A total of 24 patients had a positive blood culture for KP; nine patients (37.5%) were positive for the string test (hvKP) while 15 (62.5%) were negative (non-hvKP). In both groups, the patients were old (mean age, hvKP 80.4 vs. non-hvKP 75.7 years) and more often male (five patients (55.6%) vs. 12 patients (80.0%)). No statistically significant difference was found between the two groups in terms of comorbidities, such as diabetes mellitus, chronic obstructive pulmonary disease, chronic kidney disease, and malignancy. No statistical difference was seen in abscess formation (two patients [22.2%] vs. one patient (6.7%)), SOFA score (5.2±4.8 vs. 4.7±3.4), APACHE II score (19.6 (15.0-20.0) vs. 17.0 (11.2-20.8)), septic shock (five patients (55.6%) vs. four patient (26.7%)), duration of hospitalization (37.2 (12.0-51.0) vs. 32.3 (9.5-21.0)), and 30-day mortality (two patients (22.2%) vs. two patients (13.3%)). Two cases with hvKP died within 24 h. No significant difference was seen in the infection sources; respiratory infection (2 (22.2%) vs. 1 (6.7%)), hepatobiliary infection (2 (22.2%) vs. 7 (46.7%)), and genitourinary infection (1 (11.1%) vs. 5 (33.3%)). Conclusions Critically ill patients with hvKP infection showed characteristics similar to those reported previously. However, the disease could rapidly become severe and have a poor prognostic outcome.

The opportunistic pathogen Klebsiella pneumoniae (K. pneumoniae) can colonize mucosal surfaces and spread from mucosae to other tissues, causing fatal infections. Medical equipment and the healthcare setting can become colonized by Klebsiella species, which are widely distributed in nature and can be found in water, soil, and animals. Moreover, a substantial number of community-acquired illnesses are also caused by this organism worldwide. These infections are characterized by a high rate of morbidity and mortality as well as the capacity to spread metastatically. Hypervirulent Klebsiella strains are thought to be connected to these infections. Four components are critical to this bacterium's pathogenicity-the capsule, lipopolysaccharide, fimbriae, and siderophores. Siderophores are secondary metabolites that allow iron to sequester from the surrounding medium and transport it to the intracellular compartment of the bacteria. A number of variables may lead to K. pneumoniae colonization in a specific area. Risk factors for infection include local healthcare practices, antibiotic use and misuse, infection control procedures, nutrition, gender, and age.

Klebsiella pneumoniae bacteremia is known to present a virulent clinical course, including multiple metastatic infections, which is not uncommon in Asia. However, there are limited data on the incidence and risk factors for ocular involvement in K. pneumoniae bacteremia. We retrospectively reviewed the medical records of all patients with K. pneumoniae bacteremia who underwent ophthalmologic examination in a tertiary center in Seoul, Korea, from February 2012 to December 2020. Two retinal specialists reviewed the findings of the ophthalmologic examinations and classified them as endophthalmitis, chorioretinitis, and no ocular involvement. Of 689 patients, 56 [8.1%; 95% confidence interval (CI) 6.2-10.4] had ocular involvement, and 9 (1.3%; 95% CI 0.6-2.5) were diagnosed with endophthalmitis. Of 47 patients with chorioretinitis, 45 (95.7%) improved with systemic antibiotic therapy alone. Community-onset bacteremia (100% vs 62.1% vs 57.4%, P = 0.04), cryptogenic liver abscess (55.6% vs 11.8% vs 8.5%, P = 0.003), and metastatic infection (66.7% vs 5.8% vs 10.6%, P < 0.001) were more common in endophthalmitis than in no ocular involvement or chorioretinitis. In the multivariable analysis, cryptogenic liver abscess [adjusted odds ratio (aOR), 6.63; 95% CI 1.44-35.20] and metastatic infection (aOR, 17.52; 95% CI 3.69-96.93) were independent risk factors for endophthalmitis. Endophthalmitis was not associated with 30-day mortality. Endophthalmitis is rare in Asian patients with K. pneumoniae bacteremia. Targeted ophthalmologic examination in those with cryptogenic liver abscess, metastatic infection, or ocular symptoms may be more appropriate than routine examination of all patients.

The hypermucoviscous-like phenotype has been described in Klebsiella pneumoniae species complex (KpSC) and was described as a contributor of increased virulence. This study described the characterization and whole-genome sequencing of an antibiotic susceptible and hypermucoviscous-like Klebsiella michiganensis 9273 clinical isolate.

Here, we report the genome sequence of a K. michiganensis clinical isolate obtained from a urinary tract infection exhibiting the hypermucoviscous-like phenotype. The draft genome sequence consisted of 145 contigs and ~ 6.6 Mb genome size. The annotation revealed 6648 coding DNA sequences and 56 tRNA genes. The strain belongs to the sequence type (ST) 50, and the OXY-1 beta-lactam resistance gene, aph(3')-Ia gene for aminoglycoside resistance and multidrug efflux pumps were identified. The fyuA siderophore receptor of yersiniabactin siderophore was identified. Increased virulence was observed in Galleria mellonella larvae model and increased capsule production was determined by uronic acid quantification. The clinical implications of this phenotype are unknown, but the patient outcome might worsen compared to susceptible- or MDR-classical K. michiganensis isolates.

Klebsiella pneumoniae (Kpn) is one of the most common gram-negative bacilli causing lung, urinary tract, and biliary tract infections. However, as a distinct entity from classic Kpn, hypervirulent Kpn causing liver abscess, endophthalmitis, and lung abscess with poor prognoses has been reported mainly in East and Southeast Asia since the mid-1980s. Although the definition of hypervirulent Kpn is unclear, the hypermucoviscosity of Kpn is considered an important feature of hypervirulence. We present a case of emphysematous pyelonephritis accompanied by septic shock and acute kidney injury caused by hypermucoviscous Kpn infection that was successfully treated by intensive treatment. A 70-year-old woman with type 2 diabetes mellitus was diagnosed with emphysematous pyelonephritis, and string test-positive Kpn was detected in blood and urine cultures and percutaneous catheter drainage fluid from the renal pelvis. The patient was treated with intensive therapies including antibiotics, ventilator management, and continuous hemodiafiltration (CHDF) using AN69ST, which can absorb cytokines. During the course of treatment, the infection was complicated by pyogenic spondylitis, which was cured by antimicrobial therapy, and the patient was transferred to another hospital for rehabilitation on day 119 after admission. Hypermucoviscous Kpn infection often has a severe course, and it is important to initiate multidisciplinary treatment at an early stage, including rifampicin, which is expected to inhibit the viscosity of hypermucoviscous Kpn. In the current case, immediate CHDF using AN69ST was also considered a life-saving treatment because it improved both volume overload and neutrophil-activated hypercytokinemia.

Emphysematous prostatic abscess (EPA) is a rare condition characterized by gas and abscess accumulation in the prostate. In this case report we report a successfully treated EPA with liver abscess due to Klebsiella pneumoniae in a 49-year-old man. He was admitted with abdominal pain and fever. Physical examination revealed tender, palpable resonance urinary bladder, and prostatic tenderness on rectal digital examination. High inflammatory markers were found. Abdominal computer tomography (CT) confirmed EPA. The patient was treated with broad-spectrum antibiotics, strict blood glucose control, suprapubic catheterization, and transurethral deroofing of the prostatic abscess. After three weeks patient discharged in good condition.

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is epidemically transmitted globally, but few studies focused on the prevalence in district-level hospitals. In this study, we investigated CRKP strains collected from nine district hospitals from September 2019 to September 2020, aiming to determine the resistance mechanisms, virulence profiles, and molecular epidemiological characteristics of CRKP in district hospitals in Southwest China.

A total of 51 CRKP strains were collected from 9 district-level hospitals. Matrix-assisted laser desorption/ionization-time of flight mass spectrometer was used for strain identification review, and the micro-broth dilution method was used for antibiotic sensitivity detection. Molecular epidemiological investigation of strains was performed by multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) methods. PCR and efflux pump inhibition tests were used to detect CRKP resistance mechanisms. PCR and serum killing tests were used to detect capsular serotype, virulence-related genes, and virulence validation.

The CRKP strains in district hospitals presented high levels of MIC50 and MIC90 in carbapenem antibiotics especially ertapenem and meropenem. A total of 90.2% (46/51) CRKP strains were detected as carbapenemase producers, and the proportion of strains co-expressing carbapenemases was 11.8% (6/51). All CRKP strains were grouped into eight MLST types, and ST11 was the most prevalent genotype. A total of 11.8% (6/51) CRKP isolates were positive for the string test, and three strains of hypervirulent and carbapenem-resistant K. pneumoniae (HV-CRKP) were positive in serum killing test. The molecular typing of all the CRKP isolates was grouped into 29 different PFGE patterns, and 40 ST11 isolates belonged to 20 different PFGE clusters.

CRKP strains showed high-level antibiotic resistance and virulence phenotype in district hospitals in Southwest China, which suggested that we should immediately pay attention to the rapid dissemination of the CRKP in regional hospitals. Our study will provide new insights into the epidemiology of CRKP in regional hospitals, which will help regional hospitals develop nosocomial infection prevention and control policies tailored to local conditions.

Pyogenic liver abscesses (PLAs) are a suppurative infection of the hepatic parenchyma responsible for significant morbidity and mortality. PLAs are categorized into a variety of mechanisms: (1) via the portal vein, (2) through the biliary tract, (3) via the hepatic artery, (4) from trauma, (5) contiguously via direct extension, and (6) cryptogenically. The pathogenesis of PLA, which informs treatment, can often be discerned based on host factors, clinical presentation, and causative microorganisms. The Streptococcus anginosus group, hypervirulent Klebsiella pneumoniae , and multidrug-resistant gram-negative pathogens have emerged as microbiologically challenging organisms to treat. The identification of hypervirulent K. pneumoniae should prompt for assessment for metastatic spread and consideration of prolonged antimicrobial treatment. Abdominal imaging is indispensable in characterizing PLAs and facilitating source control interventions. Source control remains the most critical aspect of PLA management, followed by antimicrobial therapy. Empiric antibiotics for PLAs are informed by the suspected etiology of PLA formation. Duration of antimicrobial therapy is individualized and dependent on multiple components, including the success of achieving source control, host factors, mechanism of PLA development, and the illness course of the individual-factoring in clinical, biochemical, and radiographic parameters.

Hypermucoviscosity is a hallmark of hypervirulent Klebsiella pneumoniae (hvKP). However, the molecular basis of its regulation is largely unknown. We hypothesize that hypermucoviscosity is modulated via two-component signal transduction systems (TCSs). In-frame deletion mutants of all 33 response regulators of hvKP ATCC43816 were generated using CRISPR/CAS and evaluated for their impacts on hypermucoviscosity. The response regulator OmpR is required for hypermucoviscosity in vitro and virulence in vivo in a mouse pneumonia model. The ΔompR mutant lost its mucoidy but retained its capsule level and comparable rmpADC expression, so transcriptomic analysis by RNA-Seq was performed to identify differentially expressed genes (DEGs) in ΔompR mutant. The top 20 Gene Ontology terms of 273 DEGs belong to purine ribonucleotide triphosphate biosynthetic and metabolic process, transmembrane transport, and amino acid metabolism. Among the overexpressed genes in the ΔompR mutant, the atp operon encoding F-type ATP synthase and the gcvTHP encoding glycine cleavage system were characterized further as overexpression of either operon reduced the mucoviscosity and increased the production of ATP. Furthermore, OmpR directly bound the promoter region of the atp operon, not the gcvTHP, suggesting that OmpR regulates the expression of the atp operon directly and gcvTHP indirectly. Hence, the loss of OmpR led to the overexpression of F-type ATP synthase and glycine cleavage system, which altered the energetic status of ΔompR cells and contributed to the subsequent reduction in the mucoviscosity. Our study has uncovered a previously unknown regulation of bacterial metabolism by OmpR and its influence on hypermucoviscosity. IMPORTANCE Hypermucoviscosity is a critical virulent factor for Klebsiella pneumoniae infections, and its regulation remains poorly understood at the molecular level. This study aims to address this knowledge gap by investigating the role of response regulators in mediating hypermucoviscosity in K. pneumoniae. We screened 33 response regulators and found that OmpR is essential for hypermucoviscosity and virulence of K. pneumoniae in a mouse pneumonia model. Transcriptomic analysis uncovered that genes involved in energy production and metabolism are highly upregulated in the ΔompR mutant, suggesting a potential link between bacterial energy status and hypermucoviscosity. Overexpression of those genes increased production of ATP and reduced mucoviscosity, recapitulating the ΔompR mutant phenotype. Our findings provide new insights into the regulation of K. pneumoniae hypermucoviscosity by a two-component signal transduction system, highlighting the previously unknown role of OmpR in regulating bacterial energy status and its influence on hypermucoviscosity.

Increased antibiotic resistance presents a health problem worldwide. The World Health Organization published a list of pathogens considered a priority for designing new treatments. Klebsiella pneumoniae (Kp) is a top-priority microorganism, highlighting the strains that produce carbapenemases. Developing new efficient therapies or complementing existing treatments is a priority, and essential oils (EOs) provide an alternative. EOs could act as antibiotic adjuvants and enhance antibiotic activity. Employing standard methodologies, the antibacterial activity of the EOs and their synergic effect with antibiotics were detected. A string test was used to identify the impact of the EOs over the hypermucoviscosity phenotype presented by Kp strains, and Gas Chromatography-Mass Spectrometry analysis identified EOs and the composition of EOs. The potential of EOs for designing synergistic therapies with antibiotics to combat the infection of KPC diseases was demonstrated. In addition, the alteration of the hypermucoviscosity phenotype was shown as the principal mechanism of a synergic action between EOs and antibiotics. The differential composition of the EOs lets us identify some molecules that will be analyzed. Synergic activity of EOs and antibiotics can provide a solid platform for combating multiresistant pathogens that represent a severe health sector problem, such as Kp infections.