Granulicatella infections: Comprehensive review of an elusive opportunistic pathogen

Abstract

Granulicatella species, previously classified as nutritionally variant streptococci, have emerged as important opportunistic pathogens. Although typically part of the normal oral, gastrointestinal, and genitourinary flora, these fastidious Gram-positive cocci can cause serious infections in both immunocompetent and immunocompromised individuals. Their identification often proves difficult due to slow growth and unusual nutritional requirements, which limit the reliability of conventional culture methods. This narrative review consolidates data from over 100 case reports and clinical studies to present a comprehensive overview of Granulicatella infections. Infective endocarditis appears as the most frequently reported and life-threatening condition, often affecting the aortic and mitral valves. Patients with prosthetic valves or congenital heart defects face a higher risk. Delayed diagnosis frequently results in complications such as heart failure, systemic emboli, and renal dysfunction. Granulicatella species also contribute to osteomyelitis, pulmonary infections, brain abscesses, gastrointestinal sepsis, and infections related to implanted medical devices. Effective management typically involves beta-lactam antibiotics combined with aminoglycosides, although antimicrobial resistance remains a concern. Surgical intervention often proves necessary, especially in cases with prosthetic material or severe complications. Outcomes are generally favorable when infections are identified early and managed effectively. However, delayed recognition and suboptimal therapy continue to contribute to poor prognoses in some patients. This review emphasizes the need to improve clinical awareness and establish standardized diagnostic and therapeutic approaches to address the challenges posed by Granulicatella infections.

Keywords: Granulicatella; Infective endocarditis; Opportunistic pathogen; Nutritionally variant streptococci; Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry; Antibiotic resistance; Osteomyelitis; Septic shock; Molecular diagnostics; Biofilm infections

Core Tip: Granulicatella species, formerly known as nutritionally variant streptococci, are increasingly recognized as significant pathogens in infective endocarditis and other systemic infections. This narrative review synthesizes published case reports and series to highlight the diverse clinical manifestations, diagnostic challenges, and treatment outcomes associated with Granulicatella and Abiotrophia infections. By underscoring the rarity and complexity of these organisms, this work emphasizes the need for heightened clinical awareness and more standardized diagnostic approaches.