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Updated: Aug 14, 2026
Experimental Human Pneumococcal Carriage
Published on: February 15, 2013
Gram-positive anaerobic cocci
1Department of Medical Microbiology, Southmead Health Services NHS Trust, Bristol, United Kingdom.
Abstract:
Gram-positive anaerobic cocci (GPAC) are a heterogeneous group of organisms defined by their morphological appearance and their inability to grow in the presence of oxygen; most clinical isolates are identified to species in the genus Peptostreptococcus. GPAC are part of the normal flora of all mucocutaneous surfaces and are often isolated from infections such as deep organ abscesses, obstetric and gynecological sepsis, and intraoral infections. They have been little studied for several reasons, which include an inadequate classification, difficulties with laboratory identification, and the mixed nature of the infections from which they are usually isolated. Nucleic acid studies indicate that the classification is in need of radical revision at the genus level. Several species of Peptostreptococcus have recently been described, but others still await formal recognition. Identification has been based on carbohydrate fermentation tests, but most GPAC are asaccharolytic and use the products of protein degradation for their metabolism; the introduction of commercially available preformed enzyme kits affords a physiologically more appropriate method of identification, which is simple and relatively rapid and can be used in routine diagnostic laboratories. Recent reports have documented the isolation in pure culture of several species, notably Peptostreptococcus magnus, from serious infections. Studies of P. magnus have elucidated several virulence factors which correlate with the site of infection, and reveal some similarities to Staphylococcus aureus. P. micros is a strongly proteolytic species; it is increasingly recognized as an important pathogen in intraoral infections, particularly periodontitis, and mixed anaerobic deep-organ abscesses. Comparison of antibiotic susceptibility patterns reveals major differences between species. Penicillins are the antibiotics of choice, although some strains of P. anaerobius show broad-spectrum beta-lactam resistance.
Insights
Gram-positive anaerobic cocci (GPAC) are often implicated in serious infections. Advances in identification methods and studies of virulence factors are crucial for understanding and treating these challenging pathogens.
Area of Science:
- Microbiology
- Clinical Infectious Diseases
- Bacterial Pathogenesis
Background:
- Gram-positive anaerobic cocci (GPAC) are commensal flora but also significant pathogens in various infections.
- Inadequate classification and identification challenges have historically limited research on GPAC.
- Recent studies highlight the need for taxonomic revision and improved diagnostic methods.
Purpose of the Study:
- To review the current understanding of GPAC, focusing on classification, identification, and clinical significance.
- To discuss recent advances in identifying GPAC and understanding their virulence factors.
- To compare antibiotic susceptibility patterns among different GPAC species.
Main Methods:
- Review of existing literature on GPAC classification and identification.
- Analysis of nucleic acid studies for taxonomic revision.
- Evaluation of preformed enzyme kits for GPAC identification.
- Examination of studies on virulence factors of specific GPAC species (e.g., P. magnus, P. micros).
- Comparison of antibiotic susceptibility data for various GPAC species.
Main Results:
- Nucleic acid studies suggest a need for significant reclassification at the genus level.
- Preformed enzyme kits offer a more accurate and rapid identification method compared to traditional fermentation tests.
- Peptostreptococcus magnus and Peptostreptococcus micros are increasingly recognized as important pathogens.
- Virulence factors of P. magnus are being elucidated, showing similarities to Staphylococcus aureus.
- Significant inter-species differences in antibiotic susceptibility exist, with penicillins generally being the treatment of choice, though resistance is noted in P. anaerobius.
Conclusions:
- GPAC classification requires revision, with ongoing formal recognition of new species.
- Improved laboratory identification methods are available and essential for routine diagnostics.
- Understanding the specific virulence of species like P. magnus and P. micros is critical for infection management.
- Tailored antibiotic strategies are necessary due to varying susceptibility patterns among GPAC species.
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