Streptococcus

Streptococcus is a genus of gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. These bacteria are spherical or ovoid in shape, often found in pairs or chains, and are classified into several species that cause a wide range of infections in humans.

A photomicrograph of Streptococcus pyogenes bacteria, 900x Mag.

Classification

Streptococci are classified based on their hemolytic properties into alpha (partial hemolysis), beta (complete hemolysis), and gamma (non-hemolytic) streptococci. Additionally, they are also classified based on Lancefield grouping, a serotype classification that uses specific antigens found on the bacteria's cell walls.

Pathogenic Species

Among the many species of Streptococcus, some are particularly known for their pathogenicity in humans:

• Streptococcus pneumoniae: A leading cause of pneumonia, meningitis, sinusitis, and otitis media.
• Streptococcus pyogenes (Group A): Causes strep throat, rheumatic fever, impetigo, cellulitis, necrotizing fasciitis, and toxic shock syndrome.
• Streptococcus agalactiae (Group B): Can cause neonatal sepsis and meningitis, as well as infections in pregnant women and adults with underlying diseases.
• Streptococcus mutans: One of the main contributors to tooth decay.
• Streptococcus suis: Causes infections in pigs but can also infect humans, leading to meningitis, septicemia, endocarditis, and deafness.

Diagnosis and Treatment

The diagnosis of streptococcal infections usually involves collecting a sample from the affected area (throat, blood, wound, etc.) and performing a culture test. Rapid antigen detection tests are often used for diagnosing strep throat.

Treatment typically involves antibiotics, most commonly penicillin, amoxicillin, or erythromycin. Vaccines are available for Streptococcus pneumoniae, and research is ongoing for vaccines against other Streptococcus species.

Impact on Human Health

Streptococcal infections range from minor throat and skin infections to life-threatening conditions such as necrotizing fasciitis and streptococcal toxic shock syndrome. Rheumatic fever, a complication of untreated strep throat, can cause long-term heart damage.

See Also

• Bacteria
• Pneumonia
• Meningitis
• Rheumatic fever

References

• Ferretti, J. J., Stevens, D. L., & Fischetti, V. A. (Eds.). (2016). Streptococcus pyogenes: Basic Biology to Clinical Manifestations. Oklahoma City (OK): University of Oklahoma Health Sciences Center.
• Walker, M. J., Barnett, T. C., McArthur, J. D., Cole, J. N., Gillen, C. M., Henningham, A., ... & Nizet, V. (2014). "Disease manifestations and pathogenic mechanisms of Group A Streptococcus". Clinical Microbiology Reviews, 27(2), 264-301.
• Wyres, K. L., & Lambertsen, L. M. (2021). "
• "Genomic insights into the pathogenicity and antimicrobial resistance of Streptococcus agalactiae". Clinical Microbiology Reviews, 34(1), e00027-20.
• Mitchell, J. (2011). "Streptococcus mitis: walking the line between commensalism and pathogenesis". Molecular Oral Microbiology, 26(2), 89-98.
• Gottschalk, M., Xu, J., Calzas, C., & Segura, M. (2010). "Streptococcus suis: a new emerging or an old neglected zoonotic pathogen?". Future Microbiology, 5(3), 371-391.
• Bogaert, D., De Groot, R., & Hermans, P. W. (2004). "Streptococcus pneumoniae colonisation: the key to pneumococcal disease". The Lancet Infectious Diseases, 4(3), 144-154.

External Links

• Group A Streptococcal (GAS) Disease (CDC)
• Group B Strep (GBS) (CDC)
• Pneumococcal Disease (CDC)

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