Chapter 70 – Staphylococci
Karsten Becker, MD
Professor, Medical Microbiology, Virology and Infection Epidemiology
Westfalian Wilhelms-University of Münster
University Hospital of Münster
Institute of Medical Microbiology
Münster, Germany
Barbara Kahl, MD
Senior Researcher, Medical Microbiology, Virology and Infection Epidemiology
Westfalian Wilhelms-University of Münster
University Hospital of Münster
Institute of Medical Microbiology
Münster, Germany
ABSTRACT
The genus Staphylococcus comprises about 40 validly described and proposed species with the coagulase-positive species Staphylococcus aureus and the coagulase-negative species S. epidermidis and S. haemolyticus as the most common causes of hospital infections caused by staphylococci. Many staphylococcal species are both commensal microorganisms and pathogens. In particular, S. aureus has re-emerged as one of our most feared pathogens, becoming increasingly virulent and resistant to antibiotic agents. This versatile pathogen harbors a wide array of virulence factors to enable colonization, invasion, aggression, and persistence processes. The study of slow-growing variant forms of S. aureus (i.e., the small-colony variants) has helped in the understanding of the persistent and recurrent infections. In the last two decades, methicillin-resistant S. aureus (MRSA) strains have become endemic in hospitals worldwide, rendering all β-lactam antibiotics (penicillins, cephalosporins, penems) ineffective. Recently, community-associated MRSA (CA-MRSA) in persons without previous healthcare exposure as well as livestock-associated S. aureus strains were increasingly reported. The majority of CA-MRSA strains have acquired the Panton-Valentine leukocidin (PVL) encoding genes, thereby greatly increasing its virulence. All these new strains and variants present challenges for clinical microbiologists, infection preventionists, and epidemiologists.
Last Revised: 12/13/09 10:36 PM
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