Methicillin-resistant Staphylococcus aureus: etiology, at-risk populations and treatment


Hoşgör Limoncu M. , Ermertcan Ş. , Taşlı H. , Eraç B. , Yurtman A. N.

in: Methicillin-resistant Staphylococcus aureus: etiology, at-risk populations and treatment, Charles L. Kolendi, Editor, NOVA Science Publishers Inc. , New-York, pp.329-364, 2010

  • Publication Type: Book Chapter / Chapter Vocational Book
  • Publication Date: 2010
  • Publisher: NOVA Science Publishers Inc.
  • City: New-York
  • Page Numbers: pp.329-364
  • Editors: Charles L. Kolendi, Editor

Abstract

After beta-lactamase resistant antibiotics, including methicillin, nafcillin and cephalosporins had been introduced to the clinical use; the first methicillin-resistant Staphylococcus aureus (MRSA) isolates were described in 1961. Since then, MRSA clones have become a problem in health-care institutions throughout the world. Community acquired MRSA (CA-MRSA) isolates have also threatened human health for the last two decades. In multicentral surveillance studies, MRSA prevalence was determined as 1-2 % in North European countries but it may reach up to 80 % in some Far East countries.

Many risk factors have been found to be associated with MRSA infections. Recent hospitalization or surgery, residence in long-term care facilities, dialysis, broad-spectrum antibiotic usage and indwelling percutaneous medical devices or catheter are the most common risk factors for nosocomial MRSA infections. The risk factors for CA-MRSA infections have not been well established but several important factors have been described in the literature: HIV infection, recent antibiotic usage, intravenous and intranasal drug usage, living in closed populations, lower socioeconomic status, homelessness, non-hygienic tattoo and health-care workers.

The infection or colonization of health-care workers with MRSA is highly important since it is a cause of transmission and an increase in its incidence. Cellulites, boils and furuncles are among the most common clinical presentations of skin and soft tissue infections (SSTIs) caused by MRSA. These organisms are also responsible for severe infections such as endocarditis, pneumonia and bacteremia. In addition to invasive infections, MRSA produces a variety of toxins that lead to some clinical manifestations such as staphylococcal scalded skin syndrome and toxic shock syndrome. Although CA-MRSA has been traditionally associated with SSTI, there are increasing reports of pneumonia, bacteremia and infective endocarditis caused by CA-MRSA. Hospital acquired MRSA (HA-MRSA) produces more severe clinical conditions associated with increased mortality and morbidity among patients.

Treatment options for both mild SSTI and severe nosocomial infections are limited due to increasing antimicrobial resistance. After MRSA isolates emerged, glycopeptide antibiotics (vancomycin and teicoplanin) have been used more commonly and this resulted in the occurrence of isolates with reduced susceptibility or resistance to vancomycin. Trimetoprim-sulfamethoxazole, rifampin, linezolid, doxycycline, clindamycin and occasionally fluoroquinolones have been used in treating mild SSTIs. In more severe invasive infections, besides vancomycin, other parenteral agents such as linezolid, daptomycin, and tigecycline are commonly used. This review will focus on etiology, at-risk populations and treatment options of MRSA infections.