Research Information System
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
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.