Community-associated methicillin-resistant Staphylococcus aureus: Reconsideration of therapeutic options

Abstract

Methicillin resistance, long recognized as characteristic of nosocomial Staphylococcus aureus, has increasingly been identified in community-acquired strains in the past 15 years. The genotypes of community-associated methicillin-resistant S. aureus (MRSA) are different from nosocomial strains, and unlike nosocomial strains, they have a distinctive methicillin-resistance chromosomal cassette (designated type IV), are usually susceptible to multiple classes of antimicrobials other than beta-lactams, carry a distinctive virulence factor (the Panton-Valentine leukocidin), cause mainly skin and soft tissue infection and less frequently, necrotizing pneumonia, and involve predominantly children and young adults. Outbreaks have been reported in certain segments of the population (eg, football players, wrestlers, prison inmates, and native people) that often do not have the established risk factors for MRSA. However, these strains have also caused infections likely acquired in an institutional health care setting. Delay in starting appropriate antibiotic therapy for severe infections caused by MRSA can be life-threatening. This requires a reconsideration of the empiric choice of an anti-staphylococcal beta-lactam for seriously ill patients with suspected community-associated S. aureus infections.

Inappropriate Antibiotic Use in Soft Tissue Infections

“…Third, the low treatment failure rate in our cohort may be due to low virulence strains of community-acquired MRSA with high levels of susceptibility to a combination of sulfamethoxazoletrimethoprim, clindamycin, and levofloxacin. Studies 25,26 have demonstrated that there are differences between community-acquired and hospital-acquired MRSA infections and that community-acquired MRSA infections are usually mild and responsive to multiple classes of non-␤-lactam antibiotics. Fourth, the determination of cure or failure was done by retrospective medical record analysis.…”

Prevention of Recurrent Staphylococcal Skin Infections

“…By 2005, several centers across the U.S. reported that CA-MRSA accounted for nearly 75% of all staphylococcal infections [43]. These high rates of CA-MRSA necessitated changes in empiric antibiotic therapy when MRSA was suspected [52], particularly for SSTI in which well over 50% of infections in most centers were due to CA-MRSA [43, 44, 51, 53, 54]. More recently, Gerber et al performed a retrospective, observational study using the Pediatric Health Information System (PHIS), a database of clinical and financial data from >40 tertiary care children’s hospitals in the U.S. Over the 6-year study period, the investigators identified nearly 60,000 children with S. aureus infections, 51% of whom had infection with MRSA; SSTI comprised 61% of these infections [55].…”

The critically ill patient and regional anesthesia

“…Culturing the tip might help to guide antibiotic choice. If bacteremia is suspected, parallel blood cultures should be drawn ideally before the start of empiric antibiotic treatment, which needs to consider the resistance profile of the institution and the colonization risk of the patient with multiresistant organisms [14][15][16][17].…”