Twenty-Five Year Epidemiology of Invasive Methicillin-Resistant Staphylococcus aureus (MRSA) Isolates Recovered at a Burn Center
ARMY INST OF SURGICAL RESEARCH FORT SAM HOUSTON TX
Pagination or Media Count:
Over the past two decades, an epidemiologic emergence of methicillin-resistant Staphylococcus aureus MRSA infections has occurred from that of primarily hospital-associated to community-associated. This emergence change has involved MRSA of different pulsed-field types PFT, with different virulence genes and antimicrobial resistance patterns. In this study, we evaluate the changes in PFT and antimicrobial resistance epidemiology of invasive MRSA isolates over 25 years at a single burn unit. Isolates were tested by pulsed-field gel electrophoresis PFGE, broth microdilution antimicrobial susceptibility testing, and PCR for the virulence factors Panton Valentine leukocidin PVL and arginine catabolic mobile element ACME, and the resistance marker staphylococcal chromosomal cassette mec SCCmec. Forty isolates were screened, revealing stable vancomycin susceptibility MIC without changes over time but decreasing susceptibility to clindamycin and ciprofloxacin. The majority of PFGE types were MRSA USA800 carrying the SCCmec I element and USA100 carrying the SCCmec II element. No strains typically associated with community-associated MRSA, USA300 or USA400, were found. USA800 isolates were predominately found in the 1980s, USA600 isolates were primarily found in the 1990s, and USA100 isolates were found in the 2000s. The PVL gene was present in only one isolate, the sole USA500 isolate, from 1987. The virulence marker ACME was not detected in any of the isolates. Overall, a transition was found in hospital-associated MRSA isolates over the 25 years, but no introduction of community-associated MRSA isolates into this burn unit. Continued active surveillance and aggressive infection control strategies are recommended to prevent the spread of community-acquired MRSA to this burn unit.
- Anatomy and Physiology
- Medicine and Medical Research