Methicillin-resistant Staphylococcus aureus at a Veterans Affairs Medical Center (1986-96)

Area of Science:

• Infectious Diseases
• Epidemiology
• Microbiology

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) is a significant pathogen in healthcare settings.
• Understanding MRSA epidemiology is crucial for infection control and patient management.
• Previous studies have documented MRSA's prevalence, but long-term evolutionary trends require further investigation.

Purpose of the Study:

• To characterize the epidemiology of pathogenic MRSA isolates over an 11-year period.
• To identify trends in MRSA incidence, sources, and patient populations.
• To understand the phenotypic diversity and potential epidemic strains of MRSA.

Main Methods:

• Descriptive epidemiological study of 504 MRSA isolates from 490 inpatients.
• Data collected from 1986 to 1996 at the Veterans Affairs Medical Center in Oklahoma City.
• Phenotypic characterization and weekly tabulations of MRSA isolates.

Main Results:

• MRSA resistance rates increased for 8 years, then decreased starting in 1994.
• A shift was observed from nosocomial MRSA in wounds/urines to community-acquired MRSA in sputa/wounds, though 72% remained nosocomial.
• MRSA from intensive care unit (ICU) patients were more frequently from respiratory tracts; increases in nosocomial and community-acquired MRSA in ICU patients were noted.
• Sixty-nine distinct MRSA phenotypes were identified, with three identified as epidemic strains around 1989.

Conclusions:

• MRSA epidemiology is a complex, continuously evolving process with multifactorial influences.
• The emergence of diverse MRSA phenotypes presents a divergent threat to patients.
• Long-term surveillance and characterization are essential for managing MRSA in healthcare settings.