Multiply antibiotic-resistant Staphylococcus aureus: introduction, transmission, and evolution of nosocomial...

Area of Science:

• Infectious Diseases
• Medical Microbiology
• Hospital Epidemiology

Background:

• A multiply antibiotic-resistant Staphylococcus aureus (MRSA) strain was introduced into a hospital setting by an inter-state transfer burn patient.
• The MRSA strain subsequently transmitted to 34 patients over 15 months, despite adherence to standard wound precautions.

Observation:

• Infections included pneumonia, empyema, bacteremia, endocarditis, osteomyelitis, and burn/wound infections, with a mortality rate of 50% (17 of 34 patients).
• The transmission occurred from a burn unit to a surgical intensive care unit (SICU) involved in a chloramphenicol study for bowel sepsis.
• The MRSA acquired chloramphenicol resistance by acquiring R-plasmids, leading to four distinct epidemic strains identified through phage typing, plasmid analysis, and antibiograms.

Findings:

• Phage typing and plasmid analysis confirmed the spread of MRSA between units and identified patient and personnel reservoirs.
• The emergence of chloramphenicol resistance in the MRSA strain complicated treatment and facilitated its spread.
• The outbreak was successfully controlled by adding rifampin to vancomycin therapy for infected patients, leading to the eradication of the carrier state.

Implications:

• This case highlights the significant threat posed by multiply antibiotic-resistant organisms in healthcare settings.
• Effective control requires comprehensive infection surveillance, rapid diagnostics, and targeted antimicrobial stewardship.
• The study underscores the importance of understanding resistance mechanisms and transmission dynamics for outbreak management.