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Reemergence of epidemic methicillin-resistant Staphylococcus aureus in a general hospital associated with changing
C C Linnemann1, P Moore, J L Staneck
1Infection Control Department, University of Cincinnati Hospital, Ohio.
Abstract:
An epidemic of methicillin-resistant Staphylococcus aureus (MRSA) infections involving 323 patients occurred at the University of Cincinnati Hospital from 1977 to 1981. Subsequently, endemic MRSA persisted in the hospital for 6 years, until 1987, when a new epidemic began with 223 patients becoming infected over 3 years. Between the two epidemics, there was a major change in the MRSA recovered from infected patients, as demonstrated by three epidemiologic markers. Antibiograms showed that the tetracycline-resistant MRSA involved in the first epidemic was replaced by tetracycline-susceptible MRSA in the second epidemic; bacteriophage typing indicated that the original epidemic strain, D11/83A/85, had been replaced by new strains, many of which were susceptible to phage 54; and restriction endonuclease analysis of plasmid DNA confirmed that a single strain was involved in the first epidemic and that multiple strains were present in the second epidemic. The epidemiology of MRSA infections in the hospital changed with the change in staphylococcal strains. The first epidemic was hospital based with most infections occurring in surgical patients, and the burn unit was the major reservoir. In contrast, 28% of the patients in the second epidemic had community-acquired infections, and nursing home patients were an important source of these infections. Also, 29% of the hospital-acquired infections in this epidemic occurred in nonsurgical patients. This time the burn unit was not a reservoir of infection, but other intensive care units were. The increased diversity of strains of MRSA in the second epidemic might be related to increased transmission in the community and more widespread transmission in the hospital.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) strains evolved significantly between two hospital epidemics. The second epidemic featured diverse, community-acquired MRSA strains, shifting epidemiology and transmission patterns.
Area of Science:
- Infectious Diseases
- Microbiology
- Epidemiology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant public health threat.
- Hospitals are critical environments for MRSA transmission and evolution.
- Understanding strain dynamics is crucial for effective infection control.
Purpose of the Study:
- To analyze the epidemiological and microbiological changes in MRSA strains during two distinct epidemics at a single hospital.
- To investigate the shift in MRSA strain characteristics and their impact on infection patterns.
Main Methods:
- Utilized antibiograms to assess antimicrobial resistance patterns.
- Employed bacteriophage typing to differentiate MRSA strains.
- Conducted restriction endonuclease analysis of plasmid DNA to determine strain diversity.
Main Results:
- The first epidemic (1977-1981) involved tetracycline-resistant MRSA, primarily hospital-acquired, with the burn unit as a reservoir.
- The second epidemic (1987 onwards) featured tetracycline-susceptible MRSA with diverse strains, including community-acquired infections and nursing home sources.
- MRSA transmission shifted from surgical patients and burn units to broader hospital areas and community settings.
Conclusions:
- A significant evolution in MRSA strains occurred between the two epidemics, marked by changes in resistance, phage susceptibility, and genetic diversity.
- The emergence of diverse MRSA strains contributed to a broader epidemiological profile, including community and nursing home-acquired infections.
- These findings highlight the dynamic nature of MRSA and the need for adaptive infection control strategies.