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Effectiveness of contact isolation during a hospital outbreak of methicillin-resistant Staphylococcus aureus
J A Jernigan1, M G Titus, D H Gröschel
1University of Virginia Health Sciences Center, Charlottesville, USA.
Abstract:
Contact isolation has been recommended by the Centers for Disease Control and Prevention for the prevention of nosocomial transmission of methicillin-resistant Staphylococcus aureus (MRSA), but there are few data which prospectively quantitate the effectiveness of contact isolation for this purpose. During an outbreak of MRSA in a neonatal intensive care unit between July 18, 1991 and January 30, 1992, weekly surveillance cultures were performed on all patients. Sixteen of 331 admissions became colonized with MRSA, and 3 (19%) developed infections: bacteremia, conjunctivitis, and dialysis catheter site infection. The isolates from all 16 patients were submitted to plasmid profile analysis and restriction enzyme analysis of whole cell DNA. All of the patients had identical chromosomal patterns and plasmid profiles, which differed from control isolates from other wards, indicating that the outbreak resulted from spread of a unique strain. None of 144 personnel who were cultured after recent contact with newly colonized patients during the outbreak were found to carry MRSA, which suggests that patients were the reservoir for transmission rather than caregivers. The most probable source for each individual transmission was determined based on proximity in time and space and shared exposure to caregivers. The rate of transmission of MRSA from patients on contact isolation was significantly lower (0.009 transmissions per day on isolation) than the rate for patients not on isolation (0.140 transmissions per day unisolated, relative risk = 15.6, 95% confidence interval 5.3-45.6, p < 0.0001). The authors conclude that the risk of nosocomial transmission of MRSA was reduced 16-fold by contact isolation during the outbreak in this neonatal intensive care unit. These data confirm the results of previous studies which have suggested that contact isolation was effective in controlling the epidemic spread of methicillin-resistant Staphylococcus aureus.
Insights
Contact isolation significantly reduced methicillin-resistant Staphylococcus aureus (MRSA) transmission in a neonatal intensive care unit. This infection control strategy lowered MRSA spread by 16-fold, confirming its effectiveness in preventing nosocomial infections.
Area of Science:
- Infectious Diseases
- Hospital Epidemiology
- Microbiology
Background:
- Nosocomial transmission of methicillin-resistant Staphylococcus aureus (MRSA) is a significant concern.
- Contact isolation is recommended by the CDC for MRSA prevention, but prospective data on its effectiveness are limited.
- An MRSA outbreak in a neonatal intensive care unit (NICU) provided an opportunity to evaluate contact isolation.
Purpose of the Study:
- To prospectively quantitate the effectiveness of contact isolation in preventing nosocomial transmission of MRSA during an outbreak.
- To determine the transmission rate of MRSA in a NICU setting with and without contact isolation.
- To identify the source and pattern of MRSA spread during the outbreak.
Main Methods:
- Weekly surveillance cultures were performed on all NICU patients during the outbreak.
- MRSA isolates underwent plasmid profile analysis and restriction enzyme analysis of whole cell DNA.
- Transmission rates were calculated for patients on contact isolation versus those not isolated, and relative risk was determined.
Main Results:
- Sixteen of 331 NICU admissions were colonized with MRSA; 3 developed infections.
- All outbreak isolates shared identical chromosomal patterns and plasmid profiles, indicating a unique strain.
- The transmission rate of MRSA was 16-fold lower for patients on contact isolation (0.009/day) compared to those not isolated (0.140/day).
- Caregivers did not carry MRSA, suggesting patients were the primary reservoir.
Conclusions:
- Contact isolation significantly reduced the risk of nosocomial MRSA transmission by 16-fold during the NICU outbreak.
- These findings confirm the effectiveness of contact isolation in controlling the epidemic spread of MRSA.
- Implementing and adhering to contact isolation protocols is crucial for preventing MRSA spread in healthcare settings.