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A five year outbreak of methicillin-susceptible Staphylococcus aureus phage type 53,85 in a regional neonatal unit
M H Wilcox1, P Fitzgerald, J Freeman
1Department of Microbiology and Neonatal Medicine, Leeds General Infirmary and University of Leeds, UK.
Abstract:
We identified a 5-year outbreak of a methicillin-susceptible Staphylococcus aureus (MSSA) strain, affecting 202 babies on a neonatal unit, by routine weekly phage typing all S. aureus isolates. Multiple staged control measures including strict emphasis on hand hygiene, environmental and staff surveillance sampling, and application of topical hexachlorophane powder failed to end the outbreak. S. aureus PT 53,85 (SA5385) was found on opened packs of Stomahesive, used as a neonatal skin protectant. Only following the implementation of aseptic handling of Stomahesive, and the use of topical mupirocin for staff nasal carriers of SA5385, and for babies colonized or infected with S. aureus, did the isolation rate of SA5385 decline. DNA fingerprinting indicated that > or =, 95% of SA5385 isolates were clonal. In vitro death rates of SA5385 on Stomahesive with human serum were significantly lower than on Stomahesive alone (P = 0.04), and on cotton sheet with serum (P = 0.04), highlighting the potential of this material as a survival niche. Phage typing remains a valuable, inexpensive and simple method for monitoring nosocomial MSSA infection.
Insights
A five-year neonatal outbreak of methicillin-susceptible Staphylococcus aureus (MSSA) was traced to a skin protectant. Aseptic handling and mupirocin treatment successfully controlled this persistent hospital infection.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Neonatal Care
Background:
- A prolonged five-year outbreak of methicillin-susceptible Staphylococcus aureus (MSSA) affected 202 neonates.
- Standard infection control measures, including hand hygiene and environmental sampling, were ineffective in eradicating the MSSA strain.
Purpose of the Study:
- To identify the source and effective control strategies for a persistent MSSA outbreak in a neonatal unit.
- To evaluate the role of a specific skin protectant material as a potential reservoir for MSSA.
Main Methods:
- Routine weekly phage typing of all Staphylococcus aureus isolates.
- DNA fingerprinting to assess isolate clonality.
- In vitro susceptibility testing of the MSSA strain on different materials.
Main Results:
- The outbreak strain, Staphylococcus aureus PT 53,85 (SA5385), was identified on opened packs of Stomahesive, a neonatal skin protectant.
- SA5385 exhibited significantly lower in vitro death rates on Stomahesive with human serum compared to other conditions, indicating it as a survival niche.
- Implementation of aseptic Stomahesive handling and topical mupirocin for nasal carriers and colonized/infected neonates led to a decline in SA5385 isolation rates.
Conclusions:
- Phage typing is a valuable tool for monitoring nosocomial MSSA infections.
- Stomahesive served as a critical survival niche for the MSSA outbreak strain.
- A combined strategy of aseptic technique and targeted antimicrobial therapy was effective in controlling the prolonged neonatal MSSA outbreak.