A five year outbreak of methicillin-susceptible Staphylococcus aureus phage type 53,85 in a regional neonatal unit

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 ≥ 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.