Combatting a Tobramycin-resistant Staphylococcus aureus outbreak in a neonatal intensive care unit: the impact of hygiene intervention and antibiotic substitution.

BACKGROUND: Outbreaks of antibiotic-resistant bacteria in neonatal intensive care units (NICUs) is a significant risk to these vulnerable infants. This study describes a decade-long outbreak of tobramycin-resistant Staphylococcus aureus (TRSA) and the interventions implemented to try and resolve it. METHODS: A TRSA outbreak was suspected in a Swedish NICU in 2010 when four infants developed bacteremia with TRSA spa type t084. The outbreak was confirmed by point prevalence surveys of infants and staff, and monitored through active screening of infants. Several interventions were implemented to combat the outbreak, e.g. hygiene interventions were implemented (2010, 2014), the NICU was reconstructed (2012-2013), tobramycin was substituted for amikacin (2014) and a continued summary of screening results were distributed as a reminder to adhere to hygiene routines. RESULTS: Retrospective analysis of previous samples revealed TRSA presence as early as 2009. The S. aureus prevalence significantly decreased from 71% (2010-2011) to 52% (2013) following the hygiene intervention and pre-pasteurization of donor human milk (DHM). However, the proportion of TRSA persisted. The proportion of TRSA started to significantly decrease only after the ward was reconstructed and the antibiotic regimen was modified, ultimately leading to the apparent resolution of the outbreak in 2019, five years after the change in antibiotic regimen. No TRSA septicemia cases occurred after the change in antibiotic regimen and TRSA in the environmental screenings were no longer detected after 2012. CONCLUSIONS: Our findings underscore the interplay between the ward environment and neonatal colonization, emphasizing that successful outbreak control requires a combination of adherence to hygiene routines, pasteurization of DHM, and a correct antibiotic regimen. CLINICAL TRIAL NUMBER: Not applicable.