Objective: To use whole genome sequencing to describe the likely origin of an outbreak of Pseudomonas aeruginosa in a neonatal unit.
Design: Outbreak investigation.
Setting: The neonatal intensive care unit service of a major obstetric tertiary referral center.
Patients: Infants admitted to the neonatal unit who developed P. aeruginosa colonization or infection.
Methods: We undertook whole genome sequencing of P. aeruginosa strains isolated from colonized infants and from the neonatal unit environment.
Results: Eighteen infants were colonized with P. aeruginosa. Isolates from 12 infants and 7 environmental samples were sequenced. All but one of the clinical isolates clustered in ST253 and no differences were detected between unmapped reads. The environmental isolates revealed a variety of sequence types, indicating a large diverse bioburden within the unit, which was subsequently confirmed via enterobacterial repetitive intergenic consensus-polymerase chain reaction typing of post-outbreak isolates. One environmental isolate, obtained from a sink in the unit, clustered within ST253 and differed from the outbreak strain by 9 single-nucleotide polymorphisms only. This information allowed us to focus infection control activities on this sink.
Conclusions: Whole genome sequencing can provide detailed information in a clinically relevant time frame to aid management of outbreaks in critical patient management areas. The superior discriminatory power of this method makes it a powerful tool in infection control.