MLST typing of Acinetobacter baumannii in a hospital outbreak

Abstract

Background and objective: Carbapenem-resistant Acinetobacter baumannii (CRA) is a WHO-designated priority antibiotic-resistant pathogen. In this study, we performed Multi-Locus Sequence Typing (MLST) for the clinical and environmental CRA isolates recovered from an investigation of a hospital CRA outbreak. Methods: CRA was recovered from 58 patients and multiple environmental sites. Twenty-four clinical and 11 environmental isolates were selected for MLST. MALDI-TOF and OXA-51 gene PCR were used for identification of Acinetobacter baumannii. MLST was done by Sanger sequencing. Fisher’s exact test was used for analysis of categorical variables. Results: Extensive patient screening and environmental sampling identified the hospital laundry as the likely source of CRA outbreak across multiple wards. CRA isolates of ST345 from hospital laundry cooler machine was identical to that of 11 patients across different wards. CRA isolates of ST1145 from three laundry linen racks were identical to that of seven patients across different wards. CRA isolates of ST2207 found in another linen rack were identical to that in three other patients across different wards. Antimicrobial susceptibility patterns of CRA isolates could not accurately differentiate between different ST. Conclusion: MLST result demonstrated the link between contamination of laundry cooler and environment and the hospital polyclonal CRA outbreak.