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Clean clothes or dirty clothes? Outbreak investigation of carbapenem-resistant Acinetobacter baumannii related to laundry contamination through multilocus sequence typing (MLST)

Published online by Cambridge University Press:  08 November 2022

Alfred Lok Hang Lee*
Department of Microbiology, Prince of Wales Hospital, Hong Kong
Eddie Chi Ming Leung
Department of Microbiology, Prince of Wales Hospital, Hong Kong
Ben Wai Hong Wong
Department of Microbiology, Prince of Wales Hospital, Hong Kong
Leo Chun Hei Wong
Department of Microbiology, Prince of Wales Hospital, Hong Kong
Yoyo Lok Yiu Wong
Department of Microbiology, Prince of Wales Hospital, Hong Kong
Rosana Ka Yin Hung
Infection Control Team, New Territories East Cluster, Hospital Authority, Hong Kong
Sindy Sin Yee Ho
Infection Control Team, New Territories East Cluster, Hospital Authority, Hong Kong
Viola Chi Ying Chow
Department of Microbiology, Prince of Wales Hospital, Hong Kong Infection Control Team, New Territories East Cluster, Hospital Authority, Hong Kong
Author for correspondence: Dr Alfred Lok Hang Lee, E-mail:



To investigate the source in an outbreak of carbapenem-resistant Acinetobacter baumannii (CRA) in a general hospital due to contamination of a laundry evaporative cooler and the laundry environment using multilocus sequence typing (MLST).


For CRA culture, clinical samples were collected from infected patients and close contacts, and environmental sampling was performed in patient surroundings and laundry facilities. MLST was used for the molecular typing of representative CRA isolates. Bacterial isolates with identical sequence types were considered epidemiologically linked and attributable to the same source. OXA genes in Acinetobacter baumannii were detected using polymerase chain reaction (PCR).


In total, 58 patients were affected in this outbreak. The mean patient age was 75.3, and 50% were female. The most common diagnoses at admission were skin and soft-tissue infection (n = 12, 20.7%) and pneumonia (n = 12, 20.7%). OXA-23 was positive in 64.7% of isolates. A CRA isolate from the evaporative cooler in the laundry was identical to that of 11 patients across 3 wards, belonging to ST345. Isolates from 3 laundry linen racks were identical to those of 7 patients from 3 wards, classified as ST1145. Isolates found on another linen rack and a pajama shelf were identical to isolates from 3 other patients from 2 wards, belonging to ST2207. There was no significant difference between sequence type distributions of clinical and environmental isolates (P = .12), indicating high likelihood of CRA originating from the same source.


MLST confirmed that contamination of the laundry evaporative cooler and surrounding environment caused a polyclonal CRA hospital outbreak. Hospital laundry is an important area for infection control and outbreak investigations of CRA.

Original Article
© The Author(s), 2022. Published by Cambridge University Press on behalf of The Society for Healthcare Epidemiology of America

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