Molecular characterization of a suspected IMP-type carbapenemase-producing outbreak reveals two simultaneous outbreaks in a tertiary-care hospital.

Objective: To describe IMP-type carbapenemase-producing outbreaks at Galdakao University Hospital between March 2021 to December 2021.

Design: Outbreak report.

Setting: Galdakao University Hospital is a tertiary-care hospital in the Basque Country (northern Spain).

Patients: All patients with a positive IMP-type carbapenemase producing  (IMP-PA) culture were included in this study, both colonization and infection cases.

Methods: An outbreak investigation was conducted, in which molecular epidemiology analysis [pulsed-field gel electrophoresis and whole-genome sequencing (WGS)] and environmental screenings were performed.

Results: Between March and December 2021, 21 cases of IMP-PA were detected in Galdakao University Hospital: 18 infection cases and 3 colonization cases. In total, 4 different pulsotypes were detected belonging to 4 clones according to WGS: ST175 (n = 14), ST633 (n = 3), ST179 (n = 3), and ST348 (n = 1). IMP-13 was detected in most isolates belonging to the ST175 clone and in all ST179 and ST348 clones, whereas IMP-29 was detected in isolates belonging to the ST633 clone. Clinical isolates belonging to the ST175 clone were isolated mainly from patients admitted to the respiratory ward, and isolates belonging to the ST633 clone from patients admitted to the ICU. Two environmental isolates belonging to the ST175 clone were detected in the respiratory ward.

Conclusions: Molecular and genomic epidemiology revealed that there had been 2 independent IMP-PA outbreaks, one of long duration in the respiratory ward and the other more limited in the ICU.