Containing a PER-1-producing Pseudomonas aeruginosa outbreak linked to sink contamination in an intensive care unit

Healthcare-associated infections in intensive care units (ICUs) are associated with reservoirs such as sinks and drainage systems that sustain biofilms and disseminate Gram-negative bacteria. Between July 2021 and November 2022, an increase in PER-1-producing Pseudomonas aeruginosa (PaePER) was detected in the ICU of a university hospital in Uruguay.

The objective was to describe the clinical epidemiology, confirm the environmental source and assess the impact of control measures.

An outbreak investigation was conducted. Cases were ICU patients with at least one PaePER-positive sample; all other ICU patients were considered exposed. Data collection included clinical and laboratory surveillance, observation of healthcare processes and targeted environmental sampling of seven sinks. Isolates were identified by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS); antimicrobial susceptibility was assessed using VITEK2 (bioMérieux), E-test and disk diffusion; extended-spectrum β-lactamase production was evaluated by double-disk synergy and bla _PER-1 was confirmed by polymerase chain reaction. Clonal relatedness was assessed by pulsed-field gel electrophoresis (PFGE). Control measures included discontinuation of patient room sink use, relocation of medication preparation, renewal of drainage systems and scheduled decontamination with a solution of 15% acetic acid.

Among 1221 exposed patients, 31 were affected (attack rate: 2.8%): 25 infections and six colonisation episodes. Eighty-three clinical isolates were recovered, mainly from respiratory and blood samples. Isolates showed high resistance to ceftazidime, cefepime, ceftazidime/avibactam, ceftolozane/tazobactam and amikacin, with preserved susceptibility to carbapenems and cefiderocol. PaePER was recovered from four of seven sinks. PFGE confirmed a single ST309 clone.

Sinks and drainage systems acted as the source of a PaePER outbreak. Targeted interventions rapidly interrupted transmission.