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

Abstract

Background: 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. Aim: The objective was to describe the clinical epidemiology, confirm the environmental source and assess the impact of control measures. Methods: 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 (bioMerieux), 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 dis continuation of patient room sink use, relocation of medication preparation, renewal of drainage systems and scheduled decontamination with a solution of 15% acetic acid. Findings: 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. Conclusion: Sinks and drainage systems acted as the source of a PaePER outbreak. Targeted interventions rapidly interrupted transmission.