An outbreak of OXA-23-producing carbapenem-resistant Acinetobacter baumannii among ICU-patients with COVID-19 likely occurred by transmission through inanimate surfaces, potentially facilitated by a contaminated positioning pillow shared between patients, according to researchers in a new study published in BMC. Subsequent rapid spread may have been caused by exposure to respiratory secretions contaminating healthcare worker’s gloves and gowns during prone positioning.
Challenges in adhering to infection prevention and control guidance and escalation of antimicrobial usage during the COVID-19 pandemic led to a surge of hospital-acquired multidrug-resistant bacteria, including carbapenem-resistant Acinetobacter baumannii, say Zingg, et al. (2024). In this report, the researchers reveal potential reservoirs and transmission routes implicated in an outbreak of OXA-23-producing carbapenem-resistant A. baumannii (CRAB) among intensive care unit (ICU) patients with COVID-19 at a tertiary-care center in the northwestern part of Switzerland with more than 40,000 hospital admissions annually.
During the COVID-19 pandemic, patients with SARS-CoV-2 infection were frequently repatriated from institutions abroad and transferred between various Swiss hospitals based on the availability of hospital resources. At the USB, COVID-19 patients needing intensive care, were cohorted in a dedicated area of the ICU.
In September 2021, a bronchial sample from one patient in this dedicated ICU cohort revealed OXA-23-producing CRAB. Subsequent outbreak investigation included environmental and patient screening, collection of epidemiological and clinical data and performance of detailed infection prevention and control audits. All CRAB derived from patients and environmental samples were analyzed using next generation sequencing (NGS) to investigate genetic relationship.
Control audits were performed by the infection prevention and control team and had two main focuses. First, the handling of personal protective equipment (PPE) by healthcare workers (HCWs), especially during prone positioning of the patients in the ICU was audited. Secondly, the cleaning and disinfection procedures performed by the environmental services staff were looked at to uncover any potential breach.

Floor plan of the COVID-19 cohort within the intensive care unit. Red circle: index patient with OXA-23-producing Acinetobacter baumannii in 07/2021; purple circles: patients with detection of OXA-23-producing A. baumannii throughout the cohort within six days, two months later. Courtesy of BMC/Springer Nature
Upon detection of the outbreak, all patients hospitalized on the entire ICU were screened for colonization with CRAB. The following body sites were screened to assess colonization: wounds, catheter insertion sites, rectum, urine, tracheal secretion for ventilated patients and nasopharyngeal swabs for non-ventilated patients. Swabbing was performed; cross-sectional screenings of all patients in the COVID-19 cohort were performed on a weekly basis.
Due to the regular exchange of patients between the COVID-19 cohorts of the ICU and the general ward, all patients hospitalized in the COVID-19 cohort of the general ward were screened likewise. Patients were screened for colonization with CRAB of the rectum, urine, wounds, and puncture sites, as well as the respiratory tract if mechanically ventilated.
For outbreak investigation purposes, environmental screening swabs of high-touch areas were obtained to identify potential transmission sources.
From July to October 2021, OXA-23-producing CRAB was recovered from six patients hospitalized in the COVID-19 cohort-ward of the ICU of the USB. The index patient had been repatriated from Serbia in July 2021 due to COVID-19 and placed under contact and droplet precautions in a single room during the entire hospital stay. OXA-23-producing CRAB was detected in a screening sample collected at admission from the urine and, during the course of hospitalization, from clinical respiratory tract specimens. Seventy-six days after the index patient’s death, massive counts of OXA-23-producing CRAB were recovered from a clinical respiratory tract specimen of a second COVID-19 patient and subsequent screening revealed CRAB colonization of the respiratory tract in four additional COVID-19 patients in neighboring rooms within six days.
Zingg S, et al. Outbreak with OXA-23-producing Acinetobacter baumannii in a COVID-19 ICU cohort: unraveling routes of transmission. Antimicrobial Resistance & Infection Control. Vol. 13, article number 127. 2024).