Box 4 Surveying and Managing MDRO cluster

A multidisciplinary IPC team has been established at the National Institute for Infectious Diseases “Lazzaro Spallanzani” in Rome in order to implement measures to prevent and control HAIs. A specific protocol concerns the laboratory-based surveillance of the following MDR alert organisms (carbapenem-resistant Acinetobacter spp., Klebsiella spp., Escherichia coli and Pseudomonas aeruginosa; MRSA; VRE) and Clostridioides difficile. After receiving an alert, the operative group of the IPC team performs a targeted epidemiological investigation, the results of which are discussed by the IPC team in order to implement corrective measures. In accordance with the hospital’s surveillance programme aimed at detecting carbapenem-resistant bacteria, rectal swabs were taken in the ICU from all patients on admission and then once weekly for the entire duration of their stay.

From December 2016 to April 2017, 13 alerts referring to carbapenem-resistant Acinetobacter baumannii (CRAB) isolates were collected from seven ICU patients. Epidemiological data, including time of infection and transfer to other wards, patient movements within the ICU and occupied rooms, strongly suggest a potential cluster. CRAB is a well-known nosocomial pathogen causing serious, often life-threatening, infections and outbreaks. To confirm the cluster hypothesis, the IPC team decided to perform molecular typing on the 13 isolates: 9 cultured from clinically relevant samples and the remaining 4 obtained from rectal swabs. Whole Genome Sequencing (WGS) and traditional multilocus typing (MLST) revealed the presence of two types of clusters. These results allowed to identify two patients who were likely the source of two separate transmission chains. The two patients came from two distinct hospitals and shared a narrow temporal and spatial overlap of their stay, supporting the conclusion that two separate transmission events are likely to have occurred.

Immediately following the alarm, investigations were undertaken to reveal possible breaches in the isolation precautions employed, but nothing was found. However, to contain the outbreak, isolation precautions, room and equipment cleaning, and disinfection procedures were audited and reinforced through an on-the-job education session. No other cases occurred either in the ICU or in the clinical wards where patients were subsequently transferred.