Community-acquired in name only: A cluster of carbapenem-resistantAcinetobacter baumanniiin a burn intensive care unit and beyond

Abstract

Objective:To describe an investigation into 5 clinical cases of carbapenem-resistant Acinetobacter baumannii (CRAB).Design:Epidemiological investigation supplemented by whole-genome sequencing (WGS) of clinical and environmental isolates.Setting:A tertiary-care academic health center in Boston, Massachusetts.Patients or participants:Individuals identified with CRAB clinical infections.Methods:A detailed review of patient demographic and clinical data was conducted. Clinical isolates underwent phenotypic antimicrobial susceptibility testing and WGS. Infection control practices were evaluated, and CRAB isolates obtained through environmental sampling were assessed by WGS. Genomic relatedness was measured by single-nucleotide polymorphism (SNP) analysis.Results:Four clinical cases spanning 4 months were linked to a single index case; isolates differed by 1–7 SNPs and belonged to a single cluster. The index patient and 3 case patients were admitted to the same room prior to their development of CRAB infection, and 2 case patients were admitted to the same room within 48 hours of admission. A fourth case patient was admitted to a different unit. Environmental sampling identified highly contaminated areas, and WGS of 5 environmental isolates revealed that they were highly related to the clinical cluster.Conclusions:We report a cluster of highly resistant Acinetobacter baumannii that occurred in a burn ICU over 5 months and then spread to a separate ICU. Two case patients developed infections classified as community acquired under standard epidemiological definitions, but WGS revealed clonality, highlighting the risk of burn patients for early-onset nosocomial infections. An extensive investigation identified the role of environmental reservoirs.

Carbapenem-resistant Acinetobacter baumannii: A challenge in the intensive care unit

“…Similarly, Salehi et al (2018) and Raro et al (2017) analyzed the isolates of A. baumannii from patients, staff, and the environment, and emphasized the circulation of CRAB as a nosocomial pathogen in different wards of hospitals, particularly in ICUs. Shenoy et al also identified highly contaminated areas and confirmed the role of environmental reservoirs by investigating five clinical CRAB infection cases (Shenoy et al, 2020). It should be noted that although environmental contamination of CRAB in ICUs has gained increasing attention, research about whether specific clone was responsible for both environmental colonization and ICU infections is still lacking.…”

Extensive acquisition of carbapenem-resistant Acinetobacter baumannii in Intensive Care Unit patients is driven by widespread environmental contamination

“…This situation, in a country where CRAB prevalence is reported to be highest globally, 28 is in stark contrast to those described in monoclonal outbreaks in hospitals in low-prevalence high-income countries. 4,7–9 The prevalence of CRAB in the ICU was also found to be higher than previously appreciated, likely owing to our environmental screening.…”

“…Recent studies have demonstrated the utility of whole-genome sequencing (WGS) for high-resolution characterisation of such single-centre outbreaks or populations. 4,[8][9][10] Endemic hospital A. baumannii populations, however, can be composed of multiple phylogenetic clusters. 11,12 WGS has been employed to assess multi-centre CRAB populations, revealing that individual hospitals harbour multiple clusters and that these may be found across multiple hospitals.…”

Clinical Pathogen Genomics

“…WGS of isolates from a suspected outbreak allows for determination of clonality, correlation with regional and national data, and establishment of transmission timelines. 21 , 22 , 23 , 24 Although other methods exist for determining isolate clonality (eg, pulsed-field gel electrophoresis), only WGS also identifies ARGs and virulence genes, and finely resolves degrees of relatedness. 23 , 25 , 26 WGS is also the preferred method for fungal genotyping in outbreak investigations, because many of these pathogens lack a preexisting typing scheme.…”