Molecular epidemiology, microbiological features and infection control strategies for carbapenem-resistant Acinetobacter baumannii in a German burn and plastic surgery center (2020-2022)

Abstract

Background: Carbapenem-resistant Acinetobacter baumannii (CRAB) frequently causes both healthcare-associated infections and nosocomial outbreaks in burn medicine/plastic surgery and beyond. Owing to the high antibiotic resistance, infections are difficult to treat, and patient outcomes are often compromised. The environmental persistence capability of CRAB favors its transmission in hospitals. A comprehensive analysis and understanding of CRAB epidemiology and microbiology are essential for guiding management.

Methods: A three-year retrospective cohort study (2020-2022) was conducted in a German tertiary burn and plastic surgery center. In addition to epidemiological analyses, microbiological and molecular techniques, including whole-genome sequencing, were applied for the comprehensive examination of isolates from CRAB-positive patients.

Results: During the study period, eight CRAB cases were found, corresponding to an overall incidence of 0.2 CRAB cases per 100 cases and an incidence density of 0.35 CRAB cases per 1000 patient-days. Six cases (75%) were treated in the burn intensive care unit, and four cases (50%) acquired CRAB in the hospital. Molecular analyses comprising 74 isolates supported the epidemiologic assumption that hospital acquisitions occurred within two separate clusters. In one of these clusters, environmental CRAB contamination of anesthesia equipment may have enabled transmission. Furthermore, molecular diversity of CRAB isolates within patients was observed.

Conclusions: CRAB can pose a challenge in terms of infection prevention and control, especially if cases are clustered in time and space on a ward. Our study demonstrates that high-resolution phylogenetic analysis of several bacterial isolates from single patients can greatly aid in understanding transmission chains and helps to take precision control measures.

Keywords: Acinetobacter baumannii; Carbapenem; Epidemiology; Infection prevention and control; Microbiology; Resistance; Whole-genome sequencing.

Fig. 1

Epidemiologic curve of cases with carbapenem-resistant Acinetobacter baumannii

Fig. 2

Positive environmental samples in the operating theatre. A Anesthesia tower in the operating theatre. B Documentation workplace in the operating theatre. Positive sites are marked with “X”

Fig. 3

Dendrogram based on the average nucleotide identity (ANI) values of carbapenem-resistant Acinetobacter baumannii isolates (n = 74), along with the detected carbapenemase genes, sequence types (STs) and cgMLST results. The leaf color indicates the individual patient; environmental isolates are shown in black. Strains were grouped on the basis of their phylogenetic relatedness (G_#) via ANI and SNP analysis (30 SNPs was considered the cut-off for group designation). Cyan arrows show references for SNP calling; red stars signify deviations of SNP results (indicating the group) from ANI analysis. +: =< 35 SNPs to one reference of the group