Persistence of Carbapenem-Resistant Acinetobacter baumannii in intensive care units environment

Abstract Background: Acinetobacter baumannii(A. baumannii) is a major pathogen that causes nosocomial infections in intensive care units (ICUs). The present study aimed to analyse the distribution of A. baumannii in 2 ICUs and in the hands of ICU workers, focusing on antimicrobial susceptibility genes, carbapenem resistance genes, disinfectant resistance genes and cluster evolution. Methods: A. baumannii isolates were obtained from 2 ICU environments and ICU workers’ hand during 2016-2018. Antibiotic susceptibility testing was carried out according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Polymerase Chain Reaction (PCR) was performed for to detect OXA-type genes, metallo-β-lactamase genes and qac genes. Multilocus sequence typing (MLST) using both the Oxford and Pasteur schemes, repetitive extragenic palindromic PCR (REP-PCR) and enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) were used to determine the epidemiologic relationships of the A.baumannii isolates. Global optimal eBURST was used to assess clonal complexes. Results: Among the environmental A.baumannii isolates, 11 strains were obtained from patients’ surrounding high-touch surfaces, 10 from medical equipment and 6 from nurses’ station objects. Antimicrobial susceptibility testing results revealed that a majority of the A.baumannii strains (23/34, 67.65%) were considered as extensively drug resistant (XDR), and 11.76% (4/34) were considered as multidrug-resistant (MDR). In addition, a total of 26/34 (76.47%) strains were carbapenem-resistant Acinetobacter baumannii (CRAB). The Pasteur MLST scheme showed that 97.06% of the A. baumannii strains belonged to 8 sequence types (STs), while the Oxford scheme succeeded in allocating only 82.35% of the isolates. The most dominant ST in the Pasteur scheme was ST2, whereas ST195 was predominant in the Oxford scheme. The STs obtained from the Pasteur scheme correlated well with the REP-PCR patterns. OXA-51 was detected in 94.12% (32/34) isolates. OXA-23 is the most common carbapenemase gene among CRAB isolates (88.46%, 23/26). The prevalence of qacΔE1 was 79.41% (27/34). QacΔE1, OXA-51, OXA-23 and VIM were present in 58.82% (20/34) of the isolates. Conclusions: A.baumannii strains harbouring the qacΔE1, OXA-51, OXA-23 and VIM genes are widely circulating in ICUs and the hands of healthcare workers. ST2/ST195 (Pasteur/Oxford) were the predominant epidemic type of A.baumannii in ICUs.