Abstract
BackgroundAcinetobacter baumannii has emerged as one of the common multidrug resistance pathogens causing hospital-acquired infections. This study was conducted to elucidate the distribution of antimicrobial resistance genes in the bacterial population in Thailand. Multidrug-resistant A. baumannii (MDR A. baumannii) isolates were characterized phenotypically, and the molecular epidemiology of clinical isolates in 11 tertiary hospitals was investigated at a country-wide level.MethodsA total of 135 nonrepetitive MDR A. baumannii isolates collected from tertiary care hospitals across 5 regions of Thailand were examined for antibiotic susceptibility, resistance genes, and sequence types. Multilocus sequence typing (MLST) was performed to characterize the spread of regional lineages.ResultsST2 belonging to IC2 was the most dominant sequence type in Thailand (65.19%), and to a lesser extent, there was also evidence of the spread of ST164 (10.37%), ST129 (3.70%), ST16 (2.96%), ST98 (2.96%), ST25 (2.96%), ST215 (2.22%), ST338 (1.48%), and ST745 (1.48%). The novel sequence types ST1551, ST1552, ST1553, and ST1557 were also identified in this study. Among these, the blaoxa-23 gene was by far the most widespread in MDR A. baumannii, while the blaoxa-24/40 and blaoxa-58 genes appeared to be less dominant in this region. The results demonstrated that the predominant class D carbapenemase was blaOXA-23, followed by the class B carbapenemase blaNDM-like, while the mcr-1 gene was not observed in any isolate. Most of the MDR A. baumannii isolates were resistant to ceftazidime (99.23%), gentamicin (91.85%), amikacin (82.96%), and ciprofloxacin (97.78%), while all of them were resistant to carbapenems. The results suggested that colistin could still be effective against MDR A. baumannii in this region.ConclusionThis is the first molecular epidemiological analysis of MDR A. baumannii clinical isolates at the national level in Thailand to date. Studies on the clonal relatedness of MDR A. baumannii isolates could generate useful data to understand the local epidemiology and international comparisons of nosocomial outbreaks.
Highlights
Acinetobacter baumannii has emerged as one of the common multidrug resistance pathogens causing hospital-acquired infections
A. baumannii is frequently found to be resistant to a class of last-resort antibiotics, carbapenems, and these strains are known as carbapenem-resistant A. baumannii (CRAB)
This study demonstrated that the presence of the blaoxa-23 gene was closely correlated with carbapenem resistance, and this gene was predominantly carried in MDR A. baumannii isolates
Summary
Acinetobacter baumannii has emerged as one of the common multidrug resistance pathogens causing hospital-acquired infections. The most common infections caused by A. baumannii are related to nosocomial infections, including ventilationassociated pneumonia, skin and soft tissue infections, and bloodstream infections [3, 4]. This organism is well known for its remarkable ability to resist almost all available antibiotics due to its capability of adapting and acquiring resistance genes. According to the annual national antibiogram report 2019, the National Antimicrobial Resistance Surveillance Center, Thailand (NARST), A. baumannii complex isolates showed less than 50% susceptibility rates with almost all the currently used antibiotics except colistin [7]. PDR A. baumannii has emerged in regional hospitals in Thailand [8,9,10]
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