Predominance of international clone 2 multidrug-resistant Acinetobacter baumannii clinical isolates in Thailand: a nationwide study

<jats:title>Abstract</jats:title><jats:sec> <jats:title>Background</jats:title> <jats:p><jats:italic>Acinetobacter baumannii</jats:italic> 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 <jats:italic>A. baumannii</jats:italic> (MDR <jats:italic>A. baumannii</jats:italic>) isolates were characterized phenotypically, and the molecular epidemiology of clinical isolates in 11 tertiary hospitals was investigated at a country-wide level.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>A total of 135 nonrepetitive MDR <jats:italic>A. baumannii</jats:italic> 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.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>ST2 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 <jats:italic>bla</jats:italic>oxa-23 gene was by far the most widespread in MDR <jats:italic>A. baumannii,</jats:italic> while the <jats:italic>bla</jats:italic>oxa-24/40 and <jats:italic>bla</jats:italic>oxa-58 genes appeared to be less dominant in this region. The results demonstrated that the predominant class D carbapenemase was <jats:italic>bla</jats:italic>OXA-23, followed by the class B carbapenemase <jats:italic>bla</jats:italic>NDM-like, while the <jats:italic>mcr</jats:italic>-1 gene was not observed in any isolate. Most of the MDR <jats:italic>A. baumannii</jats:italic> 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 <jats:italic>A. baumannii</jats:italic> in this region.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusion</jats:title> <jats:p>This is the first molecular epidemiological analysis of MDR <jats:italic>A. baumannii</jats:italic> clinical isolates at the national level in Thailand to date. Studies on the clonal relatedness of MDR <jats:italic>A. baumannii</jats:italic> isolates could generate useful data to understand the local epidemiology and international comparisons of nosocomial outbreaks.</jats:p> </jats:sec>