Abstract
BACKGROUND The multidrug resistance (MDR) phenotype is frequently observed in Acinetobacter baumannii, the most clinically relevant pathogenic species of its genus; recently, other species belonging to the A. calcoaceticus-A. baumannii complex have emerged as important MDR nosocomial pathogens.OBJECTIVES The present study aimed to verify the occurrence of metallo-β-lactamase genes among distinct Acinetobacter species in a hospital located in the Brazilian Amazon Region.METHODS Antimicrobial susceptibility profiles were determined by broth microdilution. The genetic relationships among these isolates were assessed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Pyrosequencing reads of plasmids carrying the bla NDM-1 gene were generated using the Ion Torrent™ platform sequencing.FINDINGS A total of six isolates carried bla NDM-1: A. baumannii (n = 2), A. nosocomialis (n = 3), and A. pittii (n = 1); three carried bla IMP-1: A. baumannii, A. nosocomialis, and A. bereziniae. Resistance to colistin was observed for an NDM-1-producing A. nosocomialis isolate. Diverse PFGE patterns and sequence types were found among A. nosocomialis and A. baumannii isolates. The bla NDM-1 sequence was inserted in a Tn125 transposon, while the bla IMP-1 was found as a gene cassette of the class 1 integron In86.MAIN CONCLUSIONS To the best of our knowledge, this is the first report describing the dissemination of bla NDM-1 among distinct Acinetobacter species recovered from the same hospital in South America.
Highlights
The multidrug resistance (MDR) phenotype is frequently observed in Acinetobacter baumannii, the most clinically relevant pathogenic species of its genus; recently, other species belonging to the A. calcoaceticus-A. baumannii complex have emerged as important MDR nosocomial pathogens
Carbapenem resistance due to the production of metallo-β-lactamases (MβLs) has rarely been reported in A. baumannii as well as in non-baumannii species.(4,10,11) IMP-type MβLs have only been reported in Acinetobacter spp. isolated from hospitals located in the state of São Paulo,(4,10) south-eastern Brazil, while NDM-1-producing isolates have been sporadically described in hospitals located in the three different states of the Southern region.(5,6,11)
Genotyping by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) - The clonal relationships of MβL-producing Acinetobacter spp. isolates belonging to the same species were investigated by PFGE using the CHEF DR II system (Bio-Rad, Hercules, California) and ApaI restriction enzyme (New England BioLabs, MA, USA), as previously described.(9) MLST was performed for those isolates belonging to the A. calcoaceticus-A. baumannii complex by double-stranded DNA sequencing of internal regions of seven housekeeping genes according to the Institute Pasteur scheme
Summary
The multidrug resistance (MDR) phenotype is frequently observed in Acinetobacter baumannii, the most clinically relevant pathogenic species of its genus; recently, other species belonging to the A. calcoaceticus-A. baumannii complex have emerged as important MDR nosocomial pathogens
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