Emergence of carbapenem- resistant Pseudomonas alcaligenes and Pseudomonas paralcaligenes clinical isolates with plasmids harbouring blaIMP-1 in Japan

Introduction. The emergence of carbapenem-resistant Pseudomonas species producing metallo-fl-lactamase (MBL) has become a serious medical problem worldwide. IMP -type MBL was firstly detected in 1991 in Japan. Since then, it has become one of the most prevalent types of MBLs.Hypothesis/Gap statement. Avirulent species of Pseudomonas, such as Pseudomonas alcaligenes, function as reservoirs of drug resistance-associated genes encoding carbapenemases in clinical settings.Methodology. Active surveillance for carbapenem-resistant Gram-negative pathogens was conducted in 2019 at a hospital in Tokyo, Japan. Of the 543 samples screened for carbapenem-resistant isolates, 2 were species of Pseudomonas. One was from a stool sample from a medical staff member, and the other was from a stool sample from a hospitalized patient.Results. Whole-genome sequencing showed that the former isolate was a strain of P. alcaligenes, and the latter was a strain of Pseudomonas paralcaligenes, a species close to P. alcaligenes. Both isolates were resistant to all carbapenems and harboured blaIMP-1 genes encoding IMP -1 MBL, which conferred resistance to carbapenems. The blaIMP-1 genes of P. alcaligenes and P. par-alcaligenes were located on the plasmids, pMRCP2, 323125 bp in size, and pMRCP1333, 16592 bp in size, respectively. The sequence of 82 % of pMRCP2 was 92 % similar to the sequence of a plasmid of P. aeruginosa PA83, whereas the sequence of 79 % of pMRCP1333 was >95 % similar to the sequence of a plasmid of Achromobacter xylosoxidans FDAARGOS 162. The genomic environments surrounding the blaIMP-1 of pMRCP2 and pMRCP1333 differed completely from each other.Conclusions. These results indicate that the two isolates acquired blaIMP-1 from different sources and that P. alcaligenes and P. paralcaligenes function as vectors and reservoirs of carbapenem-resistant genes in hospitals.