[First outbreak report of VIM-1 metallo-beta-lactamase producing Pseudomonas aeruginosa in Japan]

Emergence and spread of VIM-type metallo-β-lactamase-producing Pseudomonas aeruginosa clinical isolates in Japan

OBJECTIVES

The aim of this study was to determine the genetic and epidemiological properties of Pseudomonas aeruginosa strains producing VIM-type metallo-β-lactamases isolated from patients in Japan.

METHODS

A total of 1860 clinical isolates of carbapenem-resistant P. aeruginosa were obtained from patients hospitalised in Japan from 2012-2018. Carbapenem-resistant P. aeruginosa isolates were screened for bla_VIM genes by PCR. Antimicrobial susceptibility was determined by the broth microdilution method. The whole genomes of these isolates were sequenced using a next-generation sequencer, and phylogenetic analysis was performed using single nucleotide polymorphism concatemers. Multilocus sequence typing (MLST) was performed and drug resistance genes were identified using whole-genome sequence data.

RESULTS

Of 1860 isolates, 25 bla_VIM-positive isolates were screened in nine medical settings in Japan. The population of VIM-producing P. aeruginosa significantly increased between 2012 and 2018. All 25 bla_VIM-positive isolates were resistant to imipenem, meropenem and ciprofloxacin but were susceptible to colistin. The isolates harboured bla_VIM-1, bla_VIM-2, bla_VIM-24, bla_VIM-60 or the novel variant bla_VIM-66 and belonged to four different sequence types (STs), including ST179, ST233, ST235 and ST1816. The 11 isolates harbouring bla_VIM-24, bla_VIM-60 or bla_VIM-66 were obtained from a single hospital, all belonging to ST1816. VIM-24, VIM-60 and VIM-66 had an amino acid substitution (Arg228Leu) compared with VIM-2.

CONCLUSIONS

The number of P. aeruginosa strains producing VIM-type MBLs has increased in medical settings in Japan. Pseudomonas aeruginosa ST1816 producing VIM enzymes with Arg228Leu substitution have emerged and evolved in a medical setting in Japan.

Molecular characteristics of carbapenem-resistant Pseudomonas aeruginosa isolated from urine in Hyogo, Japan

OBJECTIVES

To investigate the molecular characteristics and epidemiology of metallo-β-lactamase-producing Pseudomonas aeruginosa from urine of urinary tract infection patients in Hyogo Prefecture, Japan.

METHODS

Carbapenem-resistant P. aeruginosa isolated from the urine of 21 urinary tract infection patients in three general hospitals in Hyogo Prefecture (Japan) were collected between 2007 and 2014. Their antibiotic susceptibilities, metallo-β-lactamase screening test, metallo-β-lactamase gene sequencing, multilocus sequence typing and repetitive-sequence-based polymerase chain reaction were determined for epidemiological analyses to investigate the genetic characteristics.

RESULTS

Out of 21 isolates, 13 (61.9%) were positive for metallo-β-lactamase. There were 11 (52.4%) isolates with IMP-1 in them, one (4.5%) isolate with IMP-7 and one (4.5%) isolate with VIM-1. Metallo-β-lactamase-positive isolates were mainly identified as ST235, and metallo-β-lactamase-negative isolates were STs 357, 277, 234, 439 and 639. Repetitive-sequence-based polymerase chain reaction showed metallo-β-lactamase-positive isolates were grouped in eight clusters, and ST235 isolates with IMP-1 from three hospitals belonging to the identical group I, the other ST235 isolates with IMP-7 and VIM-1 were from two hospitals belonging to group II.

CONCLUSIONS

Metallo-β-lactamase-positive P. aeruginosa of ST235 isolates with IPM-1 were mainly identified from the urine of urinary tract infection patients in Hyogo, Japan. A ST235 isolate with VIM-1 was found for the first time. Further investigation is necessary to follow the spread of metallo-β-lactamase-positive isolates.

Evaluation of the double-disk synergy test for New Delhi metallo-β-lactamase-1 and other metallo-β-lactamase producing gram-negative bacteria by using metal-ethylenediaminetetraacetic acid complexes

New Delhi metallo-β-lactamase-1 (NDM-1), one of the metallo-β-lactamases (MBLs), has been identified from clinical isolates worldwide. Rapid detection of NDM-1 producers is necessary to prevent their dissemination. Seven types of EDTA complexes were evaluated as MBL inhibitors in double-disk synergy tests (DDSTs), resulting in detection of the first isolate of NDM-1-producing Escherichia coli (NDM-1 Dok01) in Japan. NDM-1 Dok01 was detected when EDTA magnesium disodium salt tetrahydrate (Mg-EDTA), EDTA calcium disodium salt dihydrate, EDTA cobalt disodium salt tetrahydrate and EDTA copper disodium salt tetrahydrate were used as MBL inhibitors. The sensitivity and specificity of DDSTs using Mg-EDTA for 75 MBL producers and 25 non-MBL producers were 96.0% and 100%, respectively. These findings indicate that the DDST method using Mg-EDTA can detect MBL-producing strains, including NDM-1 producers.