Emergence of Carbapenem-Resistant Providencia rettgeri and Providencia stuartii Producing IMP-Type Metallo-ß-Lactamase in Japan.

Four Providencia rettgeri isolates and one Providencia stuartii isolate were obtained from urine samples of five patients in 2018 in Japan. All of the isolates were resistant to imipenem and meropenem, and three were highly resistant to both carbapenems, with MICs of 512 µg/ml. The three highly carbapenem-resistant isolates harbored blaIMP-70, encoding a variant of IMP-1 metallo-ß-lactamase with two amino acid substitutions (Val67Phe and Phe87Val), and the other two harbored blaIMP-1 and blaIMP-11, respectively. Whole-genome sequencing revealed that an isolate harbored two copies of blaIMP-1 on the chromosome and that the other four harbored a copy of blaIMP-11 or blaIMP-70 in a plasmid. Expression of blaIMP-70 conferred carbapenem resistance in Escherichia coli Recombinant IMP-70 and an IMP-1 variant with Val67Phe but without Phe87Val had significant higher hydrolytic activities against meropenem than recombinant IMP-1, indicating that an amino acid substitution of Val67Phe affects increased activities against meropenem in IMP-70. These results suggest that Providencia spp. become more highly resistant to carbapenems by acquisition of two copies of blaIMP-1 or by mutation of blaIMP genes with amino acid substitutions, such as blaIMP-70.

Emergence and Evolution of Unique Plasmids Harboring blaIMP-70 and blaCTX-M-253 in Multidrug-Resistant Providencia rettgeri.

Although the prevalence of carbapenem-resistant Enterobacterales remains low in Japan, these bacteria are a growing problem worldwide, owing to their multidrug resistance phenotype. We isolated a multidrug-resistant Providencia rettgeri strain, NR1418, harboring a rare blaIMP variant, blaIMP-70, a novel blaCTX-M variant, designated blaCTX-M-253, and blaMOX-1. This strain is resistant to ß-lactams, amikacin, levofloxacin, and colistin. Genomic analysis revealed that NR1418 carries two plasmids, designated pNR1418-1 and pNR1418-2. The pNR1418-1 plasmid harbors blaCTX-M-253, blaTEM-1, and blaMOX-1, while the pNR1418-2 plasmid harbors blaIMP-70, which is located in a class 1 integron. Both plasmids exhibit high similarities with the plasmid of the P. rettgeri isolate BML2526, which also harbors blaIMP-70 and was identified in the same region of Japan as NR1418 at a different point in time. This indicates the possibility of the emergence and evolution of IMP-70-producing P. rettgeri and suggests that the plasmid of BML2526 may have occurred following recombination of the two plasmids harbored by NR1418. Further, blaIMP-70 and blaCTX-M-253 were found on unique plasmids, indicating that they likely evolved through mutations and recombination. IMPORTANCE Although Providencia rettgeri is an opportunistic pathogen, its intrinsic resistance to colistin and tigecycline makes the treatment of carbapenem-resistant P. rettgeri challenging. We isolated a multidrug-resistant P. rettgeri strain which harbored a rare blaIMP variant, blaIMP-70, a novel blaCTX-M variant, blaCTX-M-253, and blaMOX-1 from a urinary sample obtained in Osaka, Japan. We investigated its genetic structure and evaluated the evolution of the plasmids carrying these genes. We show that blaIMP-70, blaCTX-M-253, and blaMOX-1 are present on unique plasmids and that they have high similarities to the plasmid of another IMP-70-producing P. rettgeri isolate that was identified as being from the same location. The evolution of plasmids through mutations and recombination may play a role in the development and spread of multidrug resistance.