Emergence of Carbapenem-resistant Clinical Isolates of Species.

is a genus of Gram-negative and non-spore forming bacteria belonging to the family , which causes opportunistic infections in humans. Of the 10 species identified to date, three, , and , are clinically important. causes diarrhea, including outbreaks arising from food-borne infections, and and have been found to cause hospital acquired urinary tract infections. Four isolates of and one isolate of were obtained from urine samples of five patients in Japan in 2018. All five isolates were highly resistant to carbapenems. Three isolates harbored , encoding a variant of IMP-1 metallo-β-lactamase, with two amino acid substitutions (Val67Phe and Phe87Val), one isolate harbored two copies of and one isolate harbored . Expression of conferred carbapenem resistance in . Recombinant IMP-10, an IMP-1 variant with Val67Phe but without Phe87Val, had significant higher hydrolytic activities against meropenem than recombinant IMP-1, indicating that the Val67Phe amino acid substitution alters activities against meropenem in IMP-70. These results suggest that species. become more highly resistant to carbapenems by acquisition of two copies of or by mutations in that result in amino acid substitutions, such as .