AUTHOR=Yoon Eun-Jeong , Choi You Jeong , Park Sun Hee , Shin Jeong Hwan , Park Sung Gyun , Choi Jong Rak , Jeong Seok Hoon 

TITLE=A Novel KPC Variant KPC-55 in Klebsiella pneumoniae ST307 of Reinforced Meropenem-Hydrolyzing Activity

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.561317

DOI=10.3389/fmicb.2020.561317

ISSN=1664-302X

ABSTRACT=<p>A novel <italic>Klebsiella pneumoniae</italic> carbapenemase (KPC) variant, KPC-55, produced by a <italic>K. pneumoniae</italic> ST307 strain was characterized. <italic>K. pneumoniae</italic> strain BS407 was recovered from an active surveillance rectal swab of a patient newly admitted to a general hospital in Busan, South Korea. Carbapenemase production was confirmed by the modified Hodge test, and the MICs of β-lactams were determined by the broth microdilution method. The whole genome was sequenced. Cloning and expression of the <italic>bla</italic><sub>KPC–55</sub> gene in <italic>Escherichia coli</italic> and MIC determination were performed. The enzyme KPC-55 was used for kinetic assays against β-lactams and compared with the KPC-2 enzyme. The new allele of the <italic>bla</italic><sub>KPC</sub> gene had a T794A alteration compared to the <italic>bla</italic><sub>KPC–2</sub> gene, resulting in the amino acid substitution Y264N in the middle of the β9-sheet. Compared to the KPC-2-producing strain, the KPC-55-producing strain exhibited a lower level of resistance to most β-lactam drugs tested, however, the KPC-55 enzyme catalyzed aztreonam and meropenem at an increased efficiency compared to the catalytic activity of KPC-2. KPC subtypes could have varied phenotypes due to alterations in amino acid sequences, and such an unexpected resistance phenotype emphasizes the importance of detailed characterizations for the carbapenemase-producing Enterobacterales.</p>