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

Abstract

A novel Klebsiella pneumoniae carbapenemase (KPC) variant, KPC-55, produced by a K. pneumoniae ST307 strain was characterized. K. pneumoniae 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 bla KPC–55 gene in Escherichia coli 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 bla KPC gene had a T794A alteration compared to the bla KPC–2 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.

Multiple Novel Ceftazidime-Avibactam-Resistant Variants of bla KPC-2 -Positive Klebsiella pneumoniae in Two Patients

“…All these bla KPC-2 variants conferred resistance to ceftazidime-avibactam and restored susceptibility to carbapenems. The mechanism for the KPC-79 enzyme might be that the β9-sheet and the following hinge to the α12-helix of KPC enzymes, which is proximal to the KPC-2 enzyme active site, is a variable region ( 36 ), KPC alleles like KPC-44 can have one- to 15-amino acid insertions in this region ( 37 ). On the flip side, the KPC-33, KPC-35, and KPC-78 enzymes presented with mutation within the Ω-loop, which enhanced ceftazidime affinity and reduced avibactam binding ( 38 ).…”

Multicenter Performance Evaluation of MALDI-TOF MS for Rapid Detection of Carbapenemase Activity in Enterobacterales: The Future of Networking Data Analysis With Online Software

“…The MALDI-TOF hydrolysis assay has the advantage of being able to detect carbapenemase activity regardless of the enzyme produced, including novel enzymes emerging at any given time which are not detected by predefined PCR tools usually used in diagnostics (Yoon et al, 2020). In addition, false positive results can also occur when PCR tools are used, due to the appearance of novel variants which lack carbapenemase activity, such as KPC-28 and OXA-163 (Dortet and Naas, 2017;Oueslati et al, 2019), or with reduced carbapenemase activity, such as OXA-232 and OXA-244 (Potron et al, 2013;Hoyos-Mallecot et al, 2017).…”

Inhibition of β-lactamase function by de novo designed peptide

“…These enzymes can hydrolyze carbapenems, cephalosporins and penicillins which limits the treatment options against gram-negative bacteria [5,44]. Newer variants of carbapenemases are constantly emerging, such as, the KPC-55 variant, which inactivates aztreonam and meropenem [45], and NDM-19 which can function in the presence of low concentrations of zinc [46]. Among different classes of β-lactamases, Class B MBLs are most challenging due to their ability to hydrolyze and develop…”