Background Klebsiella pneumoniae is responsible for nosocomial infections, and the prevalence of blaKPC and its variants, including blaKPC−2 and blaKPC−144, contributes to antibacterial resistance. As a newly identified variant, blaKPC−144 is still inadequately defined regarding its mechanisms of resistance and its epidemiological traits. Therefore, we investigated β-lactam resistance in blaKPC−2- and blaKPC−144-harbouring K. pneumoniae isolates and elucidated their molecular epidemiological and genetic characteristics while assessing their prevalence, particularly that of blaKPC−144, in β-lactam-resistant K. pneumoniae. Methods We isolated three blaKPC−144- and nine blaKPC−2-harbouring strains from among 40 carbapenem-resistant K. pneumoniae isolates. The agar dilution method was used to determine the minimum inhibitory concentration of the blaKPC−144- and blaKPC−2-harbouring strains and transformants. Additionally, PCR and whole-genome sequencing of the genetic background of those genes were performed. Multilocus sequence typing and pulsed-field gel electrophoresis were used to investigate the clonal correlation of the blaKPC−144- and blaKPC−2-positive strains. Molecular docking was performed to analyse the affinity of the compounds for various antibiotics. Results Compared with blaKPC−2-positive strains, the blaKPC−144-positive strains exhibited significantly increased susceptibility to ertapenem and imipenem (MIC values decreased > 8-fold to the range of 2–4 µg/ml) but concurrently exhibited heightened resistance to ceftazidime and ceftazidime/avibactam (MIC values increased > 2-fold to the range of 32–64 µg/ml). Cloning blaKPC−2 and blaKPC−144 into Escherichia coli DH5α recapitulated the respective resistance profiles, directly attributing the divergent phenotypes to the gene variants themselves. Three different sequence types (ST11, ST15, and ST656) and eight pulsed-field gel electrophoresis subtypes (A to H) were classified. Conjugation experiments revealed that blaKPC−2 could be horizontally transmitted via plasmids, whereas blaKPC−144 displayed no discernible conjugative transfer. Whole-genome sequencing and comparative genomic analysis revealed that blaKPC−2 was located on IncFII-type plasmids flanked by conserved insertion sequences (IS26-ISKpn27-tnpR), whereas blaKPC−144 was chromosomally integrated with an inverted upstream–downstream sequence orientation. The molecular docking results revealed that KPC-144 has the strongest affinity for ceftazidime (− 8.2 kcal/mol) because of the interaction of Ile173-Pro174-Gly175-Asp176 in the Ω-loop, whereas KPC-2 has stronger affinity for carbapenems (ertapenem and imipenem) and cefotaxime. Conclusion Compared with blaKPC−2-positive K. pneumoniae isolates, the blaKPC−144-positive K. pneumoniae isolates and transformants were resistant to ceftazidime/avibactam and had increased carbapenem susceptibility; the molecular docking results confirmed these characteristics. This study demonstrates that blaKPC−144 likely spreads through chromosomal vertical transmission, resulting in a resistance profile distinct from that of blaKPC−2, necessitating the development of subtype-specific treatment strategies.

Investigating the prevalence of KPC-2 and the variant KPC-144 in carbapenem-resistant Klebsiella pneumoniae and elucidating its molecular epidemiological and genetic characteristics

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2026年5月20日

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Kaichun Lin,
Lili Zhu,
Pan Lü,
Jian Zhou

摘要

Background

Klebsiella pneumoniae is responsible for nosocomial infections, and the prevalence of bla_KPC and its variants, including bla_KPC−2 and bla_KPC−144, contributes to antibacterial resistance. As a newly identified variant, bla_KPC−144 is still inadequately defined regarding its mechanisms of resistance and its epidemiological traits. Therefore, we investigated β-lactam resistance in bla_KPC−2- and bla_KPC−144-harbouring K. pneumoniae isolates and elucidated their molecular epidemiological and genetic characteristics while assessing their prevalence, particularly that of bla_KPC−144, in β-lactam-resistant K. pneumoniae.

Methods

We isolated three bla_KPC−144- and nine bla_KPC−2-harbouring strains from among 40 carbapenem-resistant K. pneumoniae isolates. The agar dilution method was used to determine the minimum inhibitory concentration of the bla_KPC−144- and bla_KPC−2-harbouring strains and transformants. Additionally, PCR and whole-genome sequencing of the genetic background of those genes were performed. Multilocus sequence typing and pulsed-field gel electrophoresis were used to investigate the clonal correlation of the bla_KPC−144- and bla_KPC−2-positive strains. Molecular docking was performed to analyse the affinity of the compounds for various antibiotics.

Results

Compared with bla_KPC−2-positive strains, the bla_KPC−144-positive strains exhibited significantly increased susceptibility to ertapenem and imipenem (MIC values decreased > 8-fold to the range of 2–4 µg/ml) but concurrently exhibited heightened resistance to ceftazidime and ceftazidime/avibactam (MIC values increased > 2-fold to the range of 32–64 µg/ml). Cloning bla_KPC−2 and bla_KPC−144 into Escherichia coli DH5α recapitulated the respective resistance profiles, directly attributing the divergent phenotypes to the gene variants themselves. Three different sequence types (ST11, ST15, and ST656) and eight pulsed-field gel electrophoresis subtypes (A to H) were classified. Conjugation experiments revealed that bla_KPC−2 could be horizontally transmitted via plasmids, whereas bla_KPC−144 displayed no discernible conjugative transfer. Whole-genome sequencing and comparative genomic analysis revealed that bla_KPC−2 was located on IncFII-type plasmids flanked by conserved insertion sequences (IS26-ISKpn27-tnpR), whereas bla_KPC−144 was chromosomally integrated with an inverted upstream–downstream sequence orientation. The molecular docking results revealed that KPC-144 has the strongest affinity for ceftazidime (− 8.2 kcal/mol) because of the interaction of Ile173-Pro174-Gly175-Asp176 in the Ω-loop, whereas KPC-2 has stronger affinity for carbapenems (ertapenem and imipenem) and cefotaxime.

Conclusion

Compared with bla_KPC−2-positive K. pneumoniae isolates, the bla_KPC−144-positive K. pneumoniae isolates and transformants were resistant to ceftazidime/avibactam and had increased carbapenem susceptibility; the molecular docking results confirmed these characteristics. This study demonstrates that bla_KPC−144 likely spreads through chromosomal vertical transmission, resulting in a resistance profile distinct from that of bla_KPC−2, necessitating the development of subtype-specific treatment strategies.