Extended-Spectrum β-Lactamase-Producing Klebsiella pneumoniae in Southwest China: Molecular Characteristics and Risk...

The objective of this study was to investigate the molecular characteristics and risk factors of bloodstream infection (BSI) caused by extended-spectrum beta-lactamase producing Klebsiella pneumoniae (ESBL-Kpn).

Bacterial species were identified using the matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) (Bruker Daltonik GmbH, Bremen, Germany), while antimicrobial susceptibilities were assessed using the MicroScan WalkAway 96 Plus system (Siemens, Germany) and the microbroth dilution method. Polymerase chain reaction (PCR) was employed to detect common extended-spectrum beta-lactamase resistance genes (bla _SHV, bla _TEM, bla _CTX-M). Multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), capsular serotyping, and serum resistance tests were utilized to analyze the molecular characteristics among the isolated strains. Additionally, a logistic regression analysis was conducted to identify the risk factors associated with BSI caused by ESBL-Kpn.

A total of 371 Klebsiella pneumoniae (K. pneumoniae) strains were isolated from blood samples collected at the Affiliated Hospital of Southwest Medical University between January 2020 and June 2023, among which 45 were confirmed to produce ESBL. Twenty-eight STs were identified, with ST15 being predominant. Most strains exhibited resistance to multiple antibiotics, with bla _CTX-M-15 as the predominant ESBL resistance genes. Nine strains (n=9, 20%) of bacteria exhibited high serum resistance, and 27 strains matched capsular serotypes predominantly K17. Multivariate analysis indicated that transferred patients, prior use of cephalosporin antibiotics, and prolonged hospital stay were independent risk factors for ESBL-Kpn BSI.

BSI caused by ESBL-Kpn exhibit high resistance rates. The newly identified ST6835 and ST6837 indicate the emergence and spread of novel clones in Southwest China, highlighting the imperative for enhanced surveillance of ESBL-producing strains.