To improve prescribing of empiric therapy, the local molecular epidemiology of extended-spectrum beta-lactamases (ESBLs) and Klebsiella pneumoniae carbapenemases (KPCs) in bloodstream isolates of K. pneumoniae were evaluated. Isolates resistant to third generation cephalosporins were screened phenotypically for ESBLs and carbapenemases, and subsequently confirmed by PCR for the presence of ESBL (blaTEM, blaSHV and blaCTX-M) and carbapenemase (blaKPC, blaVIM, blaNDM and blaOXA-48) genes. Hydrolytic activity (functional gene expression) was quantified using a nitrocefin degradation assay and correlated to ceftazidime or meropenem MIC. Clonality was assessed by repetitive element-based PCR. Beta-lactamases were functionally expressed in 13 isolates (15.5%); 7 (53.8%) harboured blaCTX-M-15 and 6 (46.2%) carried the blaKPC-2 gene. Correlation of hydrolytic activity to MIC yielded a coefficient of 98% for isolates expressing ESBLs alone and 56% for carbapenemase producers. Four unique ESBL-expressing clones and five carbapenem-resistant clones were identified. All 13 resistant isolates were susceptible to ceftazidime/avibactam (MIC ≤ 8/4 mg/L).
Keywords: Bacteremia; Gram-negative bacteria; Multidrug resistance; Resistance mechanism.