Molecular Characterization of Colistin- and Carbapenem-Resistant Klebsiella pneumoniae: mgrB Mutations and Clonal Diversity in Pediatric Intensive Care Isolates.

Colistin- and carbapenem-resistant Klebsiella pneumoniae (ColR CrKp) cause important health problems in pediatric intensive care units (PICUs) due to its ability to harbor multiple resistance genes and spread of high-risk clones. In this study, molecular epidemiological characteristics, transferable resistance genes, and mgrB alterations of ColR CrKp isolated from PICU were investigated. Isolates were identified by MALDI-TOF MS, and antimicrobial susceptibility tests were performed using disk diffusion method, gradient strip test, and broth microdilution method. Extended spectrum beta-lactamase, AmpC beta-lactamase, carbapenemase, 16S rRNA methyltransferase, plasmid-mediated quinolone resistance, and mcr-1 to -5 genes were investigated by polymerase chain reaction. Sanger sequencing was performed to obtain bla_OXA-48-like and mgrB sequences. Pulsed-field gel electrophoresis and multilocus sequence typing were used to determine the clonal spread of the isolates. Ten ColR CrKp harboring bla_OXA-48 (70%), bla_OXA-232 (20%), bla_CTX-M (90%), armA (20%), qnrB (20%), and qnrS (50%) were identified. No mcr genes were found, whereas mgrB mutations through modifications (A7T, C88T, and A121G) and insertion of an IS-1-like insertion sequence were determined. Isolates belonged to ST 14, ST 37, ST 101, ST 147, ST 661, ST 985, and ST 2096. It is crucial to determine the antimicrobial resistance properties and the clonal spread of the isolates to guide the treatment decisions, implement effective infection control measures, and develop novel antimicrobial strategies.