Molecular Epidemiology of Extensively Drug-Resistant mcr Encoded Colistin-Resistant Bacterial Strains Co-Expressing Multifarious β-Lactamases

Abstract: Plasmid-mediated colistin resistance (Col-R) conferred by mcr genes endangers the lasttherapeutic option for multifarious β-lactamase-producing bacteria. The current study aimed toexplore the mcr gene molecular epidemiology in extensively drug-resistant (XDR) bacteria. Col-Rgram-negative bacterial strains were screened using a minimum inhibitory concentration (MIC)breakpoint ≥4 μg/mL. Resistant isolates were examined for mcr variants, extended-spectrum β-lactamase, AmpC, and carbapenemase genes using polymerase chain reaction (PCR). The MICbreakpoints for mcr-positive strains were determined using broth microdilution and E-test strips.Overall, 19/718 (2.6%) gram-negative rods (GNRs) harboring mcr were identified, particularly inpus (p = 0.01) and tracheal secretions (p = 0.03). Molecular epidemiology data confirmed 18/19 (95%)mcr-1 and 1/19 (5%) mcr-2 genes. Integron detection revealed 15/17 (88%) Int-1 and 2/17 (12%)Int-2. Common co-expressing drug-resistant β-lactamase genes included 8/16 (50%) blaCTM-1, 3/16(19%) blaCTM-15, 3/3 (100%) blaCMY-2, 2/8 (25%) blaNDM-1, and 2/8 (25%) blaNDM-5. The MIC50 andMIC90 values (μg/mL) were as follows: Escherichia coli, 12 and 24; Klebsiella pneumoniae, 12 and 32;Acinetobacter baumannii, 8 and 12; and Pseudomonas aeruginosa, 32 and 64, respectively. Treatmentof XDR strains has become challenging owing to the co-expression of mcr-1, mcr-2, multifariousβ-lactamase genes, and integrons.

(PDF) Molecular Epidemiology of Extensively Drug-Resistant mcr Encoded Colistin-Resistant Bacterial Strains Co-Expressing Multifarious β-Lactamases. Available from: https://www.researchgate.net/publication/351014294_Molecular_Epidemiolo… [accessed Jan 09 2025].