In recent years, nosocomial infections due to multidrug resistant Klebsiella pneumoniae strains have been increasing, associated with growing trend of resistance to beta-lactams and fluoroquinolones (FQs) worldwide. In this study, prevalence of beta-lactamase genes and resistance mechanisms to FQ were analyzed in 191 clinical K. pneumoniae isolates derived from respiratory tract infections in a teaching hospital in Yangon, Myanmar. The major extended-spectrum beta-lactamase gene was blaCTX-M, which was detected in 33% of isolates, with CTX-M-15 being dominant. Fourteen isolates (7.3%) harbored carbapenemase genes that were genotyped as blaNDM-1, blaNDM-5, or blaNDM-7. The most common plasmid-mediated quinolone resistance (PMQR) gene was aac6'-Ib-cr (51.8%), followed by qnrB (41.9%), oqxAB (23%), and qnrS (15.2%). In quinolone-resistance determining region of GyrA, eight different types of mutation were identified for FQ-resistant isolates, with double mutations at two positions (S83F, D87A) being most common (54.6%). Isolates with double mutations (three patterns) showed higher minimal inhibitory concentration to levofloxacin (LVX) (≥64 μg/mL) than those with a single mutation. PMQR gene profiles, including aac6'-Ib-cr and any other gene(s), were generally related to higher resistance level to LVX. K. pneumoniae isolates with different profiles of beta-lactamase genes and FQ-resistance determinants were mostly classified into ST15 or its single-locus variant (SLV). The most common NDM gene, blaNDM-5, was detected in ST975 (ST15-SLV) isolates and an ST4000 isolate. The present study revealed the wide spread of FQ-resistant K. pneumoniae clinical isolates acquiring various FQ-resistance determinants and beta-lactamases that were presumably derived from a single clonal lineage in a hospital in Myanmar.
Keywords: Klebsiella pneumoniae; Myanmar; carbapenemase; extended-spectrum beta-lactamase (ESBL); plasmid-mediated quinolone resistance (PMQR); quinolone resistance determining region (QRDR).