High Frequency of ۱۶S Ribosomal RNA Methyltransferases among Klebsiella pneumoniae Isolates: First Report of rmtA, rmtD, rmtE and rmtF Resistance Genes in Iran

Aims: ۱۶S ribosomal RNA methyltransferases (RMTases) confer high-level resistance to aminoglycosides and are increasingly reported among Gram-negative bacilli, especially Klebsiella pneumoniae isolates. The objectives of the present study were to assess the resistance to aminoglycosides, the presence of RMTase genes, and the multilocus sequence typing (MLST) in urinary K. pneumoniae isolates. Materials & Methods: In this study, ۱۰۰ K. pneumoniae isolates were tested for susceptibility to amikacin and gentamicin by broth microdilution test according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Then the prevalence of RMTase genes was determined, and alleles and ST type of two selected isolates were identified by MLST. Finally, the isolates were genetically typed using Enterobacterial Repetitive Intergenic Consensus (ERIC) method. Findings: Broth microdilution assay showed that resistance to amikacin and gentamicin was ۷۰ and ۵۲%, respectively. In addition, ۴۰% of the strains were resistant to both aminoglycosides. Also, rmtC (۵۹.۸%) gene was the most common type of RMTase genes investigated, followed by rmtA (۵۱.۲%), rmtD (۴۷.۶%), rmtF (۴۳.۹%), rmtE (۴۱.۵%), armA (۴۱.۵%), and rmtB (۷.۳%). K. pneumoniae isolates were assigned into two sequence types: ST۵۱ and ST۱۴۹. Using ERIC-PCR method, ۳-۷ different bands and ۲۱ ERIC-PCR profiles were detected among the studied isolates. Conclusion: The high frequency of aminoglycoside resistance and the increased presence of ۱۶S RMTases in K. pneumoniae strains are of great concern in Iran. Molecular typing showed high genetic diversity among the studied isolates. However, ST۵۱ and ST۱۴۹ were reported for the first time in Iran and could be considered as emerging strains.  

Keywords:

Klebsiella pneumoniae , Aminoglycoside , Multilocus sequence typing , Antibacterial agent.