Prevalence and molecular characterisation of 16S rRNA methyltransferase genes mediating aminoglycoside resistance in Gram-negative bacteria from cancer patients: A tertiary care study in India

Introduction: Infections significantly contribute to morbidity and mortality in cancer patients, with Gram-negative bacteria (GNB) posing a major threat due to multidrug resistance (MDR). High-level aminoglycoside resistance, driven by 16S rRNA methyltransferases (16S RMTases) limits treatment options. This study aimed to determine the prevalence of 16S RMTase genes in clinical GNB isolates from a tertiary cancer care centre in North Kerala.
Methods: A prospective cross-sectional study analysed 592 non-duplicate GNB isolates collected from June 2021 to May 2022. Bacterial identification was performed using standard techniques and MALDI-TOF MS. Antimicrobial susceptibility testing was done using the VITEK 2 system. Aminoglycoside-resistant isolates were subjected to PCR for detecting 16S RMTase genes (armA, rmtA, rmtB, rmtC, rmtD, rmtE, rmtF).
Results: Urinary tract infections (33%) and bloodstream infections (26%) were predominant. Escherichia coli (38.3%) and Klebsiella pneumoniae (27%) were the most common species. Among 267 aminoglycoside-resistant isolates, 134 (50%) carried 16S RMTase genes, primarily rmtB (n = 57), armA (n = 42), and rmtF (n = 13), with co-occurrence in 22 isolates. No rmtA, rmtC, rmtD, or rmtE genes were detected.
Conclusion: The prevalence of 16S RMTase genes, especially rmtB and armA, underscores the challenge of MDR GNB in cancer patients. Rapid detection and effective therapeutic strategies, along with coordinated surveillance, are essential to mitigate the impact of MDR infections in healthcare settings.