Exploring genetic determinants of antimicrobial resistance in strains of human and animal origin from India.

Introduction: Antimicrobial resistance (AMR) in , the causative agent of brucellosis, is of growing concern, particularly in low and middle-income countries. This study aimed to explore the genetic basis of AMR in strains from India.

Methods: Twenty-four isolates from humans and animals were subjected to antimicrobial susceptibility testing and whole-genome sequencing.

Results: Resistance to doxycycline (20.80%), ciprofloxacin (16.67%), cotrimoxazole (4.17%), and rifampicin (16.67%) was observed. Genome analysis revealed efflux-related genes like , , , , , and across all isolates, however, classical AMR genes were not detected. Mutations in key AMR-associated genes such as , , and were identified, intriguingly present in both resistant and susceptible isolates, suggesting a complex genotype-phenotype relationship in AMR among spp. Additionally, mutations in efflux genes were noted in resistant and some susceptible isolates, indicating their potential role in resistance mechanisms. However, mutations in AMR-associated genes did not consistently align with phenotypic resistance, suggesting a multifactorial basis for resistance.

Discussion: The study underscores the complexity of AMR in and advocates for a holistic multi-omics approach to fully understand resistance mechanisms. These findings offer valuable insights into genetic markers associated with AMR, guiding future research and treatment strategies.