Multidrug Resistance and Virulence Traits of Isolated from Cattle: Genotypic and Phenotypic Insights.

Non-typhoidal is a leading cause of foodborne illness worldwide and presents a significant One Health concern due to zoonotic transmission. Although antibiotic therapy remains a standard approach for treating salmonellosis in severe cases in animals, the widespread misuse of antibiotics has contributed to the emergence of multidrug-resistant (MDR) strains. This study provides insights into the genotypic and phenotypic characteristics among isolates from necropsied cattle. A total of 1008 samples were collected from necropsied cattle. subspecies were identified by MALDI-TOF MS and subsequently confirmed by serotyping. The biofilm-forming ability of the isolated bacteria was assessed using a crystal violet assay. The motility of the isolates was assessed on soft agar plates. Additionally, the antimicrobial resistance genes (ARGs) and virulence genes were investigated. Antimicrobial resistance patterns were investigated against 19 antibiotics representing 9 different classes. species were isolated and identified in 27 necropsied cattle. Dublin was the most prevalent serotype (29.6%). Additionally, all the isolates were biofilm producers at different levels of intensity, and 96.3% of the isolates exhibited both swarming and swimming motility. Furthermore, virulence genes, including , , , and , were detected in all the isolates. The highest resistance was observed to macrolides (azithromycin and clindamycin) (100%), followed by imipenem (92.6%), and chloramphenicol (85.2%). All isolates were multidrug-resistant, with a multiple antibiotic resistance (MAR) index ranging between 0.32 and 0.74. The aminoglycoside resistance gene was detected in all the isolates (100%), whereas the distribution of other antimicrobial resistance genes (ARGs) varied among the isolates. The increasing prevalence of MDR poses a significant public health risk. These resistant strains can reduce the effectiveness of standard treatments and elevate outbreak risks. Strengthening surveillance and regulating antibiotic use in livestock are essential to mitigating these threats.