Comparative Analysis of Multidrug Resistance and Virulence in Interconnected Clinical and Environmental Salmonella...

Antimicrobial resistance and inadequate sanitation, particularly in developing nations such as Pakistan, exacerbate the impact of Salmonella, a leading cause of foodborne and clinical infections worldwide. Effective surveillance and source tracking are hindered by a lack of comprehensive analyses linking clinical and environmental strains, despite increasing reports of resistant variants. This study uses disk diffusion, conventional PCR, and ERIC-PCR to compare clinical and environmental Salmonella strains from Karachi, with an emphasis on antibiotic resistance, virulence factors, and genetic relatedness. Multidrug resistance is highly prevalent, with 63% of clinical strains (41/65) (MARi: 0.3-0.8) and 34.5% of environmental strains (22/55) (MARi: 0.4-0.7) exhibiting resistance to multiple antibiotics. All strains were capable of forming biofilms, and the correlation between MARi and biofilm formation in both sources was weak and non-significant (p > 0.05). All strains from both sources harbored core virulence genes; however, three genes, fimA, spvR, and acrA, were significantly more prevalent in clinical than in environmental strains (p < 0.001 and p = 0.023). ERIC-PCR showed low to moderate DI (0.45 to 0.75) across different clinical Salmonella serovars and moderate DI across different environmental serovars, indicating heterogeneous and homogeneous genetic relatedness. These results suggest a crucial and underexplored connection between environmental and clinical Salmonella reservoirs, implying potential environmental contamination from clinical sources. The coexistence of multidrug resistance and virulence highlights the critical need for integrated surveillance strategies to minimize the risk of widespread outbreaks.