Molecular identification of <i>CdtB</i> and <i>TviA</i> virulence genes of <i>Salmonella typhi</i> isolated from cholelithiasis patients in Erbil City, Iraq

Gallstone disease (GSD), particularly cholecystitis accompanied by gallstones, is a prevalent global health concern with significant morbidity and mortality rates. Typhoid fever is a public health issue in low- and middle-income countries. The severity of the pathogenesis depends on Salmonella’s possession of several virulence factors encoded on Salmonella pathogenicity islands (SPIs). This study aimed to isolate and identify Salmonella typhi, the causative agent of typhoid fever, in clinical samples from cholelithiasis patients in Erbil City, Iraq. A cross-sectional study was conducted from October 2023 to March 2024, involving 125 patients diagnosed with gallbladder disease. Gallstone, bile, and gallbladder tissue samples were collected and analyzed for bacterial growth. Biochemical and cultural studies confirmed antibiotic susceptibility and Vitek2 system identification. The present study used a traditional PCR assay to detect Salmonella typhi pathogenicity genes. This study found the virulence genes CtdB and TviA using specific primers. Out of 125 samples, 101 (80.8%) showed bacterial growth, with 8 (6.4%) positive for S. typhi and 93 (74.4%) positive for other bacterial species. Gallstones had the highest proportion of S. typhi isolation 5 (4%). Antibiotic susceptibility testing revealed significant resistance to commonly used antibiotics like ampicillin, ciprofloxacin, chloramphenicol, and trimethoprim-sulfamethoxazole. However, the strains demonstrated better susceptibility to various antibiotics. The molecular result showed the virulence genes, including CtdB and TviA, were detected in all (100%) isolated strains. S. typhi's virulence characteristics significantly contributed to gallbladder infections and multidrug-resistant strains (MDR).