Antibiogram, Virulence Genes, and Biofilm-Forming Ability of Clinical Serovars: An Study.

serovar Typhi and Paratyphi are causative agents of enteric fever. Typhi persists as a biofilm on gallstones. Hence, we studied the biofilm formation, antibiogram, and virulence genes of serovars. Antibiogram of serovars from human blood and stool samples were studied by Kirby-Bauer disk diffusion method and biofilm by microtiter plate method. We studied the minimum inhibitory concentration of the isolates by Vitek-2 semiautomated system. Polymerase chain reaction was done to detect and genes. Of the 55 isolates studied, 36 (65.45%) were Typhi, 13 (23.63%) were Paratyphi A, 2 (3.64%) were Typhimurium, and 4 (7.28%) were spp. Resistance to ciprofloxacin and nalidixic acid were found to be 81.8% and 92.7%, respectively. Chloramphenicol and cotrimoxazole-susceptible strains were 98.18%. One each of Typhi, Paratyphi A, and . isolates formed weak biofilm at 28°C. However, at 37°C eight Typhi produced weak biofilm in the presence of bile. One Paratyphi A and two spp. formed weak biofilm in the absence of bile. All the isolates had the gene. Typhimurium had and genes. Bile may contribute to biofilm formation and persistence of the Typhi on gallstones, which may lead to carrier state. Changing antibiotic susceptibility pattern of serovars is observed in our geographic area. The presence of A and genes indicate the ability of invasiveness and intracellular survival.