History

Object: Salmonella Typhi is a gram-negative bacterium that is responsible for typhoid fever, it is usually contracted by ingestion of food or water that is contaminated with the excrements of people that carry the organism and must survive the gastric pH barrier in the stomach prior to adherence in the small intestine. Methods: 48 clinical isolates of Salmonella Typhi were collected from different government hospital laboratories / Baghdad for the period from 7-8-2020 to 11-22 2020.They characteries by phenotypic methods then used VITEK2 compact system to confirm that all isolates were S. Typhi. Congo red and microtiter plate mehods used to detect biofilm formation. In order to study some genes specific primers were used, PCR was performed to find the virulence genes (invA, tviA, pilS and orfL) .Results: from 48 S. Typhi isolates. Congo red method 45(93.75%) isolates were non forming biofilm and 3(6.25%) forming biofilm while microtiter plate revealed four types of biofilm divided in non biofilm formation isolates 3(4.2%) ,weak biofilm 1(2.08%) , moderate biofilm 3(6.25%) and strong biofilm 42(87.52%) .Then PCR technique produced 284 bp for the invA gene ,599 bp for the tviA gene,502pb for the pilS gene and 550 pb for orfL gene were present in the isolates at a rate of (100% , 16.66%, 4.16% and 4.16 ) respectively. Strong biofilm has all genes (invA, tviA, pilS and orfL) genes in different percentages (87.52%,54.16%,22.91%, and 2.08%) respectively, while moderate biofilm has less numbers and percentage than strong biofilm (6.25%,4.16%,4.2%and 2.08) respectively. Weak and non biofilm have only invA and tviA genes with less nombers and percentages