Epidemiological profile and molecular characterization of Salmonella Typhi strains isolated in Pará State, Brazil

Abstract

Salmonella enterica serotype Typhi, the etiological agent of typhoid fever, a systemic disease that causes prolonged fevers with intestinal disorders and may progress to bowel perforation. In Pará State, Brazil, the endemicity reflects a great number of outbreaks and sporadic cases in different municipalities. The aim of this present study was to carry out an epidemiologic and molecular characterization of Salmonella Typhi strains isolated in Pará State. Four virulence genes (viaB, prt, fliC-d and invA) were analyzed in 75 cases with typhoid fever isolation from blood cultures and stool cultures in the period 2009 to 2011. In order to investigate the cross-reactivity, six other species of enterobacteria (Escherichia coli, Salmonella Paratyphi, Salmonella Typhimurium, Salmonella Panama, Proteus mirabilis, and Shigella flexneri) were included. Samples were analyzed and 64% of them are from male subjects and 36% from female ones, with a significant difference between sexes (p = 0.0209). The analysis of annual distribution of typhoid cases highlights the biggest event in 2010, with 31 cases. Most of the cases was detected in blood culture (72%) compared to fecal culture (28%) (p = 0.0002). Conventional PCR with four pairs of primers identified S. Typhi correctly, producing four positive bands observed in 100% of samples. In the genetic analysis, the S. Typhi strains were highly similar to the genes analyzed which remained stable throughout the analysis since their isolation. Thus, the four pairs were specific primers capable of being used in the identification and characterization of S. Typhi.