Shiga toxin-producing Escherichia coli O157:H7 detected by multiplex PCR in culture and human feces

SALINAS AG,; LUCERO C; ESCUDERO M; LAZARTE V; VELÁZQUEZ L; GUZMÁN A; RIGO H ; CORREA S.

San Luis

Congreso; XXII Reunión Científica Anual de la Sociedad de Biología de Cuyo; 2009

Universidad Nacional de San Luis y la Universidad de La Punta.

Shiga toxin-producing Escherichia coli (STEC) causes symptomsfrom acute diarrhea to hemolytic uremic syndrome. The aim of thepresent study was to establish the detection limit (DL) of stx1 andstx2 genes of STEC by multiplex PCR (mPCR), from culture (C)and artificially contaminated human faces (HF). Two STEC strainswere used: one local (1) and one reference (2) strains. To establishthe DL in C, both strains were cultured in trypticase soy broth for18 h at 37ºC. Then, serial dilutions were performed from 107 to 100CFU/ml, and 1 ml of each dilution was tested by mPCR. To establishthe DL in HF, 1 g of a pediatric sample was inoculated with 1ml of each strain using inocula of 109 and 107 CFU/ml, and culturedin 9 ml of EC broth at 37°C. Samples were taken for mPCRat different times: 0, 3, 6, 18 and 24 h. In C, the DL was 9 x 102CFU/ml for strain (1) and 4,7 x 103 CFU/ml for strain (2). In HF,the stx2 gene was amplified at any tested time for both inocula.The stx2 gene was also detected by mPCR from the feces of a 3-year-old patient with diarrhea, after 2 h of EC enrichment. ThemPCR on HF might reduce the diagnostic time of STEC in 48 h.