Molecular Characterization of Enterotoxigenic Escherichia coli : Effect on Intestinal Nitric Oxide in Diarrheal Disease

Abstract

This study was aimed to investigate the effect of enterotoxigenic E. coli (ETEC)-induced diarrhea on fecal nitric oxide (NO) and intestinal inducible nitric oxide synthase (iNOS) expression in rats. E. coli isolates were gotten from infants diarrheal samples. Multiplex polymerase chain reaction (PCR) was used to detect the presence of eltA gene for heat-stable (ST) enterotoxigenic E. coli and eltB for heat-labile (LT) enterotoxigenic E. coli. Disk diffusion method was used to determine the antibiotic susceptibility of the organisms. Biofilm formation was detected by thiazoylblue tetrazolium bromide dye in a 96-well plate. Fecal NO was measured using standard griess reaction system. Reverse transcription PCR was used to investigate the expression of iNOS expression. Although none of the ETECs isolated in this study belonged to the classic serotype, serogroup O6 and O8 were found to be associated with ETECs. Among the three ETECs, two were found to be multidrug resistant. The biofilm production abilities of all the ETECs were found to exist between weak and moderate biofilm producers. Fecal NO was found to be elevated in both LT and ST-induced diarrheal groups but there was no corresponding intestinal iNOS expression. This suggests that the elevated NO could be as a result of up-regulation of constitutive NOS rather than iNOS.