Determination the Effect of ST Enterotoxin Isolated from Enterotoxigenic Escherichia coli Strains on Colon Cancer from Diarrhea Patients in Basra Hospitals
A total of (375) stool samples and rectal swabs were collected from patients in all age group suffering from watery diarrhea the collection from patients admitted to seven main hospitals in Basra city From (375) patients, 167 females and 208 males were involved in this study Specimens were cultured on Mac Conkey agar plates and incubated at 37degC overnight. From each plate lactose fermenter colonies with typical appearance of E. coli were selected and inoculated on Eosin methylene blue (EMB) agar medium for preliminary characterization the colonies showing characteristic metallic sheen on EMB agar were picked up and considered as presumptive E. coli. All presumptive E. coli identified by conventional biochemical tests for E.coli bacterial identification, API 20E system The results showed that (115) was diarrhoea samples were positive for E.coli, 13 out of 115 were positive for Enterotoxigenic E.coli (ETEC) PCR results revealed that out of 13 positive ETEC isolates, only two isolates showed positive results for heat labile (Lt) 6 positive for heat stable (St) and 5 were positive for both genes Sequencing some DNA fragments of the expected length obtained after PCR were purified. The toxicity of ST toxin was examined through experimental animals (Balb/c) mice. Four mice from six injected intraperitoneally (I.P. with 0.25 ml crude ST enterotoxin were died after 24 hours of injection; six mice that have been administered ST crude enterotoxin orally were survived. The abdomen was opened and the entire intestine all groups were removed for the interpretation of toxin effect and immediately fixed in 10% formalin in overnight at 4degC The results showed macroscopically changes between normal (control) and injected mice with ST toxin degenerated features with stomach and intestine compared to normal mouse. Cell line viability assay using HCT 116 human colorectal cancer cells were used to investigate the effect of toxin ST on the viability of the colon cancer cells. Our results indicated that bacterial enterotoxins could inhibit DNA synthesis in human colon cancer cells and stopped poliferation of the cells. The viability decreased from 94% to 38% when the HCT116 cells in one well were treated by toxin ST directly (1 ml ST in concentrate 0.04 mg/100 ml)