Frequency of enterohaemorrhagic Escherichia coli isolated from patients with acute diarrhea in Tabriz hospitals

Diarrhea is a major cause of morbidity in all age groups worldwide. Bacteria can cause 24% of infectious diarrhea which accounts for 70% mortality in affected children of <5 years old.Among the bacterial agents Salmonella spp, entero pathogenic E. coli, Campylobacter spp, Shigella spp and clostridia are the main causes of diarrhea. Escherichia coli O175 is an emerging cause of foodborne illness that presents with acute diarrhea. It transmits through the contaminated water, direct or indirect contact with animals and also through person to person contact.In addition to diarrhea, 2-7% of the patients infected with enterohemorrhagic E. coli (EHEC) will possibly develop haemolytic uremic syndrome (HUS) or acute renal failure. This study was conducted to determine the frequency of enteric pathogens with special reference to enterohaemorrhagic E. coli O157. A total of 1020 fecal specimens were collected from patients with acute diarrhea in Imam Khomeini and Children hospital of Tabriz. Direct examination was carried out for leukocytes, erythrocytes, parasite ova and trophozoites by wet mount preparation and the specimens also were cultured in selective and differential culture media for pathogenic bacteria. E. coli isolates were further typed usingspecific antisera and EHEC isolates were subjected to susceptibility testing against routinely used antibiotics. Entamoeba histolytica and Giardia lamblia were detected in 91(8.9%) and 51(5%) of cases.Pathogenic enteric bacteria were also isolated and recorded as E. coli O157 (n=6, 0.58%), E. coli O111 (n=15, 1.47%), E. coli O26 (n=13, 1.27%), Campylobacter jejuni (n=35, 3.4%), Salmonella spp. (n=177 17.3%) and Shigella spp (9.5%). All EHEC isolates were recovered from children <5 years old. In serological tests, 139 (13.5%) isolates of E. coli showed autoagglutination, which suggest their probable dependence to EAEC (entero aggregative E. coli). Based on information collected from the EHEC positivepatient's files, no sign of anemia or kidney disorder was detected. Entero pathogenic E. coli isolates are not usually tested in most of the routine diagnostic laboratories, so these medically important bacteria remain undiscovered, unless in an epidemic situation. Our findings of 3.3 % enterohaemorrhagic E.coli and the presense of 0.58 % E. coli O157 shows less frequency for these athogenic bacteria and are in accordance with reports from other countries.