Frequency of five Escherichia Coli pathotypes in Iranian adults and children with acute diarrhea

Abstract

Backgroundknowledge about the distribution of Escherichia Coli (E. coli) pathotypes in Iran is limited to studies with small scale and limited scope. This nation-wide survey aims to provide a more generalizable estimate of pathogenic E. coli distribution in Iran.\n\nMethodsDuring January 2013 and January 2014, stool samples were collected from 1306 acute diarrhea cases of 15 provinces. Culture-positive E. coli samples were tested with PCR for detection of five E. coli pathotypes (STEC, ETEC, EPEC, EAEC, and EIEC). Frequency of these pathotypes was estimated for different provinces, age groups, and months/seasons.\n\nResultsOf 1305 diarrheal samples, 979 were E. coli-positive (prevalence: 75.0%; 95% CI: 72.6, 77.3%). Pathogenic E. coli was detected in 659 diarrheal samples (prevalence: 50.5%; 95% CI: 47.8, 53.2%). STEC and EIEC was the most and the least frequent pathotypes (35.4% and 0.3%, respectively). ETEC (14.0%) and EPEC (13.1%) were the second and the third frequent pathotypes, respectively. EAEC was not highly prevalent (4.3%). Fars and Razavi Khorasan provinces had the highest and lowest frequencies (88.7% and 34.8%, respectively). E. coli pathotypes were more frequent in warmer (i.e., spring and summer) than cooler (i.e., fall and winter) seasons. The highest frequency of pathogenic E. coli was observed in infants and children under 5 years (73% each). There was no association between sex and pathogenic E. coli infection.\n\nConclusionsDiarrheagenic E. coli may be an important cause of acute diarrhea in adults and children in Iran. STEC and ETEC seem to be widespread and show a peak in warmer seasons. This finding could impact the recommended use of STEC and ETEC vaccines during warmer seasons, especially for infants, young children and elderlies. Monitoring the rate of diarrheagenic E. coli infection, E. coli serotypes, and their antibiotic resistance is recommended for evaluations of time-trends and effectiveness of interventions.\n\nAuthor summaryEscherichia coli, also known as E. coli is a bacterium of the genus Escherichia that is normally found in the lower intestine of human. Most E. coli strains are harmless, but some can cause infection in the gastrointestinal tract, causing diarrhea. These pathogenic E. coli strains are classified based on their mechanism of pathogenesis. In this regard, five important E. coli strains include Shiga toxin-producing E. coli (STEC), enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), enteroaggregative E. coli (EAEC), and enteroinvasive E. coli (EIEC). In a national survey conducted in Jan 2013 till Jan 2014, we collected 1305 diarrheal samples from 15 (out of 31) provinces of Iran. Of these, 979 samples (75%) were E. coli-positive in the culture test. Molecular tests showed that 659 samples were pathogenic E. coli, suggesting that 50.5% of the diarrhea cases were induced due to pathogenic E. coli infection. The most prevalent pathogenic E. coli strains in Iran were STEC (35.4%) and ETEC (0.3%), and were more commonly detected in warmer seasons, infants, and children less than five years. So, the use of vaccines, especially for STEC and ETEC, during warmer seasons and for infants, young children and elderlies are recommended.