Epidemiological characteristics and virulence genes of diarrheagenic Escherichia coli from diarrheal patients in Chaoyang district of Beijing

ObjectiveTo understand the epidemiological characteristics and the distribution of virulence genes of diarrheagenic E. coli (DEC) isolated from diarrheal patients in Chaoyang district of Beijing.

MethodsStool specimens collected from diarrheal patients in sentinel hospitals in Chaoyang were cultured during 2014–2017. The virulence genes were tested by real-time PCR, diarrheagenic E. coli were identified by detecting seven genes, including eae, stx1, stx2, lt, st, aggR and ipaH, the distribution of other important genes, including bfpA, astA, escV, pic, perA, ehxA, pet and ipaBCD were also detected.

ResultsA total of 94 DEC strains were isolated from 1 977 stool specimens (4.75%), the proportion of DEC isolation was increased along with age group increasing. The proportion of enteroaggregative E. coli (EAEC) and enteropathogenic E. coli (EPEC) in the isolates from age group 0–5 years was 59.62% and 23.08%. The proportion of enterotoxigenic E. coli (ETEC) in the isolates from age group ＞5 years was 59.52%. Up to 81.25% EPEC (13/16) strains carried no bfpA, belonging to atypical EPEC (aEPEC). Among 38 EAEC strains, 39.47% carried astA, 68.42% carried pic, 92.11% carried pet. Among 30 ETEC strains, 46.67% carried st, 56.67% carried lt, 53.33% carried astA, and 3.33% carried both st and lt. All 4 enterohemorrhagic E. coli (EHEC) strains carried eae, escV and ehxA. Among 6 enteroinvasive E. coli (EIEC) strains, 16.67% carried ipaBCD, 33.33% carried astA.

ConclusionThe DEC isolates from diarrheal patients in Chaoyang were dominated by EAEC, ETEC and EPEC, aEPEC accounted for the majority of EPEC. Infants and young children were mainly infected with EAEC, and adults were mainly infected with ETEC. The virulence genes of diarrheagenic E. coli showed diversity, and astA existed in multi-types of diarrheagenic E. coli.