Molecular epidemiology and antimicrobial resistance of diarrheagic Escherichia coli among children with acute diarrhea

Abstract

Objective To learn the distribution, epidemiology and antimicrobial susceptibility of diarrheagenic Escherichia coli (DEC) isolated from patients with acute diarrhea among children less than 5 years old. Methods Totally 684 stool samples collected from Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology between August 1, 2015 and September 30, 2016 were tested by culture and identified the common pathogens. PCR was applied to detect the virulence genes of DEC. Meanwhile, serotyping of enteropathogenic E. coli (EPEC) was performed by slide agglutination tests for all the isolates of EPEC. An antimicrobial sensitivity test was performed using the agar dilution method. Results A total of 149 (21.7%) enteric bacteria pathogens were isolated from 684 specimens. DEC was found in 54 cases, ranked 2nd among the pathogenic bacteria. DEC tended to occur in summer/autumn periods. EPEC was the most frequent DEC genotype, accounted for 50% (27/54). Among EPEC, atypical EPEC was dominant, accounted for 77.8% (21/27) and typical EPEC only accounted for 22.2% (6/27). Followed by enteroaggregative E.coli 20.4% (11/54), enterotoxigenic E.coli 14.8% (8/54), enteroinvasive E. coli and Shiga toxin-producing E.coli 3.7% (2/54), 7.4% (4/54) cases were co-infected with more than one DEC genotypes. About 17/18 of suspicious DEC isolates can get the same genotypes by commercial multiplex PCR kit and single PCR test. Among the 27 EPEC strains, only 11(40.7%) strains can be detected by the slide agglutination serotyping method. More than 50% (27/54) of DEC isolates were resistant to conventional first-line antibiotics (ampicillin, trimethoprim-sulfamethoxazole) and cefazolin, cefuroxime, cefotaxime, but relatively low resistance to cefoxitin, amikacin, piperacillin/tazobactam, imipenem and meropenem. However, there was still a 9.2% (5/54) resistance rate to carbapenems. Conclusions DEC strains exhibited a high frequency of resistance to many antibiotics. Empirical antimicrobial therapy of severe DEC infection faces the challenge from the high resistance to ampicillin, trimethoprim-sulfamethoxazole. Even worse, some strains were resistant to relatively efficient drugs imipenem and meropenem. It is necessary to strengthen the epidemiological survey and antimicrobial resistance of DEC. Key words: Diarrhea; Escherichia coli; Virulence; Escherichia coli infections; Drug resistance, bacterial; Epidemiologic studies