Molecular and phenotypic characterization of enteroaggregative Escherichia coli clinical isolates and their antibiotic resistance pattern

Abstract number: P1624

Alikhani M.Y., Aslani M.M., Zavari A., Zamani A.R.

Objective(s): Enteroaggregative Escherichia coli (EAEC) is an emerging category of diarrheagenic E. coli. EAEC can induce growth impairment and malnutrition in children, even in children without diarrhea. The aim of the present study was to investigate the frequency of EAEC in children with diarrhea and their antibiotic resistance patterns.

Methods: Stool specimens from 140 children under 12 years of age with acute diarrhea were collected. The specimens were cultured for E. coli using standard methods, and then screened for EAEC using a PCR and HeLa cell adherence. PCR to detect gene of the EAEC-associated plasmid pCVD432 were performed. Adherence of EAEC was examined by a method described by Scaletsky et al. Antimicrobial susceptibility testing was performed using the Bauer-Kirby method according to protocols of CLSI. The reference strains, E. coli 17-2, E. coli K12 and E. coli ATCC 25922 were included as a quality control in all assays.

Results: 15 (10.8%) EAEC were detected in 700 E. coli colonies tested with pCVD432 PCR. Of the EAEC isolates 13 (86.7%) showed AA pattern. In overall, 73.3% of the EAEC isolates were resistant to at least one of 14 antimicrobials tested. The isolates were resistant to ampicillin (100%), erythromycin (100%), Cephalothin (78.6%), co-trimoxazole (71.4%), tetracycline (64.2) and Nalidixic acid (57.1%), cefexim (50%), amoxiclav (50%), ceftriaxone and cefotaxime (42.8%). Considerable numbers of isolates were also reduced susceptible to ciprofloxacin (42.8%) and norfloxacin (7.1%). Multidrug resistance to antibiotics was observed in 8 cases (53.3%) and the major resistance profile was ampicillin – erythromycin – Cephalothin.

Conclusions: EAEC is a diarrheal pathogen of emerging importance. The pCVD432 PCR showed good correlation with the HeLa cell adhesion assay, as 86.7% of pCVD432 positive isolates were confirmed as EAEC. However, compared to the assay for AA adherence the PCR has been found to be simple and specific in epidemiological studies. This study showed that EAEC isolates were highly resistance to tetracycline, co-trimoxazole and ampicillin, which are commonly used antibiotics in our area. It has been explained that the increased antibiotic resistance was due to a readiness for transfer of antibiotic resistance via conjugation probably encoded by the pCVD plasmid. Guidelines for appropriate use of antibiotics in developing countries need updating.

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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