Comparison of virulence markers and antibiotic resistance in enterotoxigenic Escherichia coli isolated ten years apart in Tehran

  • Nader Shahrokhi Molecular Biology Unit, Pasteur Institute of Iran, Tehran 13164, Iran
  • Saeid Bouzari Molecular Biology Unit, Pasteur Institute of Iran, Tehran 13164, Iran
  • Anis Jafari Molecular Biology Unit, Pasteur Institute of Iran, Tehran 13164, Iran
Keywords: Antibiotic resistance, colonization factor antigens, enterotoxigenic Escherichia coli, heat-labile toxin, heat-stable toxin

Abstract

Introduction: Enterotoxigenic Escherichia coli (ETEC) causes diarrhoea by producing heat-labile (LT) or heat-stable (ST) enterotoxins after colonizing the small intestine by means of colonization factors (CFs). Although detection of the toxins is sufficient for verification of ETEC isolates, toxin-positive strains may be further analyzed for the presence of CFs. Antibiotics may shorten the duration of diarrhoea caused by ETEC, but the rapid emergence of resistant strains limits their usefulness.

Methodology: ETEC isolates collected 10 years apart were compared for the prevalence of toxin types, CFs and antibiotic resistance. DNA/DNA hybridization with digoxigenin (DIG)-labeled probes was used for the detection of toxin types, and CF-typing was performed by DNA hybridization using DIG-labeled probes for cfaD and CS6 with slide agglutination. Disk diffusion was used to determine antibiotic resistance. The presence of class 1 integrons was detected by PCR.

Results: ST-positive isolates were the most prevalent among the isolates from 1988, but a significant shift towards LT-gene carriage was observed in the 1998 group. CFA/I and CFA/IV were the most common CF types within both groups. The most prevalent resistance patterns among these isolates were ACSTSXT followed by ASTSXT and ASSXT.

Conclusion: Our study of the two groups of isolates showed that the rate of LT and ST gene carriage, as well as antibiotic resistance markers, has changed in the ten years separating the two bacterial populations. These variations show the importance of monitoring pathogenic bacteria to obtain a near realistic picture of the circulating bacterial pathogens.

Author Biographies

Nader Shahrokhi, Molecular Biology Unit, Pasteur Institute of Iran, Tehran 13164, Iran

Assistant Professor in Medical Biotechnology

Molecular Biology Dept.

Saeid Bouzari, Molecular Biology Unit, Pasteur Institute of Iran, Tehran 13164, Iran

Professor in Medical Microbioklogy

Molecular Biology Dept.

Anis Jafari, Molecular Biology Unit, Pasteur Institute of Iran, Tehran 13164, Iran

Assistant Professor in cell biology

Molecular Biology Dept.

Published
2010-10-07
How to Cite
1.
Shahrokhi N, Bouzari S, Jafari A (2010) Comparison of virulence markers and antibiotic resistance in enterotoxigenic Escherichia coli isolated ten years apart in Tehran. J Infect Dev Ctries 5:248-254. doi: 10.3855/jidc.1206
Section
Original Articles