title: Comparison of virulence markers and antibiotic resistance in enterotoxigenic Escherichia coli isolated ten years apart in Tehran.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Molecular Biology Unit, Pasteur Institute of Iran, Tehran 13164, Iran. shahrokhi@pasteur.ac.ir
authors.forename: Nader
authors.initials: N
authors.lastname: Shahrokhi
authors.forename: Saeid
authors.initials: S
authors.lastname: Bouzari
authors.forename: Anis
authors.initials: A
authors.lastname: Jafari
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000942:Antigens, Bacterial / Q000235:genetics; D001427:Bacterial Toxins / Q000235:genetics; D002675:Child, Preschool; D004269:DNA, Bacterial / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D024881:Drug Resistance, Bacterial; D054307:Enterotoxigenic Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity*; D004768:Enterotoxins / Q000235:genetics; D004927:Escherichia coli Infections / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007492:Iran; D008826:Microbial Sensitivity Tests; D009693:Nucleic Acid Hybridization; D016133:Polymerase Chain Reaction; D037521:Virulence Factors / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D000942:Antigens, Bacterial; D001427:Bacterial Toxins; C098406:CS6 antigen, E coli; C069375:CfaD protein, E coli; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D037521:Virulence Factors; C034151:heat stable toxin (E coli); C027538:heat-labile enterotoxin, E coli