title: Resistance Pattern and Molecular Characterization of Enterotoxigenic Escherichia coli (ETEC) Strains Isolated in Bangladesh.
abstract: BACKGROUND
  Enterotoxigenic Escherichia coli (ETEC) is a common cause of bacterial infection leading to acute watery diarrhea in infants and young children as well as in travellers to ETEC endemic countries. Ciprofloxacin is a broad-spectrum antimicrobial agent nowadays used for the treatment of diarrhea. This study aimed to characterize ciprofloxacin resistant ETEC strains isolated from diarrheal patients in Bangladesh.
  
  
  METHODS
  A total of 8580 stool specimens from diarrheal patients attending the icddr,b Dhaka hospital was screened for ETEC between 2005 and 2009. PCR and Ganglioside GM1- Enzyme Linked Immuno sorbent Assay (ELISA) was used for detection of Heat labile (LT) and Heat stable (ST) toxins of ETEC. Antimicrobial susceptibilities for commonly used antibiotics and the minimum inhibitory concentration (MIC) of nalidixic acid, ciprofloxacin and azithromycin were examined. DNA sequencing of representative ciprofloxacin resistant strains was performed to analyze mutations of the quinolone resistance-determining region of gyrA, gyrB, parC and parE. PCR was used for the detection of qnr, a plasmid mediated ciprofloxacin resistance gene. Clonal variations among ciprofloxacin resistant (CipR) and ciprofloxacin susceptible (CipS) strains were determined by Pulsed-field gel electrophoresis (PFGE).
  
  
  RESULTS
  Among 1067 (12%) ETEC isolates identified, 42% produced LT/ST, 28% ST and 30% LT alone. Forty nine percent (n = 523) of the ETEC strains expressed one or more of the 13 tested colonization factors (CFs) as determined by dot blot immunoassay. Antibiotic resistance of the ETEC strains was observed as follows: ampicillin 66%, azithromycin 27%, ciprofloxacin 27%, ceftriazone 13%, cotrimaxazole 46%, doxycycline 44%, erythromycin 96%, nalidixic acid 83%, norfloxacin 27%, streptomycin 48% and tetracycline 42%. Resistance to ciprofloxacin increased from 13% in 2005 to 34% in 2009. None of the strains was resistant to mecillinam. The MIC of the nalidixic acid and ciprofloxacin of representative CipR strains were 256 μg/ml and 32μg/ml respectively. A single mutation (Ser83-Leu) in gyrA was observed in the nalidixic acid resistant ETEC strains. In contrast, double mutation in gyrA (Ser83-Leu, Asp87-Asn) and a single mutation in parC (Glu84-Ly) were found in ciprofloxacin resistant strains. Mutation of gyrB was not found in either the nalidixic acid or ciprofloxacin resistant strains. None of the ciprofloxacin resistant strains was found to be positive for the qnr gene. Diverse clones were identified from all ciprofloxacin resistant strains by PFGE analysis in both CF positive and CF negative ETEC strains.
  
  
  CONCLUSIONS
  Emergence of ciprofloxacin resistant ETEC strains results in a major challenge in current treatment strategies of ETEC diarrhea.
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Yasmin A
authors.initials: YA
authors.lastname: Begum
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: K A
authors.initials: KA
authors.lastname: Talukder
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Ishrat J
authors.initials: IJ
authors.lastname: Azmi
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Shahnaij
authors.affiliation: Molecular Microbiology and Microbial pathogenesis program, Division of Biology and Biomedical Sciences, Washington University in St. Louis, MO, United States of America.
authors.forename: A
authors.initials: A
authors.lastname: Sheikh
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Salma
authors.initials: S
authors.lastname: Sharmin
authors.affiliation: Department of Microbiology and Immunology, the Sahlgrenska Academy at University of Gothenborg, Sweden.
authors.forename: A-M
authors.initials: AM
authors.lastname: Svennerholm
authors.affiliation: International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Firdausi
authors.initials: F
authors.lastname: Qadri
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D001459:Bangladesh / Q000453:epidemiology; D002939:Ciprofloxacin / Q000494:pharmacology / Q000627:therapeutic use*; D003967:Diarrhea / Q000150:complications / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D024881:Drug Resistance, Bacterial; D054307:Enterotoxigenic Escherichia coli / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000150:complications / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics; D005260:Female; D006801:Humans; D008297:Male; D009154:Mutation
chemical_list: D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D002939:Ciprofloxacin