title: Distribution of class 1 integrons with IS26-mediated deletions in their 3'-conserved segments in Escherichia coli of human and animal origin.
abstract: Class 1 integrons play a role in the emergence of multi-resistant bacteria by facilitating the recruitment of gene cassettes encoding antibiotic resistance genes. 512 E. coli strains sourced from humans (n = 202), animals (n = 304) and the environment (n = 6) were screened for the presence of the intI1 gene. In 31/79 integron positive E. coli strains, the gene cassette regions could not be PCR amplified using standard primers. DNA sequence analysis of 6 serologically diverse strains revealed atypical integrons harboured the dfrA5 cassette gene and only 24 bp of the integron 3'-conserved segment (CS) remained, due to the insertion of IS26. PCR targeting intI1 and IS26 followed by restriction fragment length polymorphism (RFLP) analysis identified the integron-dfrA5-IS26 element in 27 E. coli strains of bovine origin and 4 strains of human origin. Southern hybridization and transformation studies revealed the integron-dfrA5-IS26 gene arrangement was either chromosomally located or plasmid borne. Plasmid location in 4/9 E. coli strains and PCR linkage of Tn21 transposition genes with the intI1 gene in 20/31 strains, suggests this element is readily disseminated by horizontal transfer.
authors.affiliation: School of Biological Sciences, University of Wollongong, Wollongong, New South Wales, Australia.
authors.forename: Fay E
authors.initials: FE
authors.lastname: Dawes
authors.forename: Alexander
authors.initials: A
authors.lastname: Kuzevski
authors.forename: Karl A
authors.initials: KA
authors.lastname: Bettelheim
authors.forename: Michael A
authors.initials: MA
authors.lastname: Hornitzky
authors.forename: Steven P
authors.initials: SP
authors.lastname: Djordjevic
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Walker
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology; D017124:Conserved Sequence; D004283:Dog Diseases / Q000382:microbiology; D004285:Dogs; D004926:Escherichia coli / Q000145:classification / Q000187:drug effects / Q000235:genetics*; D004927:Escherichia coli Infections / Q000382:microbiology* / Q000662:veterinary*; D017353:Gene Deletion; D006801:Humans; D032023:Integrons; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents