Submitted to: Antimicrobial Agents and Chemotherapy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2000
Publication Date: 3/1/2001
Citation: Goldstein, C., Lee, M.D., Sanchez, S., Jackson, C.R., Phillips, B., Register, B., Grady, M., Liebert, C., Summers, A.O., White, D.G. 2001. Incidence of class 1 and 2 integrases in clinical and commensal bacteria from livestock, companion animals and exotics. Antimicrobial Agents and Chemotherapy. Vol. 45. No. 3. P. 723-726. Interpretive Summary: Antimicrobial resistance is a major health concern in both human and veterinary medicine. Because of the growing concern of the failure of antimicrobials in disease treatment, mechanisms of antimicrobial resistance are being intensely studied in both Gram-negative and Gram- positive bacteria. One such mechanism of antimicrobial resistance gene dissemination in bacteria is the integron. Integrons harbor antimicrobial resistance genes and can facilitate the transfer of these genes from bacteria to bacteria. The prevalence of two of the four classes of integrons in bacteria isolated from livestock, companion animals, and exotic birds was studied. Class I integrons from E. coli isolates were widely disseminated among poultry, swine, and cattle (66%, 86%, and 75% of isolates, respectively); whereas class II integrons were less prevalent (average = 12% of isolates). Scientists and veterinarians will use this information to further understand the transmission of antimicrobial resistance in the animal population and as a basis for how to prevent further spread of these genes.
Technical Abstract: Many pathogenic and commensal organisms are multi-drug resistant due to exposure to various antibiotics. Often, this antimicrobial resistance is encoded by integrons occurring on plasmids or integrated into the bacterial chromosome. Integrons are commonly associated with bacterial genera in the family Enterobacteriaceae. We determined that class 1 integrases were present in approximately 46% of the isolates from the family Enterobacteriaceae; class 2 integrases were present only among Escherichia coli and Salmonella. Seven percent of veterinary isolates were positive by DNA: DNA hybridization for class 3 integrase, but could not be confirmed by PCR. None of the veterinary isolates possessed the class 4 integrase gene. The distribution of these integrase genes was variable within the Enterobacteriaceae family where some or all integrase classes were absent from a particular genus. There was also considerable variability in the distribution of these integrases within a species, depending on the animal host. Unlike the class 1 integrases, the other integrase class, intI2 appears to be more restricted in their distribution among the Enterobacteriaceae. There is also considerable variability in the distribution of the class 1 integrases within E. coli isolated from different food animals. The class 1 integrases are the most widely disseminated of the four classes among the family Enterobacteriaceae from both clinical and normal flora of animals.