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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Food Safety and Enteric Pathogens Research » Research » Publications at this Location » Publication #147565
Title: AVOIDANCE OF FALSE PCR RESULTS WITH THE INTEGRON-RETRON JUNCTION IN MULTIPLE ANTIBIOTIC RESISTANT SALMONELLA ENTERICA SEROTYPE TYPHIMURIUM

Author
item CARLSON, STEVEN
item WU, M - LOUISIANA TECH UNIV

Submitted to: Molecular and Cellular Probes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2003
Publication Date: 8/20/2003
Citation: CARLSON, S.A., WU, M.T. AVOIDANCE OF FALSE PCR RESULTS WITH THE INTEGRON-RETRON JUNCTION IN MULTIPLE ANTIBIOTIC RESISTANT SALMONELLA ENTERICA SEROTYPE TYPHIMURIUM. MOLECULAR AND CELLULAR PROBES. 2003. v. 17(4). p. 183-186.

Interpretive Summary: Salmonella infections continue to cause disease throughout the world. Salmonella strain DT104 (DT104) further represents a major health concern since it is resistant to multiple antibiotics. Multiresistance is conferred by an integron structure that contains 5 different antibiotic resistance genes. The integron structure is located between thdF and a retron. That is, the thdF-retron junction may be a "hot-spot" for insertion of exogenous DNA. Surprisingly, we found that the thdf-retron site was apparently "integron-free" in some multiresistant DT104 isolates. This phenomenon was not observed if the isolate was grown in the presence of two antibiotics. This demonstrates that, within some individual clinical isolates of DT104, there exists a small subpopulation of integron-free bacteria. Consequently, it appears that the thdF-retron junction is an inaccurate predictor of integron status in DT104 unless multiresistance is used as a selection tool during enrichment. This research will be of value to scientists and diagnosticians.

Technical Abstract: Salmonella infections continue to cause gastrointestinal and systemic disease throughout the world. Salmonella enterica serotype Typhimurium phagetype DT104 (DT104) further represents a major health concern due to its acquisition of resistance to multiple antibiotics. The multiresistance phenotype of DT104 is conferred by a 40-kb integron structure that contains 5 different antibiotic resistance genes. The integron structure is located between thdF and a retron, a bacteriophage product that is found specifically in Salmonella enterica serotype Typhimurium but not in other serotypes. That is, the thdF-retron junction may be a "hot-spot" for insertion of exogenous DNA, such as integrons or pathogenicity islands. Our objective was to investigate the utility of a 450 bp thdF-retron amplicon as an indicator of an insertless thdF-retron junction in Salmonella enterica serotype Typhimurium. Surprisingly, we found that the thdf-retron PCR was positive in some multiresistant DT104 isolates. This phenomenon was not observed if the isolate was enriched in the presence of two antibiotics. This demonstrates that, within some individual clinical isolates of DT104, there exists a small subpopulation of integron-free bacteria. Consequently, it appears that the thdF-retron amplicon is an inaccurate predictor of integron status in Salmonella enterica serotype Typhimurium unless multiresistance is used as a selection tool during enrichment.