Molecular Clonality and Detection of Class 1 Integron in Multidrug-Resistant Salmonella enterica Isolates from Animal and Human in Iran

A total of 70 multidrug-resistant (MDR) Salmonella isolates (44 human and 26 poultry) were examined. The conserved segment-PCR, restriction fragment length polymorphism-PCR analysis, and DNA sequencing were used to determine the presence and cassette content of integrons. The genetic relatedness among the isolates was examined by pulsed-field gel electrophoresis (PFGE). The rate of integron carriage for MDR Salmonella isolates was 91.4% and integron-positive isolates belonged to six distinct serovars. Out of 64 integron-positive isolates, only four Salmonella Paratyphi C isolates could transfer integrons to Escherichia coli K12 by conjugation. Thirty-three PFGE types were detected in 52 integron-positive isolates, including 22, 4, 3, 2, 1, and 1 patterns among Salmonella serovars Enteritidis, Typhimurium, Paratyphi C, Paratyphi B, Paratyphi A, and Havana, respectively. The human and poultry Salmonella Enteritidis isolates from different regions with identical integrons had closely related PFGE patterns. Of the four integron-positive Salmonella Typhimurium isolates, the two poultry isolates with identical integron had very closely related PFGE patterns whereas the two human isolates with different integrons showed unrelated PFGE patterns. PFGE showed undistinguishable patterns in Salmonella Paratyphi C isolates with identical cassettes but revealed relatively unrelated patterns in those with different cassettes. Relatively unrelated and identical PFGE patterns were found in two Salmonella Paratyphi B and three Salmonella Paratyphi A isolates with the same integrons, respectively. In conclusion, PFGE patterns demonstrated more genetic relatedness among each Salmonella serovar with identical class 1 integrons than the same serovar with different class 1 integrons.