Multiple-Antibiotic Resistance in Salmonella enterica Serovars Isolated in Iran Harboring Class 1 Integrons

Aims: This research was carried out to detect the content and distribution of class 1 integrons in multidrug resistant Salmonella isolates.
Materials and Methods: Eighty four clinical isolates of Salmonella serovars were subjected to molecular detection of class 1 integrons following the antimicrobial susceptibility test using disk diffusion method and MIC determination.
Results: Eleven isolates (13.1%) which were resistant to at least 4 groups of antimicrobial agents considered as MDR (multidrug resistant) Salmonella serovars. The intI1 gene and internal variable regions (IVRs) of class 1 integron were detected in 50 (59.5%) and 35 (70%) of Salmonella clinical isolates respectively. Analysis of the sequence data revealed four gene cassette arrays including the dhfr7 (0.8 kb), aadA1 (1kb), blaP1 (1.2 kb), dhfr1-aadA1 (1.6 kb) with eight IVR distribution patterns.
Conclusion: Detection of class 1 integron carrying gene cassettes which confer resistance to different classes of antibiotics such as aminoglycosides, ß-lactams and trimethoprim confirms that integron-mediated antimicrobial gene cassettes are prevalent in Salmonella serovars isolated in Iran.