Detection of class 1 integron-associated gene cassettes and tetracycline resistance genes in Escherichia coli isolated from ready to eat vegetables

Background: Ready to eat (RTE) vegetables are easily accessible healthy foods that are commonly consumed globally, including in Indonesia. However, these RTE vegetables contain potential contamination from patho- gens and multi -drug resistant bacteria. Therefore, in the present study, we examined the presence of tetracycline - resistant E. coli (TRE) isolates from RTE vegetables. Methods: Susceptibility to antimicrobial agents was determined using the Kirby -Bauer disc di ffusion method. Characterisation of antibiotic resistant genes was performed using PCR and sequencing of tetracycline resistant gene, integron and gene cassette from the TRE isolates. Results: The isolates collected in this study were resistant not only to tetracycline, but also to streptomycin. Some isolates also displayed resistance to kanamycin (77.8%), chloramphenicol (11.1%), and cipro floxacin (5.6%). All of the isolates contained integrons ( intI1 ) and the tetA gene; tetB was not detected in our study. Further analysis showed that some isolates (38.8%) contained the dfr A 7 gene cassette, which encodes dihydrofolate reductase, which is responsible for resistance to trimethoprim. Of all the isolates that presented integrons, 11 isolates (61.1%) did not carry gene cassettes. These empty integrons have the potential to convert themselves rapidly into multigraviton strains. Conclusions: TRE isolates contain the tetA gene and integron 1. Only 38.8% of the isolates that have been identi fied contain the dfrA7 gene cassette, which is responsible for trimethoprim antibiotic resistance. Further identi fication of genes conferring resistance to other antibiotics is necessary to better characterise antibiotic resistance.