Detection of Class 1 Integrons in Drug-Resistant Bacteria Isolated from Raw Meat and Milk of Lahore, Pakistan

Background: The problem of antimicrobial resistance in foodborne bacteria has become an increasing threat to the world as antibiotics no longer have an effect on the infections. Objective: The aim of this study was to identify antibiotic resistance genes and class 1 integrons in bacterial isolates of the raw meat and milk samples of Lahore in Pakistan. Methods: Meat and milk samples were collected and processed by means of serial dilution and biochemical identification to obtain nineteen ampicillin-resistant bacterial strains. The test was done on five antibiotics according to CLSI guidelines against cefixime, nitrofurantoin, tobramycin, doxycycline, and imipenem. PCR amplification and sequencing were done to determine resistance genes (IntI1, tetA, strA) and the phylogeny analysis was done with MEGA6 software. PCR and AST results were validated by positive (IntI1-positive E. coli) and negative (ATCC 25922) controls. Result: Class 1 integrons (IntI1) was found in 57.8% of the isolates frequently along with tetA and strA genes. The majority (95%) of the isolates were resistant to three or more antibiotic classes. Homology of IntI1 gene sequences was also found to be very close with the XerC superfamily of integrases and was deposited in the NCBI database bank by the accession numbers MK894883, MK894885, MK894884 for strains C6/M4/M7 respectively. This was further done by detecting and amplifying tetracycline resistance gene in strain C6 (MN746283). Conclusion: The study shows the presence of class 1 integrons and resistance genes in ampicillin resistant bacterial isolates of food sources in Lahore. These findings, however, are indicators of resistance gene presence and not prevalence of the population at large because the isolates were already selected in advance based on their antibiotic resistance. There is an immediate necessity in improved food safety and antimicrobial stewardship.