Multidrug-Resistant Shiga Toxin-Producing Escherichia coli Isolated from Philippine Native Swine (Sus scrota L.)

The interest in the use of Philippine native swine (PNS) as a product alternative to the white hybrid has been growing in the Philippines. However, PNS raised in low-cost production systems are prone to infection by zoonotic pathogens, such as the Shiga toxin-producing Escherichia coli (STEC) that causes diarrhea and life-threatening complications. The multidrug-resistant (MDR) strains of STEC further aggravate the problem as they serve as reservoir of antibiotic resistance genes. This study aimed to detect the occurrence of MDR STEC in 57 fecal samples of weaning-and market-age PNS. In addition, the class 1 integrons of the MDR STEC were characterized due to their ability to capture antibiotic resistance genes and hitchhike in mobile genetic elements, thereby spreading resistance. Fifty-three out of fifty-seven PNS or 93% were found to be positive for the presence of STEC by amplifying the stx1 gene. Disk diffusion assay against 12 antibiotic agents showed that the STEC isolates are most resistant to tetracycline (73.58%), ampicillin (37.74%), trimethoprim/sulfamethoxazole (32.08%), and streptomycin (32.08%). Seventeen STEC isolates exhibited the MDR phenotype and contained class 1 integron (intI1). Four aadA (adenylyltransferase, streptomycin resistance) and dfrA (dihydrofolate reductase, trimethoprim resistance) gene variants were identified in the variable region of the class 1 integrons. The results of this study will be useful in devising effective management practices that would control the presence and spread of this pathogen in the farm.