Detection of resistant and virulent genes of Escherichia coli (E. coli) and Staphylococcus sp. isolated from pneumo-enteritic goats in Chittagong of Bangladesh

Abstract

An investigation was conducted to evaluate the prevalence of common bacterial pathogens specially Staphylococcus sp., E.coli in pneumoenteritic goats. For this, fecal and nasal swab samples were subjected to various cultural and biochemical tests to isolate these bacterial pathogens. Cultural sensitivity test followed by identification of resistant genes to evaluate the drug resistance phenomena of isolated bacterial pathogens and virulent genes specific to both organisms were also studied. From nasal swab samples 28% (42) were found to be positive for Staphylococcus sp. in all cultural and biochemical tests. E. coli isolates were screened out from both fecal and nasal swab samples that reflected 26% (78) of prevalence in affected goats. Subsequently, cultural sensitivity test revealed most bacterial isolates were resistant to commonly used antibiotics like ampicillin, oxacillin, trimethoprim-sulfamethoxazole and tetracycline but some isolates showed variable in sensitivity. The screening of the presence of Stx1 and Stx2 virulent genes as well as tetA, blaTEM, sul2 resistant genes in E. coli isolates and resistant genes mecA, vanA, tetM in Staphylococcal isolates was done by PCR. This study disclosed the isolation rates of Stx1 and Stx2 are 5% (95% CI 0.0013-0.249) and 30% (95% CI 0.119-0.543) respectively whereas the isolation rates of tetA, blaTEM and sul2 are 45 (95% CI 0.23-0.684), 45 (95% CI 0.23-0.684) and 70% (95% CI 0.457-0.881) in fecal E. coli and 50 (95% CI 0.118-0.881), 83.4 (95% CI 0.358-0.995) and 83.4% (95% CI 0.358-0.995) respectively in nasal E. coli. In Staphylococcal isolates, the prevalence of mecA, vanA and tetM are 42.9 (95% CI 0.176-0.711), 0 and 28.6% (95% CI 0.084-0.581) respectively. Gene sequencing was done commercially and the sequences were compared with other known sequences published in GenBank, and revealing highest nucleotide similarity showed 100% (Stx1). Phylogenetic tree was prepared using mega6 software. In this study, it was shown that, virulent and antibiotic resistant bacteria were isolated from pneumoenteritic goats indicating random uses of antibiotics or it might be cross infection from the environment. Therefore, awareness against random uses of antibiotics in food animals should be strengthened in commercial as well as smallholder goat farms.