Genotypic identification of coliforms isolated from cases of subclinical mastitis among pastoral herds in parts of Kaduna State, Nigeria

Abstract

Background: Mastitis caused by Staphylococcus aureus was initially considered the major problem in dairy herds, but over the last few decades, the incidence of coliform mastitis has increased among the pastoral herds in Nigeria due to poor environmental and milking hygiene. Hence, this study was aimed at genotypic identification of coliform bacteria isolated from cases of bovine mastitis among pastoral herds in parts of Kaduna State, Nigeria.
Methods: A cross-sectional survey of 30 herds of cows across 7 Local Government Areas of Kaduna State, Nigeria, was conducted. One hundred and forty seven cows were proportionately selected by purposive sampling technique. The milk samples were aseptically collected and bacteriologically screened for coliform bacteria following standard bacteriological techniques. Nine out of 12 coliforms identified phenotypically were selected for PCR amplification and sequencing of their 16S rRNA gene. The Basic Local Alignment Search Tool (BLAST) analysis of the sequences obtained was done on the National Centre for Biotechnology Information (NCBI) data base, and isolates confirmed based on similarity to 16S rDNA sequences in the Gen Bank
Results: Five of the 9 coliforms were confirmed to be Klebsiella pneumoniae (prevalence rate, 3.4%) and 4 were confirmed to be Escherichia coli (prevalence rate, 2.7%).
Conclusion: This study shows that raw milk of mastitic cows can serve as a vehicle for the spread of pathogens such as K. pneumoniae and E. coli which, according to the Department of Health and Human Services of the United States Public Health Services, are potential threats to public health and safety of humans, animals and plant products.

Keywords: pastoral herds, subclinical mastitis, cows, PCR, 16s rRNA, sequencing