Characterization of E. Coli and Staphylococcus aureus isolated from Clinical and Subclinical cases of bovine mastitis in the Limpopo Dairy Farm (Limpopo, South Africa)

Abstract

Background: Staphylococcus species and Eschericia Coli has been predominantly found to cause mastitis in dairy farms. Milk harbor various pathogenic microorganisms that causes foodborne and intramammary infections. The aim of this study was to characterize Staphylococcus spp. and Eschericia coli spp. isolated from clinical and subclinical cases of bovine mastitis in the Limpopo dairy farm. Methods: Semi structured questionnaire was used prior milk sampling to acquire farm management strategies. A total of 253 milk samples were collected from the dairy farm between 2018 and 2019. California mastitis test was done to screen for mastitis and culture methods were used for the isolation and identification of E. coli and Staphylococcus species. Further identification and biochemical confirmation for bacterial isolates were performed using API test kit and automated VITEK® 2 system. Eschericia coli isolates were characterized using a multiplex PCR. Automated VITEK® 2 system and Kirby Bauer disc diffusion method were also used to determine antibiotic susceptibility of the isolates. Results: The study reported fair farm practices and management system with low mastitis burden. California mastitis test revealed an overall mastitis on 94/250 (37%) of the samples. Of 94 samples cultured, a total of 32 (34%) were positive for E. coli strains and 48 (51%) were positive for Staphylococcus spp. [Staphylococcus sciuri 19 (40%) and Staphylococcus xylosus 10 (21%)]. Out of 32 Escherichia coli isolates 27 (93%) and 19 (66%) were detected with astA gene and sta which encodes for enteroaggregative E. coli respectively. Most Staphylococcus species isolates were highly resistant to Erythromycin (93%); Nalixidic acid (86%). The presence of pathogenic E. coli and Staphylococcus species in milk may pose health risks or problem and improving sanitary conditions may reduce the burden of mastitis. For future studies, further analysis of both E. coli and Staphylococcus species to determine virulence and resistant genotyping in order to investigate possible mutations is recommended.