Antimicrobial-resistant bacteria isolated from clinical mastitis cases

Bovine clinical mastitis is a global problem because it decreases milk quality and quantity. Treatment of bovine clinical mastitis becomes more complicated due to the emergence of antimicrobial resistance of the causative pathogen. The purposes of this study were to identify bacteria from clinical mastitis cases and investigate their antimicrobial resistance. Using standard bacterial culture techniques, bacteria were isolated from milk samples of cattle with clinical mastitis. Identification was performed through colony morphology, Gram-staining, and biochemical assays. Antimicrobial susceptibility was tested against seven antimicrobials using disk diffusion method. Identified bacteria included Escherichia coli, Enterobacter aerogenes, Pseudomonas sp., and Staphylococcus aureus, among others. Multridrug-resistance bacteria were identified. E. coli was resistant to all tested antimicrobials, E. aerogenes was resistant to multiple classes of antimicrobials, particularly beta-lactams and macrolides. Pseudomonas sp. was sensitive only to gentamicin. The S. aureus isolate demonstrated resistance to beta-lactam antimicrobials. The identification of multidrug-resistant bacteria in milk samples from clinical mastitis cases highlights the importance of antimicrobial stewardship.