Antimicrobial resistance profiles of selected mastitogenic bacteria on smallholder farms in Buyanja Sub-county, Rukungiri district, Uganda

Abstract

This study investigated antimicrobial resistance patterns of four most incriminated bacteria in mastitis infections in cattle, i.e., Escherichia Coli, Staphylococcus aureus, Klebsiella and Streptococcus spp. The descriptive-observatory study aimed at understanding the pathologies of udders of cows and the magnitude of antimicrobial resistance in milk. This was done by examining 54 composite milk samples taken from 25 smallholder dairy farms in Buyanja Sub-county, Rukungiri district, Uganda. Bacteria isolated from milk using blood and Mac Conkey’s agar were identified by biochemical tests. Their antibiotic resistance was determined using drug impregnated disc diffusion method. Clinical mastitis was prevalent in 4% and subclinical mastitis in 83% of the animals. Udders of clinical mastitis cases presented with swellings, bruises, warts, wounds and lacerations. Two cows had pus in milk, one had a swollen udder with colostrum milk and another had a deep wound on the upper lateral part of the udder. Out of the 54 samples with subclinical mastitis, 39 tested positive for the bacteria of interest in this study. Staphylococcus aureus and Escherichia coli had the highest prevalence (33.3%), followed by Klebsiella and Streptococcus (30.8%) and (2.6%) respectively. Streptococcus exhibited 100% susceptibility to the drugs used except Gentamicin to which it was 100% resistant. Klebsiella showed resistance to Cefoxitin and Penicillin (100%), Gentamicin (75%), Tetracycline (66.7%), and Streptomycin (0.0%). It showed susceptibility to streptomycin (50%), Tetracycline (33.3%), Gentamicin (8.3%), Cefoxitin and penicillin (0.0%). Staphylococcus aureus exhibited resistance to Penicillin (92.3%), Gentamicin and Tetracycline (61.5%), Cefoxitin (7.7%) and streptomycin (0.0%). It was susceptible to Cefoxitin (92.3%), streptomycin (53.8%) and Tetracycline (38.5%). E. coli showed resistance to Penicillin (100%), Gentamicin (53.8%), Cefoxitin and Tetracycline (30.8%) and expressed susceptibility to Cefoxitin, Streptomycin, Tetracycline (69.2%), Gentamicin (30.8%) and Penicillin (0.0%). Generally, the highest resistance was found with Penicillin at 94.9% followed by Gentamicin at 64.1% and Tetracycline at 51.3%. There was more susceptibility to Streptomycin (59.0%) followed by Cefoxitin (56.4%) and Tetracycline at 48.7%. Veterinary practitioners should initiate programs aimed at sensitizing farmers about udder health care and judicious use of antibiotics. A microbial susceptibility tests should be done before treatment for mastitis to reduce on costs incurred on ineffective treatments.