Antimicrobial resistance patterns of Staphylococcus Aureus isolates in a veterinary laboratory in Nyeri, Kenya

Abstract

Staphlococcus aureus is a bacteria of veterinary and public health importance where it causes a vast array of pathogenic infections. In human, they cause skin and soft tissue infections, bloodstream infections, pneumonia and bone or joint infections. In animals, they can cause many infections one of the most common being mastitis which is a major concern in dairy farming. It causes swelling of the mammary tissues and changes in consistency of milk. Infections of the udder with various pathogens have led to the use of intra-mammary antibiotics which are mostly sold over-the-counter without prescriptions. Farmers and animal health service providers usually treat animals without antimicrobial sensitivity testing and this has over time contributed to resistance of bacteria to antibiotics. In addition to antimicrobial resistance, interaction between humans and animals and animal products can lead to transfer of resistance genes across species. The over-use of this antibiotics is leading to the silent antimicrobial Tsunami. The aim of the study was to determine the proportion of Staphylococcus aureus isolates in samples submitted at the Regional Veterinary Investigation laboratory, Karatina and also to determine Antimicrobial susceptibility patterns of the isolates through a retrospective study. From 452 samples submitted. 96% were milk samples and 4% were organs sampled during postmortem examination. From the samples 239 (53%) were Staphylococcus isolates with 108 (24%) being Staphylococcus aureus isolates. Antimicrobial susceptibility patterns were observed for 8 antibiotics, highest resistance being for Ampicillin 50%, followed by Cotrimoxazole 44.4 %, Sulphamethoxazole 44.4%, Streptomycin 26.9%, Chloramphenicol 15.7%, Kanamycin 13.9%, with the least resistance being for Gentamycin 2.8% and Tetracycline 1.99%. Isolates showed increasing resistance towards common antibiotics used to treat animals. A multi-disciplinary approach by the farmers, animal health and human health providers, government agencies and all relevant stakeholders would help to control this silent Pandemic. Use of laboratory facilities would help animal health service providers and farmers to identify suitable drugs to treat animals. Regulating and monitoring use and access of antibiotics would help avert over-use and misuse of antibiotics.