Isolation, Identification and Determination of Antimicrobial Susceptibility Pattern of Important Bacterial Isolated from Subclinical Mastitis in Western Tigray, Ethiopia

A cross sectional study was carried out from November 2017 to June 2018 in Western Zone of Tigray, North West Ethiopia with the objectives of identifying the etiologies of subclinical mastitis and their antimicrobial drug susceptibility pattern. From 122 California Mastitis Test positive quarter samples examined, 114(93.44%) were found culture positive for one or more bacterial species. From the species of bacteria isolated Staphylococcus aureus with a prevalence of 57(42.43%) and Staphylococcus epidermidis with a relative prevalence of 47(33.07%) were the first and second predominate isolated species found in this study. The third predominant bacterial species isolated in this study is Enterobacter aerogens with relative prevalence of 10(7.46%) whereas Proteus species with 7(5.22%) prevalence, Escherichia coli 5(3.73%), Klebsiella pneumonias 4(2.99%) and Pseudomonas aeruginosa 4(2.99%) were with the lowest prevalence of bacterial agent identified. Of total isolated bacterial species, 38 isolates of three bacterial species were tested for drug susceptibility to six antimicrobial discs. In the current study, Staphylococcus aureus is found susceptibility for Vancomycin (92%); Gentamycin (92%); Ciprofloxacin (83%) and Chloroamphenicol. Susceptibility to Vancomycin (100%), Gentamycin (80%), Ciprofloxacin (100%), tetracycline (80%) and Chloroamphenicol (50%) was found in case of Staphylococcus epidermidis whereas the antimicrobial susceptibility test of Escherichia coli indicated that susceptible to Chloroamphencole (100%), Ciprofloxacin (100%), Gentamycin (75%) and Tetracycline (75%). Higher resistance to Penicillin (100%) and 50% susceptibility to Tetracycline was observed in case of Staphylococcus aureus. In the other hand Staphylococcus epidermidis, a 100% resistance to Penicillin and 50% susceptibility to Chloroamphenicole was observed. Moreover, 100% resistance to Penicillin and Vancomycin was found in Escherichia coli. Lack of strategic control measures and improper attention to the health of the mammary glands contribute to the higher infestation rate and insusceptibility to commonly used drugs. Based on the findings of the present study, avoiding indiscriminate use of antimicrobial therapies and regular antimicrobial susceptibility test of bacterial pathogen should be conducted.