Antibiogram of bacterial pathogens isolated from subclinical mastitis in Kombolcha, South Wollo, Ethiopia

Abstract

The present investigation was carried out to study the prevalence of bacterial pathogens responsible for subclinical mastitis in cattle and their antibiogram pattern to selected antibiotics. The study was carried out on lactating cows in small holder dairy farms in and around Kombolcha, South Wollo, Amhara region, Ethiopia. Accordingly, 110 healthy lactating cows were randomly selected from different farms for screening subclinical mastitis by using California Mastitis Test (CMT). Milk samples with positive results (1, 2, 3) on CMT were processed for isolation and identification at Kombolcha Regional Veterinary laboratory by culturing and requisite biochemical tests. 62 out of 110 lactating cows were found positive for subclinical mastitis, affecting one or two quarters, giving a prevalence of 56%. Out of 62 positive milk samples, a total of 88 different bacterial isolates were isolated and the biochemical tests identified 8 bacterial species. The most predominant species were S.epidermidius (n=23; 26.1%), followed by S. aureus (n=16; 18.2%), E. coli (n=14 or 15.9%), S. dysagalactiae (n=10; 11.4%), S. faecalis (n=8; 9.1%), S. agalctiae (n=7; 8%), Entrobacter (n=5; 5.7%), and B. cerius (n=5; 5.7%). The antibiogram of the bacterial isolates to standard antibiotic discs determined by disc diffusion method revealed the highest sensitivity to gentamicin and ciprofloxacin followed by chloramphenicol, in decreasing order. However, Most of the isolates were resistant to routinely used antibiotcis like penicillin G, streptomycin and tetracycline. Present study highlights the higher prevalence rates of subclinical mastitis in the study area and resistance of bacterial isolates to routinely used antibiotics. Judicious use of antibiotics based on antibiotic sensitivity and pharmacokinetics in mastitis control program is recommended to reduce the chances of treatment failure and related economic losses.

Keywords: Antibiogram, Antibiotic Discs, Bovine subclinical mastitis, Ethiopia