Prevalence and antimicrobial susceptibility of Salmonella species from lactating cows in dairy farm of Bahir Dar Town, Ethiopia

Salmonella is the most important disease causing bacteria in persons as well as in animals. Antimicrobial-resistant Salmonella can be transmitted from animals to humans through consumption of contaminated food and food products. Thus, this study was conducted to determine the prevalence and antimicrobial susceptibility of Salmonella species from lactating cows in dairy farms of Bahir Dar town. A cross-sectional study was conducted in Bahir Dar town from November 2012 to June 2013. Identification of Salmonella spp. was made biochemically with Kliger Iron agar (KIA), Urea agar, Sulfur Indole Motility (SIM), Lysine Deoxycholate agar (LDC) and Simmons citrate agar. Antibacterial sensitivity of the isolates was tested using the Kirby-Bauer test. Thus, out of the total 384 milk samples collected, 36 (9.35%) were positive for Salmonella spp. Salmonella isolates in this study were highly resistant to ampicillin (94.4%) followed by tetracycline (52.8%) and trimethoprim-sulfamethoxazole (38.9%). However, the isolates showed high susceptibility to fluoroquinolones (norfloxacin and ciprofloxacin) at 100 and 93.9%, respectively followed by gentamicin (94.44%). Likewise, the Salmonella isolates showed 72.22% of multidrug-resistance (resistance to two or more antibiotics) in the study area. In conclusion, the incidence of multidrug-resistant Salmonella spp. isolated from milk of lactating cows was high in the study area. Furthermore, the study also revealed the high rate of drug resistance pattern to commonly used antibiotics among the isolated Salmonella spp.