Isolation, identification and antimicrobial susceptibility profiles of Salmonella isolates from dairy farms in and around Modjo town, Ethiopia

Abstract

Foodborne bacterial diseases are a serious challenge to human and animal health. Salmonella is a zoonotic foodborne pathogen and the etiologic agent of salmonellosis. A cross-sectional study was conducted from January 2016 to April 2016 on small scale and large scale dairy farms in and around Modjo town, Ethiopia. The main objectives of the study were to isolate and identify Salmonella from lactating cows, personnel’s’ and equipment at farms and to determine the in vitro antimicrobial resistance profiles of the isolates. A total of 266 samples consisting of fresh cow milk, fecal sample, pooled milkers’ hand swab, pooled bucket swab, tank swab, and tank milk were collected from 21 dairy farms (n=20 smallholders, n=1 large scale farm). The samples were examined for the presence of Salmonella following standard techniques and procedures outlined by the International Organization for Standardization. Kibry-Bauer disk diffusion test was used for the antimicrobial susceptibility testing. Salmonella was isolated from 28/266 (10.5%) of the total samples. Out of the 28 Salmonella isolates, 18 (64.3%), 3 (10.7%) and 7(25%) were from lactating cows, personnel’s’, and equipment, respectively. Out of the 28 isolates subjected to antimicrobial susceptibility testing, all isolates were resistant to at least one or more antimicrobials tested. Accordingly, 96.4% (27/28), 82.1% (23/28) and 75.0% (21/28) isolates were resistant to tetracycline, kanamycin and nalidixic acid, respectively. Multiple drug resistance (resistance to two or more antimicrobials) was detected in 27(96.4%) of the isolates. Multiple antimicrobial resistance was observed in 100% (18/18), 7.4% (2/23) and 100% (7/7) of isolates obtained from lactating cows, personnels’, and equipment, respectively. High proportion of multiple antimicrobial resistant isolates (96.4%) in