DETECTION OF POSSIBLE SOURCES OF LISTERIA MONOCYTOGENES AND OTHER LISTERIA SPECIES AND THEIR ANTIMICROBIAL RESISTANCE PROFILES ALONG HARAMAYA UNIVERSITY DAIRY FARM OPERATIONAL STAGES, OROMIA REGIONAL STATE, ETHIOPIA

Abstract

Listeriosis is one of the most important emerging bacterial infections worldwide that arises mainly from the consumption of contaminated food including raw milk. A cross-sectional study was conducted from December 2017 to May 2018 in Haramaya University Dairy Farm. The objective of this study was to detect the possible sources of L. monocytogenes and other Listeria species along Haramaya University Dairy Farm’s operational stages and to assess the antimicrobial resistance profiles on the isolates. Purposive type of study with random sampling method was used to select six dairy operational stages and fourteen sampling locations within the farm. A standard culture reference method recommended by ISO 11290 Protocols was applied for laboratory procedures. The isolates were tested for resistance against selected antimicrobials using disk diffusion technique. Out of 200 samples, 40 (20%) were positive for overall Listeria species from all operational stages and the majority of sampling locations were also positive. The distribution of Listeria species at operational stages were 30%, 26.7%, 20%, 18.6% and 10% at cow barn, milk supply, silage and milk from cow teat, milking operation and milk auditing respectively. L. monocytogenes was detected in 11(5.5%) of all samples with 2.8%, 6.6%, 7.5% and 10% from milking operation, milk supply station, feed and watering and cow barn and milk from cow teat respectively. The frequency of other Listeria species were, L. innocua (5%), L. gray (3%), L. ivanovii (2.5%), L. seeligeri (2%) and L. welshimeri (2%) in descending order. The tested isolates were found resistant at varied frequency to tetracycline (55%), penicillin (45%) and amoxicillin (20%) were observed. Likewise 54.5% of L. monocytogenes showed resistance to tetracycline and equal (27.3%) isolates were resistance to each of amoxicillin and streptomycin. Of the total isolates, 82.5% shows single to multi drug resistance in which 14 (35%), 10 (25%), 7(17.5%) and 2(5%) isolates were resistance to single, two, three and four drugs respectively. The detected L. monocytogenes and other Listeria species from majority of sampling stages and sampling locations can act as sources of milk contamination that becomes a public health risk. Therefore, hygienic practices should be implemented at all stages and locations for prevention and control of Listeria and the resistant isolates.