Isolation, Phenotypic Characterization and Public Health Implications of Listeria Monocytogenes Circulating in Smallholder Dairy Farms of Kombolcha Town And Kutaber District, South Wollo Zone, Amhara Regional State of Ethiopia

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Addis Ababa University


Listeria monocytogenes is a bacterium of veterinary and public health importance, worldwide. Listeriosis in humans is the main food-borne zoonotic illness resulted from consuming dairy and other food products contaminated with mainly Listeria monocytogenes. A cross-sectional study was conducted from November 2020 to May 2021 to isolate Listeria monocytogenes from raw bovine milk samples, to determine the Antibiogram of isolates and to understand its public health implication in smallholder dairy farms of Kombolcha town and Kutaber district of South Wollo zone, Amhara regional state, Ethiopia. A total of 384 samples were collected from dairy producers using a simple random sampling technique. Listeria species isolation was performed, according to standard bacteriological procedures, using Buffered Listeria Enrichment broth (BLEB) and Polymyxin Acriflavine Lithium-chloride Ceftazidime Aesculin Mannitol (PALCAM) agar and for confirmation and species identification: carbohydrates utilization, hemolysis, Christie Atkins Munch Peterson (CAMP) and Listeriolysin 0 latex agglutination tests was carried out. The antimicrobial susceptibility test using 9 commonly used antimicrobial drugs against 15 Listeria monocytogenes isolates, and a questionnaire survey were also conducted. From the total of 384 samples the overall prevalence of Listeria species was 12.8% (49/384) and specifically for Listeria monocytogenes was 4% (15/384). In this study, listeriosis is significantly associated with farm management systems and herd size. Based on the antimicrobial susceptibility test, it was found that Listeria monocytogenes was sensitive to most drugs except Sulfamethoxazole and nalidixic acid which in both showed 100% resistance. 13.3% of L. monocytogenes isolates were also resistant to oxytetracycline, tetracycline, procaine penicillin G and cloxacillin. A structured interview was administered to 70 respondents. Thus, 76.7% of dairy farmers and 20 % of public respondents consume raw milk and 39% of participants were knowledge of zoonotic disease. This presence of Listeria monocytogenes in raw milk and its multi-drug resistance pattern is an indication of a serious public health risk. Therefore, creating awareness on milk safety, implementation of milk and personal hygienic practices, implementation of countrywide surveillance and further research to estimate its prevalence both in animals and humans is strongly recommended.



Antibiotic susceptibility, Dairy, Listeria monocytogenes, south Wollo