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.
