Detection of plasmid in Listeria monocytogenes isolated from fresh raw milk in Nigeria
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Date
2014-10-30
Authors
Enurah, L. U.
Aboaba, O. O.
Nwachukwu, S.C.U.
Smith, S. I.
Fowora, M.N.
Journal Title
Journal ISSN
Volume Title
Publisher
Animal and Veterinary Sciences
Abstract
Aims: To determine the presence of plasmids in Listeria monocytogenes strains isolated from fresh raw milk from healthy cattle in Nigeria and also determine its role in antibiotics resistance since this organism is a food borne pathogen of
public health importance. Methods and results: Isolation of Listeria monocytogenes was done using selective enrichment and isolation protocol, as recommended by United States Department of Agriculture (USDA) and Association of Analytical
Chemists/ International Dairy Federation (AOAC/ IDF). Identification was by phenotypic characterization and confirmed
using β-haemolytic activity, phosphatidyl inositol phospholipase-C (PIPLC) assay and polymerase chain reaction (PCR) .
Strains identified as Listeria monocytogenes from the six zones were determined and results expressed as rate of prevalence in
graph. Twenty-three strains of Listeria monocytogenes isolated from 305 samples of fresh raw milk were screened for the
presence of plasmid DNA using the method of Ehrenfeld and Clewel and agarose gel electrophoresis. One isolate was found to
harbour one plasmid with molecular weight of 14.62kb. The plasmid was cured using different concentrations of acridine
orange. Antibiotic sensitivity test was carried out on both the wild strain (with plasmid) and cured strain using disc diffusion
method of Bauer-Kirby and it was found that the wild strain was resistant to seven of the twelve antibiotics used while the
cured strain was resistant to only one. Conclusions: There is a possibility of the presence of strains of Listeria monocytogenes
that can harbour plasmids. This could confer antibiotic resistance to the strains and thus make antibiotic therapy unsuccessful.
The increase in the number of antibiotics which the cured strain of Listeria monocytogenes was susceptible to in this study
showed that plasmid may play a significant role in antibiotics resistance. The Fulani herdsmen who take fresh raw milk
without boiling or pasteurization may serve as carriers of resistant strains of Listeria monocytogenes and help in its spread in
the environment through faecal pollution.
Description
Scholarlyarticle
Keywords
Fresh Raw Milk , Listeria monocytogenes , Plasmid , Antibiotic Resistance , Research Subject Categories::NATURAL SCIENCES
Citation
Uwanibe, E.L., Olugbo, A.O., Ugwumba, N.S.C., Ifeanyi, S.S., Adenike, F. and Ignatius, N.C., 2014. Detection of plasmid in Listeria monocytogenes isolated from fresh raw milk in Nigeria. Animal and Veterinary Sciences, 2(6), p.169.