OCCURRENCE OF Escherichia coli O157:H7 ON CABBAGE, LETTUCE AND CARROT GROWN ON FARMS USING CATTLE MANURE AS FERTILIZER IN ZARIA, NIGERIA
OCCURRENCE OF Escherichia coli O157:H7 ON CABBAGE, LETTUCE AND CARROT GROWN ON FARMS USING CATTLE MANURE AS FERTILIZER IN ZARIA, NIGERIA
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Date
2014-07
Authors
AJAEGBU, Ernest Chinedu
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Abstract
There have been a number of outbreaks associated with E. coli O157:H7, most of which are
the result of consumption of contaminated fresh produce. In the present study, the
occurrence of E. coli O157:H7 on fresh produce cultivated in farms using cattle manure as
fertilizer was determined. Questionnaires were administered to 18 farmers growing
cabbage, lettuce and carrot to determine some of their farming practices that may contribute
to contamination of these vegetables during cultivation up to the point of harvest. A total of
360 samples of cabbage, lettuce and carrot and soils were collected over a period of 3
months from 18 farms, out of which 300 samples (50 cabbage, 50 lettuce, 50 carrot and 50
each of their respective soils) were collected from farms using organic fertilizer
(experimental farms) and 60 samples (10 cabbage, 10 lettuce, 10 carrot and 10 each of their
respective soils) from farms using inorganic fertilizer (control farms). The samples wereThere have been a number of outbreaks associated with E. coli O157:H7, most of which are
the result of consumption of contaminated fresh produce. In the present study, the
occurrence of E. coli O157:H7 on fresh produce cultivated in farms using cattle manure as
fertilizer was determined. Questionnaires were administered to 18 farmers growing
cabbage, lettuce and carrot to determine some of their farming practices that may contribute
to contamination of these vegetables during cultivation up to the point of harvest. A total of
360 samples of cabbage, lettuce and carrot and soils were collected over a period of 3
months from 18 farms, out of which 300 samples (50 cabbage, 50 lettuce, 50 carrot and 50
each of their respective soils) were collected from farms using organic fertilizer
(experimental farms) and 60 samples (10 cabbage, 10 lettuce, 10 carrot and 10 each of their
respective soils) from farms using inorganic fertilizer (control farms). The samples were
placed in sterile polythene bags, labeled and transported to the laboratory for analysis.
These samples were enriched in modified tryptone soya broth and cultured on sorbitol
MacConkey agar supplemented with cefixime and tellurite (CT-SMAC). Colourless
isolates were picked and stored on nutrient agar slants. Conventional biochemical tests,
Microbact 12E and latex agglutination test kit (Wellcolex) were used to screen, confirm as
E. coli and serotype the stored isolates respectively. The results obtained showed that of the
150 vegetables and 150 soil samples collected from the experimental farms, 4 (2.7%) E.
coli O157:H7 isolates were obtained from vegetables and 4 (2.7%) from soil. But of the 60
samples collected from the control farms, no E. coli O157:H7 isolate was obtained from the
vegetables and soil samples. The eight E. coli O157:H7 isolates obtained were subjected to
Enzyme Immuno-Assay (EIA) using Ridascreen verotoxin ELISA kit to test for theproduction of verotoxins. The result obtained showed that of the eight isolates tested,
verotoxin was detected in only two of the isolates. The antibiotic sensitivity results showed
that all the isolates were resistant to at least one antibiotics especially cloxacillin but were
all susceptible to gentamicin and ciprofloxacin. From the questionnaires, it was deduced
that the use of cattle manure as fertilizer is a major risk factor associated with the
occurrence of E. coli O157:H7 on cabbage, lettuce and carrot grown on such farms. The
study concluded that the major risk factor associated with on-farm contamination of fresh
produce is the use of cattle manure and that the use of cattle manure as fertilizer in these
farms was the major source of contamination of vegetables grown on them with E. coli
O157:H7. Farmers need to be educated on the risk associated with the use of cattle manure
as fertilizer and on ways to reduce contamination of fresh produce in the farm. Adequate
precautions need to be taken in the course of preparing these vegetables for human
consumption. Also, there is the need to curb the abuse and misuse of antibiotics in animal
production, human and veterinary medicine.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES,
AHMADU BELLO UNIVERSITY, ZARIA
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF
THE DEGREE OF MASTERS OF SCIENCE IN VETERINARY PUBLIC HEALTH
AND PREVENTIVE MEDICINE.
DEPARTMENT OF VETERINARY PUBLIC HEALTH AND PREVENTIVE
MEDICINE
FACULTY OF VETERINARY MEDICINE
AHMADU BELLO UNIVERSITY, ZARIA
NIGERIA
Keywords
OCCURRENCE,, Escherichia coli O157,, H7,, CABBAGE,, LETTUCE,, CARROT GROWN,, FARMS,, CATTLE MANURE,, FERTILIZER,, ZARIA,, NIGERIA