The Prevalence of Food Borne Pathogens with Patiicular Emphasis on Escherichia coli 0157:H7 in Retail Meat in Addis Ababa
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Date
2014-07
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Addis Ababa University
Abstract
The primary objective of this study was to determine the incidence of some food borne pathogens
in retail beef samples, and also assess the hygienic status of the retail beef with respect to
microbial load and micro flora. During the period between November 200 I and July 2002, a total
of 200 beef samples (500g per sample) consisting of 100 sliced and 100 minced beef samples
were purchased from 20 butchers' shops in four city zones of Addis Ababa. Microbiological
analysis of the beef samples based on cultural, microscopic and serological methods has revealed
the following results. The mean Mesolithic aerobic plate counts (MAPC) of the sliced and the
minced beef samples were 8.21 log cfu/g and 8.24 log Cfll/g, respectively. There was no
statistically significant difference between the mean MAPC vallles of the sliced and the minced
beef samples (P > 0,05, to" =0.877, at 45 d.f), Of the 25 sliced and the 22 minced beef
samples, 23 and 19 beef samples respectively, were of unacceptable quality due to high
Mesolithic aerobic counts levels. The mean total coli form counts of the sl iced and the minced
beef samples were 7.02 log cfu/g and 6.44 log cfll/g, respectively. The mean co lints of
Staphylococci in the sliced and the minced beef samples were 6.68 log cfu/g and 6.91 log cfu/g
respectively. Although carcinogenicity of the strains was not assessed, 4 of the 25 sliced beef
and 4 of the 22 minced beef samples had staphylococci counts (> 7 log cfu/g) near the threshold
for production of detectable Staphylococcus enterotoxin (S£). In the sliced beef samples,
micrococci (40.8%), staphylococci (29.1%), Bacillus spp. (l3J%) and the Enterobacteriaceae
(10.4%), in their order, were the four top leading dominant mesophilic aerobic bacteria (MAB)
whereas in the minced beef samples micrococci (41.2%), the Enterobacteriaceae (19.69%), other
gram negative rods (OGPR) (12.73%) and, Bacillus spp (IOJ) in their order, dominated the
Mesolithic aerobic flora. Shillelagh were not detected in any of the 200 beef samples. Salmonellae
were detected in 2 (I %) of the 200 beef sample. The two isolated strains belonged to Salmonella
serogroup D and were sensitive to all the ten antimicrobials tested. Of the total 200 beef samples
screened, only I (0.5%) sliced beef sample was found to be positive for E. coli 0 157:H7 and the
. isolated single strain was resistant to cephalothin, amoxicillin and ampicillin but was susceptible
to the remaining seven antimicrobials used in the test. Virulence of the isolated E. coli 0157:H7
was not detetmined. This work is the first report on the occurrence of the serotype in beef in
Ethiopia and may serve as a pedestal in launching more comprchensive investigation to
conclusively establish the occurrence of virulent strains. Considering the very poor hygienic
standard of the retail beef as evidenced by the high microbial load, the count of staphylococci and
the incidence 0 f salmonellae, and E. coli 0 157:H7, the consumption of raw or under cooked beef
should be discouraged. Based on tentative observations of some factors that might have
contributed to the poor hygienic conditions of the beef samples, a flow chart-based potential critical points are outlined
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Biology