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3.8.1.2 Presumptive Test and Confirmation
Presumptive and confirmed total coliform and fecal coliform counts were determined using the most-probable-number MPN method. Aliquots of homogenate
and dilutions up to 1ml were added in triplicate to lauryl tryptose broth containing Durham tubes and incubated at 35
° C. At 24 and 48 hours, tubes were checked for gas
production, and transfers were made from positive tubes with a sterile loop to tubes containing brilliant green broth and EC broth. Brilliant green tubes were incubated at
35 °
C and EC tubes were incubated at 45 °
C. Tubes were checked for gas production at 24 and 48 hours. An MPN standard table for 3-tube dilution was used to calculate the
number of coliforms.
3.8.1.3 Recording results
Recording of MPNg from the standard 3-tube table was as such: If from the 3 dilutions in the first set 10
-1
, 2 positive tubes, second set 10
-2
had 1 positive tube, and third set 10
-3
had 2, then the reading would be 2, 1, 2; when seen from the MPN table the set 2, 1, 2 would give 27 MPNg Appendix Table 4. This was the manner in which
the results were quantified using the 3-tube MPN table.
.
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4. RESULTS AND DISCUSSION
4.1 Salmonella
In this research study, out of the 36 samples analyzed, 19 were suspected of Salmonella
species being present thereby further identification process, serological test was carried out for this 19 samples. Out of the 19 suspected samples, 6 samples were
confirmed to be Salmonella serovars. The 6 confirmed isolates are given in Table 4.0. The samples from serology test confirmed two Salmonella species: S.Weltevreden and
S. Agona. Both serovars occurred in some of the samples obtained from RTE food
outlets I and II, respectively. S.Weltevreden was found in Outlet I and was isolated from utensils washing water, tea towels, and food preparation tables . S.Agona was found in
outlet II and was isolated from utensils washing water and food preparation tables . There were no Salmonella species were isolated from RTE food outlet III. The serology
results are presented in Table 5.0. It is noted that only one form of serovar is observed in outlet I and outlet II but in
different types of samples. This would most probably indicate that cross-contamination of some sort occurred during the processing period most probably from tables tops onto
tea towels being mistakenly placed on the contaminated surfaces, water then was contaminated whilst washing dirty equipment for food preparation placed or used on the
preparation tables. That is, the raw materials especially the meat products having being contaminated with the bacteria may have being the cause for contamination of the
samples analyzed. On the other hand water could have been the likely source for the cross-contamination. That is, likely from the water source as ground water is used for
washing the utensils. However, contaminating the tea towel and the table surface would have to be through contaminated utensils washed in the water or washed food items or
hands of persons washing the utensils having touched the tables and tea towels so in turn contamination occurred.
In ready-to-eat food outlets, there are so many things that could account for the presence of pathogenic bacteria like the two serovars found in this research. Raw foods
especially of animal origin contaminated with Salmonella; infected individuals preparing the food; contaminated water source; and pests and insects are some of the
common ways food contact surfaces may be cross-contaminated.
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