O K.O, O C.N, A B.E, O A.E, O B.A.
bacteria, calabar, contamination, nigeria, vegetables
O K.O, O C.N, A B.E, O A.E, O B.A.. Bacteriological Study Of Vegetables From Markets Of Calabar Cross-River State Southeastern Nigeria.. The Internet Journal of Public Health. 2010 Volume 1 Number 2.
Vegetables are those plants which are consumed in relatively small quantities as a side-dish or as a relish with staple food. In order to keep them from losing their full turgidity, harvested vegetables often require low temperature and moist environment during storage. As a result, vegetable in the form of leaves are often sprinkled with water after harvesting and during exposure in the open market. The moist condition of the vegetables fostered by the sprinkling of water together with low temperature condition encourages the growth of microorganisms. These conditions also facilitate direct contamination by microorganisms through the handlers (buyers and sellers). Indirect contamination may also occur as a result of poor hygienic environment of the market. Consequently, harvested vegetables so soon begin to spoil if not sold immediately. However, cleaning processes reduce the number of microorganisms. This study of bacteriological quality of vegetables was aimed at estimating the level of bacterial contamination of the vegetables commonly sold in different markets of Calabar metropolis and to determine the safety of the vegetables for human consumption.
Materials And Methods
The vegetable samples numbering fifteen (five samples from each market) were bought, from three different markets namely: Akim, Marian and Watt, in Calabar metropolis. Calabar is located in the world map on coordinates 40 571 N, 80 191E in the eastern part of Nigeria with an estimated population of 1.2 million people. South Eastern Nigeria has a tropical continental climate with distinct wet and dry seasons
Handling and Washing of the Vegetables
Sterile polythene bags were used to collect and transport the purchased samples to the Laboratory. A pair of forceps was flamed, allowed to cool, used to pick the samples and transferred into sterile containers. Sterile distilled water was poured into these containers. Washing was done by shaking and rocking of the containers.
Method of Culturing the Washings from the vegetables
Serial dilution of the washings was done in which 1ml of each washing was added into a test-tube containing 9ml of sterile distilled water. Serial tenfold dilution was carried out from 10-1 to 10-10. This was followed by pour plate technique. One millilitre aliquot of each dilution from 10-2, 10-5 and 10-7 were cultured into Blood agar, MacConkey agar and Nutrient agar plates respectively. The lid was replaced in each case. Rocking of these plates were done as soon as the agar were poured, so as to have the microorganisms evenly separated during growth. Solidification of these agars was followed by incubation at 370C for 24hrs. After 24hrs, colonies were observed, counted and recorded.
Sub culturing of the Cultures
The colonies were purified by sub culturing then in fresh nutrient agar plates. After purification, the isolates were maintained using nutrient agar slant and were kept in the refrigerator at 40C for identification.
Identification of Various Isolates Obtained in the Cultures
The following biochemical tests were carried out for the characterization and identification of the organisms, viz: Gram’s stain, Catalase test, Indole test, Oxidase test, Sugar fermentation test, Motility test, Coagulase test, Citrate Utilization test, Hydrogen sulphide production test, Voges-Proskauer test, Methyl red test and haemolytic reaction on blood agar.
Estimation of Intensity of Contamination
The bacteria isolates from the vegetables in Akim market are shown in table 1. Altogether 53 bacteria isolates were made.
The bacteria isolates from the vegetable samples from Marian market are shown in table 2. Altogether 52 isolates were made. Again
From the Watt market, 48 bacteria isolates were made (table 3).
Table 4 shows a comparison of the bacteria isolates from the three markets of Calabar metropolis. From total of 153 bacteria isolates made from the three markets, 53(34.64%) were from Akim market, 52(33.99%) were from Marian market and 48(31.37%) were Watt market. Although the isolates from Akim and Marian markets were slightly higher than that of Watt market, they were not significantly higher (P>0.05) than that of the Watt market.
Of the seven bacteria species namely
The distribution of individual bacteria isolates on the vegetables is shown in table 5. Of the seven bacteria species,
The percentage distribution of the isolates on the vegetables is represented in figure 1. Of the 153 bacteria isolates, 61(39.87%) were from fluted pumpkin leaves, 42(27.45%) from cucumber, 38(24.84%) from tomatoes, 8(5.23%) from onions and 4(2.61%) from pepper. The distribution of the isolates on the different vegetable was statistically significant (P<0.05). Fluted pumpkin had the highest number of isolates followed by cucumber, tomatoes, onions and pepper.
The viable bacteria counts from the different vegetables bought from markets of Calabar metropolis were shown in figure 2.
In Calabar Markets, the commonly sold vegetables such as
The bacteria isolates from the vegetable samples were
The higher incidences of
All the bacteria isolated were opportunistic pathogens, in that; they usually cause infection if suitable opportunity arises. This suitable opportunity could be seen in a person with weak natural immunity probably due to poor health, malnutrition, infection with HIV or drug therapy.
Adequate care should be taken in processing these vegetables to destroy the microorganisms before they enter inside the human body and obtain favourable conditions which could support their increase in number; thereby causing food-borne disease or food poisoning to the detriment of the human health.