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Prevalence of Bacterial Loads on some Fruits and Vegetables Sold in Kaduna Central Market, Northwestern Nigeria



Negbenebor Helen Ehimemen, Mairami Fatima Mukhtar and Nura Salisu
 
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ABSTRACT

Background and Objective: Fruits and vegetables served as the major sources of plant proteins, vitamins and fibers that support human health. This study was conducted to assess the bacteriological quality of various fruits and vegetables sold in Kaduna central market, northern Nigeria. Materials and Methods: Samples of the fruits and vegetables were procured from the market and analyzed using serial dilution technique and inoculation was done on MacConkey and nutrient agar and incubated for 48 h. Results: The result obtained showed the presence of six bacterial species: Staphylococcus aureus, Streptococcus sp., Enterobacter sp., Escherichia coli, Citrobacter sp. and Klebsiella sp. Staphylococcus aureus was the most abundant (with 80% relative occurrence) while Streptococcus sp. was the least abundant (with 2% relative occurrence). Conclusion: It was concluded that 6 different bacterial species prevailed on the fruits and vegetables sold in Kaduna central market: The result therefore implied that people consuming these fruits and vegetables are at a higher risk of pneumonia and toxic shock syndrome due to Staphylococcal infection, strep throat, rheumatic fever, scalded skin syndrome, scarlet fever and puerperal fever due to S. aureus, gastrointestinal disorders due to E. coli and bronchopneumonia due to Klebsiella sp. There is therefore; the urgent need for orienting the general populace on the inherent dangers associated with consumption of these types of fruits and vegetables without thorough disinfection.

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  How to cite this article:

Negbenebor Helen Ehimemen, Mairami Fatima Mukhtar and Nura Salisu, 2019. Prevalence of Bacterial Loads on some Fruits and Vegetables Sold in Kaduna Central Market, Northwestern Nigeria. Journal of Applied Sciences, 19: 20-24.

DOI: 10.3923/jas.2019.20.24

URL: https://scialert.net/abstract/?doi=jas.2019.20.24
 
Copyright: © 2019. This is an open access article distributed under the terms of the creative commons attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.

INTRODUCTION

Fruits and vegetables are vital sources of nutrient to human beings. They give the body the necessary vitamins, fats, minerals and oil in the right proportion for human growth and development1. However, the existence of fruits and vegetables is threatened by various factors such as changes in climatic condition, pest, inadequate rainfall and the activities of different bacterial communities. These bacterial biofilms cause spoilage and associated clinical symptoms. Spoilage is defined by Tournas2 as any change in the condition of food in which the food becomes less palatable or even toxic; these changes may be accompanied by alterations in taste, smell, appearance or texture. The colonization process involves the ability of the bacteria to establish itself within the host. This is initiated when bacteria (following adhesion and release of enzymes) depolymerises certain specific cell wall polymers (such a proto pectin, the cementing substance) of the produce3. Susceptibility of fruits and vegetables is largely due to differential chemical composition such as pH and moisture contents. The higher pH (near neutrality) and moisture contents are associated with their greater predisposition to bacterial activities. The occurrence of bacterial species on fruits and vegetables is recognized as a source of potential health hazard to man and his animals. This is due to their production of bacteriotoxins compounds which are capable of inducing several critical clinical symptoms in man following ingestion or inhalation; even though they differ in their degree and manner of toxicity. These microbes found in produce may have other, less direct, impacts on human health. Exposure to non-pathogenic microbes associated with plants may influence the development of allergies and the consumption of raw produce may represent an important means by which new lineages of commensal bacteria are introduced into the human gastrointestinal system4. The contamination of fruits and vegetables by bacteria could also be as a result of poor handling practices in food supply chain, storage conditions, distribution, marketing practices and transportation5. This study therefore, aimed at investigating the prevalence and occurrence of different bacterial communities on the fruits and vegetables sold in Kaduna central market with the view of identifying the different species of bacteria with their potential toxigenicity. The results of this research was also intended to be used in suggesting possible ways of minimizing or avoiding possible health problem associated with these bacterial species.

MATERIALS AND METHODS

The samples were collected from Kaduna central market (Kaduna north local Government area), located along Ahmadu Bello Way, Kaduna state, Nigeria (lat 10°31'06.29'N and long 7°25'36.57'E). They include: Pepper (Capsicum annum L.), Tomato (Lycopersicum esculentum Mill.), Irish potato (Solanum tuberosum L.), Garden egg (Solanum melongena L.), Carrot (Daucus carota L.), Cucumber (Cucumis sativus L.), Water melon (Citrullus lanatus Thunb.), Onion (Allium cepa L.), Sweet potato (Ipomoea batatas L.) and Okra (Albelmoschus esculentus L.). The samples were collected twice monthly between April, 2017 to August, 2017 from whole seller and retailer, put into a clean polythene bag and labelled, respectively. The samples were kept in the refrigerator at 4°C for later use.

Bacterial isolation from fruits and vegetables: The methodology of Dashwood et al.6 and Balali et al.7 were used in the isolation of microbial flora from the fruits and vegetables. The surface were sterilized with 0.1% Mercury chloride (HgCl) for 2 min then rinsed three times with distilled water. A sterile blade and forceps were use to cut small section of the tissue containing both the healthy and the rotten portion. The cut potions were pounded with pistil and mortar to make paste.

Inoculation and incubation: Streaking method was used for inoculation of the organisms on different agar plates (MacConkey Agar, Mannitol Salt Agar, Salmonella-Shigella Agar and Blood Agar). The pulverized sample was transferred to the edge of an agar plates with a sterilized wire loop and then a parallel, non-overlapping streaks were made on the surface of the already solidified agar plates. Streaked plates were incubated in the incubator for8 24 h at 37°C.

Characterization of bacterial isolates: The various colonies observed in the plates were distinguished on the basis of their cultural characteristics such as colony size, shape, color, consistency and haemolytic characteristics as described by Fawole and Oso9. Bacterial growth was sub-cultured on NA and was preserved in NA slants. The representative bacterial colonies distinguished on the basis of their cultural characteristics were smeared thinly on grease free microscopic slide and Gram-stained. The stained smears were then examined microscopically under the oil immersion objectives. The organisms recovered from the deteriorated vegetables were grouped on the basis of their Gram-reaction, cell morphology and cell arrangement. Isolates were further characterized using biochemical test described by Faiers et al.10 and Wreghitt and Morgan-Capner11.

Statistical analysis: The data obtained were subjected to one way analysis of variance and a significance test for differences between sample variances using the least significance difference (LSD) in the comparison of means at 5% level of significance.

RESULTS

Biochemical characterization: The results of the biochemical characterization of Gram-positive bacterial biofilms on the vegetables in central Market Kaduna was presented in Table 1. The result showed that Staphylococcus aureus was the most prevalent Gram-positive bacteria while Streptococcus spp. was the least abundant. Similarly, biochemical characterization of Gram-negative bacterial isolates from the vegetables indicated that E. coli, Klebsiella spp. and Citrobacter are the major Gram-negative bacterial populations found associated with the fruits and vegetables in central market, Kaduna (Table 2).

Prevalence of the isolates: The result for the relative abundance of different bacterial species in the fruits and vegetables was presented in Table 3. The result showed that S. aureus had the highest occurrence with 80% while Streptococcus spp., has the least with 2%.

DISCUSSION

Fresh fruits and vegetables are extraordinary dietary sources of nutrients, micronutrients, vitamins and fibers for human and an essential basic material for the food industry. They are widely exposed to microbial contamination through contact with soil, dust and water. Handling at harvest and post harvest processing has also been established to cause spoilage and loss of quality. Fruits and vegetables harbor a wide range of microbial contaminants as reported by Long et al.12. The major bacterial populations that are generally present on fruits and vegetables include species of Pseudomonas spp., Bacillus spp., Enterobacter spp., Sarcina spp., Staphylococcus spp., Streptococcus spp., Lactobacillus spp. and Leuconostoc spp. as stressed by Erin13. Most of the vegetables were not really fresh as they stayed in the market for long periods resulting to their spoilage14.

Table 1:Biochemical characterization of Gram-positive bacterial in vegetables and fruits from Kaduna
Image for - Prevalence of Bacterial Loads on some Fruits and Vegetables Sold in Kaduna Central Market, Northwestern Nigeria
Hem: Haemolysis reaction, Coa: Coagulase reaction, DNA: Deoxyribonucleic acid, Man: Mannitol fermentation, Bil: Bile solubility, Cat: Catalase, +/ -: Partial positive

Table 2:Biochemical characterization of Gram-negative bacteria on vegetables and fruits from Kaduna
Image for - Prevalence of Bacterial Loads on some Fruits and Vegetables Sold in Kaduna Central Market, Northwestern Nigeria
Ind: Indole, MR: Methyl red, VP: Voges proskauer, Cit: Citrate test, Mot: motility, Urea: urea, S/F: Sugar fermentation

Table 3:Abundance of different bacterial species in the fruits and vegetables from kaduna central market
Image for - Prevalence of Bacterial Loads on some Fruits and Vegetables Sold in Kaduna Central Market, Northwestern Nigeria

More so, most of the vegetables were grown under irrigation water containing enteric bacteria, viruses, protozoa or helminths, which subsequently increases the probability of the isolation of pathogens from harvested produce as reported by Uzeh et al.15 .

The extent of spoilage depends on micro-organisms involved. Uzeh et al.15 reported that S. aureus was found in carrots, cucumber, cabbage and lettuce at food outlets within Lagos Metropolis. The presence of Staphylococcus and Streptococcus species in the vegetables observed in this study agrees with the work of Erin13 who reported the presence of Staphylococcus spp. in pawpaw, orange and kola nut at Sango Market, Ilorin. However, Wells and Butterfield16 reported Salmonella, Shigella and gastro-intestinal viruses as the major pathogens associated with food poisoning in England and the United States. The presence of other bacterial species of E. coli, Enterobacter spp., Citrobacter spp. and Klebsiella spp. in the vegetables obtained from Kaduna central market conforms to the findings of Rangel et al.17 in which they reported the presence of E. coli in lettuce, apple, salads, coleslaw, melons, sprouts and grapes. The presence of E. coli, Klebsiella, Citrobacter, Edwardsiella and Enterobacter may lead to diarrheal diseases. It is also a well known enteric pathogen of man in nosocomial infections. This is in conformity with the findings of Pigott18 that, the majority of human infections are caused by Klebsiella pneumoniae and Klebsiella oxytoca. The presence of Citrobacter spp. in the vegetables agrees with the findings of Uzeh et al.15 who reported Citrobacter spp. in carrots, cucumber, cabbage and lettuce within Lagos Metropolis. Citrobacter spp. is reported to be resistant to some antibiotics such as Penicillin. This result was in conformity with several studies conducted by many researchers in an attempt to determine or identify the microbial population responsible for vegetable spoilage. A study conducted by Manani et al.19 among the vegetable to identify bacteria causing spoilage, 8 samples was collected and 21 isolates were recovered from them. The bacteria found to spoil the vegetables were identified as Klebsiella, Bacillus, E. coli, Staphylococcus, Pseudomonas and there prevalence in vegetable sample was found to be 33.33, 23.80, 14.28, 14.28 and 14.28%, respectively. This result was also in conformity with the present research. In another study conducted by Adebayo-Tayo et al.20 on microorganisms associated with spoilage of stored vegetables including cabbage in Uyo metropolis, Akwa-Ibom, Nigeria showed that Escherichia coli (28.6%) were the most predominant bacterial isolates associated with vegetable spoilage in Uyo metropolis. This was followed by Enterobacter spp. (21.4%), Staphylococcus aureus (14.3%), Erwinia spp. (14.3%) and Pseudomonas spp. (14.3%) while Salmonella spp. (7.1%) was least predominant. The finding of this study was also in conformity with that of Aminu and Ali21 who investigated and assess the microorganisms associated with spoilage of Watermelon (Citrillus lanatus) who found that Enterobacter (23%) were the most predominant bacterial isolates associated with spoilage of water melon tested, followed by Staphylococcus aureus and Salmonella spp. (21%) each, Escherichia coli (19%), while Klebsiella spp. It was found to cause gastro-enteritis, acute gastroenteritis characterized by the symptoms of vomiting, nausea, fever, chills, abdominal pain and watery (dehydrating) diarrhea occurring 12-24 h after ingestion of contaminated food or water21. Bacterial food poisoning have been implicated in the consumption of food contaminated by bacteria, most of the bacteria obtained from this study were enteric bacteria which are found in the soil and air. There is therefore the urgent need for orienting the general populace on the inherent dangers associated with consumption of these types of fruits and vegetables without thorough disinfection.

CONCLUSION

It was concluded that six bacterial species were found associated with the vegetables and fruits sold in Kaduna Central market, 2 Gram-positive (Staphylococcus aureus and Streptococcus sp.) and 4 Gram-negative (E. coli, Klebsiella sp., Enterobacter sp. and Citrobacter). These organisms have been known to produce toxins in fruits and vegetables they invade, thereby posed health hazard for their consumption. Good handling and use of clean water for washing the fruits and vegetables ought to be advocated especially by the retailers and consumers.

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