Identification And Characterization Of Microorganisms Present In Food And Environments

ABSTRACT

Street vended food and beverages prepared are often contaminated with several organisms. However, there is less information regarding common microorganisms present in food selling environments. This research sought to isolate, identify and quantify microorganisms present in food selling environment in a University in Ibadan, Nigeria. Culture media were prepared and taken to 5 different eateries selling food to students. Swabbing was done floors and table tops of the canteens, Dish washing water was sampled, and culture media plates were exposed to air for 30 minutes in each canteen. The plates were immediately taken to the laboratory for organism culture, isolation and identification. Organisms with the highest colony forming unitsn(10 -7) within this study were ; Bacillus cereus, Athrobacter spp., Micrococuss leutus, Moraxella spp. etc. Organisms obtained from the canteen environment and their percentage of occurrence in the following decreasing order are ; Bacillus cereus (25%), Arthrobacter spp. (20%), Micrococuss luteus (16%), Moraxella spp. (9%), Lactobacillus spp. (7%), Proponiobacterium spp. (6%), Pseudomonas putida (5%), Leuconostoc spp. (4%), Bacillus subtilis (2%), and fungi; Aspergillus niger (5%), Aspergillus flavus (2%), Pitchia spp. (2%), Geotrichium spp. (1%), sycephalastum sebi (1%), Rhizopus stolonifera (1%) and Penicillium camemberti (1%). In conclusion the environment where food is processed and sold around the university seems to be threatened with pathogens. We therefore recommend better sanitation and management of these areas.

INTRODUCTION

Street vended foods (SVF) or ready to eat foods are food and beverages that are prepared and sold in public places by the street vendors or cafeteria for human consumption (Omemu and Aderoju, 2008). These foods are sources of nutrition for low-income earners at affordable prices in large urban areas in Nigeria. Some foods often sold as SVF vary in different countries depending on culture. The common ones are; rice, beans, salads, beef, chicken and gravy etc. Street vended foods in Nigeria are sold in central business areas and busy places such as school premises, market places, train and bus terminals to mention few (Cardinale et al., 2005).

Researchers have identified street vended food foods as vehicles for the transmission of food borne diseases that could be life-threatening (Bereda et al., 2016; Adams and Moss, 2008). Several studies have labeled street vended foods as food prepared under unhygienic conditions with high degree of contamination(Rane et al., 2011, Omemu and Aderoju, 2008). These foods are usually stored at unfavourable temperatures and sold at temporary sites like kiosks, make-shift accommodation and push carts to mention a few (Omemu and Aderoju, 2008). In most cases, portable water is not available at vending sites for domestic use, crockery are done in bowls or buckets and sometimes without soap. This could promote bacteria growth in the food processing environment, and the bacteria can be parasitic and be transferrable to human host causing food borne diseases (CDC, 2013). There is need for time to time research that shows awareness in risk behind consumption of SVF from unhygienic environment, such research could help health care providers to formulate policies and provide solutions that will minimize food-borne diseases. Current study aimed to isolate and identify microorganisms present in the environments where foods are vended in and around a University in Ibadan, South-west Nigeria.

Study design and Culture Media

Nutrient Agar (NA), Potatoes Dextrose Agar (PDA) were prepared into petri dishes, and taken to 5 different cafeterias (Four within the school and one at the school entrance). The cafeterias were assigned code names RC, MG, LL, YC and S2 for confidential purpose. Some culture media plates were exposed in strategic area inside of these eateries for 30 minutes in order to monitor the microorganisms present in the environment where the foods were being served. From each cafeteria, dish washing water was taken, and cotton wet with distilled water was used to swab table tops and floors then transferred laboratory to determine microorganism around materials used in the cafeteria. Liquid of samples collected were dropped on NA and PDA, incubated for 48 hours for growth of bacteria.

Isolation and Identification Techniques

Pour Plate Method

Five samples (10-1, 10-4 and 10-7) were used for the pour plate isolation method. In this method, 1ml sample was further taken and dispensed into the centre plate of the petri dishes from each of the ten- tube sterilized cultured media (NA & PDA) were then poured aseptically on the inoculate at the centre dishes. The plates were gently rotated clockwise and anti-clockwise three times to allow the inoculums spread every. The culture sample were then incubated at 350C (NA plates for bacteria isolation) and 250C (PDA for yeasts and moulds isolation) for 24hrs and 72hrs respectively according to cheesebrough (2002).

Slant Preparation

About 20ml of homogenized sample of NA and PDA prepared with sterilization procedures and dispensed into bottle (or universal bottle) to be filled a little bit higher than half of the bottle. The screw cap was then tightly closed before sterilizing in the autoclave for 15 minutes. The bottles were then slanted on staining rack for 24hrs for the medium to solidify. Characterized sample from each of the above were than sub-cultured into the slant medium contained in the bottle for storage. These served as back-up reference samples devoid of contamination.

Characterization (Colonial, Cultural, Morphological)

Streaking Method

10mls of homogenized and sterilized sample of NA and PDA prepared in the above were equally dispensed into petri dishes and allowed to solidify. For a representatives colony thus;- flame an inoculating loop into red hot and allow to cool. There was gentle stabbing of the reference colony for sub-culturing. Lines were streaked on to new plates to subculture colonies of interest to produce pure cultures.

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The isolates were sub-cultured using streak plate techniques and Characterization and classification of every representative colony that grew on culture plates NA and PDA into sizes, colours, pigmentation, consistency was carried out as described by cheesebrough (2002)

DICUSSION

Today, food borne illness has become a major public health concern especially in developing countries where street vended foods forms an integral part of the food supply chain (Gould, et al., 2016). Current study isolated, identified and quantified microorganisms present in food selling environment in a University in Nigeria. This research work was centered on determining the microbial profile of the environment in which different food vendors in and around a university campus in Ibadan Nigeria dispensed their food. Sixteen different microorganisms were isolated and bacteria constituted 90% of the organisms from the cafeterias. Number of organisms obtained in this study was higher compared to number of organisms obtained in some previous studies by Oranusi et al., 2013 and Nyenje et al, 2012 who isolated nine organisms in South eastern Nigeria and seven organisms in Alice, South Africa respectively.

Two of the organisms (Arthrobacter spp, and Penicillium camemberti) were not obtained from samples collected within the University premises. More numbers of cafeterias assessed may contribute to high number of organisms that were isolated. This high microbial content of food could also be due to the nature of handling and hygiene of the cafeteria staff as well as the customers patronizing the cafeterias. However, observing more areas of the cafeteria may provide more bacteria isolates finding from Lim et al. (2016) isolated over seventy pathogenic organisms in some different surface area in a cafeteria kitchen. Bacillus cereus constitutes the major bacteria specie found in the environment, table surfaces and wash water of the cafeterias sampled. This organism is a natural soil dwelling bacteria, and this might explain the reason why the population of this organism was dominant within this study as this suggest that food and food environment must have a lot of soil contaminant in them. This finding was in tandem with the study conducted by Lim et al. (2017) who found Bacillus cereus to be the most dominant organism in their study accounting for close to one-thirds (33%) of all the microorganisms isolated within their study. This finding also tallied with Oranusi et.al (2013), and Babiye (2017) studies which also isolated Bacillus cereus in large heavy proportions. Interestingly in our study Escherichia coli which is a well-known food pathogen and contaminant was not isolated from any of our samples, reason for this remains unknown. Similarly, Escherichia coli was not found in study conducted by Nyenje et al. (2012) in Cape Province South Africa

Some Fungi were also found among isolated organisms which were possible due to the fact that culture media were exposed while within the cafeteria and some of these fungi could have been airborne giving them the opportunity to also contaminate food and utensils. The fungi isolates obtained from the cafeterias is similar to study done by Oranusi et.al (2013) who also found fungi such as Aspergillus niger and Aspergillus fumigatus in their study. In contrast, Nyenje et al.(2012) in their study did not isolate any fungi from the samples used in cafeteria environment in their study. The cafeteria outside the school had the highest number of colonies of bacteria and this might be due to the fact that this cafeteria in particular was run and serviced uninspected, and thus personal hygiene seemed to be very poor and lacking in this kind of particular canteen.

The rate at which food borne illness keep increasing is as a result of inadequate supervision and monitoring by food safety officers or health care providers. A lot of the organisms isolated within this study have been known to produce all kinds of toxins and can lead to or cause food poisoning. These toxins have been linked to be causative agents of many diseases and ailament e.g Aspergillosis was studied to be caused by Aspergillus spp, phycomycosis by Rhizopuz spp, and geotrichosis by geotrichium, Candidium. Our finding agrees with report by Christison et al. (2008), who suggested that unwholesome handling practices by food handlers plays a role in microbial contamination of food.

Their seems to be lack of health implication awareness, inadequate of training, poor hygiene practice among food handlers (Islam, et al., 2016). Current finding suggests that unwholesome practice by vendors can lead to food contamination as the environment in which food is served and prepared is very important. Consequently, isolation of the above microbes and may other ones has corroborated the report of FDA (2016) in which they submitted that infectious organisms are common causes of food poisoning. FDA (2016) went further to say that infectious organisms or their toxins can contaminate food at any point of preparation, processing, production, growing, harvesting, storing and shipping.

CONCLUSION

The present study revealed that street vended foods within and/or around university community may have high microbial contaminants which constitute an important potential hazard to human health. Street vended foods have become major sources of serious health problem due to microbial contamination and therefore more attention should be given to this area of research. Also, food sellers, should be trained on good health practices, clean environment, drainage for waste water, effective garbage disposal system and other wholesome practices.

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