The research was conducted to isolate and characterize various bacterial populations associated with fruits spoilage in Gwagwalada market Abuja, Nigeria. Seven different most commonly consumed fruits viz: oranges (Citrus sinensis), Tomatoes (Lycopersicon lycopersicum), Banana (Musa spp.), Mango (Mangifera indica), Red pepper (Capsicum sp), Guava (Psidium guajava) and Water melon (Citrullus lanatus) were used for the study. The fruits that showed decayed symptomatology were collected and transported in separate polythene bags to the laboratory where the rotten parts were isolated, cultured on four bacteriological media: Mannitol Salt Agar (MSA), MacConkey Agar (MA), Salmonella Shigella Agar (SSA) and Blood Agar (BA). Characterization of the isolates was done on the basis of cultural characteristics and biochemical tests. The result obtained revealed eight different bacterial species associated with the spoilage of fruits in Gwagwalada market. These bacteria are Staphylococcus aureus (25%), Escherichia coli (17%), Bacillus (19%), Klebsiella (10%), Pseudomonas (10%), Lactobacillus (10%), Micrococcus (07%) and Salmonella (07%). This implies that consumption of such spoilt fruits renders the risk of certain clinical symptoms to the consumers. Therefore people should avoid consumption of such spoilt fruits.

Most of our foods are excellent source for rapid microbial growth. Food materials contain organic substances in plenty and sufficient amount of water, and they may be either neutral or slightly acidic in nature [1]. They are subjected to natural contamination by many different kinds of microorganisms, including pathogens. Metabolic activities of microbes alter the condition of food, resulting in its spoilage [2]. The airborne microbes fall on fruits and vegetables and enter through the ruptured skin. The microorganisms present in the soil reach the processing plant through the crops [3]. Several insects are also responsible for the transference of microbes to the food. In general, the keeping quality of food depends on the success of preventing the entry of micro-organisms and restricting their growth [1]. Differences in microbial profiles of various fruits result largely from unrelated factors such as resident micro flora in the soil, application of non-resident micro flora via animal manures, sewage or irrigation water, transportation and handling by individual retailers [4].

In developing countries such as Nigeria, continued use of untreated waste water and manure as fertilizers for the production of fruits and vegetables is a major contributing factor to contaminations [5,6]. It is estimated that about 20-25% of the harvested fruits are decayed by pathogens during post-harvest handling even in developed countries. It has been known that fruits constitute commercially and nutritionally important indispensable food commodity [7]. Fruits are highly perishable products; the quality is affected by post-harvest handling, transportation, storage and marketing. The improper handling, packaging, storage and transportation may result in decay and production of microorganisms, which become activated because of the changing physiological state of the fruits [8].

Microorganisms especially bacteria and fungi have been identified as major organisms causing deterioration of various fruits by the secretion of extracellular cell wall degrading enzymes [9]. Most of the reported outbreaks have been associated with bacterial contamination, particularly members of the Enterobacteriaceae [10]. A large number of lactic acid bacteria, coliforms, moulds and yeast have been reportedly implicated in food spoilage as they use the carbohydrate content of the foods for undesirable fermentation processes [11]. The microorganisms normally present on the surface of raw fruits may consist of chance contaminant from the soil or dust.  These include bacteria or fungi that have grown and colonized by utilizing nutrient exuded from plant tissue. Among the group of bacteria commonly found include faecal coli forms such as Klebsiella and Enterobacter [12]. The study was aimed to determine bacterial species associated with spoilage of some fruits (oranges (Citrus sinensis), Tomatoes (Lycopersicon lycopersicum), Banana (Musa spp.), Mango (Mangifera indica), Red pepper (Capsicum sp), Guava (Psidium guajava) and Water melon (Citrullus lanatus) in Gwagwalada market, Abuja Nigeria

Study Area
The Study area is Gwagwalada market which is part of Abuja Municipal Area Council (AMAC). The AMAC is located between latitude 8°40’ and 9°20’ North of the equator and longitude 6°40’ and 7°40’ east of the Greenwich meridian. The Abuja Federal Capital Territory (FCT) has a land mass of approximately 8000sq km of which the FCC occupies about 250sq km with population recent census at 778,567 for Abuja Municipal Area Council [13].

Samples Collection
A total seventy (70) samples, ten (10) each of orange, tomato, banana, mango, pepper, guava and water melon were purchased from different vendors within Gwagwalada market Abuja Nigeria. The spoiled samples were taken to the laboratory for use. The decaying portions were subjected for bacterial identification [14]. The sample names were coded for easy reference on the basis of their types (Table 1).

Preparation of Media
The composition of the supplied agar medium was 28g per 1000 ml and 38 grams per 1000ml for Nutrient agar (NA), per 100 for Mac Conkey agar, 51.5 grams per 1000ml for Salmonella–Shigella agar and 40 gram per 1000ml for Blood agar, thus the amount required was weighted and taken in to reagent bottle and used to prepare 1000 ml of agar solution. Then distilled water was added up to 1000 ml in accordance with manufacturer’s instruction and the reagent bottle was sterilized in autoclave at a temperature of 121ºc for 15 minutes at about 1.30 hours [15].

Isolation of Bacteria
Five grams (5g) of decayed portion from each sample was weighed and washed in 10 ml of sterile distilled water. MacConkey, Nutrient agar, Salmonella–Shigella agar and Blood agar were inoculated with 0.1 ml of the rinse water using the Pour Plate Technique. The plates were allowed to solidify, inverted and incubated at 37ºC for 24h for colony formation. Each colony was isolated in a pure form by sub culturing for further studies and identification. Distinctive morphological properties of each pure culture such as colony form, elevation of colony and colony margin were observed. Further microbial identification was based on the methods of Holt., et al. [16].

Bacteria Identification
The distinct colonies that develop in the pure culture plate were observed for the morphological and cultural characteristics including the nature of margin, elevation, shape, colour and transparency and Gram staining [16-18] and set of Biochemical Characterization i.e. indole test, Methyl-Red test, Vogues-Proskauer test and Citrate utilization test, catalase test, coagulase test and oxidase test by standard method given by Sherman [17] and Holt., et al. [16].

Morphological Characterization of the Isolates
The morphological characteristics of the recovered isolates are presented in (Table 2). Total of twenty nine (29) isolates were characterized on the basis of colony morphology and the staining characteristics. It was found that 16 isolates were Gram negative while 13 isolates were Gram positive.

Biochemical characterization of the isolates
The biochemical characterization of the recovered isolates is presented in (Table 3). Total of thirty four isolates were characterized based on indole, methyl-red, Vougues Proskeaur, citrate utilization, catalase, coagulase, oxidase and motility tests. Nitrate, lactose and mannitol fermentation were also conducted.

Frequency of bacteria isolates
The frequency of bacteria isolates associated with spoilage of fruits in Gwagwalada market Abuja, Nigeria is presented in (Table 4). The percentage occurrence of the organisms is as follows; Staphylococcus aureus (25%), Escherichia coli (17%), Bacillus (19%), Klebsiella (10%), Pseudomonas (10%), Lactobacillus (10%), Micrococcus (07%) and Salmonella (07%).

The colonization of fruits by the invading microorganism is a critical phase in the microbial spoilage of produce. The colonization process involves the ability of the microorganism to establish itself within the produce. This is initiated when the microorganism degrade certain specific cell wall polymers such as prospecting, the cementing substance of the fruits following adhesion and release of enzyme. The magnitude of the symptoms of the induced disease is a reflection of the extent of colonization [19].

The study was aimed to determine bacteria isolates responsible for spoilage of various fruit at Gwagwalada market, Abuja Nigeria. A total of twenty nine (29) bacteria isolates were recovered which are grouped into 7 species. The bacterial isolates were characterized on the basis of colony morphology, staining characteristics and biochemical test. It was observed that 17 isolates were Gram positive, while 12 isolates were Gram negative. The result obtained from the data shows that the bacteria found in spoiled fruits samples include; Staphylococcus aureus (25%), Escherichia coli (17%), Bacillus (19%), Klebsiella (10%), Pseudomonas (10%), Lactobacillus (10%), Micrococcus (07%) and Salmonella (07%) and. This shows Staphylococcus was the highest occurring organism and found in all the fruit samples tested. The detection of the bacteria isolatesin this study showed poor hygienic standard in handling of the fruits, it could be also be from contamination during harvest. Most of the organisms found in this study are those commonly found in soil and water. But the presence of other indicator organisms like E. coli, Salmonella and Klebsiella in those vegetable samples might be the result of possible contamination during sales or unhygienic handling of stored fruits. The presence of Escherichia coli, Salmonella and Klebsiella in this study is an indication of faecal contamination of the food as a result of possible unhygienic handling [20].

The high microbial contamination observed in this study may also be a reflection of storage conditions and how long these produces were kept before they were obtained for selling. More importantly, bacteria on the produce may multiply over time depending on the storage conditions [21]. Several studies were conducted on isolation and characterization of microorganisms responsible for spoilage of fruits. The finding of this study was in conformity with that of Kumar., et al. [22] on Isolation and Characterization of Microorganisms Responsible for Different Types of Food Spoilages The result obtained from their study shows that the bacteria found in spoiled fruits samples was Bacillus, Klebsiella, Pseudomonas, E. coli, Lactobacillus, Staphylococcus, Micrococcusand there prevalence was 18%, 15%, 14%, 10%, 7%, 5%, 4% respectively. The result of this study justifies the findings of Aminu.,et al. [23] on isolation and identification of microorganisms associated with spoilage of watermelon (Citrus lanatus)In Sabon-Gari Market Kano Nigeria. Their result shows that Bacillus cereus(23%) were the most predominant bacterial isolates associated with spoilage of water melon tested, followed by Staphylococcus aureusand Salmonella sp (21%) each, Escherichia coli(19%), while Klebsiella spp. and Micrococcus were least predominant with 12% and 10% respectively.

Conclusively, the results of the present study revealed that the spoiled fruits (orange, tomato, banana, mango, pepper, and guava and water melon) samples are mainly contaminated with Bacillus cereus, Staphylococcus aureus, Salmonella sp, Escherichia coli, Lactobacillus, Klebsiella and Micrococcus. Presence of these bacteria on fruits most especially Coliforms pose a serious threat to health of consumers as the organismcould produce toxins, which are lethal when consumed. It is therefore necessary and important that both the farmers and sellers to take necessary and appropriate precautions in preventing contamination and eating of contaminated fruits. This will however reduce the risk of toxins associated with bacterial contamination which are deleterious to human health.