The geographical location of this study is Imiringi community situated in Ogbia local government area of Bayelsa State in the Niger Delta region of Nigeria. Imiringi is located between longitude E6⁰ 022 and latitude N4⁰ 053 3. The community hosts several oil and gas facilities which have been in existence for over 30 years. Natural gas is flared into the environment in the area. Like other areas in the Niger Delta region, two predominant seasons occur in the study area viz: wet and dry seasons.

The samples were collected in sterile universal containers by opening the bottles under sterile conditions. The sample containers were covered, labelled appropriately and transported to the laboratory immediately for analysis.

Nutrient Agar, MacConkey agar and Salmonella-Shigella agar were used to enumerate total heterotrophic bacteria, Enterobacteriaceae bacteria and Salmonella-Shigella counts. The water samples were serially diluted and pour plate method previously described by Pepper and Gerba 4 and Benson 5 was employed to determine the bacterial population. Approximately 1.0ml of the diluted water samples was aseptically plated in the different media and incubated at 37oC for 24- 48 hours. Then after, the colonies that grew on the different agar plates were counted and expressed as colony-forming units per millilitre of the water samples. The different colonies were isolated into nutrient agar plates for identification.

The isolates that grew on different agar plates were characterized based on the biochemical tests previously described by Cheesbrough 6 and Benson 5. The resultant characteristics were compared with those of known taxa following the guide provided by Cheesbrough 6 and Bergey s Manual of Determinative Bacteriology by Holt et al. 7. Besides, the black colonies suggest the presence of Salmonella species, while the pink colonies are indications of Shigella species 89. The isolates were further streaked in Kligler iron agar, Thiosulphate citrate bile salt sucrose agar and Mannitol Salt Agar plates and the resultant characteristics were compared with the scheme of Cheesbrough 6.

Graph pad prism 5 and SPSS software version 20 were used to carry out the statistical analysis of the bacteria population. One-way analysis of variance was carried out at P = 0.05, and Tukey Honestly Significance Difference (HSD) was used to determine the source of the observed differences were the number of observation is 3.

The bacteria density of groundwater from Imiringi in Bayelsa state, Nigeria is shown in Figures 1-3. In Locations A, B, C and D, the microbial density were ranged from 2.97±0.88 x 10⁴ cfu/ml, 3.93±1.34 x 10⁴ cfu/ml, 6.03±1.13 x 10⁴ cfu/ml and 3.73±0.61 x 10⁴ cfu/ml, respectively (for total heterotrophic bacteria counts) (Figure 1), 4.17 x 10² cfu/ml, 4.77±1.32 x 10² cfu/ml, 4.33±0.09 x 10² cfu/ml and 5.43±0.37 x 10² cfu/ml (for Enterobacteriaceae bacteria counts) (Figure 2) and 0.00±0.00cfu/ml, 0.00±0.00cfu/ml, 1.48±0.93 x 10² cfu/ml and 0.85±0.44 x 10² cfu/ml, respectively (for Salmonella-Shigella counts) (Figure 3). Statistically, there was no significant difference (p>0.05) across the various locations for each of the parameters (total heterotrophic bacteria, Enterobacteriaceae bacteria and Salmonella-Shigella counts). The absence of Salmonella-Shigella counts in Location A and B, suggests that the water is of better quality with respected to Salmonella and Shigella species when compared to Location C and D. The absence of significant variation is an indication of similar groundwater quality in the study area. The bacteria density in this study is higher than the World Health Organization/Food and Agricultural Organization allowable limit of 1.0 x 10² cfu/ml in drinking water 1101112 and Standard Organization of Nigeria maximum permissible level of 10 cfu/ml for total coliform in potable water 113. This is an indication that the water is not fit for human consumption without treatment for bacterial quality. The bacterial in the study would have been in the tank used for water storage before being taken for domestic use.

Figure 4 shows the frequency of occurrence of bacteria isolated from the water samples from the study area. The prevalence of bacteria isolated in the water samples were Aeromonas species (8.00%), Citrobacter species (7.50%), Escherichiacoli (20.75%), Klebsiella species (5.50%), Pseudomonas species (12.00%), Salmonella species (2.25%), Shigella species (3.25%) and Staphylococcus species (40.75%). Staphylococcus species has the highest occurrence frequency, and this may be associated with handling processes before consumption. Staphylococcusaureus is a normal flora in human skin, therefore it may have entered the water due to human activities, while Salmonella species has the least occurrence frequency. The bacteria encountered in this study may have been introduced into the water due to human contact. Some of these isolates may have entered the groundwater through leakage of septic tanks and soakaway pits possibly due to the high water table in the area during the wet season (the season the study was conducted). The isolates found in this study have been previously detected in potable water sources in Nigeria 1. Some of the bacteria are of public health concern and have been linked to water-borne diseases such as diarrhoea. The occurrence of these bacteria isolates suggests that the water sources are not fit 14 for human consumption. For instance, Escherichia coli could cause intestinal disease characterized by diarrhoea, nosocomial pneumonia, dysentery and urinary tract infections 1516, and it’s associated with faecal materials. Some Shigella species causes Shigeollosis characterized by symptoms like diarrhoea, fever, and stomach cramps. Also, Salmonella species are enteric pathogens that cause enteric fever, intestinal diseases with symptoms like nausea, vomiting, fever and even death 1617. Some species of Staphylococcus such as Staphylococcus aureus produces toxins. The toxins may increase the severity of certain diseases such as food poisoning, septic and toxic shock syndrome, and the intensity depends on the individual susceptibility to the toxins 1516. Furthermore, some species of Pseudomonas such as Pseudomonas aeruginosa could cause bacteremia and septicemia. Klebsiella causes several diseases depending on the species. For instance, Klebsiella pneumoniae which causes urinary tract infection, pneumonia, intra-abdominal infection, bloodstream infection, meningitis, pyogenic liver abscess 18 and wound infections when it gets to susceptible sites in the human body. Klebsiella pneumoniae are often characterized by fevers and chills, rash, light-headedness, flu-like symptoms, cough and breathing issues. According to Antonara and Ardura 19, Citrobacter species are opportunistic pathogens that could lead to invasive diseases, such as infections of the urinary tract, respiratory tract, central nervous system, skin, and soft tissues in humans. The authors further reported that the bacteria could cause osteomyelitis, suppurative arthritis, bacteremia, endocarditis, endophthalmitis, and intra-abdominal infections, especially in neonates and immunocompromised individuals. Specifically, Citrobacter freundii and Citrobacter koseri are species that could cause urinary tract infections, and they can also be found in wounds and respiratory tracts 2021. Aeromonas species are a group of gram-negative bacteria that survive well in aquatic ecosystems. Aeromonas species causes enteric infection characterized by acute watery diarrhoea to dysenteric illness with symptoms like abdominal cramps, nausea, vomiting and fever 22. Other possible diseases caused by Aeromonas species include extraintestinal infections including septicemia, wound, urinary tract and ear infections. Of these 17 species of Aeromonas, only 3 is of clinical importance 23. Aeromonas species secrete enterotoxins which could cause illness in healthy as well as in immunocompromised individuals 23. According to Drancourt 22, Aeromonas caviae is the most prevalent species, and Aeromonas veronii could cause rare cholera-like illness and dysenteric diarrhoea in susceptible hosts.