Contamination Levels of Groundwater, Antimicrobial Resistance Patterns, Plasmid Profiles and Chlorination Efficacy in Ongata Rongai, Kajiado North County, Kenya
Wahome, Caroline Nyawira
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Water contamination is a serious threat to human health especially if the contaminant is from sewage. Ground water is increasingly used as a water source in urban settlements due to limited sources of fresh surface water. This has increased the vulnerability of underground water sources to sewage and waste water contamination and therefore exposing the population to infections by various water borne pathogens such as bacteria, viruses and protozoa. Exposure to these bacteria coupled with the rising incidences of antimicrobial resistance in various bacterial species has made patient management a great challenge. Ongata Rongai was chosen for this study because it represents the current state of the impact of unregulated urbanization and population pressure on natural resources. In the present study, the microbial quality of several boreholes, used by residents of Ongata Rongai, Kajiado North County was assessed to determine their safety for human consumption and to highlight the potential occurrence of water-borne diseases. The microbiological quality of the water sources was performed using the heterotrophic plate count (HPC) method and Most Probable Number (MPN) technique, while standard culture methods were used for bacteria isolation. Efficacy of water disinfection using 1% NaOCl was also assessed. The results obtained indicated that the water quality of the boreholes was poor over the study period. Indicator organisms which include typical coliforms and fecal coliforms were present exceeding the acceptable maximum limits prescribed by the World Health Organization and the Kenya Bureau of Standards. Heterotrophic plate Count (HPC) yielded counts as high as 5.64x104 (±1.77x104) CFU’s per milliliter and there was no significant difference among the total counts (p=0.320 at p>0.05)) from the four sampling sites. The coliforms counts were as high as 1.12x102 (±8.8x101) MPN/100ml with no significance (p=0.483 at p>0.05) among the counts from the sampling sites. Numerous organisms that are potential enteric pathogens such as Vibrio sp, Salmonella sp., Shigella sp., P. aeruginosa and E. coli were isolated from the water samples. There was high incidences of resistance to many antibiotics particularly Sulfamethoxazole (98.5%), kanamycin (95.3%) and ampicillin (87.5%). The most active antibiotics were chloramphenicol with resistance level of 45.4% and streptomycin (59.4%). All the isolates responded to disinfection by 1% NaOCl although Vibrio sp. and P. aeruginosa required double the recommended dosage. Plasmid profile studies revealed that multi-drug resistant isolates did contain plasmids varying in number from 1 to 3 and also in size ranging from 3.5 kb to 11.5 kb . There was a notable relatedness among the plasmid profiles from the isolates which might be an indication that resistance to certain antibiotics might be plasmid mediated. The study indicates that water from the studied boreholes was not suitable for human consumption and may pose a serious threat to the health of consumers and therefore calls for urgent intervention. On-site treatment of water at all ground water outlets is a viable short term solution. High levels of antibiotic resistance are of concern in the management of infections caused by these organisms. Further studies are needed to identify the sources of contamination in order to curb the negative effect of contaminated water.