Relationship Between Microbial and Physico-Chemical Pollutants and Reistance of Water-Borne Diarrhoea-Related Bacteria Against Antibiotics in Thiba River Basin, Kenya
Njagi, Muturi Stephen
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Bacteria-related water-borne diarrhoea is amongst major cause of illness and death to children under five years in developing countries. Reports by health workers in Thiba river basin indicate that this diarrhoea and levels of resistance of the bacteria causing it against the commonly used antibiotics to treat it are on increase. This study was to isolate and identify the bacteria responsible for water-borne diarrhoea in Thiba river basin and to determine the levels of their resistance against commonly used antibiotics. Also the levels of microbial and physico-chemical pollutants of Thiba river basin water and rain water; and their relationship with the antimicrobial resistance of the bacteria causing water-borne diarrhoea against the commonly used antibiotics in this region were to be determined. A total of 168 water samples were obtained, distributed uniformly in upper, middle and lower zones within Thiba river basin in September 2016 during dry season and in October 2016 during wet season. Rain water samples were also taken as control. Entero-pathogenic bacteria causing water-borne diarrhoea were isolated by use of Membrane Filter Technique (MFT) and selective media. Vitek 2 System: 07.01 test and other biochemical tests were used to identify the species, which were enumerated using the most probable number (MPN). Kirby-Bauer Disc Technique was used to determine antimicrobial susceptibility. The mean levels of physico-chemical pollutants were measured using different methods. Total suspended solids were measured using glass-fibre filters; total nitrogen and total phosphorus using persulfate in acid and heavy metal ions (Cd2+, Cu2+, Zn2+ and Cr3+) using flame atomic absorption spectrometry. Microbial contaminants’ levels were estimated using the most probable number (MPN) of coliforms and pathogenic E. coli bacteria. Of the total 168 samples analysed, 143 samples were detected with at least pathogenic bacteria. Those identified were Salmonella paratyphi, Pseudomonas aeruginosa, Salmonella enteritidis, Shigella flexineri, Klebsiella pneumonia, Enterobacter liquefaciens, Proteus mirabilis and Escherichia coli. Salmonella spp., Pseudomonas aeruginosa, Shigella flexineri and E. coli were resistant to erythromycin, with Salmonella showing the highest resistance; while Klebsiella pneumoniae and Shigella flexineri were resistant to methicillin. Of the bacteria tested, 75 % showed moderate sensitivity to minocycline, cotrimoxazole, chloramphenicol, ampicillin, ciprofloxacin, metronidazole and lincomycin antibiotics, with highest sensitivity during dry season. Student’s T-test and Single-factor ANOVA statistical tests showed no significance difference on mean values of levels of these microbial and physico-chemical pollutants in the Thiba river basin water across the sampled zones and within the two seasons at p=0.05. However, the mean values of these pollutants were found to be significant as they were higher than those admissible by World Health Organisation, except for Cu2+. Positive correlation was established between the increased levels of physico-chemical pollutants and increased resistance of the pathogenic bacteria causing water-borne diarrhoea against commonly used antibiotics in Thiba river basin using Pearson’s Correlation Coefficient and Bivalent Regression (R2=0.58) tests. Therefore, the study showed that the Thiba river basin river water had significant levels of water-borne bacteria pathogens, with 53 % of them showing some resistance against commonly used antibiotics for treatment of the diarrhoea they cause to the basin residents living there. It also found some modulating effect of the Thiba river water contaminants on bacteria antimicrobial resistance, as increase in pollutants increased bacteria resistance against the antibiotics. The national government and county governments of Embu and Kirinyaga should have constant surveillance of microbial resistance of bacteria causing water-borne diarrhoea for prompt treatment. In addition, there should be improvement of sanitation of Thiba river basin water and beyond.