Physico-Chemical And Bacteriological Quality Of Water, And Antimicrobial Susceptibility Of Pathogenic Isolates From Selected Water Sources In Samburu South

ABSTRACT

Water is the most critical resource in the Samburu District of Northern Kenya. The region has one permanent river, the Uaso Ng’iro. Use pressure by man, domestic and wild animals is high in all water sources, which include dams, laggas, and dry river bed wells. The primary objective of this study was to investigate the bacteriological and physicchemical quality of water from these sources, so as to shed some light on the causes of perpetual diarrheal diseases and their likely responses to commonly used antibiotics. Samples were collected quarterly over 1 year. During sample collection, the physicochemical conditions of water such as temperature, pH, conductivity, alkalinity, salinity and water color were recorded. A total of 207 water samples were collected and their microbial quality determined based on the most probable number (MPN) of coliforms, total plate count, feacal coliform counts and presence or absence of E. coli. To isolate water borne bacterial pathogens, samples were inoculated in to appropriate enrichment and selective media and the recovered bacteria characterized using relevant biochemical and serological tests. The pathogenic isolates were subjected to the Kirby Bauer and Epsilometer tests to determine their sensitivity to antibiotics commonly used in first line treatment of enteric infections. The color of water from most source types except boreholes and springs was not aesthetically acceptable for direct drinking. Alkalinity, pH and conductivity values in all water sources except the boreholes were within the recommended limits for potable water, set by World Health Organization (WHO) and Kenya Bureau of Standards (KBS). Dissolved oxygen was within acceptable levels while only springs had salinity levels less than 250 mg L-1 , the set limit for potable water. On the basis of total plate count 85% of the water samples were unfit for human consumption. Mean MPN was highest in dams at 643coliforms mL-1 and lowest in springs and boreholes at 35coliforms mL-1 . As such, the water from dams, rivers, springs, laggas and dry river bed wells was unfit for human consumption. However, on the basis of presence of feacal coliforms, all water sources do not meet the standards for potability. The bacterial pathogens isolated were Shigella flexineri, Shigella boydii, Aeromonas hydrophilla, and Salmonella spp. (non-typhi). Pathogenic isolates from springs and permanent rivers were mainly Klebsiella and Pseudomonas spp., considered to be of little clinical significance. Recovered S. flexineri isolates were susceptible to cefotaxime, gentamicin, ciprofloxacin and cefuroxime, but resistant to cotrimoxazole and, chloramphenicol. However some of the recovered S. flexineri isolates were resistant to ampicillin, the antibiotic recommended for treatment of dysentery. S.boydii and Aeromonas. spp. displayed complete resistance to ampicillin. S. flexineri isolates were compared using Pulsed-field gel electrophoresis with NotI restriction enzymes. Isolates resistant to ampicillin had similar pulsotypes to those susceptible to it. Although boreholes and springs had better quality water, Samburu District water did not meet the WHO and KEBS requirement for potability. Most pathogenic isolates were susceptible to commonly used antibiotics. Pulsed field gel electrophoresis revealed no genetic evidence of difference in strains, where resistance to ampicillin occurred. Water monitoring in Samburu should be carried out over a longer period of time using more rapid and discriminatory procedures. Appropriate and affordable water disinfection techniques such as boiling and filtration for the area should be designed.