Isolation, Identification And Antimicrobial Testing Of Salmonella Typhi From Water And Food Samples In Mwea Region, Kirinyaga County, Kenya..

ABSTRACT

Typhoid fever is a major cause of human mortality throughout large areas of the world. Human typhoid occurs following the ingestion of the Salmonella typhi bacteria, mostly found in contaminated water, animal products or close association with an infected individual. This study aimed to investigate the major factors contributing to the persistent attacks by typhoid fever among people of Mwea region. In addition, the study also aimed at investigating the microbial load of the water and food samples, resistance pattern of Salmonella typhi isolates and identification of Salmonella typhi serotype isolated from foods (cow milk, raw cow’s offals, mango peelings) and water samples in Mwea. To identify factors that predispose people of Mwea to typhoid fever, a questionnaire was used. Twenty five grams of food sample (offal and mango peelings) was weighed and put in a blender with 75 ml of sterile distilled water for 2 minutes. This mixture became a 10-1 dilution. Aseptically, 1 ml of the mixture was put in a tube having 9 ml of diluents.This mixture was labeled 10-2 dilution. Further dilutions were achieved by putting 1 ml of the succeeding dilutions in tubes containing 9 ml diluent to realize ten-fold dilutions. Inoculation was done in Selenite F broth and then incubated at 37 0C for 24 h. Hundred milliliters of each of the samples of milk, river and paddy rice plot water, was filtered using membrane filters of pore size 0.45 μm, 47 mm diameter. The filters were placed in Selenite F broth for selective enrichment and further put in an incubator at 37 0C for 24 h. The cultures were then streaked on XLD (xylose lysine deoxycholate) agar and Salmonella - Shigella agar. Pure isolates of these colonies were confirmed by biochemical tests. Serotyping of the confirmed Salmonella isolates was done using slide agglutination tests. Colonies on nutrient agar were counted using colony counter technique and the plates having 30 to 300 colonies were recorded. Antibiotic susceptibility tests were performed based on Kirby Bauer disc diffusion method done on Mueller – Hinton agar. Sampling took a period of four months. Analysis of the results was done using Chi-square test which was used to determine the association between predisposing factors and cases of typhoid fever, Analysis of variance (ANOVA) at 5% confidence level was used to compare the means of the results of sample analysis and all numeric analysis for the total plate count was made using arcsine logarithm bacterial count values in Excel spreadsheet. Ages of the respondents, level of education, occupation, kitchen and personal hygiene, hand washing practices, method of human and animal waste disposal, presence of blocked sewage system in the area, sources of water and water treatment method were significantly associated with transmission of Salmonella typhi while method of food storage and disposal of used water did not influence transmission of Salmonella typhi. The food and water samples that tested positive for Salmonella typhi in Mwea region were actually contaminated with the pathogen. Salmonella typhi isolates in Mwea were sensitive to Chloramphenicol, ceftriaxone, ampicillin, Co-trimoxazole and ciprofloxacin. However they were highly resistant nalidixic acid. Officers from the department of public health in Kirinyaga County should sensitize residents of Mwea on the need of maintaining high hygiene levels coupled with provision of safe drinking water by the water company so as to prevent a typhoid fever outbreak in the area.