Epidemiology and antibiotic susceptibility of Vibrio cholerae associated with the 2017 outbreak in Kasese district, Uganda

Abstract

Background: Uganda is among the 51 countries where cholera outbreaks are common with epidemics occurring predominantly along the western border with Democratic Republic of Congo (DRC), Kampala city slums, Busia district which is a border town with Western Kenya, Mbale district and the Karamoja Sub-region. This report summarizes findings from the epidemiologic investigation, which aimed at identifying the mode of transmission and antibiotic susceptibility patterns of the Vibrio cholerae isolated in Kasese district, Uganda. Methods: A descriptive cross-sectional study was carried out between 2017 and 2018 to describe the epidemiology of the cholera epidemic in Kasese district, Uganda. Rectal swabs were collected from 69 suspected case-persons and cultured on Thiosulphate-Citrate-Bile-Salts Sucrose (TCBS™; SEIKEN Japan) agar and incubated at 37 °C for 18– 24 h. The isolates were serotyped with polyvalent 01 antiserum and monovalent serotype Inaba and Ogawa antisera (Denka Seiken, Tokyo, Japan) to determine which serotype was responsible for the outbreak. Antimicrobial susceptibility testing was performed using the Kirby-Bauer disk diffusion method on Mueller-Hinton agar. A list of discharged patients was obtained from the isolation units of Bwera hospital and Kagando hospital and the individuals were followed to the community where they live. Questionnaires were administered to a total of 75 participants who were either the cases or relatives to the case. GPS points of the homes of the cases and pictures of potential source infection were also taken and cases were mapped. Results: A total of 222 cases were recorded in the Kasese District outbreak between the month of September 2017 and January 2018 with the case fatality rate (CFR) of 1.4%. Children below the age of 14 years contributed the biggest proportion of the cases (70%) and out of these, 33% were aged below 5 years. Culture isolated 69 V. cholerae 01 serotype Inaba from the total of 71 samples. Salmonella typhi was Isolated from the other two samples which were negative for V. cholerae. Antibiotic susceptibility using Kirby-Bauer disc diffusion method was done on isolates from 69 participants and showed 100% resistance to Ampicillin and over 50% were resistant to trimethoprim/Sulfamethoxazole whereas gentamicin showed 100% susceptibility. Environmental assessment revealed rampant cases of open defecation. Conclusion: Though we did not culture water to confirm contamination with Vibrio cholerae, we hypothesize that the cholera epidemic in Kasese 2017 was sparked off by consumption of contaminated water following the heavy floods that washed away latrines into water sources in Bwera, Isango and Nakiyumbu sub-counties. V. cholerae was also highly resistant to the commonly used antibiotics.