Genetic relationship and correspondence of Salmonella Typhi isolated from water samples in typhoid outbreak localities with food handlers and contact by using Pulsed Field Gel Electrophoresis (PFGE)

Introduction Kelantan remains as the highest endemic area in Malaysia for typhoid cases with the incidence rate of 3.29 and 2.8 per 100,000 populations in 2008 and 2010. Salmonella Typhi is the causative pathogen of this illness which transmitted through fecal oral route, causing human is the only known reservoir for this organism. However, some typhoid cases related to contaminated water had also been reported. Objective To investigate the genetic diversity and relatedness of Salmonella Typhi isolated from water sample, and stool samples from food handlers and contacts in typhoid outbreak locality, Pasir Mas, Kelantan. Methods Nine Salmonella Typhi isolated from food handlers and contact while another one isolated from water sample were obtained from Makmal Kesihatan Awam Kota Bharu Kelantan between March to April 2013 and confirmed by biochemical test and serotyping. Pulsed field gel electrophoresis (PFGE) was performed according to CDC PulseNet Protocol and Bio-Rad CHEF MAPPER XA System. Dice Coefficient of Similarity (F value) was calculated for all isolates and a dendogram were constructed using Fingerprinting QuestTM software. The result was compared with previous data collected and interpreted according to the guidelines of Tenover et. al. (1995). Results & Discussion All nine isolates from food handlers and contacts showed similar PFGE pattern with the isolate from water sample, suggesting the disease was transmitted through water samples from well which is located in the typhoid outbreak area. Moreover, the PFGE pattern was unique and had never been found in S. Typhi previously isolated in Kelantan according to our PFGE database. Conclusion There are two possibilities of the source of the outbreak. The carriers among food handlers and contact might contaminated the water and causing the outbreak or vice versa.