Pulsed-Field Gel Electrophoresis Analysis of Salmonella enterica serovar Typhi Isolates in the North-East Region of Peninsular Malaysia between 2002 and 2009

Aim: This study was conducted to ascertain, retrospectively, the genetic diversity and distribution of S. Typhi strains in Kelantan, isolated from patients with acute typhoid, asymptomatic carriers and environmental samples in Kelantan between the years 2002-2009.

Methodology: Two hundred and sixty individual S. Typhi isolates were characterized using pulsed-field gel electrophoresis (PFGE) using XbaI restriction enzyme, and results were interpreted according to standard guidelines.

Results: Thirty-eight pulsotypes (designated X001 to X038) and six major relatedness-clusters were found. Cluster B was predominant and accounted for 78% of the total isolates. Strains X001, X002 and X009 were found in both acute and asymptomatic subjects; and strain X023, which was found in a water sample in 2008, was also found in acute patients in 2004 and 2005. S. Typhi strains that were found in typhoid carriers were also found in acute patients.

Conclusions: These findings suggest close circulation of a few strains of S. Typhi that perpetuate the disease in the state, unlike developed countries where the high diversity of strains reported was because of immigration. Since there was no difference in the strains found between carriers and acute patients, host- rather than pathogen-factors were likely to be associated with development of the typhoid carrier state. The finding of S. Typhi in both the environment and acute typhoid patients indicate the resilience of the pathogen and the need to improve water sanitation in order to control the transmission of the disease in this state.