Molecular subtyping of Salmonella enterica serovar paratyphi a from Southeast Asia

From 1987 to 1996, forty-two isolates of Salmonella paratyphi A were collected from Taiwan, China and other Southeast Asian countries. Pulsed-field gel electrophoresis (PFGE) was used to differentiate the genomic DNA of these isolates with four different restriction enzymes, Xba I, Not I, Spe I and Avr II. Based on the PFGE profiles obtained, Avr II allowed the most discriminatory results among these restriction endonucleases, By Avr II digestions, 42 isolates of S, paratyphi A were differentiated into three clones. The predominant clone accounted for 85.7% of the tested strains (36 in 42 isolates) and was found in many countries of Southeast Asia, Thus, S, paratyphi A appears to have limited genetic diversity in evolutionary process.