Primers for Salmonella serovar detection by polymerase chain reaction.

Salmonella serovar detection was studied by polymerase chain reaction (PCR). The primers were designed from Salmonella specific clone, A18:2 which was previously constructed and studied for genus specificity through colony hybridization. The primers were subsequently tested for specificity and sensitivity and showed that they amplified DNA fragment of all Salmonellae tested but did not amplify all isolates of non-Salmonellae tested. The amplified fragment was confirmed and increased sensitivity by nested PCR. Salmonella isolates amplified by the primers in the first round PCR were all positive in the second round. The sensitivity in the first and second round were 7 pg and 80 fg, respectively. The result indicated that the primers can be used as molecular tool for future field survey of Salmonella both in food and in clinical specimens.

Salmonella enteritidis outbreak in Thailand: study by random amplified polymorphic DNA (RAPD) analysis.

An outbreak of Salmonella enteritidis in Thailand was reported in 1990. The majority of isolates were found in chicken and human throughout the country. The continuation of a high rate of spreading which is presently continuing prompted us to investigate possible clonal involvement in the outbreak. One hundred and twenty five isolates of S. enteritidis which were isolated between 1990-1993 were clonally identified by the technique of Random Amplified Polymorphic DNA (RAPD) analysis. Eight profiles were found indicating the presence of 8 clones, designated no. 1-8. The predominant clone was profile no. 4 which was encountered in 93.6% of tested isolates while the rest of the profile comprised only 0.8-1.6%. The predominant clone was distributed mainly in isolates from chickens and humans which is suggestive that the profile no. 4 is the major clone involved in this outbreak and that chickens were the source of S. enteritidis infection. The information from the Microbiology Laboratory at Ramathibodi Hospital revealed that nearly 40% of S. enteritidis were isolated from blood specimens. This may reflect the invasiveness of S. enteritidis in Thailand. We concluded that the outbreak involved the single clone, RAPD profile no. 4 which may disperse dominantly during the epidemic.