POSSIBLE USE OF A POLYMERASE CHAIN-REACTION METHOD FOR SPECIFIC DETECTION OF SALMONELLA IN BEEF

A rapid and sensitive polymerase chain reaction (PCR) method for the d etection of Salmonella isolates with different serotypes is described. Based on the DNA sequence of a cloned 1.8 kb HindIII DNA fragment whi ch could hybridize with all the Salmonella isolates tested but not wit h any of the non-Salmonella isolates including Enterobacteriaceae clos ely related to Salmonella, oligonucleotide fragments ranging from 18- to 26-mer were synthesized and tested for their possible use as the PC R primers. Results showed that three oligonucleotides, called TS11, TS 4 and TSS could be used in pairs of TS11/TS4 and TS11/TS5 for the PCR detection of salmonellae with various serotypes. Under the conditions described, non-Salmonella isolates did not generate any false positive results. For primers TS11/TS4, the molecular weight of the PCR produc t amplified with Salmonella DNA was 1179 bp while for primers TS11/TS5 , the molecular weight amplified was 375 bp. Primer TS5 could also be used as a checking probe to identify the PCR product amplified from pr imers TS11/TS4. Study of the detection sensitivity showed that DNA fro m N x 10(0) or N x 10(1) cells of Salmonella could be detected unambig uously either with primers TS11/TS5 or with primers TS11/TS4. When the se PCR primers were used for the detection of salmonellae in beef, N x 10(0)-N x 10(1) cells per gram of beef could be detected and the endo genously contaminated microflora in the food sample did not interfere with the detection.