Possible use of a polymerase chain reaction method for specific detection of Salmonella in beef

Abstract

A rapid and sensitive polymerase chain reaction (PCR) method for the detection of Salmonella isolates with different serotypes is described. Based on the DNA sequence of a cloned 1.8 kb HindIII DNA fragment which could hybridize with all the Salmonella isolates tested but not with any of the non- Salmonella isolates including Enterobacteriaceae closely related to Salmonella, oligonucleotide fragments ranging from 18- to 26-mer were synthesized and tested for their possible use as the PCR primers. Results showed that three oligonucleotides, called TS11, TS4 and TS5 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 product 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 primers TS11/TS4. Study of the detection sensitivity showed that DNA from N × 10 0 or N × 10 1 cells of Salmonella could be detected unambiguously either with primers TS11/TS5 or with primers TS11/TS4. When these PCR primers were used for the detection of salmonellae in beef, N × 10 0∼N × 10 1 cells per gram of beef could be detected and the endogenously contaminated microflora in the food sample did not interfere with the detection.