Rapid detection of Salmonella enterica serovar Typhimurium DT104 strains by the polymerase chain reaction

Abstract

Background: Infection with Salmonella enterica is a major public health concern in developed countries, and multidrug-resistant strains have become increasingly prevalent. S. enterica serovar Typhimurium DT104 (DT104) strains are prevalent in livestock in Japan and include numerous strains of multidrug-resistant S. enterica. Epidemiological analysis of these strains is critical for both agriculture and public health; however, diagnostic tests for these strains have yielded inconsistent results.

Results: We developed a rapid, simple, and inexpensive polymerase chain reaction test to detect multi-drug resistant DT104 strains. We designed primers specific to the prophage ST104 sequence encoded by DT104 strains and assessed the specificity of these primers by assaying a panel of 50 S. enterica isolates. Amplification products of the expected size were generated from the genomes of each of the DT104 strains; however, the ST104 primers failed to amplify products from non-DT104 strains of S. enterica serovar Typhimurium or other S. enterica serovars. Furthermore, a probe generated using the ST104 primers detected a restriction fragment encoding the ST104 region of DT104 by Southern hybridization.

Conclusions: The ST104 primers exhibit specificity to DT104 strains and are suitable for epidemiological applications.

Fig. 1

Nucleotide sequence of the ST104 erf-like gene. The ST104 sequence was amplified from Salmonella enterica serovar Typhimurium DT104 by using the ST104 primers

Fig. 2

Southern blot hybridization analysis of Salmonella enterica strains. The ST104 sequence was amplified from S. enterica serovar Typhimurium DT104 with the ST104 primers and used as a probe for Southern blot analysis of S. enterica strains. A representative image of the fingerprinting pattern of DT104 after restriction digestion with XbaI is depicted in the left lane. The result of a subsequent Southern blot hybridization experiment, using the digoxigenin (DIG)-11-deoxyuridine triphosphate-labeled ST104 PCR fragment, is depicted in the right lane