The BAX PCR assay for screening Listeria monocytogenes targets a partial putative gene lmo2234

The BAX PCR for screening Listeria monocytogenes is a commercial PCR assay for specifically targeting L. monocytogenes, a foodborne pathogen that can contaminate a variety of foods and cause a potentially fatal disease, listeriosis, among high-risk populations. The high specificity (> 98%) of this PCR assay is achieved by targeting a species-specific genomic region (approximately 400 bp) presumably found only in L. monocytogenes. In this study, the identity of the BAX PCR-targeted genomic region was determined by using PCR cloning, DNA sequencing, and basic local alignment search tool (BLAST) analysis of the amplicon sequences of an L. monocytogenes serotype 1/2a strain. BLAST analysis identified the BAX PCR amplicon (GenBank accession no. AY364605) as a 423-bp genomic region between nucleotides 224,409 and 224,831 in the genome of L. monocytogenes (serotype 1/2a strain EGD-e), including a 145-bp noncoding region and a 278-bp partial coding sequence of a putative gene, lmo2234. The translated amino acid sequence (92 amino acids) of this partial coding region is highly conserved between L. monocytogenes and Listeria innocua (93% homology). Reverse-position-specific BLAST analysis identified a conserved domain in Lmo2234 that was similar (95.3% aligned, E value = 9E-18) to the consensus amino acid sequence of sugar phosphate isomerases/epimerases (National Center for Biotechnology Information conserved domain database accession no. COG 1082.1, IolE), indicating that Lmo2234 might be involved in bacterial carbohydrate transport and metabolism.