Detection of the pediocin gene pedA in strains from human faeces by real-time PCR and characterization of Pediococcus acidilactici UVA1

The newly isolated strain UVA1 was identified as a Pediococcus acidilactici by carbohydrate fermentation profile, growth at 50°C and 16S rDNA sequencing. The partially purified bacteriocin was heat resistant up to 100°C, active over a wide range of pH (2 to 9) and susceptible to proteolytic enzymes. The molecular weight, estimated by SDS-PAGE, was similar to that of pediocin AcH/PA-1 (4.5 kDa). P. acidilactici UVA1 harboured a 9.5-kb plasmid that could be cured easily, which resulted in the loss of the antimicrobial activity. Southern hybridization using the DIG-labelled pedA-probe established that the bacteriocin gene was plasmid-borne as for all pediocin described so far. Nucleotide sequence of the whole operon (3.5 kb) showed almost 100 % similarity to the pediocin AcH/PA-1 operon. The mRNA transcript for pedA could be detected in P. acidilactici UVA1 but not in the cured derivative, confirming the expression of the pedA-gene in UVA1. Using a new real-time PCR assay, eleven out of seventeen human faecal samples tested were found to contain pedA-DNA.We identified and characterised the first pediocin produced by a human intestinal Pediococcus acidilactici isolate and successfully developed a new real-time PCR assay to show the large distribution of pedA-containing strains in baby faecal samples.The lactic acid bacteria are an inhomogeneous group which includes among others the genera Pediococcus, Enterococcus, Lactococcus, Lactobacillus and Streptococcus. Among the Pediococcus group, P. acidilactici and P. pentosaceus are widely used for fermentation of food products like vegetable and meat products. By production of organic acids, resulting in pH decrease, they contribute to control the microbial succession during fermentation. They also act as protective cultures preventing the growth of food-borne pathogens such as Listeria monocytogenes or Staphylococcus aureus [1] and by doing this, they extend storage life and enhance safety of food products [2,3]. Beside pro