horA-Speciric real-time PCR for detection of beer-spoilage lactic acid bacteria

Beer-spoilage bacteria have long been a problem for brewers. Among the most problematic beer spoilers are several species of the Gram-positive genera Lactobacillus and Pediococcus. Current methods of detecting and identifying these organisms are time-consuming and do not differentiate between bacteria capable of spoiling beer and benign bacteria. The horA-specific real-time polymerase chain reaction (rPCR) described here identifies beer-spoilage organisms based not on their identity, but on the presence of a gene that we show to be highly correlated with the ability of an organism to grow in beer. The horA hop-resistance gene has been shown to be associated with beer spoilage by isolates from four Lactobacillus spp. and one Pediococcus sp. We document the presence of the horA gene in one additional genus and 11 additional species, with many of these bacteria commonly found as beer spoilers. The use of horA-specific rPCR allows for a substantial reduction in the time required for detection of potential beer spoilage bacteria and efficiently discriminates between those organisms that have the horA gene (highly likely to spoil beer) and those organisms that do not have the gene (much less likely to spoil beer).