Development and validation of a quantitative real-time PCR assay for the detection of Leuconostoc carnosum in meat products

The lactic acid bacterium Leuconostoc carnosum is a noteworthy spoilage organism in the context of the food industry, given its prevalence in meat products. Furthermore, there is also evidence that L. carnosum may have a key role in salt- and nitrite-reduced product formulations. At present, there do not exist any selective culture methods for L. carnosum , and only a limited number of publications are available on molecular diagnostic detection methods. Therefore, in this study a real-time PCR assay was developed and validated for the purpose of tracking the exact growth behaviour at species level of L. carnosum in meat products. The quantitative polymerase chain reaction (qPCR) method based on the lysA gene showed a specificity of 100% when tested with bacterial strains of the target species and relevant non-target species. The detection limit in artificially contaminated cooked ham samples was 6 x 10 2 cfu/g. The newly qPCR was validated in a native sample context by determining the quantitative growth of the target species using the new qPCR and a literature-based reference qPCR. The findings show that the two methods produce similar results in terms of detection and quantification, demonstrating a close agreement between them. This study successfully implemented a TaqMan qPCR method for the detection of L. carnosum in cooked ham and is valuable for facilitating the execution of challenge tests concerning the spoilage process of salt- and nitrite-reduced meat products. This will substantially support further research in the development of effective strategies to ensure food quality and safety. • This study successfully implemented a TaqMan quantitative polymerase chain reaction (qPCR) method for detecting Leuconostoc carnosum in meat products. • The new real-time PCR method can facilitate the execution of challenge tests concerning the spoilage process of salt- and nitrite-reduced meat products. • The detection limit in artificially contaminated cooked ham samples was 6 x 10 2 cfu/g. • The new qPCR produces similar results in terms of detection and quantification compared to a literature-based reference qPCR. • The present investigation confirmed the high prevalence of L. carnosum in cooked ham.