Food Microbiology

Statement of the Problem: The genus Salmonella continues to be a major health issue. In Europe, more than 90000 of salmonellosis cases were confirmed in 2015 (1.9% increase respect to 2014), being serovar Enteritidis and Typhimurium the most prevalent ones, representing 45.7% and 15.8%. Conventional culture methods are lengthy and time-consuming, for this reason, the development of new methods that allow early detection of these pathogens is of high interest. Molecular methods have the ability of overcoming the previous limitations, being DNA amplification techniques the most attractive approach. In this sense, in recent years isothermal DNA amplification techniques have gained a lot of interest over other more stablished techniques, such as PCR/ qPCR, as providing several added-on advantages (no need of expensive equipment, many alternatives for product detection, etc.) One of these techniques with increase interest is loop-mediated isothermal amplification (LAMP).

 

Methodology: A selection of the most appropriate genetic targets was done, based on previously published studies, being selected invA for Salmonella spp. detection, STM4497 and safA for Typhimurium and Enteritidis serotyping respectively. Specificity and sensitivity assays were accomplished to ensure correct performance, and finally were implemented as the detection strategy after a simple pre-enrichment and DNA extraction. These new methods were compared against qPCR.

 

Findings: The newly designed assays performed excellent in terms of specificity, but presented lower sensitivity than qPCR. This problem was overcome with a pre-enrichment step. The evaluation of the performance of the assays in spiked food samples (turkey, chicken and egg) indicated that they may be implemented in routine food-testing. Conclusion & Significance: The developed methodology is suitable for routine food analysis, and may be used, either in a sequential mode or for directly assessing the presence of a specific serovar. LAMP represents a valid alternative to conventional DNA amplification techniques, and will allow costs reduction.