Introduction: Lactic acid bacteria (LAB), of which over 260 species have been described to date, are widely used in food fermentation to produce a variety of tasty foods. They can also have numerous health-promoting effects and effectively combat pathogens in food. A less studied group are the 21 species of the genus Weissella, although they are frequently found in fermented foods.

Objective: We aimed to isolate novel Weissella strains in order to evaluate their potential as food protecting cultures.

Results: In recent years, we have compiled a strain collection of more than one thousand LAB that were isolated from milk samples and teat canal biofilms of milk cattle. In this environment, we found 22 Weissella strains comprising six species. Binary matrices obtained from Random Amplified Polymorphic DNA (RAPD) experiments revealed that most of them could be assigned to different subspecies. However, two isolates of W. paramesenteroides and two isolates of W. thailandensis showed identical banding patterns. Eight food pathogens were selected to test how well the Weissella isolates inhibit them. The data from the spot-on-lawn tests showed that 14 of the 22 isolates had strong activity, seven had medium activity and one isolate had low activity. Among those, isolates of W. paramesenteroides were the most effective. They were also the only species that were able to produce hydrogen peroxide as an inhibiting agent. No correlation was found in relation to acid production. In summary, Streptococcus dysgalactiae, various Escherichia coli strains and Staphylococcus aureus were efficiently inhibited by almost all Weissellae, while Klebsiella pneumoniae, Streptococcus uberis, and Enterococcus faecalis were efficiently inhibited by four or less isolates.

Conclusions: The Weissella wild-type strains isolated here show a high potential for combating pathogenic bacteria in food. They will therefore be subjected to further investigations with regard to their use as starter, probiotic or protective cultures.