Abstract
Lactococcus lactis strains, being intensely used in the dairy industry, are particularly vulnerable to members of the so-called 936 group of phages. Sanitization and disinfection using purpose-made biocidal solutions is a critical step in controlling phage contamination in such dairy processing plants. The susceptibility of 36 936 group phages to biocidal treatments was examined using 14 biocides and commercially available sanitizers. The targets of a number of these biocides were investigated by means of electron microscopic and proteomic analyses. The results from this study highlight significant variations in phage resistance to biocides among 936 phages. Furthermore, rather than possessing resistance to specific biocides or biocide types, biocide-resistant phages tend to possess a broad tolerance to multiple classes of antimicrobial compounds.
Highlights
Strains of Lactococcus lactis are among the most economically important lactic acid bacteria (LAB), being utilized in over two thirds of all commercial milk fermentations, and playing a vital role in the production of fermented products such as cheeses, buttermilk, and sour cream (Deveau et al, 2006)
An overview of the results produced by biocide exposures can be found in Figure 1, where the effect of biocides on the titer of a selection of nine representative phages has been outlined
Little variance in resistance between phages was observed upon exposure to Benzalkonium chloride (BAC) (Figure 1A), with G being the only phage exhibiting substantial resistance, suffering less than a two log reduction after 30 min exposure time
Summary
Strains of Lactococcus lactis are among the most economically important lactic acid bacteria (LAB), being utilized in over two thirds of all commercial milk fermentations, and playing a vital role in the production of fermented products such as cheeses, buttermilk, and sour cream (Deveau et al, 2006). Significant technological and procedural advances have been made in an attempt to control phage contamination These include (i) heat treatment of milk via pasteurization; (ii) high pressure treatments; (iii) the use of strain rotations and so-called direct vat starters (DVS) to prevent the Biocidal Inactivation of Lactococcus lactis Bacteriophages proliferation of phages, along with the concomitant development of phage-resistant strains for use in these rotations (Moineau, 1999); (iv) the improvement of dairy plant facilities, such as plant design optimization and the use of closed vats (Allison and Klaenhammer, 1998); and (v) the utilization of commercial chemicals for the sanitization and disinfection of plant equipment and facilities. While these strategies have been relatively effective, with complete product loss very rare (Madera et al, 2004), phage-associated fermentation issues are still a very common occurrence in dairy plants, probably because phages have adapted to overcome one or more of the imposed hurdles (Atamer et al, 2011; Mercanti et al, 2012; Murphy et al, 2014)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
