Detection of Airborne Lactococcal Bacteriophages in Cheese Manufacturing Plants

Abstract

The dairy industry adds starter bacterial cultures to heat-treated milk to control the fermentation process during the manufacture of many cheeses. These highly concentrated bacterial populations are susceptible to virulent phages that are ubiquitous in cheese factories. In this study, the dissemination of these phages by the airborne route and their presence on working surfaces were investigated in a cheese factory. Several surfaces were swabbed, and five air samplers (polytetrafluoroethylene filter, polycarbonate filter, BioSampler, Coriolis cyclone sampler, and NIOSH two-stage cyclone bioaerosol personal sampler) were tested. Samples were then analyzed for the presence of two Lactococcus lactis phage groups (936 and c2), and quantification was done by quantitative PCR (qPCR). Both lactococcal phage groups were found on most swabbed surfaces, while airborne phages were detected at concentrations of at least 10 3 genomes/m 3 of air. The NIOSH sampler had the highest rate of air samples with detectable levels of lactococcal phages. This study demonstrates that virulent phages can circulate through the air and that they are ubiquitous in cheese manufacturing facilities.

Characterization of Bioaerosols from Dairy Barns: Reconstructing the Puzzle of Occupational Respiratory Diseases by Using Molecular Approaches

“…Airborne dust was sampled at one site each from 13 Holstein dairy barns (eastern Quebec, Canada). Three different air samplers were used, namely, the Institute of Occupational Medicine cassettes (SKC, Ancaster, ON, Canada) or IOM samplers, loaded with 25-mm-diameter gelatin membranes (SKC) and plugged into a Giliar-5 pump (Levitt-Sécurité Limitée, Dorval, QC, Canada), at 2 liters/min (50% cutoff size of 4.0 m); the Coriolis (Bertin Technologies, Montigny-le-Bretonneux, France), which collects 100% of the particles of 4.4 m, at 100 liters/min and loaded with 15 ml of 0.9% saline solution; and the NIOSH two-stage bioaerosol cyclone (BC 251) sampler (31,42), plugged into an AirCon-2 pump (Gilian) and sampling at 10 liters/min for particulate size separation. The size distribution for each stage (50% cutoff size) of the NIOSH sampler was as follows: 2.1 m for the first stage and 0.41 m for the second stage.…”

Lactic Acid Bacteria Resistance to Bacteriophage and Prevention Techniques to Lower Phage Contamination in Dairy Fermentation

“…Phage aerolization can occur during air displacements around contaminated places (fluids or surfaces) or by liquid splashes. Virulent phages can circulate through the air far away from their aerosolization source due to the ability to bind to small particles (< 2.1 µm) [118]. Taking into account high levels of phages detected in the air, it is hard to precisely determine whether phage propagation already took place or if it is likely to occur.…”

“…Also, the formation of biofilms on dairy equipment can lead to serious phage problems. Moreover, phages were detected at high levels on various equipments and objects found in cheese plants, such as walls, pipes, door handles, floors, office tables and even on cleaning materials [118]. Raw milk handling, cheese milk processed in open vats and whey handling can lead to spreading of phages in the air.…”

Bacteriophages in Dairy Industry: PCR Methods as Valuable Tools

“…casei/paracasei). The technique has been adapted to detect phages in milk samples (Binetti et al, 2005;Dupont et al, 2005;del Río et al, 2007), in cheese whey (Brüssow et al, 1994;Labrie and Moineau, 2000), in the equipment within the factory (Verreault et al, 2011, Kleppen et al, 2011 or even from air samples (Verrault et al, 2011) with a detection limit of 10 3 -10 4 phage particles per milliliter. S. thermophilus bacteriophages have been identified in industry milk fermentation samples as yogurt and cheese whey, after phage DNA extraction and subsequent PCR (Brüssow et al, 1994) or by direct PCR of milk (Binetti et al, 2005;Dupont et al, 2005, del Río et al, 2007.…”

“…Additionally, the use of different fluorochromes enables the identification of multiple bacteriophage species in the same reaction Martín et al, 2008;Verreault et al, 2011).…”