The formation of biofilms in dairy processing plants can reduce equipment efficiency, contribute to surface deterioration, and contaminate dairy products by releasing the microorganisms they contain, which may cause spoilage or disease. However, a more representative identification of microbial communities and physico-chemical characterization requires to detach and recover adequately the entire biofilm from the surface. The aim of this study is to develop an efficient technique for in-plant biofilm sampling by growing a strain of Pseudomonas azotoformans PFl1A on stainless-steel surface in a dynamic CDC biofilm reactor system using tryptic soy broth (TSB) and milk as growth media. Different techniques, namely, swabbing, scraping, sonic brushing, synthetic sponge, and sonicating synthetic sponge were used and the results were compared to a standard ASTM International method using ultrasonication. Their efficiencies were evaluated by cells enumeration and scanning electron microscopy. The maximum total viable counts of 8.65 ± 0.06, 8.75 ± 0.08, and 8.71 ± 0.09 log CFU/cm2 were obtained in TSB medium using scraping, synthetic sponge, and sonicating synthetic sponge, respectively, which showed no statistically significant differences with the standard method, ultrasonication (8.74 ± 0.02 log CFU/cm2). However, a significantly (p < 0.05) lower cell recovery of 8.57 ± 0.10 and 8.60 ± 0.00 log CFU/cm2 compared to ultrasonication were achieved for swabbing and sonic brushing, respectively. Furthermore, scanning electron microscopy showed an effective removal of biofilms by sonic brushing, synthetic sponge, and sonicating synthetic sponge; However, only the latter two methods guaranteed a superior release of bacterial biofilm into suspension. Nevertheless, a combination of sonication and synthetic sponge ensured dislodging of sessile cells from surface crevices. The results suggest that a sonicating synthetic sponge could be a promising method for biofilm recovery in processing plants, which can be practically used in the dairy industries as an alternative to ultrasonication.

The aim of this study was to evaluate the ability of microorganisms isolated from the dairy industry to form biofilms and to investigate the efficacity of organic peroxyacids (peracetic, perpropionic and perlactic acids and BioDestroy®) to eradicate those biofilms. Eighteen microorganisms were isolated from Quebec dairy processing plants that have issues associated with biofilm formation and were presumptively identified by MALDI-TOF mass spectrometry. The single-species biofilm-producing ability of the isolates was then evaluated using 96-well microplates. Eight out of eighteen (8/18) of these isolates were identified as moderate or strong biofilm producers, and ten out of eighteen (10/18) resulted as negative or weak biofilm producers. The efficacy of above-mentioned disinfectants was tested on the stronger biofilm producing bacteria using the MBEC (Minimum Biofilm Eradication Concentration) assay. After 5 min, all the disinfectants tested successfully eradicated both the single and mixed biofilms when applied following the recommended concentration. However, the efficacy of organic peroxyacids was significantly variable at lower concentrations. For example, 25 ppm of BioDestroy® were sufficient to eradicate all the biofilms, except for Pseudomonas azotoformans PFl1A. Unfortunately, microscopic observations highlighted those dead cells were still attached to the surfaces. In conclusion, our results suggest that some microorganisms found in dairy plants can produce tenacious biofilms that are, however, still susceptible to disinfectants, including organic peroxyacids. Further studies would be needed in order to confirm these observations using a dynamic method to mimic in vivo conditions. IMPORTANCE Biofilm forming microorganisms are a major issue in the food industry, including dairy industry, because of their negative impact on products quality. Biofilms are difficult to remove by clean-in-place (CIP) procedures commonly used in processing plants and may be less sensitive to sanitizers. Therefore, it is important to identify these microorganisms, in order to develop biofilm control strategies. The results gathered in the present study could contribute to this aim, even though it was carried out using only static methods.

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<p>The ability of microorganisms to form biofilms has become a major problem in the dairy industry in Canada, notably by affecting the quality and the safety of the by-products. Established biofilms are difficult to remove during the CIP cleaning system and may become resistant to sanitizers. Therefore, it is important to identify and characterize the microorganisms associated to biofilm in the Canadian dairy industry, allowing to develop improvement strategies of biofilm control. The purpose of this study is to evaluate the ability to form biofilms by spoilage microorganisms isolated in processing plants in Canada. For this purpose, 19 strains were isolated from problems associated with the formation of biofilms in the dairy industry and identified using a MALDI-TOF mass spectrometer. The single species biofilm production of these isolates was then measured after a crystal violet coloration using 96-well microplates. The results revealed different biofilm formation profiles depending of the isolates in culture medium. Indeed, 7/19 isolates are moderate or strong biofilm producers and 12/19 isolates are negative or weak biofilm producers. Furthermore, enzymatic treatments revealed that the composition of the biofilms was different depending of the species but also the isolates. In conclusion, the results suggest that some of the isolates collected in the dairy industry have the ability to produce moderate or strong biofilms and thus, to facilitate the persistence of other spoilage microorganisms but also potential pathogenic microorganisms such as <em>Listeria monocytogene</em>s. The characterization of those biofilms will be helpful to the development of an effective approach allowing a better control of the biofilms in the dairy industry.</p>

<p>The presence of biofilms on stainless steel surfaces in the dairy industry greatly limits the efficiency of the cleaning procedures. The matrix of extracellular polymeric substances produced by the embedded bacteria is largely responsible for this irreversible binding. Therefore, to detach the biofilm in its entirety from the surface for microbiological identification and physico-chemical characterization is limited with the classical methods commonly used for surface sampling such as swabbing. The objective of this study is to optimize an extraction technique of biofilm formed using a dynamic CDC bioreactor system by a strain of <em>Pseudomonas fluorescens</em> isolated from the dairy industry during a biofilm issue. Three methods: swabbing, scraping and sonic brushing were tested in order to determine which one of these techniques allows a better recovery of the biofilm. They were also compared to sonication which is the standard method established by ASTM International. The results demonstrated that the total viable counts obtained by scraping (8.65 ± 0.07 CFU/cm2) were not significantly different from those achieved by sonication (8.74 ± 0.06 CFU/cm2) in contrast to the other two approaches, while scanning electron microscopy showed an effective removal of biofilms from surfaces by sonic brushing. In conclusion, other combinations including brushing, sonication and/or scraping must be investigated for representative sampling of biofilm on the surfaces of dairy plants.</p>