Efficacy of Organic Peroxyacids for Eliminating Biofilm Preformed by Microorganisms Isolated from Dairy Processing Plants.

The aim of this study was to evaluate the ability of microorganisms isolated from the dairy industry to form biofilms and to investigate the efficacy 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 matrix-assisted laser desorption ionization-time of flight mass spectrometry. The single-species biofilm-producing ability of the isolates was then evaluated using 96-well microplates. Eight out of 18 of these isolates were identified as moderate or strong biofilm producers, and 10 out of 18 were negative or weak biofilm producers. The efficacy of the above-mentioned disinfectants was tested on the stronger biofilm-producing bacteria using the MBEC (minimum biofilm eradication concentration) assay. After 5 min, all 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 was 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 still susceptible to disinfectants, including organic peroxyacids. Further studies would be needed 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 the dairy industry, because of their negative impact on product 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 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.

Evaluation of the Efficacy of Organic Peroxyacids for Eradicating Dairy Biofilms Using an Approach Combining Static and Dynamic Methods.

The presence of biofilms in the dairy industry is of major concern, as they may lead to the production of unsafe and altered dairy products due to their high resistance to most clean-in-place (CIP) procedures frequently used in processing plants. Therefore, it is imperative to develop new biofilm control strategies for the dairy industry. This protocol is aimed at evaluating the efficacy of organic peroxyacids (peracetic, perpropionic, and perlactic acids and a commercial peracetic acid-based disinfectant) for eradicating dairy biofilms using a combination of static and dynamic methods. All the disinfectants were tested on the strongest biofilm-producing bacteria in either a single or a mixed biofilm using the minimum biofilm eradication concentration (MBEC) assay, a static high-throughput screening method. A contact time of 5 min with the disinfectants at the recommended concentrations successfully eradicated both the single and mixed biofilms. Studies are currently ongoing to confirm these observations using the Center for Disease Control (CDC) biofilm reactor, a dynamic method to mimic in situ conditions. This type of bioreactor enables the use of a stainless-steel surface, which constitutes most industrial equipment and surfaces. The preliminary results from the reactor appear to confirm the efficacy of organic peroxyacids against biofilms. The combined approach described in this study may be used to develop and test new biological or chemical formulations for controlling biofilms and eradicating microorganisms.

Comparative Study of Different Sampling Methods of Biofilm Formed on Stainless-Steel Surfaces in a CDC Biofilm Reactor.

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.