Influence of physiological cell stages on biofilm formation by< i> Bacillus cereus of dairy origin (original) (raw)
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African Journal of Microbiology Research, 2016
In the dairy industry, the biofilms formed by spore forming bacteria are not well characterized. Microscopic methods are crucial for the study of biofilm structural and architectural features. Here, a simple surface-associated non-submerged model combined to environmental scanning electron microscope (ESEM) imaging was used for the study of Bacillus cereus and Geobacillus spp. dairy biofilms. To evaluate the utility of this approach, non-submerged biofilms were compared to those developed in situ on stainless steel coupons introduced inside milk processing lines. Results reveal that both B. cereus and Geobacillus spp. are able to form specific biofilm characteristics on nonimmersed surfaces, notably an original dispersion style not previously described. Non-submerged biofilms in vitro are elaborate three-dimensional or extensive complex structures well resolved in ESEM and comparable to dairy biofilms in situ. The non-submerged surface-associated biofilm combined to ESEM imaging revealed a relevant model for the study of dairy biofilms.
International Journal of Food Microbiology, 2015
Biofilm formation of Bacillus cereus reference strains ATCC 14579 and ATCC 10987 and 21 undomesticated food isolates was studied on polystyrene and stainless steel as contact surfaces. For all strains, the biofilm forming capacity was significantly enhanced when in contact with stainless steel (SS) as a surface as compared to polystyrene (PS). For a selection of strains, the total CFU and spore counts in biofilms were determined and showed a good correlation between CFU counts and total biomass of these biofilms. Sporulation was favoured in the biofilm over the planktonic state. To substantiate whether iron availability could affect B. cereus biofilm formation, the free iron availability was varied in BHI by either the addition of FeCl 3 or by depletion of iron with the scavenger 2,2-Bipyridine. Addition of iron resulted in increased air-liquid interface biofilm on polystyrene but not on SS for strain ATCC 10987, while the presence of Bipyridine reduced biofilm formation for both materials. Biofilm formation was restored when excess FeCl 3 was added in combination with the scavenger. Further validation of the iron effect for all 23 strains in microtiter plate showed that fourteen strains (including ATCC10987) formed a biofilm on PS. For eight of these strains biofilm formation was enhanced in the presence of added iron and for eleven strains it was reduced when free iron was scavenged. Our results show that stainless steel as a contact material provides more favourable conditions for B. cereus biofilm formation and maturation compared to polystyrene. This effect could possibly be linked to iron availability as we show that free iron availability affects B. cereus biofilm formation.
Food Control, 2012
Microbial biofilms present in dairy farms may contaminate milk during milk harvest and transfer diseases from the environment to cows. In order to reduce biofilm formation with respect to the role of pH, a study involving the control of milk pH during long-term biofilm formation of Bacillus licheniformis NBRC 12195 and Lactobacillus paracasei subsp. paracasei NBRC 15889 on stainless steel coupons in different dilutions of skim milk (0.1%, 1.0% and 5.0%) was conducted. During long incubation at 30 C, pH decreased due to bacterial development in unadjusted samples. In pH-adjusted samples, pH was kept at around 7.0 by the addition of sterile sodium hydroxide. Biofilms formed on stainless steel coupons were daily stained by 0.1% Crystal Violet solution and assessed by the evaluation of optical density. The bacterial count of the suspensions showed that the control of pH enhanced the growth of bacteria in freefloating form. In contrast, optical densities of biofilms formed in the pH-adjusted samples were significantly lower than in the pH-unadjusted samples in all of three skim milk dilutions. Comparison of maximum OD values of adhered cells at different nutrient levels also implicated that for both tested strains, thicker biofilms were formed in milk dilutions at higher nutrient levels. These results suggested that, control of milk pH and milk residue level could significantly reduce biofilm formation of the tested bacteria.
Food Microbiology, 2014
Bacillus strains are often isolated from biofilms in the food industries. Previous works have demonstrated that sporulation could occur in biofilms, suggesting that biofilms would be a significant source of food contamination with spores. In this study, we investigated the properties of mono-species and mixed Bacillus biofilms and the ability of Bacillus strains to sporulate inside biofilms. Bacillus strains were able to form mono-species biofilms on stainless steel coupons, with up to 90% spores after a 48 h-incubation. These spores were highly resistant to cleaning but were easily transferred to agar, mimicking the crosscontamination of food, thereby suggesting that biofilms would be of particular concern due to a potential for Bacillus spore food contamination. This hypothesis was strengthened by the fact that Bacillus strains were able to form mixed biofilms with resident strains and that sporulation still occurred easily in these complex structures.
Sanitarno inženirstvo International Journal of Sanitary Engineering Research
Biofilms on food contact materials represent public health issues because they are resistant to cleaning and disinfection. This study aims to assess the Bacillus cereus biofilm formation capacity on silicone, polyethylene terephthalate, Teflon, and aluminium food contact materials. The biofilm biomass was analysed with the crystal violet assay method. We used the standard strain B. cereus CCM 2010, wild strain B. cereus 100 and spores of those two strains. The results show that both the vegetative form the bacteria and it spores form large amounts of biofilm on silicone, followed by polyethylene terephthalate, Teflon, and aluminium. More detailed analysis has shown that spores form more biomass on all materials in comparison to the vegetative form and that the standard strains form low levels of biofilm in contrast to the wild strains. Selecting proper material with the lowest biofilm formation potential can prevent or reduce food contamination and consequently increase food safety.
Italian Journal of Food Safety, 2016
In this study, biofilm formation of 64 <em>Pseudomonas fluorescens</em> strains isolated from milk, dairy products and dairy plants was compared. The strains were grown on Tryptic Soy Broth supplemented with 0.2% of glucose, on polystyrene microplates at 10 and 30°C for 48 h. In general, 57/64 <em>P. fluorescens</em> strains formed biofilm, although with great variability at both tested temperatures. Moreover, our results evidenced that the biofilm-forming ability of the strains was temperature- and strain-dependent. Interestingly, the ability of several isolates to form biofilms was associated with the low temperature after 48 h. Our findings evidenced that temperature was more important than incubation time for biofilm formation. Considering the origin of the strains, it is relevant to underline the importance of performing accurate cleaning and disinfection procedures on food processing surfaces.
Journal of Dairy Science, 2020
This study aims to characterize Bacillus subtilis complex group from raw, pasteurized, and packaged extended shelf-life (ESL) milk samples, to determine their biofilm potential and source-track the microbial contaminants to control their presence during processing. Isolates were characterized using multi-locus sequence typing (MLST) with 7 housekeeping genes. The primers used were designed from the coding regions with the highest number of polymorphic sites. The heat resistance profile indicated that all 12 isolates are psychrotolerant as well as thermophilic, with temperature ranges of 6°C to 55°C (B43, B44, B52, B54, B55, B56, B57), 6°C to 60°C (B46, B47, B48), and 15°C to 60°C (B49, B50). A general linear model 2-way repeatedmeasure ANOVA of the biofilm-forming potential of the isolates shows a statistically significant difference across the time of incubation (6, 12, 18, and 24 h). All isolates except 2 formed moderate to strong biofilms, with B44 having the most robust biofilm formation (3.14 ± 0.60). Scanning electron and confocal microscopy images reveal the strain specificity of the biofilm structure. The MLST analysis identified all isolates as belonging to either B. subtilis or Bacillus velezensis. All the isolates were novel sequence types (ST) when compared with the PubMLST database (https: / / pubmlst .org/) but showed relatedness to isolates in the raw milk that was processed. The closest ST are 96 for B. velezensis and 128 for B. subtilis, mostly isolated from soil. This study presents the significance of biofilms of thermophilic B. subtilis and B. velezensis and their possible perpetuation in the dairy processing plant. The information provided is a call for an innovative food contact surface or any other intervention that can minimize or prevent microbial adhesion in the processing plant, to prevent negative effects in ESL milk.
Biofilm formation in food industries: A food safety concern
Food Control, 2013
Foodborne diseases have always been a threat to human health. They are considered an emergent public health concern throughout the world. Many outbreaks have been found to be associated with biofilm. It is well documented that biofilm has become a problem in food industries as it renders its inhabitants resistant to antimicrobial agents and cleaning. In this review, biofilm formation in dairy, fish processing, poultry, meat, and Ready-To-Eat foods industries are discussed, as well as the biofilm forming abilities' of various microorganisms and the influence of food contact surface materials on biofilm formation. In addition, the conventional and emergent control strategies used to gain more proximity to efficiently maintain good hygiene throughout food industries is discussed.
Influence of Environmental Factors on Bacterial Biofilm Formation in the Food Industry: A Review
Postdoc Journal, 2015
Formation and development of bacterial biofilms in the food industry could be a cause of food contamination, compromising food safety and shelf-life. Among the factors modulating biofilm formation, this review will focus in conditions normally encountered by bacteria in food environments, especially in biofilm initiation and development. The effect of environmental factors (substratum, temperature, oxygen concentration, hydrodynamic effects, food matrix composition, and microbial interactions) on biofilm formation is multifaceted and, in many circumstances, their influence could be compensatory. A better knowledge of these factors would allow for a better control of biofilm formation, either by avoiding and/or eradicating biofilms or by defining adequate Hazard Analysis and Critical Control Point systems in the food industry.