Bacterial Biofilms on Food Contact Surfaces - a Review

134

Microbial contamination in food processing plants can play a fundamental role in food quality and safety. In this study, the microbiota in a dairy plant was studied by both 16S rRNA-and 26S rRNA-based culture-independent high-throughput amplicon sequencing. Environmental samples from surfaces and tools were studied along with the different types of cheese produced in the same plant. The microbiota of environmental swabs was very complex, including more than 200 operational taxonomic units with extremely variable relative abundances (0.01 to 99%) depending on the species and sample. A core microbiota shared by 70% of the samples indicated a coexistence of lactic acid bacteria with a remarkable level of Streptococcus thermophilus and possible spoilage-associated bacteria, including Pseudomonas, Acinetobacter, and Psychrobacter, with a relative abundance above 50%. The most abundant yeasts were Kluyveromyces marxianus, Yamadazyma triangularis, Trichosporon faecale, and Debaryomyces hansenii. Beta-diversity analyses showed a clear separation of environmental and cheese samples based on both yeast and bacterial community structure. In addition, predicted metagenomes also indicated differential distribution of metabolic pathways between the two categories of samples. Cooccurrence and coexclusion pattern analyses indicated that the occurrence of potential spoilers was excluded by lactic acid bacteria. In addition, their persistence in the environment can be helpful to counter the development of potential spoilers that may contaminate the cheeses, with possible negative effects on their microbiological quality. Cheese manufacture and ripening are affected by the metabolic activity of different types of microorganisms. When milk of optimal hygienic quality is used, the dairy microbial consortia can be simple when starter cultures are employed, or a higher degree of complexity can occur in the case of natural fermentations. The environmental microbiota from the processing plant has been often addressed as a source of microbes that may play a role in the cheese making (1-4). When lactic acid bacteria (LAB) are included in the environmental microbiota, they may actively contribute to fermentation and ripening of cheese. Conversely, when potential spoilage organisms contaminate the environment, these organisms can play a crucial role because they can be transferred from the environment to intermediates of production and may negatively affect the cheese production process and the quality of the final products. It has been demonstrated that the microbial populations involved in fermentation and ripening are often found on the processing surfaces (1, 3, 5, 6), highlighting the importance of the plant environment in potentially contributing to the microbiota of cheese. Depending on the nature of the microorganisms, the environmental microbiota can exert functional activities important for the fermentative and/or the ripening process but sometimes may also be a hazard for cheese quality and safety (7).The study of the microbial e...

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Coexistence of Lactic Acid Bacteria and Potential Spoilage Microbiota in a Dairy Processing Environment

Stellato

Filippis

Storia

et al. 2015

134

“…In particular, Pseudomonas spp. are recognized as able to form biofilms (36,(42)(43)(44), adhering to surfaces and improving their resistance to sanitation and cleaning procedures (20,45,46).…”

Section: Discussionmentioning

confidence: 99%

Overlap of Spoilage-Associated Microbiota between Meat and the Meat Processing Environment in Small-Scale and Large-Scale Retail Distributions

Stellato

Storia

Filippis

et al. 2016

146

Microbial contamination in food processing plants can play a fundamental role in food quality and safety. The aims of this study were to learn more about the possible influence of the meat processing environment on initial fresh meat contamination and to investigate the differences between small-scale retail distribution (SD) and large-scale retail distribution (LD) facilities. Samples were collected from butcheries (n ‫؍‬ 20), including LD (n ‫؍‬ 10) and SD (n ‫؍‬ 10) facilities, over two sampling campaigns. Samples included fresh beef and pork cuts and swab samples from the knife, the chopping board, and the butcher's hand. The microbiota of both meat samples and environmental swabs were very complex, including more than 800 operational taxonomic units (OTUs) collapsed at the species level. The 16S rRNA sequencing analysis showed that core microbiota were shared by 80% of the samples and included Pseudomonas spp., Streptococcus spp., Brochothrix spp., Psychrobacter spp., and Acinetobacter spp. Hierarchical clustering of the samples based on the microbiota showed a certain separation between meat and environmental samples, with higher levels of Proteobacteria in meat. In particular, levels of Pseudomonas and several Enterobacteriaceae members were significantly higher in meat samples, while Brochothrix, Staphylococcus, lactic acid bacteria, and Psychrobacter prevailed in environmental swab samples. Consistent clustering was also observed when metabolic activities were considered by predictive metagenomic analysis of the samples. An increase in carbohydrate metabolism was predicted for the environmental swabs and was consistently linked to Firmicutes, while increases in pathways related to amino acid and lipid metabolism were predicted for the meat samples and were positively correlated with Proteobacteria. Our results highlighted the importance of the processing environment in contributing to the initial microbial levels of meat and clearly showed that the type of retail facility (LD or SD) did not apparently affect the contamination. IMPORTANCEThe study provides an in-depth description of the microbiota of meat and meat processing environments. It highlights the importance of the environment as a contamination source of spoilage bacteria, and it shows that the size of the retail facility does not affect the level and type of contamination. Meat is a complex niche with chemical and physical properties that allow the colonization and development of a variety of microorganisms, especially bacteria (1, 2). Several factors can influence the occurrence of microbes in meat. After slaughtering, meat can be contaminated by microorganisms from water, air, and soil, as well as from the workers and equipment involved in the processing. In the later processing steps of the fresh meat chain (i.e., handling, cutting, and storage), abiotic factors such as temperature, gaseous atmosphere, pH, and NaCl levels select for certain bacteria, allowing colonization of the meat surface by different spoilage-related species and...

“…Biofilm formation is a major cause for concern in the food system, resulting in serious operational and maintenance costs (decreasing heat transfer and operational efficacy in heat exchange equipment, causing filter plugging and blockages of tubes in water distribution systems, increasing energy consumption, and accelerating damage to surfaces) (6). Moreover, biofilms provide a reservoir of microorganisms, increasing the risk of contamination in food processing plants and leading to critical problems in terms of public health and financial losses (7).…”

mentioning

confidence: 99%

Exposure of Escherichia coli ATCC 12806 to Sublethal Concentrations of Food-Grade Biocides Influences Its Ability To Form Biofilm, Resistance to Antimicrobials, and Ultrastructure

Capita

Riesco-Peláez

Alonso-Hernando

et al. 2014

113

b Escherichia coli ATCC 12806 was exposed to increasing subinhibitory concentrations of three biocides widely used in food industry facilities: trisodium phosphate (TSP), sodium nitrite (SNI), and sodium hypochlorite (SHY). The cultures exhibited an acquired tolerance to biocides (especially to SNI and SHY) after exposure to such compounds. E. coli produced biofilms (as observed by confocal laser scanning microscopy) on polystyrene microtiter plates. Previous adaptation to SNI or SHY enhanced the formation of biofilms (with an increase in biovolume and surface coverage) both in the absence and in the presence (MIC/2) of such compounds. TSP reduced the ability of E. coli to produce biofilms. The concentration of suspended cells in the culture broth in contact with the polystyrene surfaces did not influence the biofilm structure. The increase in cell surface hydrophobicity (assessed by a test of microbial adhesion to solvents) after contact with SNI or SHY appeared to be associated with a strong capacity to form biofilms. Cultures exposed to biocides displayed a stable reduced susceptibility to a range of antibiotics (mainly aminoglycosides, cephalosporins, and quinolones) compared with cultures that were not exposed. SNI caused the greatest increase in resistances (14 antibiotics [48.3% of the total tested]) compared with TSP (1 antibiotic [3.4%]) and SHY (3 antibiotics [10.3%]). Adaptation to SHY involved changes in cell morphology (as observed by scanning electron microscopy) and ultrastructure (as observed by transmission electron microscopy) which allowed this bacterium to persist in the presence of severe SHY challenges. The findings of the present study suggest that the use of biocides at subinhibitory concentrations could represent a public health risk.