The process of surface adhesion and biofilm development is a survival strategy employed by virtually all bacteria and refined over millions of years. This process is designed to anchor microorganisms in a nutritionally advantageous environment and to permit their escape to greener pastures when essential growth factors have been exhausted. Bacterial attachment to a surface can be divided into several distinct phases, including primary and reversible adhesion, secondary and irreversible adhesion, and biofilm formation. Each of these phases is ultimately controlled by the expression of one or more gene products. Ultrastructurally, the mature bacterial biofilm resembles an underwater coral reef containing pyramidal or mushroom-shaped microcolonies of organisms embedded within an extracellular glycocalyx, with channels and cavities to allow the exchange of nutrients and waste. The biofilm protects its inhabitants from predators, dehydration, biocides, and other environmental extremes while regulating population growth and diversity through primitive cell signals. From a physiological standpoint, surface-bound bacteria behave quite differently from their planktonic counterparts. Recognizing that bacteria naturally occur as surface-bound and often polymicrobic communities, the practice of performing antimicrobial susceptibility tests using pure cultures and in a planktonic growth mode should be questioned. That this model does not reflect conditions found in nature might help explain the difficulties encountered in the management and treatment of biomedical implant infections.

/pdf/bacterial-adhesion-seen-any-good-biofilms-lately-2f7wm9gh5j.pdf

Bacterial Adhesion: Seen Any Good Biofilms Lately?

Microbial adhesion to surfaces and the consequent biofilm formation has been documented in many different environments. Biofilms constitute a protected mode of growth that allows microorganisms to survival in hostile environments, being their physiology and behavior significantly different from their planktonic counterparts. In dairy industry, biofilms may be a source of recalcitrant contaminations, causing food spoilage and are possible sources of public health problems such as outbreaks of foodborne pathogens. Biofilms are difficult to eradicate due to their resistant phenotype. However, conventional cleaning and disinfection regimens may also contribute to inefficient biofilm control and to the dissemination of resistance. Consequently, new control strategies are constantly emerging with main incidence in the use of biosolutions (enzymes, phages, interspecies interactions and antimicrobial molecules from microbial origin). The present review will focus on describing the mechanisms involved in biofilm formation and behavior, deleterious effects associated with their presence, and some of the current and emergent control strategies, providing new insight of concern for food industry.

/pdf/a-review-of-current-and-emergent-biofilm-control-strategies-ivnrpyqr4q.pdf

A review of current and emergent biofilm control strategies

Cationic antimicrobials have been in general use within clinical and domestic settings for over half a century. Recently, the use of antiseptics and disinfectants has been questioned in such settings because of the possibility that chronic exposure of the environment to such agents might select for less susceptible strains towards these agents and towards third party antibiotics. Whilst no supportive evidence has emerged from retrospective field studies of high use environments such debate has tempered new applications for these molecules. In the clinic, use of antiseptics, together with products, such as dressings, catheters and sutures, which are impregnated with biocides has increased. Prominent amongst these biocides are the cationics. Much of the research pertaining to the mechanisms of action of cationic antibacterials was conducted in the 1960s and 1970s and has not been subject to extensive review. Analysis of available publications suggest that monoquaternary ammonium compounds (QAC, cetrimide, benzalkonium chloride), biquaternaries and bisbiguanides (Chlorhexidine, Barquat), and polymeric biguanides (Vantocil, Cosmocil) whilst having similarities in action mechanism, differ substantially in the nature of their interaction with cell envelopes. This has profound implications in terms of cross-resistance where changes in susceptibility towards QAC is not reflected in changes towards other cationics. This review examines action mechanisms for these agents and highlights key differences that render them distinct categories of antibacterial agent.

Cationic antiseptics: diversity of action under a common epithet.

Microorganisms on wet surfaces have the ability to aggregate, grow into microcolonies, and produce biofilm. Growth of biofilms in food processing environments leads to increased opportunity for microbial contamination of the processed product. These biofilms may contain spoilage and pathogenic microorganisms. Microorganisms within biofilms are protected from sanitizers increasing the likelihood of survival and subsequent contamination of food. This increases the risk of reduced shelf life and disease transmission. Extracellular polymeric substances associated with biofilm that are not removed by cleaning provide attachment sites for microorganisms newly arrived to the cleaned system. Biofilm formation can also cause the impairment of heat transfer and corrosion to metal surfaces. Some of the methods used to control biofilm formation include mechanical and manual cleaning, chemical cleaning and sanitation, and application of hot water.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1541-4337.2003.tb00012.x

Biofilm Formation and Control in Food Processing Facilities

Review--Persistence of Listeria monocytogenes in food industry equipment and premises.

The effectiveness of cleaning was investigated through food factory trials and laboratory experiments using a naturally occurring biofilm from a food factory environment and generated biofilms. The efficacy of factory cleaning and disinfection programmes was assessed by swabbing and total viable count (TVC) analysis of surfaces before cleaning, after cleaning and after disinfection. Cleaning produced a 0.91 log reduction in the attached population. Investigation of the effectiveness of a variety of cleaning methods in the removal of a naturally occurring food factory biofilm showed that the high pressure spray and the mechanical floor scrubber, which use a high degree of mechanical action, were most effective. Cleaning trials with biofilms of Pseudomonas aeruginosa or Staphylococcus aureus showed that spraying with water at pressures of 34.5, 51.7 and 68.9 bar did not significantly increase the removal, as assessed by direct epifluorescent microscopy (DEM) and swabbing and TVC analysis, beyond the three log reduction observed at 17.2 bar. The effect of spray time at 17.2 bar showed that increasing spray time from 1 to 10 s did not significantly increase removal of Ps. aeruginosa biofilm. Investigation of the optimum distance of the spray lance from the surface at 17.2 bar was found to be between 125 and 250 mm. The use of an alkaline, acidic or neutral detergent prior to spraying with water at 17.2 bar did not significantly increase the removal of Ps. aeruginosa or Staph. aureus. However, the acidic and alkaline products significantly (P = 0.05) affected the viability of Staph. aureus and Ps. aeruginosa, respectively, thereby minimizing the potential for the spread of contamination.

https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2672.1999.00790.x

Effectiveness of cleaning techniques used in the food industry in terms of the removal of bacterial biofilms

Aims The aims of the project were threefold: to survey the use of disinfectants in the UK food industry; to assess the product and environmental microflora of selected food factories for the persistence of Listeria monocytogenes and Escherichia coli; and to determine the disinfectant resistance of any persistent strains. Methods and results A survey of the use of disinfectants in the UK food industry was undertaken in which a total of 40 sites were visited and a further 77 postal questionnaires were returned from farms, food manufacture, food transport and food retail sites. Quaternary ammonium compounds (QACs) were predominantly used, applied in small volumes as a mist. Approximately 30,000 samples from the product and environment of five chilled food factories were examined for L. monocytogenes and E. coli over a 3 year period. A total of 181 L. monocytogenes and 176 E. coli isolates were ribotyped to yield 19 and 34 ribogroups, respectively. Some strains were isolated only from the product, a number only from the environment and others from both niches. Some strains were seen to be persistent for the duration of the sampling exercise (2-3 years). The most common L. monocytogenes and E. coli strains, together with two environmental L. monocytogenes strains, were assessed for any resistance to commercial disinfectants as compared with a laboratory L. monocytogenes disinfectant testing strain. The resistance of the L. monocytogenes and E. coli strains isolated from the factory were not significantly different from the laboratory control strain. Conclusions Persistent strains of L. monocytogenes and E. coli are found in the UK food industry, though this persistence is not related to their increased susceptibility to the most commonly used disinfectants. Significance and impact of the study The concept of a persistent microflora in food factories will have an impact on the future selection of suitable control options, including the use of biocides.

https://sfamjournals.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2672.92.5s1.18.x

Biocide use in the food industry and the disinfectant resistance of persistent strains of Listeria monocytogenes and Escherichia coli.

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Effectiveness of cleaning techniques used in the food industry in terms of the removal of bacterial biofilms

Biocide use in the food industry and the disinfectant resistance of persistent strains of Listeria monocytogenes and Escherichia coli.