The response of foodborne pathogens to osmotic and desiccation stresses in the food chain.

In combination with other strategies, hyperosmolarity and desiccation are frequently used by the food processing industry as a means to prevent bacterial proliferation, and particularly that of foodborne pathogens, in food products. However, it is increasingly observed that bacteria, including human pathogens, encode mechanisms to survive and withstand these stresses. This review provides an overview of the mechanisms employed by Salmonella spp., Shiga toxin producing E. coli, Cronobacter spp., Listeria monocytogenes and Campylobacter spp. to tolerate osmotic and desiccation stresses and identifies gaps in knowledge which need to be addressed to ensure the safety of low water activity and desiccated food products.

Survival and death kinetics of Salmonella strains at low relative humidity, attached to stainless steel surfaces.

Salmonella is a major pathogen of concern for low water activity foods and understanding its persistence in dry food processing environments is important for producing safe food. The studies sought to assess the survival of 15 isolates of Salmonella on stainless steel surfaces. Additionally, the aim was to select a suitable model to describe and understand the strains' survival kinetics. Salmonella isolates were dried onto stainless steel surfaces, placed in controlled temperature (25°C) and humidity (33%) conditions and their viability assessed at times from 1h to 30days. The highest survival rate was associated with S. Typhimurium DT104, S. Muenchen, and S. Typhimurium (NCTC 12023), where, after 30days, the reduction ranged from 1.3log10 cfu/surface to 1.6log10 cfu/surface. The lowest survival was linked to a S. Typhimurium strain used in European Standard disinfectant approval tests and S. Typhimurium isolated from whey powder. For most of the strains, following an initial reduction in viability in the first hours (<72h), no further reduction was seen over the 30day period; therefore a 2-population Weibull model was fitted to model the survival kinetics. The overall survival was neither serotype nor time related. All strains had two different subpopulations, one more resistant to desiccation than the other. The results indicate the possibility of the long term survival of Salmonella on environmental surfaces (at least 30days) and suggest the most suitable model to describe and predict survival kinetics. The results also identify strains that may be used to study stress response mechanisms and potential factory control measures in future studies.

Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 7. Barriers to reduce contamination of food by workers.

Contamination of food and individuals by food workers has been identified as an important contributing factor during foodborne illness investigations. Physical and chemical barriers to prevent microbial contamination of food are hurdles that block or reduce the transfer of pathogens to the food surface from the hands of a food worker, from other foods, or from the environment. In food service operations, direct contact of food by hands should be prevented by the use of barriers, especially when gloves are not worn. Although these barriers have been used for decades in food processing and food service operations, their effectiveness is sometimes questioned or their use may be ignored. Physical barriers include properly engineered building walls and doors to minimize the flow of outside particles and pests to food storage and food preparation areas; food shields to prevent aerosol contamination of displayed food by customers and workers; work clothing designated strictly for work (clothing worn outdoors can carry undesirable microorganisms, including pathogens from infected family members, into the work environment); and utensils such as spoons, tongs, and deli papers to prevent direct contact between hands and the food being prepared or served. Money and ready-to-eat foods should be handled as two separate operations, preferably by two workers. Chemical barriers include sanitizing solutions used to remove microorganisms (including pathogens) from objects or materials used during food production and preparation and to launder uniforms, work clothes, and soiled linens. However, laundering as normally practiced may not effectively eliminate viral pathogens.

Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 10. Alcohol-based antiseptics for hand disinfection and a comparison of their effectiveness with soaps.

Alcohol compounds are increasingly used as a substitute for hand washing in health care environments and some public places because these compounds are easy to use and do not require water or hand drying materials. However, the effectiveness of these compounds depends on how much soil (bioburden) is present on the hands. Workers in health care environments and other public places must wash their hands before using antiseptics and/or wearing gloves. However, alcohol-based antiseptics, also called rubs and sanitizers, can be very effective for rapidly destroying some pathogens by the action of the aqueous alcohol solution without the need for water or drying with towels. Alcohol-based compounds seem to be the most effective treatment against gram-negative bacteria on lightly soiled hands, but antimicrobial soaps are as good or better when hands are more heavily contaminated. Instant sanitizers have no residual effect, unlike some antimicrobial soaps that retain antimicrobial activity after the hygienic action has been completed, e.g., after hand washing. Many alcohol-based hand rubs have antimicrobial agents added to them, but each formulation must be evaluated against the target pathogens in the environment of concern before being considered for use. Wipes also are widely used for quick cleanups of hands, other body parts, and surfaces. These wipes often contain alcohol and/or antimicrobial compounds and are used for personal hygiene where water is limited. However, antiseptics and wipes are not panaceas for every situation and are less effective in the presence of more than a light soil load and against most enteric viruses.

Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 11. Use of antiseptics and sanitizers in community settings and issues of hand hygiene compliance in health care and food industries.

Hand washing with soap is a practice that has long been recognized as a major barrier to the spread of disease in food production, preparation, and service and in health care settings, including hospitals, child care centers, and elder care facilities. Many of these settings present multiple opportunities for spread of pathogens within at-risk populations, and extra vigilance must be applied. Unfortunately, hand hygiene is not always carried out effectively, and both enteric and respiratory diseases are easily spread in these environments. Where water is limited or frequent hand hygiene is required on a daily basis, such as for many patients in hospitals and astronauts in space travel, instant sanitizers or sanitary wipes are thought to be an effective way of preventing contamination and spread of organisms among coworkers and others. Most concerns regarding compliance are associated with the health care field, but the food industry also must be considered. Specific reasons for not washing hands at appropriate times are laziness, time pressure, inadequate facilities and supplies, lack of accountability, and lack of involvement by companies, managers, and workers in supporting proper hand washing. To facilitate improvements in hand hygiene, measurement of compliant and noncompliant actions is necessary before implementing any procedural changes. Training alone is not sufficient for long-lasting improvement. Multiactivity strategies also must include modification of the organization culture to encourage safe hygienic practices, motivation of employees willing to use peer pressure on noncompliant coworkers, a reward and/or penalty system, and an operational design that facilitates regular hand hygiene.

Importance of airborne contamination during dressing of beef and lamb carcasses.

Carcasses along slaughter lines were exposed to normal slaughterhouse air or ultraclean air provided from a unit fitted with a HEPA filter. In cattle slaughterhouses, aerobic viable counts were measured by sponging the brisket at the end of the line to determine whether the slaughterhouse air had led to contamination of the carcasses. Furthermore, a replica cattle carcass with settle plates attached was exposed to similar conditions. The greatest contamination of the plates occurred at the hide puller (P < 0.01). The use of ultraclean air reduced the deposition of organisms onto settle plates (P < 0.01). The airborne route contributed to contamination in cattle slaughterhouses, but other vectors were more important. Further study of contamination of the brisket, at the time that it was first exposed, showed that knives transfer contamination from the hide. The use of ultraclean air at this position showed that the airborne route was a contributor to contamination (P < 0.1), but it was not the greatest vector. In lamb slaughterhouses, the highest counts on settle plates were found at the fleece puller (P < 0.05). The highest counts on the lamb carcasses were found on the brisket exposed from the start of the line to just after the fleece puller (P < 0.05). There was no clear relationship between the measured counts and the concentration of organisms in the air, indicating that the airborne route in lamb slaughterhouses contributes less to carcass contamination than do the surface contacts.