A helping hand in hygiene

In 2004 the Hygiene Department of the Campden & Chorleywood Food Research Association (CCFRA), based in Chipping Campden, Gloucestershire, commenced a three-year member funded research project to investigate the exposure of ready-to-eat foods to microbial contamination from contamination transfer vectors. Three ready-to-eat food factories were chosen for study – one producing cooked, sliced ham, another producing pasta for use in a ready meal and the third producing bagged salad leaf.

• The objectives of the study were:
• To identify the vectors of microbial contamination transfer
• Determine the level of contamination on selected vectors
• Quantify the transfer of contamination from the selected vectors to an agar food model
• Rank these vectors in order of importance, with regard to microbial contamination transfer.

The work also identified three key factors that could affect contamination transfer, i.e. the microbial loading of the vector, the amount of contamination transferred from the vector to the food and the exposure frequency of the food to the vector.

The Guideline should enable manufacturers to evaluate their production process, in terms of microbial contamination transfer risk, by assessing these three key factors in relation to each class of vector, and thus focus hygiene resources. This in turn could help to reduce out-of-specification product and recalls, and increase product safety and shelf-life.

This publication, together with the experience gained by the Hygiene Department during this three year project, will allow the provision of an improved CCFRA service, to support industries in the conduct of these assessments.

Current practices

Two of the surface vectors identified during the factory visits were bare hands and gloved hands. Unlike the pharmaceutical sector, which operates within specific cleanroom standards, the hand hygiene policies and facilities provided in ready-to-eat food factories vary greatly.

In the food industry it is generally accepted that, as a bare minimum, hand hygiene policies should include the washing of hands before handling food, and that the facilities provided should be specifically for hand washing, and include water, soap and a method of hand drying. However, hand hygiene policies can extend far beyond this basic requirement. For example, they may define a specific point or points at which the hands should be washed (and gloved) during preparation for entry into the food preparation area and additional occasions when the hands should be washed or gloves changed while in the production area, e.g. after a certain period of time, after wiping your nose, sneezing into your hand, scratching, or contact with 'dirty' surfaces such as the floor.

There may be a prescribed way for employees to wash their hands or a requirement for them to undergo regular hand hygiene checks, by way of hand swabbing, generally after hand washing. Some companies even monitor hand-washing activities by way of closed circuit television.

The hand hygiene facilities, their location and their usage may also vary greatly. Factories may provide hot and cold water or mixer taps to encourage hand-washing compliance through provision of water that is of a comfortable temperature. They may install knee or sensor operated taps that avoid contamination build up and transfer from taps to hands, and hot air blowers or disposable paper towels instead of fabric towels. They may locate hand-washing stations in an area segregated from the production area, so as to reduce the spread of aerosolised bacteria from the hands.

Increasingly food factories are additionally providing bactericidal soaps, gloves of different types, barrier creams and/or alcohol hand rubs in an effort to improve hand hygiene but as yet there is no common approach and no formal guidance available to the industry on gloving.

To glove or not to glove?

One of the emerging changes in approach to food factory hand hygiene is the increasing use of gloves. However, whether this change has been driven by a real or perceived improvement in hand hygiene is unclear. As part of the CCFRA research project over 100 hygiene swabs were taken from hands and gloved hands (25cm2 area swabbed per sample) in the three different ready-to-eat food factories. Rather than take samples directly after hand washing or from freshly gloved hands, samples were taken at approximately hourly intervals throughout the production periods.

The results show that the hands and gloved hands (three different types of glove sampled - nitrile, latex and rubber) of process workers in a variety of ready-to-eat food factories can be contaminated with high numbers of micro-organisms and that gloves can be more highly contaminated than hands (Table 1).

Laboratory studies, conducted by CCFRA, to quantify the transfer of microbial contamination from these vectors to an agar food model, indicate that up to 65% of test organisms (Escherichia coli K12, Staphylococcus spp. and Listeria inoccua) are transferred from glove material on contact but only around 18% are transferred from hands (see figure 1).

For each set of data, the box plot shows the median value of the data (horizontal line in each box), the interquartile range of the data (boxed area either side of the median line), the overall spread of the data (vertical lines projecting from the boxes), and outlyer data points (*).

Washed and alcohol-scrubbed hands or pieces of three different makes of glove (nitrile and latex gloves as used and supplied by two of the ready- to-eat food factories studied) were inoculated with 0.1ml of 103 ml-1 solution of the test organism. This inoculum was spread over a 25cm2 area on the palm of the hand or the surface of the glove material and then “blotted” with a nutrient agar contact plate, with slight pressure, for two seconds. Following incubation of the contact plate, the percentage of organisms transferred from the hands or glove material to the contact plate was calculated using the formula given in Equation 1:

Equation 1.

No. of organisms transferred from surface to agar/No. of organisms in original inoculation volume x 100

Based on the high microbial loading data collected from the three ready-to-eat food factories studied, and the high transfer rates, determined by the initial laboratory investigations, it may be that the use of gloves increases the gross contamination potential by a factor of 20. Consequently, rather than improving hand hygiene, gloves may actually make the situation worse and be an unnecessary additional cost to the industry.

Future studies

These findings rank hands and gloved hands highly as microbial contamination transfer vectors. This has obvious implication with regard to the maintenance of high quality and safety standards within the food industry and possibly other industries where hands and gloved hands form an integral part of the process. Consequently, CCFRA is seeking industrial and research partners to provide finance and technical expertise to allow further research, in the form of a research club, into identifying the environmental sources of micro-organisms on hands and gloved hands and investigating their growth, survival and change in levels during use.

The previous study identified that microbial cross-contamination can be dependent on at least three factors: the microbial loading of the vector, the amount of contamination transferred from the vector to the food and the exposure frequency of the food to the vector. Other factors such as surface moisture, the pressure of contact and the time of contact may also have an influence.

As shown in table 1, the microbial loading on hands and gloved hands can be high and, in spite of increasing use of automation in many industries, many products are still subject to considerable and frequent handling. Consequently, an understanding of where hand- and glove-borne organisms come from, how their numbers fluctuate under different conditions and how they are best controlled, through good hand hygiene policy and practice, is key if the transfer of micro-organisms from hands and gloved hands to product is to be restricted.

Six years ago CCFRA produced two Guidelines on hand hygiene – Hand Hygiene in the Food Industry: a review1, and Hand and Footwear Hygiene: an investigation to define best practice2. In addition to the high ranking of hands and gloved hands as microbial contamination transfer vectors, other issues with regard to hand hygiene control, e.g., the variability of hand hygiene policies, the location and style of hand washing facilities, the increased use of disposable gloves, alcohol wipes and gels, and changing ethnic and religious practices ( e.g., presence of different skin type, use of henna on hands, religious considerations with regard to the use of alcohol for hygiene practices), make it appropriate to now also review the status of hand hygiene practices.

• The project objectives would be:
• To identify the sources of micro-organisms on hands and gloves
• To investigate the growth and change in levels of micro-organisms (the relationship between deposition, growth and removal is known as flux) on hands and gloves during use
• To confirm best practice to reduce such microbial growth and flux
• To review and update the current status of hand hygiene in the food and other industries, and
• To provide guidance on the methods relating to the design, implementation, control and monitoring of hand hygiene programs in different environments.

This work would provide manufacturers with confirmation of best practice to reduce microbial contamination and growth on hands and gloves, an up-to-date review of the current status of hand hygiene in the food and other industries, and guidance on the requirement, principles and methods relating to the design, implementation, control and monitoring of hand hygiene programmes in different environments.

Interested? Then please get in touch.