Sampling Trends from the FSIS

In the Powerpoint Document released by the FSIS ("FSIS Notice 65-07") it is stated:

"During the summer of 2007, a number of unfavorable trends emerged, causing concern about E. coli 0157:H7." They are as follows:

• The percent positive rate for E. coli O157:H7 in FSIS samples of beef products has recently gone up.
  
• The number of recalls for E. coli O157:H7 went up this summer.
  
• The number of illnesses caused by E. coli O157:H7 increased this summer.
  
• Food safety assessments at establishments producing product that tested positive by FSIS for E. coli O157:H7 raised questions about the decisions establishments made in the hazard analysis.
  

It goes on to make a list of "best practices," or things that, as the document states, "are essential to controlling E. coli O157:H7." These standards however are NOT mandatory.
No wonder we have a food safety problem. We know how to prevent the bacteria, but no one requires it.

"Zone" vs. "Spot" Contamination

The probability of bacterial contamination within a given general area of a particular production facility may form the basis of QC management for that facility. This “zone theory” concept simply divides the plant (physically or theoretically) into common areas based on similar probabilities of contaminated product or equipment. Measures are typically taken to restrict movement of materials and personnel from zones of higher contamination probabilities to “clearer” zones since “dirty” materials could increase the probability of cross contamination. Each zone may be further subdivided into “sub-zones” as needed to sensibly manage the QC of that area.

Individual swipe samples, taken from a single 4-16 sq in. surface area, would typically be considered a “spot” sample within a specified zone. Multiple spot samples, taken from a pre-determined specified large area (zone), and which are later combined or pooled by the lab would qualify as “zoned” samples. This procedure is followed in some facilities in order to more cost effectively “screen” zones within the facility. Management knows that by sampling larger surface areas within a zone, the probability of discovering contamination, if present, increases proportionally. Management would consider a positive pooled sample for the microbe(s) in question to be a good indicator that the entire zone or sub-zone was contaminated. That entire area (zone or sub-zone) would then be cleaned and sanitized as needed to correct the problem. This procedure is often used to reduce laboratory costs but also because managers know that any contaminated equipment, surface or material within a sub-zone, for example, will eventually spread to other areas within that zone or possibly to other locations throughout the facility. Further, he knows that all equipment, tools or work surfaces will be cleaned whether the positive came back from an individual sample or a pooled sample.

Surface Rinse Sampling

Wet-vacuum systems are routinely used in many private and industrial situations including some food surfaces but has not been readily used to collect surface bacteria for routine analysis. Liquid rinsing of surfaces has been proposed as a more efficient method of detaching and collecting surface pathogens, although convenient recovery of the rinse solution and suspended surface particles have presented numerous challenges in the past.

Some of the benefits of a liquid rinse, wet-vacuum collection device include consistent and repeatable volumes of formulated solutions applied and retrieved under constant application and vacuum pressures. Surface area covered per sample could be limited only by the size of the collection container, therefore would allow research or QC personnel to more effectively rinse and sample a larger surface area. Since rinse application and vacuum retrieval pressures remain consistent across the entire sampling surface, harmonization possibilities between users and facility locations could be improved. The combined affects of moving liquid (with or without surfactants or other additives) and air across the sampling surface would provide a multitude of interacting forces to improve bacterial detachment during collection. Vacuum retrieval of the surface suspension of bacteria would eliminate the elution (from the sampling device) by providing a liquid sample for the lab with pathogens already in suspension. These benefits to the laboratory would be far reaching and promote more efficient analysis, faster turn around of results and decreased probabilities of false negative results.

Elution- The Impossible Task

Elution is the final step in the sampling process before detection can take place. The bacteria are removed from the sampling device and placed in solution for detection or into nutrient broth for pre-enrichment. The fibrous material of the swabs and sponges are designed to capture and retain the bacteria. This feature of the swabs and sponges leads to a significant decrease in the number of bacteria that are removed from the sampling device and put into solution for detection. A large number of pathogens remain in the sampling device reducing the overall proficiency of the sampling method. Sponges and swabs are designed to capture and retain pathogens...getting them off is no small undertaking and in fact, may be impossible.