The Zylux Rapid Hygiene System for Measuring Cleanliness.

Ever since we became sanitarians and began to routinely perform food service inspections, we have been vexed by the question "How clean is clean?" Our careers have been punctuated by differences of opinion encountered when we cite establishments whose utensils, cookware, and work surfaces are not clean to "sight and touch." But is that standard not an aesthetic one? If the point of making inspections is to reduce the contamination levels of objects and the environment, is it our goal to ensure bacterial cleanliness, aesthetic cleanliness, or both? Those two priorities are at almost opposite ends of the spectrum in terms of their relevance to bacteria. And there are variations by degree. We generally rank levels of cleanliness as follows: The highest standard of cleanliness is "sterility required." Next comes "removal of pathogens, lowest possible level of other microorganisms," which is the definition of disinfection. Lower on the scale is the reduction of microbial numbers to levels considered "safe," or, in our parlance, sanitization; that standard is followed by aesthetic cleanliness, keeping unwanted microbes from growing, and, only last, preventing foul odors. Oh, the bane of subjectivity

Obviously, the definition of clean requires no further explanation when a surface glistens and is squeaky-dry to the touch. Or does it? At least there is absolutely no argument about the obverse side of the coin, when surfaces undulate with a bacterial mass and when emanating odors are reminiscent of a boy's high-school locker room or softripened cheese. Under those circumstances, it takes no great leap of faith to know that there is a problem. It is that gray area between the extremes for which we could never find a common ground. To complicate matters, the Food Code has given us a new paradigm of risk, with a target of hazard analysis. Therefore, not all surfaces, processes, and conditions are treated equally All this implies that sooner or later, we must embrace some objectivity in measuring degrees of cleanliness.

So we leapt at the opportunity to try a new device that quantifies, in exact terms, bacterial and other organic soiling of food contact surfaces. We now can make before-and-after comparisons and evaluate, with relative precision, the results of disinfection, sanitization, and "clean to sight and touch." In short, this field instrument helps answer the question: "How clean is clean?"

About two years ago, Biotest Diagnostics Corporation [*] became a distributor for a German import, developed by the Zylux Corporation, [**] called the Zygiene Rapid Hygiene System. We learned about it at a trade show and immediately wanted to try it out. The portable instrument and all its peripherals constitute the "Zygiene 100 Rapid Test Kit." The test is based on detection of adenosine triphosphate (ATP), which is identified by the bioluminescent light produced when ATP comes into contact with luciferin/luciferase reagents. Since ATP is found in the cells of all living things, including bacteria and meat products--to name a few--and is available once the cell wall or cell membrane is ruptured, it is an excellent and sensitive surrogate for measuring cleanliness. The kit uses this chemical principle and a sensitive light-measuring instrument with computerization to measure and document the cleanliness of any surface in a food-processing area. The purpose of the kit is to achieve and defensibly document eff ective cleaning by following the principle that if biomass is not extant on critical surfaces after cleanup, there is not enough medium for microbiological proliferation. Simply stated: no contamination, no bacterial growth.

Although the portable kit is intended for an ISO-9000 level of quality assurance, we immediately recognized its possibilities for our inspections, evaluations, and audits. We have purchased the kit and now make it an integral part of our forensic and consulting instrument complement.

The test sequence is quite simple and consists of four steps. First, spray a cleaned and dry food contact surface once with the releasing agent provided in the kit. This step does several things: It releases the ATP from somatic cells (biomass) and lyses any bacterial cells that may be present; it buffers the effects of any remaining traces of sanitizing agents; and it brings ATP up and out of cracks that otherwise would not be detected. Second, spread the releasing agent around a 2-inch-by-2-inch area with the swab provided by the kit. The swab will adsorb the applied spray containing any ATP from that area. Third, place the swab in a counting cell (in which freeze-dried counting reagents have been bonded to the inner bottom surface) and rotate three times. The ATP on the swab instantly reconstitutes the lyophilized reagent in the tube, thereby beginning the reaction. The final step is to insert the swab/tube combination into the luminometer. The measurement begins, and the reading appears both numerically and as a bar graph. "Clean" and "Dirty" indications are clearly displayed on the LCD screen. The portable unit holds up to 800 readings and automatically downloads to a desktop computer.

The kit contains an FB14 Photon Counting Luminometer, which is the heart of the system, and its battery charger, as well as one bottle of releasing agent, 10 sealed bags, each containing 10 test vials, and five containers with 20 swabs in each container. The carrying case, with its shoulder strap, is well designed as a tote and holds all equipment and supplies in an orderly and easy-to-access manner. All in all, we have found the system quite compatible with fieldwork.

The kit is an excellent teaching tool, since it can be used with real-time measurements, and it is a powerful enforcement tool, since it maintains documentation within the unit. The operating manual is clearly written, comprehensive, and well illustrated with pictures and numerous examples. It takes you stepwise through the setup and operation of the FB14 luminometer. The data capture software that comes with the kit is the Zylux Zip Version 1.25. It is IBM-compatible and uses only 8 megabytes of memory. These characteristics make it ideally suited to our portable computers, which is particularly useful since our laptops have become surrogate offices away from home. Unlike some complicated instrument interface software that we have used in the past, this one is remarkable in its simplicity. The manual that comes with the software diskettes is likewise comprehensive, easy to read, and easy to understand.

The Zygiene 100 system will detect less than 0.5 picograms of ATP from bacteria, somatic cells, or both. That number is equivalent to about 1,000 E. coli bacteria. The test reagents have a shelf life of about eight months at 4[degrees]C, and the unused, capped reagent tubes that have been removed from the bag can be stored at 4[degrees]C for later use. Replacement cost for the test reagents is considerably less than what we pay for other comparable proprietary expendables.

We would be remiss if we did not advise you about some of the nuances of data interpretation. The test readout is in relative light units (RLUs), which means the system measures luminescent units, not cells. Remember, the luminometer detects bioluminescence from ATP, a cell constituent. In searching the literature, we have found no regulatory limits on RLUs, only several admonishments to set your own limits depending on operation and use. The more we use the unit and explain its operation to our clients--and show them the "before" and "after" comparisons--the greater is our level of comfort in setting reasonable standards for how-clean-is-clean, Correlation of the ATP readings with CFUs has been attempted by various researchers, but it must be re-evaluated with each circumstance and is a complicated procedure involving filtration of the samples and differential extraction of somatic ATP and microbial ATP. In addition, there is no correlation between ATP and standard microbiological methods such as total plat e count on hard surfaces, or in any materials contaminated with other organic matter. Therefore, for our purpose, totaling the ATP readings (microbial + residue) found on a surface is the most common and reasonable approach recommended for hygiene monitoring.

The Rapid Hygiene System is not inexpensive, but it is well worth the money if your work includes validation of plant sanitation, HACCP-9000 evaluations, or training personnel in critical cleaning techniques.

(*.) Biotest Diagnostics Corporation, 66 Ford Road, Suite 131, Denville, NJ 07834. Telephone: [phone].

(**.) Zylux Corporation, 1742 Henry G. Lane Street, Marysville, TN 37801. Telephone: [phone].