Problems Related to Salmonella Contamination in Meats

292. PROBLEMS RELATED TO SALMONELLA CONTAMINATION IN MEATS

J. ti. SlLLlKER

There is no doubt that problems related to the occurrence of salmonellae in meats do exist. We have known about them for a long time. The intensification of regulatory surveillance over the presence of Salmonella in all kinds of foods has only served to bring the problems presented by meats into sharper focus.

The underlying reasons for this increased emphasis have been discussed from scores of platforms during the past year, have been the subject of innumerable articles in the scientific and trade literature, and have found their way into the popular press with alarming frequency. In view of this,it seems unnecessary to detail the events that have led to the current Salmonella emergency in the food industry. In the span of a little over 10 years we have passed from an era in which Salmonella epidemics were studied retrospectively into one in which outbreaks of diseases are often discovered while they are occurring and corrective measures can be taken. This change can hardly be looked upon as a trivial advance in public health, as it no doubt has reduced the incidence of one of man's more common afflictions.

The Salmonella emergency, to which I previously referred, vas not caused by the organized surveillance over Salmonella infections, rather it was the effect of this program that led to a drastic change in the attitude of regulatory groups, particularly the U.S. Food and Drug Administration. Up until a short time ago, the FDA characteristically took action against a particular product only after it had been discovered that the food had been the source of human illness. There was an awareness that certain products constituted potential hazards because of Salmonella contamination, but in the absence of associated disease, regulatory action was not taken. Obviously, this is no longer the policy. Currently, any product containing salmonellae is looked upon as adulterated in terms of the Food and Drug and Cosmetic Act, and accordingly it is subject to seizure whether or not hwnan illness has been traced to such contamination. The food industry is now charged with the responsibility of eliminating salmonellae from its products before they reach the marketplace. Indeed, the Salmonella group has emerged as a new indicator of wholesomeness, one which I think will, in time replace the coliform group, perhaps entirely. The legal implica- tions of this are, in themselves, quite important.

It is not my purpose to evaluate the wisdom of this change in policy, rather it is to explore the probable impact the Salmonella emergency may have on the meat processing industry. Meat products are as diverse as those of the entire food industry, If we consider, for a moment, the basic processing and merchandising practices in the food industry, it becomes obvious that meats are preserved by virtually all 293. known measures that are applied to other foods, and more often than not we depend not upon one but a combination of preservation methods. The raw material of the meat packing industry is a living animal with highly contaminated exterior surfaces but with interior tissues that are virtually sterile. From the point of slaughter the microbiology of the carcass is a study in sequential contamination. Each processing step, each preservation procedure tends to influence the microbial flora of the meat product, and as a consequence affects its stability and/or its wholesomeness,

It is manifest, then, that in discussing Salmonella problems related to meat we must segregate in each instance the type of meat product in terms of its processing history and its expected stability. We must consider the manner in which the product is merchandised and its ultimate use by the consumer.

Let us start with the raw material, the living animal. Salmonellae can be isolated from the various classes of livestock at the farm level. But the incidence is generally low, and in most cases we deal with a carrier state in the animal, as opposed to active infection. Extensive research with mine (Galton et al., 1954; Leistner et al., 1961) indicates that as the animal proceeds from the farm to the stockyards and from the holding pens to the abattoir, there is a pro- gressive increase in the incidence of Salmonella. Galton's group reported 25-90'$ of all hogs in the holding pens were positive, and fecal and ceacal swabs taken from freshly slaughtered hogs showed Salmonella in 18-80% of the samples tested. The work of Leistner and his colleagues shows a similar pattern. They found, further, the actual incidence of Salmonella in the pigs' colons could be directly related to the length of time the hogs had been held in holding pens prior to slaughter. While similar studies have not been made on other classes of livestock, it seems reasonable to postulate an increasing incidence of Salmonella in the animals as they move in the channels from the farm to the abattoir. There seems little doubt that much progress can be made toward reducing the incidence of Salmonella in the ra3.7 materials, but obviously this will require major modifications in the practices employed in transporting animals, in the design of holding pens and in the actual scheduling of livestock for slaughter in order to prevent undue exposure. But most certainly this entire matter must be classified as one of the important problems related to Salmonella in meats.

The problem of Salmonella in animals at the farm level must also be looked upon as a matter of acute concern to the meat packing industry. Fublic health workers feel strongly that Salmonella infection in livestock can be directly associated with the frequent contamination of animal feeds with salmonellae. This has been regularly attributed to the presence of rendered animal by-products as a major constituent of these feeds. It is well documented that these by-products of the meat packing industry are frequently contaminated with Salmonella. It is widely held that Salmonella maintain themselves in the livestock population through this cycle, and there is an optimistic feeling among highest echelons or public health workers that the cycle of Salmonella infection in livestock calz most easily be broken through insistence upon feeds that are free of Salmonella contamination. 294.

One may argue effectively that there are numerous sources of Salmonella infection to animals at the farm level other than feeds, and that even if feeds are completely free of contamination, the Salmonella problem in livestock still remains. It is not my purpose to argue this point, one way or another. The Federal Government has indicated that it will demand that animal feeds be free of Salmonella contamination, and at such time as this occurs we prill no doubt have a more satisfactory understanding of the importance of contaminated animal feeds in the perpetuation of Salmonella in livestock and ultimately the significance of this in terms of meat contamination.

In the meantime, the industry is charged with the responsibility of eliminating Salmonella from its rendered by-products. Con- siderable progress has been made as a result of improved sanitation, plant re-design, and the develogment of methods for the terminal destruction of Salmonella. Data from samples analyzed in my own laboratory give some idea of the improvement that has been affected already. From May, 1966, through January, 1967, we analyzed 615 samples of rendered animal by-products submitted by processors throughout the United States. Of these, 285 (46.3$) were Fositive for Salmonella. Euring the period from February, 1967, through May, 1967, we analyzed 616 samples, of which 84 (13.7s) were positive. This represents over a three-fold decrease in the incidence of positive samples. One may ask why the results from January, 1967, were included with the 1966 results. During this month 149 samples were analyzed, of which 68 (45.7%) were positive. Even an amateur statistician would conclude that this incidence for January compared more clearly with the 46.65 average for the 1966 samples than it does with the 13.7$ incidence in the remainder of 1967. It certainly appears that events during the month of January stimulated a flurry of activity that has effected the significant improvement that has been seen in the past four months.

It is perhaps inevitable that if the raw material of the packing industry is contaminated with Salmonella, so also will the fresh red meat, as it is purchased in the marketplace. Numerous studies have indicated this to be the case. For example, Wilson et al. (1961) sur- veyed 1,539 samples purchased in markets in the Cincinnati area. Salmonellae were isolated from 17% of the raw poultry, 4% of the pork, 3% of the lamb, and of the beef. In terms of the present policy of the Food and Drug Administration,14 snch food is actually subject to seizure, since it contains a deleterious agent - namely, bacteria of the genus Salmonella. In this regard, fresh meats and poultry have occupied a unique position, since they represent food from which Salmonella can be regularly isolated but against which seizure action has not been taken by the FDA. This is to be contrasted with the position of a number of European countries which regularly reject imported red meat, if salmonellae are found.

The absence of regulatory action against contaminated red meats and poultry should not be inferred as a sign of indifference on the part of public health officials. These products rank high among the foods responsible for food poisoning, in general, and salmonellosis specifically. Aside from this, it is the feeling that if a contaminated food is brought into the food preparation environment, it may serve as a source of contamination to other foods in the kitchen, even though it 295. may itself be heated to a temperature sufficient to eliminate contamination. Thus, we can look in the future to more active surveillance of Salmonella in red meats, and ultimately even to the possibility of seizure action.

It may be asked haw the processor can be held to account for the presence of Salmonella in what is actually a raw agricultural commodity, one which is contaminated at the farm level. This question becomes even more germane when one takes into account the sacred position which red meat has occupied with the agencies responsible for its production. Almost without exception, industry petitions for approval of innovations to improve quality or stability have been rejected on the basis that red meat need only be processed under sanitary condi- tions and held under adequate refrigeration and all will be well. This attitude has no doubt discouraged researchers from attempting to attack problems with the same vigor they might show in approaching solutions to difficulties with sausage, primal cured meats or canned items. In these areas a far more liberal attitude has been taken by regulatory agencies towards the fruits of research.

But the time has arrived when it is necessary to review fresh meat processing critically in terms of Salmonella control. Clearly, the problem would be easier if the incidence of Salmonella in the living animal were lower, Improvements in the microbiological quality of animal feeds may or may not improve this situation. But it will no doubt require corresponding improvement in animal husbandry on the farm, in shipment of animals, and during their holding in the yards prior to slaughter.

But it is beyond this point that I feel too little attention has been paid. One may ask whether tre have given enough consideration to the possibility of eliminating Salmonella from the surface of carcass meat before it enters the cooler. What possibilities exist for improvements in the washing procedure, for the value of in-plant chlorination, or for some other procedure which might effect a significant reduction in the level of contamination at that point where the meat has the least possible surface area in the contaminated state. Galton et al. (1954) attributed contamination of the skin of slaughtered hogs to fecal con- taminations occurring during the de-hairing process. One may ask whether careful attention has been given to re-design of the equipment used for this purpose so as to prevent the fecal oozing that generally occurs. One may ask to what degree the cooling of livers and other organs in common tanks on the killing floor may result in cross-contamination from infected to clean organs, to what degree programs to improve workmanship in the removal of the viscera might prevent the cutting of intestines which inevitably results in distribution of contaminated fecal contents over the surface of the carcass. One may ask to what degree the cutting operations could be improved so as to prevent the cross-contamination between contaminated and infected meats. In the same light, to what degree do the use of common chutes to slide meats from one depart- ment to another contribute to the overall problem of fresh meat contamination. Indeed, there are many areas in the processing of fresh meats in which improvements could be effected. No one of these would solve the overall problem, but most certainly there are many measures available, 296. short of chemical additives, antibiotics and irradiation, all of which could be expected to have desirable effects on the level of contamha- tion in the finished red meat products of the industry. The chill tank in the poultry industry receives periodic lambasting. Worse situations are found in red meat processing, but they are so numerous as to be over- looked in the overall picture.

Mention was made of the fact that meats and poultry are high on the list of foods associated with Salmonella food poisoning. If one studies the history of such outbreaks he is impressed with the fact that almost without exception the meat to which the outbreak is attributed has been a victim of the housewife's mishandling just as surely as the ultimate consumer of the product. One may wonder in what degree the current emphasis orill improve the overall problem of human salmonellosis unless consumer education in the proper handling of foods becomes a companion endeavor.

Now, let us consider cured meat products as they relate to the Salmonella problem. Fortunately, with a few exceptions, these products have not constituted an important source of human salmonellosis. For the most yart, these products are processed to temperatures sufficient to destroy salmonellae that might be present in the green product. This is true, even, of products which reach an internal temperature of only 137O F., since the process is sufficiently long to be destructive to the small nmbers of salmonellae which might contaminate the unprocessed product. However, the amount of salt and other curing ingredients which are present in these products is insufficient to be inhibitory to Salmonella. We must, therefore, attribute the relative absence of a Salmonella problem with these products to the destruction of the organisms during processing.

With respect to products such as bacon which do not receive a process sufficient to destroy Salmonella, the absence of serious outbreaks can no doubt be attributed to the common practice of adequately cooking the meat before serving.

The dry sausage products, not receiving any heat process, have likewise not been a problem, and in all probability this must be attributed to the high brine level and low pH in the finished products. As mentioned previously, most of these products contain insufficient concentrations of curing salts to be inhibitory to the growth of Salmonella, Recent studies in my laboratory have indicated that as a group the salmonellae are almost all capable of growth in the presence of as much as 7.576 brine. There have, indeed, been outbreaks of Salmonella food poisoning traced to cured meat products. In this regard, the greatest potential danger probably exists in sliced sausage products that are consumed without f'urther cooking, viz. sliced bologna, lunch- meats, etc. In many cases these products are sliced and packaged in areas that are in close proximity to raw meats or in locations having air supplies in common with raw meat processing areas. Further, the slicing and packaging operations involve considerable contact with the hands of the worker - thus another possible source of Salmonella contamination. The most sensible preventive approaches would be clear separation between raw and cooked meat operations, including control of 297.

personnel and the proper movement of air avay from finished product areas. Salmonella control over such finished products is an economic and practical impossibility. However, the prudent operator would exercise a regular sampling of his environment to make certain that no factor within it is contributing contamination to the finished product handling environment,

Our discussion of the Salmonella problem in meats must include mention of the possibility that even retorted meat products be con- sidered. Although the recent outbreak of typhoid fever in Scotland was widely attributed to a contaminated meat product, the implication that the product in the unopened can was contaminated appears to be without scientific foundation. However, there have been outbreaks of food poisoning, including salmonellosis, that have involved products receiving "sterilizing" cooks. Almost without exception such episodes have been traced to insufficient control over the potability of the chill water, e.g. the use of unchlorinated river water with its inevitable contamination with Salmonella organisms.

In summary, the Salmonella problem transgresses all facets of the meat industry, from the animal on the farm even to the finished product receiving a "botulism-type" cook. Changing philosophies among regulatory officials make it necessary for us to re-examine all phases of our processing operations, in an effort to break the Salmonella cycle at each point that a practical procedure can be devised. In many areas, as for example fresh meats, no single measure can be hoped to solve the entire problem, but the trend of the times demands that we all take the first step, because it looks as if it is going to be a long journey.

References

Galton, M. M., Smith, W. V., McElrath, H. B., and Hardy, A. V. 1954. Salmonella in Swine, Cattle and the Environment of Abattoirs. Jour. of Infectious Diseases, 95:236-245

Leistner, L., Johntges, J., Diabel, R. H., and Niven, C. F., Jr. 1961. The Occurrence and Significence of Salmonellae in Meat Animals and Animal By-product Feeds. Amer. Meat Inst. Fndn. Circular, -64:9-20

Wilson, E., Paffenbarger, R. S., Jr., Foter, M. J., and Lewis, K. H. 1961. Prevalence of Salmonellae in Meat and Poultry Products. Jour. Infectious Diseases, -109:166-171

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