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 destruc- tion 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.

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