CHAPTER VI
FOOD-BORNE PATHOGENIC BACTERIA (_Continued_)
PARATYPHOID INFECTION
The most characteristic examples of "food poisoning," popularly speaking, are those in which the symptoms appear shortly after eating and in which gastro-intestinal disturbances predominate. In the typical group-outbreaks of this sort all grades of severity are manifested, but as a rule recovery takes place. The great majority of such cases that have been investigated by modern bacteriological methods show the presence of bacilli belonging to the so-called paratyphoid group (_B. paratyphosus_ or _B. enteritidis_). Especially is it true of meat poisoning epidemics that paratyphoid bacilli are found in causal relation with them. Huebener[62] enumerates forty-two meat poisoning outbreaks in Germany in which bacilli of this group were shown to be implicated, and Savage[63] gives a list of twenty-seven similar outbreaks in Great Britain. In the United States relatively few outbreaks of this character have been placed on record, but it cannot be assumed that this is due to their rarity, since no adequate investigation of food poisoning cases is generally carried out in our American communities.
_Typical paratyphoid outbreaks._--Kaensche[64] describes an outbreak at Breslau involving over eighty persons in which chopped beef was apparently the bearer of infection. The animal from which the meat came had been ill with severe diarrhea and high fever and was slaughtered as an emergency measure (_notgeschlachtet_). On examination a pathological condition of the liver and other organs was noted by a veterinarian who declared the meat unfit for use and ordered it destroyed. It was, however, stolen, carried secretly to Breslau, and portions of it were distributed to different sausage-makers, who sold it for the most part as hamburger steak (_Hackfleisch_). The meat itself presented nothing abnormal in color, odor, or consistency. Nevertheless, illness followed in some cases after the use of very small portions. With some of those affected the symptoms were very severe, but there were no deaths. Bacilli of the _Bacillus enteritidis_ type were isolated from the meat.
A large and unusually severe outbreak reported by McWeeney[65] occurred in November, 1908, among the inmates of an industrial school for girls at Limerick, Ireland. There were 73 cases with 9 deaths out of the total number of 197 pupils. The brunt of the attack fell on the first or Senior class comprising 67 girls between the ages of thirteen and seventeen. Out of 55 girls belonging to this class who partook of beef stew for dinner 53 sickened, and 8 of these died. One of the two who were not affected ate the gravy and potatoes but not the beef. Some of the implicated beef was also eaten as cold meat by girls in some of the other classes, and also caused illness. Part of the meat had been eaten previously without producing any ill effects. "The escape of those who partook of portions of the same carcass on October 27 and 29 [five days earlier] may be accounted for either by unequal distribution of the virus, or by thorough cooking which destroyed it. Some of the infective material must, however, have escaped the roasting of the 29th, and, multiplying rapidly, have rendered the whole piece intensely toxic and infective during the five days that elapsed before the fatal Tuesday when it was finally consumed." The animal from which the fore quarter of the beef was taken had been privately slaughtered by a local butcher. No reliable information could be obtained about the condition of the calf at, or slightly prior to, slaughter. The meat, however, was sold at so low a price that it was evidently not regarded as of prime quality. In this outbreak the agglutination reactions of the blood of the patients and the characteristics of the bacilli isolated showed the infection to be due to a typical strain of _Bacillus enteritidis_.
An epidemic of food poisoning occurred in July, 1915, at and near Westerly, Rhode Island.[66] The outbreak was characterized by the usual symptoms of acute gastro-enteritis, and followed the eating of pie which was obtained at a restaurant in Westerly. All the circumstances of the outbreak showed that a particular batch of pies was responsible. About sixty persons were made seriously ill and four died. There was no unusual taste or odor to the pies to excite suspicion. The symptoms followed the eating of various kinds of pie: custard, squash, lemon, chocolate, apple, etc., that had been made with the same pie-crust mixture. _Bacillus paratyphosus_ B was isolated from samples of pie that were examined. No definite clue was obtained as to the exact source of infection of the pie mixture. It is possible that the pie became infected in the restaurant through the agency of a paratyphoid-carrier, but since there had been no change in the personnel of the restaurant for several months, this explanation is largely conjectural. Possibly some ingredient of animal origin was primarily infected.
_General characters of paratyphoid infection._--The symptoms of paratyphoid food infection are varied. As a rule the first signs of trouble appear within six to twelve hours after eating, but sometimes they may come on within half an hour, or they may not appear until after twenty-four to forty-eight hours. Gastro-intestinal irritation is practically always present, and may take the form of a mild "indigestion" or slight diarrhea or may be of great severity accompanied with agonizing abdominal pain. Fever is usual, but is generally not very high. Recovery may occur quickly, so that within two or three days the patient regains his normal state, or it may be very slow, so that the effects of the attack linger for weeks or months.
Investigators have noted the occurrence of at least two clinical types of paratyphoid infection, the commoner gastro-intestinal type just described and a second type resembling typhoid fever very closely, and occasionally not to be distinguished from it except by careful bacterial examination. It is not yet clear how these two clinical varieties are related to the amount and nature of the infecting food material. No difference in the type of paratyphoid bacillus has been observed to be associated with the difference in clinical manifestation. Possibly the amount of toxin present in the food eaten as well as the number of bacilli may exercise some influence. The individual idiosyncrasy of the patient doubtless plays a part.
While there is still some uncertainty about particular features of paratyphoid infection, a few significant facts have been clearly established: (1) Certain articles of diet are much more commonly associated than others with this type of food poisoning. The majority of recorded outbreaks are connected with the use of meat, milk, fish, and other protein foods. Vegetables and cereals have been less commonly implicated, fruits rarely. (2) In many, though not all, of the cases of paratyphoid meat poisoning it has been demonstrated that the meat concerned has been derived from an animal slaughtered while ailing (_notgeschlachtet_, to use the expressive German term). There seems reason to believe that in such an animal, "killed to save its life," the specific paratyphoid germ is present as an infection before death. Milk also has caused paratyphoid poisoning and in certain of these cases has been found to be derived from a cow suffering from enteritis or some other disorder. (3) There is evidence that originally wholesome food may become infected with paratyphoid bacilli during the process of preparation or serving in precisely the same way that it may become infected with typhoid bacilli; the handling of the food by a paratyphoid-carrier is commonly responsible for this. In a few instances the disease is passed on from case to case, but this mode of infection seems exceedingly rare and is not nearly so frequent as "contact" infection in typhoid. (4) The majority of paratyphoid outbreaks are associated with the use of uncooked or partly cooked food. A selective action is often manifested, those persons who have eaten the incriminated food substance raw or imperfectly cooked being most seriously affected, while those who have partaken of the same food after cooking remain exempt.
The discovery of the connection of paratyphoid bacilli with meat poisoning dates from the investigation by Gaertner,[67] in 1888, of a meat poisoning outbreak in Frankenhausen, a small town in Germany. This epidemic was traced to the use of meat from a cow that was slaughtered because she was ill with a severe enteritis. Fifty-eight persons were affected in varying grades of severity; the attack resulted fatally in one young workman who ate about eight hundred grams of raw meat. Gaertner isolated from the spleen of the fatal case and also from the flesh and intestines of the cow a bacillus to which he gave the name _B. enteritidis_. Inoculation experiments showed it to be pathogenic for a number of animal species. Bacilli with similar characters have since been isolated in a number of other meat poisoning epidemics in Germany, Belgium, France, and England. One well-studied instance of food poisoning due to the paratyphoid bacillus has been reported in the United States.[68]
The bacteria of the paratyphoid group are closely related to the true typhoid bacillus, but differ from the latter organism in being able to ferment glucose with gas production. They are more highly pathogenic for the lower animals than is the typhoid bacillus, but apparently somewhat less pathogenic for man. Most types of paratyphoid bacilli found in food poisoning produce more or less rapidly a considerable amount of alkali, and, if they are inoculated into milk containing a few drops of litmus, the milk after a time becomes a deep blue color. Several distinct varieties of paratyphoid bacilli have been discovered. The main differences shown by these varieties are agglutinative differences. That is, the blood serum of an animal that has been inoculated with a particular culture or strain will agglutinate that strain and also other strains isolated from certain other meat poisoning epidemics, but will not agglutinate certain culturally similar paratyphoid bacteria found in connection with yet other outbreaks. Except in this single matter of agglutination reaction, no constant distinction between these varieties has been demonstrated. The clinical features of the infections produced in man and in the higher animals by the different varieties seem to be very similar if not identical.
The bacillus discovered by Gaertner (_loc. cit._) and known as _B. enteritidis_ or Gaertner's bacillus is commonly taken as the type of one of the agglutinative varieties. Bacilli with all the characters of Gaertner's bacillus have been found in meat poisoning epidemics in various places in Belgium and Germany. Mayer[69] has compiled a list of forty-eight food poisoning outbreaks occurring between 1888 and 1911 and attributed to _B. enteritidis_ Gaertner. These outbreaks comprised approximately two thousand cases and twenty deaths. In twenty-three of the forty-eight outbreaks the meat was derived from animals known to be ill at the time, or shortly before, they were slaughtered. Sausage and chopped meat of undetermined origin were responsible for eleven of the remaining twenty-five outbreaks. Two of the _B. enteritidis_ outbreaks were attributed to _Vanille Pudding_; one, to potato salad.
In other food poisoning outbreaks a bacillus is found which is culturally similar to the Gaertner bacillus, but refuses to agglutinate with the Gaertner bacillus serum. Its cultural and agglutination reactions are almost, if not quite, identical with those of the bacilli found in human cases of paratyphoid fever which have no known connection with food poisoning. Mayer[70] gives a list of seventy-seven outbreaks of food poisoning (1893-1911) in which organisms variously designated as "_B. paratyphosus_ B" or as "_B. suipestifer_" were held to be responsible. The total number of cases (two thousand) and deaths (twenty) is about the same as ascribed to _B. enteritidis_. According to Mayer's tabulation meat from animals definitely known to be ailing is less commonly implicated in this type (ten in seventy-seven) than in _B. enteritidis_ outbreaks (twenty-three in forty-eight). Sausage and chopped meat of unknown origin, however, were connected with eighteen outbreaks.
The bacillus named _B. suipestifer_ was formerly believed to be the cause of hog cholera, but it is now thought to be merely a secondary invader in this disease; it is identical with the bacillus called _B. paratyphosus_ B in its cultural and to a large extent in its agglutinative behavior, but is regarded by some investigators as separable from the latter on the basis of particularly delicate discriminatory tests. Bainbridge, Savage, and other English investigators consider indeed that the true food poisoning cases should be ascribed to _B. suipestifer_ and would restrict the term _B. paratyphosus_ to those bacteria causing "an illness clinically indistinguishable from typhoid fever." German investigators, on the other hand, regard _B. suipestifer_ and _B. paratyphosus_ B as identical. My own investigations[71] indicate that there is a real distinction between these two types.
Bearing directly on this question is the discussion concerning the distribution of the food poisoning bacilli in nature. Most investigators in Germany, where the majority of food poisoning outbreaks have occurred, or at least have been bacteriologically studied, are of the opinion that _B. suipestifer_ (the same in their opinion as _B. paratyphosus_ B) is much more widely distributed than _B. enteritidis_ and that it occurs, especially in certain regions, as in the southern part of the German Empire, quite commonly in the intestinal tract of healthy human beings. Such paratyphoid-carriers, it is supposed, may contaminate food through handling or preparation just as typhoid-carriers are known to do. A number of outbreaks in which contamination of food during preparation is thought to have occurred have been reported by Jacobitz and Kayser[72] (vermicelli), Reinhold[73] (fish), and others. Reinhold notes that in one outbreak several persons who had nursed those who were ill became ill themselves, indicating possible contact infection. In another outbreak also reported by Reinhold it was observed that those who partook of the infected food, in this case dried codfish, on the first day were not so severely affected as those who ate what was left over on the second day. A bacillus belonging to the paratyphoid group was isolated from the stools of patients, but not from the dried codfish. These facts were interpreted as signifying that the fish had become infected in the process of preparation and that the bacilli multiplied in the food while it was standing.
There seems no doubt that certain cases of paratyphoid food poisoning are caused by contamination of the food during preparation and are, sometimes at least, due to infection by human carriers. The bacilli in such cases are usually (according to many German investigators) or always (according to most English bacteriologists) of the _B. suipestifer_ type. Other cases are due to pathogenic bacteria derived from diseased animals, and these bacteria are often, possibly always, of a slightly different character (_B. enteritidis_ Gaertner). It is still unsettled whether both types of food poisoning bacteria are always associated with disease processes of man or animals, or whether they are organisms of wide distribution which may at times acquire pathogenic properties. In certain regions, as in North Germany and England, such bacteria are rarely, if ever, found except in connection with definite cases of disease. In parts of Southwest Germany, on the other hand, they are said to occur with extraordinary frequency in the intestines of healthy men and animals. Savage[74] believes that there is some confusion on this subject owing to the existence of saprophytic bacteria which he calls "Paragaertner" forms and which bear a close resemblance to the "true" Gaertner bacilli. They can be distinguished from the latter only by an extended series of tests. The bacilli of this group show remarkable variability, and in the opinion of some investigators "mutations" sometimes occur which lead to the transformation of one type into another.[75]
In spite of the present uncertainty regarding the relationship and significance of the varieties observed, a few facts emerge plainly from the confusion: (1) The majority of meat poisoning outbreaks that have been bacterially studied in recent years have been traceable to one or another member of this group and not to "ptomain poisoning." (2) Bacteria of the _paratyphoid enteritidis_ group that are culturally alike but agglutinatively dissimilar can, when taken in with the food, give rise to identical clinical symptoms in man. (3) Food poisoning bacteria of this group, when derived directly from diseased animals, seem more likely to be of the Gaertner type (_B. enteritidis_) than of the _B. suipestifer_ type.
_Toxin production._--The problem of the production of toxin by the bacteria of this group and the possible relation of the toxin to food poisoning has been much discussed. Broth cultures in which the living bacilli have been destroyed by heat or from which they have been removed by filtration contain a soluble poison. When this germ-free broth is injected into mice, guinea-pigs, or rabbits, the animals die from the effects. Practically nothing is known about the nature of the poisonous substances concerned, except that they are heat-resistant. They are probably not to be classed with the so-called true toxins generated by the diphtheria and tetanus bacilli, since there is no evidence that they give rise to antibodies when injected into susceptible animals. In the opinion of some investigators the formation of these toxic bodies by the _paratyphoid-enteritidis_ bacilli in meat and other protein foodstuffs is responsible for certain outbreaks and also for some of the phenomena of food poisoning, the rapid development of symptoms being regarded as due to the ingested poisons, whereas the later manifestations are considered those of a true infection. Opposed to this view is the fact that well-cooked food has proved distinctly less liable to cause food poisoning than raw or imperfectly cooked food.
A large proportion of the recorded meat poisoning outbreaks are significantly due to sausages made from raw meat and to meat pies, puddings, and jellies. This is most likely because the heat used in cooking such foods is insufficient to produce germicidal results. In milk-borne epidemics also it is noteworthy that the users of raw milk are the ones affected. For example, respecting an extensive _B. enteritidis_ outbreak in and about Newcastle, England, it is stated:
In no instance was a person who had used only boiled milk known to have been affected. Thus in one family, consisting of husband, wife, and wife's mother, the two women drank a small quantity of raw milk from the farm, at the most a tumblerful, and both were taken ill about twelve hours later. The husband, on the other hand, habitually drank a pint a day, but always boiled. He followed his usual custom on this occasion, and was unaffected.[76]
When in addition it is taken into consideration that the ordinary roasting or broiling of a piece of meat is often not sufficient to produce a germicidal temperature throughout, the argument that a heat-resistant toxin is present in such cases is not conclusive. It must be remembered also that in some outbreaks those persons consuming raw or partly cooked meat have been affected while at the same time others eating well-cooked meat from the same animal have remained exempt; this would seem to indicate the destruction of living bacilli by heat, since the toxic substances formed by these organisms are heat-resistant. The view that a definite infection occurs, is favored, too, by the fact that the blood-serum of affected persons so frequently has an agglutinative action upon the paratyphoid bacillus. This would not be the case if the symptoms were due to toxic substances alone. Altogether the role of toxins formed by _B. enteritidis_ and its allies in food outside the body cannot be said to be established. The available evidence points to infection as the main, if not the sole, way in which the bacilli of this group are harmful.
_Sources of infection._--The main sources of _enteritidis-suipestifer_ infection are: (1) diseased domestic animals, the infected flesh or milk of which is used for food; (2) infection of food by human carriers during the process of preparation or serving. To these may be added a third possibility: (3) contamination of food with bacteria of this group which are inhabitants of the normal animal intestine. Considering these in order:
1. Diseased animals: The majority of the meat poisoning outbreaks are caused by meat derived from pigs or cattle. Table III gives the figures for a number of British[77] and German[78] epidemics.
TABLE III[79]
==================================================================== | | | BELONGING TO | B. ENTERITIDIS | B. SUIPESTIFER | THIS GROUP BUT | | |UNDIFFERENTIATED |--------------------+--------------------+---------------- |British|German|Total|British|German|Total| British ---------+-------+------+-----+-------+------+-----+---------------- Pig | 1 | 1 | 2 | 3 | 5 | 8 | 4 Ox or cow| 3 | 9 | 12 | 2 | 3 | 5 | 5 Calf | 0 | 7 | 7 | 2 | 2 | 4 | 0 Horse | 0 | 1 | 1 | 0 | 1 | 1 | ... Chickens | 1 | 0 | 1 | 0 | 1 | 1 | ... --------------------------------------------------------------------
Occasional outbreaks have also been attributed to infection through eating rabbit, sheep, goose, fish, shrimp, and oysters. Especially noteworthy is the relative rarity of infection from the meat of the sheep.
More definite information is needed respecting the pathological conditions caused by these bacteria in animals and the relation of such conditions to subsequent human infection. A rather remarkable problem is presented by the relation of _B. suipestifer_ to hog cholera. This bacillus, although not now considered the causal agent of hog cholera, is very commonly associated with the disease as an accessory or secondary invader, and is frequently found in the internal organs of swine after death. It might be supposed that in regions where hog cholera is prevalent human infections would be more common than in other districts, but this seems not to be the case. No connection has ever been demonstrated between outbreaks of hog cholera--in which _B. suipestifer_ is known to be abundantly distributed--and so-called _B. suipestifer_ infections in man.
Suppurative processes in cattle, and especially in calves, have given rise to poisoning from the use of the meat or milk of the infected animals. It has been often demonstrated that bacteria of the _enteritidis-suipestifer_ group are associated with inflammation of the udder in cows and with a variety of septicemic conditions in cattle and other domestic animals as well as with manifestations of intestinal disturbances ("calf diarrhea," etc.).[80] The frequency with which poisoning has occurred through the use of the meat of "emergency-slaughtered" animals has been already mentioned. K. F. Meyer[81] has reported an instance of accidental infection in a laboratory worker caused by handling a bottle of sterilized milk that had been artificially contaminated with a pure culture of _B. enteritidis_ for experimental purposes. The strain responsible for the infection had been isolated from the heart blood of a calf that had succumbed to infectious diarrhea.
2. Human contamination: In a certain number of paratyphoid food infections there is some evidence that the food was originally derived from a healthy animal and became infected from human sources during the process of preparation. In addition to the instances already mentioned (Reinhold _et al._, p. 67) the Wareham (England, 1910) epidemic[82] was considered by the investigators to be due to infection of meat pies by a cook who was later proved to be a carrier of paratyphoid bacilli. The evidence in this case, however, is not altogether conclusive. Soederbaum[83] mentions a milk-borne paratyphoid epidemic occurring in Kristiania which was ascribed to infection of the milk by a woman milker. Sacquepee and Bellot[84] report an interesting paratyphoid outbreak involving nineteen out of two hundred and fifty men in a military corps. The patients fell ill on different dates between June 14 and June 21.
It was found that an assistant cook who had been in the kitchen for several months had been attacked a little before the epidemic explosion by some slight malady which was not definitely diagnosed. He had been admitted to the hospital and was discharged convalescent. The cook, on being recalled and quarantined, stated that some days before June 10 he was indisposed with headache and anorexia. He had nevertheless continued his service in the kitchen.... _B. paratyphosus_ B (_B. suipestifer_) was repeatedly found in his stools in August, September, and October.... In all probability, therefore, the outbreak was due to food contaminated by a paratyphoid-carrier who had passed through an abortive attack of the fever.[85]
Bainbridge and Dudfield[86] describe an outbreak of acute gastro-enteritis occurring in a boarding-house; it was found that no one article of food had been eaten by all the persons affected, and there were other reasons for supposing the outbreak to be due to miscellaneous food contamination by a servant who was a carrier.
There is, therefore, ground for believing that occasional contamination of food may be brought about by bacteria of this group derived from human sources. It is not clear, however, how frequent this source of infection is, compared to infection originating in diseased animals. It must be admitted, too, that English investigators are disposed to look upon outbreaks similar to those just described as infections with _B. paratyphosus_ B, an organism which they would distinguish from the "true" food poisoning bacilli, _B. enteritidis_ and _B. suipestifer_.
3. Miscellaneous contaminations: Some investigators, especially certain German writers, regard the bacilli of the paratyphoid group as so widely distributed in nature that any attempt to control the spread of infection is like fighting windmills. According to this view the bacilli occur commonly in our everyday surroundings and thence make their way rather frequently into a variety of foodstuffs. Various German investigators have reported the presence of paratyphoid bacilli in the intestinal contents of apparently normal swine, cattle, rats, and mice and more rarely of other animals, in water and ice, in German sausage and chopped meat, and in the bodies of apparently healthy men. To what extent their alleged ubiquity is due to mistaken bacterial identification, as claimed by some English investigators, remains to be proved. There is no doubt that in some quarters exaggerated notions have prevailed respecting a wide distribution of the true paratyphoid bacteria. Savage and others believe that the hypothesis that food poisoning outbreaks are derived from ordinary fecal infection of food is quite unfounded. It is pointed out that there is good evidence of the frequent occurrence of intestinal bacteria in such food as sausages and chopped meat, and that consequently, if paratyphoid infections could occur through ordinary contamination with intestinal bacteria not connected with any specific animal infection, food poisoning outbreaks should be exceedingly common instead of--as is the case--comparatively rare.
At the present time even those who maintain that these bacilli are of common occurrence admit that their abundance is more marked in some regions than in others. Southwest Germany, for example, seems to harbor paratyphoid bacilli in relatively large numbers. Possibly local differences in distribution may account for the discrepancies in the published findings of German and British investigators.
A special case is presented by the relation of these bacilli to rats and mice. Among the large number of bacteria of the paratyphoid group is the so-called Danysz bacillus, an organism quite pathogenic for rodents, and now and again used in various forms as a "rat virus" for purposes of rodent extermination. Several outbreaks of food poisoning in man have been attributed on more or less cogent evidence to food contamination by one of these viruses either directly by accident, as in the case described by Shibayama,[87] in which cakes prepared for rats were eaten by men, or indirectly through food contaminated by mice or rats that had been infected with the virus.[88] The use of such viruses has not proved of very great practical value in the destruction of rodents, and is open to serious sanitary objections, since the animals after apparent recovery can continue to carry the bacilli of the virus and to distribute them on or near food substances.
It seems possible that rats and mice may become infected with certain bacteria of this group without human intervention, and that these infected animals may be the means of contaminating foodstuffs and so causing outbreaks of food poisoning. Proof of the frequency with which this actually occurs is naturally difficult to obtain.
There is no escape from the conclusion that in any given case of food poisoning the exact source of infection is often largely conjectural. Even when suspicion falls strongly on a particular article of food, it may not be possible to establish beyond a reasonable doubt whether the material (meat or milk) came from a diseased animal or whether it was infected from other sources (man or other animals) at some stage during the process of preparation and serving. The most definitely attested cases yet put on record are those in which it is possible to trace the infection to food derived from an ailing animal.
_Means of prevention._--The most obvious and probably the most important method of preventing infection with paratyphoid bacilli is the adoption of a system of inspection which will exclude from the market as far as possible material from infected animals. To be most effective such inspection must be directed to examination of the living animal. The milk or the meat from diseased animals may give no visible sign of abnormality. In the Ghent outbreak of 1895 the slaughter-house inspector, a veterinary surgeon, was so firmly convinced that the meat which he had passed could have had no connection with the outbreak, that he ate several pieces to demonstrate its wholesomeness. The experiment had a tragic ending, as the inspector was shortly attacked with severe choleraic symptoms and died five days later, paratyphoid bacilli being found at the autopsy. Mueller[89] also has described a case in which paratyphoid bacilli were found in meat that had given rise to a meat poisoning outbreak although the meat was normal in appearance and the organs of the animal showed no evidence of disease to the naked eye. It is evident that inspection of the live animal will often reveal evidence of disease which might be missed in the ordinary examination of slaughter-house products.
Although inspection of cows used for milking and of food animals before slaughter is highly important, it does not constitute an absolute protection. Emphasis must be repeatedly laid on the fact that meat, and especially milk that is derived from seemingly healthy animals, may nevertheless contain paratyphoid bacilli. To meet this difficulty in part the direct bacterial examination of the carcasses of slaughtered food animals has been proposed, but this seems hardly practicable as a general measure. In spite of all precautions taken at the time of slaughtering it seems probable that occasionally paratyphoid-infected meat will pass the first line of defense and be placed on the market.
This danger, which is probably not a very grave one under a reasonably good system of inspection of live animals, may be met by thoroughly cooking all foods of animal origin. It is worth noting that some of the internal organs, as the liver and kidneys, are more likely to contain bacteria than the masses of muscle commonly eaten as "meat." Sausages, from their composition and mode of preparation, and chopped meat ("hamburger steak") are also to be treated with especial care. Consumption of such foods as raw sausage or diseased goose liver (pate de foie gras) involves a relatively high risk. It is true of paratyphoid infection as of most other forms of food poisoning that thorough cooking of food greatly diminishes the likelihood of trouble.
Whatever be the precise degree of danger from food infection by healthy paratyphoid-carriers (man or domestic animals), it is obvious that general measures of care and cleanliness will be more or less of a safeguard. As with typhoid fever so all outbreaks of paratyphoid should be thoroughly investigated in order that the sources of infection may be found and eliminated. The possible connection of rats and mice with these outbreaks should furnish an additional incentive to lessen the number of such vermin as well as to adopt measures of protecting food against their visits.
FOOTNOTES:
[62] _Fleischvergiftungen u. Paratyphusinfektionen_ (Jena, 1910).
[63] _Rept. to Local Govt. Board_, N.S. No. 77 (London, 1913).
[64] _Zeit. f. Hyg._, XXII (1896), 53.
[65] _Brit. Med. Jour._, I (1909), 1171.
[66] Bernstein and Fish, _Jour. Amer. Med. Assoc._, LXVI (1916), 167.
[67] _Breslau aerztl. Ztschr._, X (1888), 249.
[68] Bernstein and Fish, _Jour. Amer. Med. Assoc._, LXVI (1916), 167.
[69] _Deutsche Viertelj. f. oeffentl. Ges._, XLV (1913), 58-59.
[70] _Op. cit._, pp. 60-62.
[71] _Jour. Infect. Dis._, XX (1917), 457.
[72] _Centralbl. f. Bakt._, I Orig., LIII (1910), 377.
[73] _Cor.-Bl. f. schweiz. Aerzte_, XLII (1912), 281 and 332.
[74] _Jour. Hyg._, XII (1912), 1.
[75] See Sobernheim and Seligmann, _Centralbl. f. Bakt._, Ref., Beilage, L (1911), 134.
[76] _Report Med. Officer of Health_ (Newcastle-upon-Tyne, 1913).
[77] Compiled from Savage, _Report of Local Gov't Board_, 1913.
[78] Mayer, _Deutsche Viertelj. f. oeffentl. Ges._, XLV (1913), 8.
[79] It must be noted that origin of the food from a diseased animal was not definitely proved in all the cases cited. Some of these cases should possibly be classed under human contamination (2).
[80] Although not directly connected with the question of food poisoning, it is of interest to note that certain diseases of birds have been traced to infection with members of this group of bacteria. In a few cases, as in several epidemics among parrots in Paris and elsewhere, the infection has been communicated to man by contact.
[81] _Jour. Infect. Dis._, XIX (1916), 700.
[82] R. Trommsdorff, L. Rajchman, and A. E. Porter, _Jour. Hyg._, XI (1911), 89.
[83] _Hygiea_, LXXV (1913), 1.
[84] _Progres med._, 3d series, XXVI (1910), 25.
[85] Ledingham and Arkwright, _The Carrier Problem in Infectious Diseases_, pp. 152-53.
[86] _Jour. Hyg._, XI (1911), 24.
[87] _Muench. med. Wchnschr._, LIV (1907), 979.
[88] See, for example, H. Langer and Thomann, _Deutsche med. Wchnschr._, XL (1914), 493.
[89] _Ztschr. f. Infektionsk. ... d. Haustiere_, VIII (1910), 237.