and others, if any injurious effect at all is to be attributed to _B.
proteus_, it is in the nature of an intoxication and not an infection (see chapter viii). So far as the existing evidence goes, the question of the responsibility of this organism for food poisoning is still an open one.
FOOTNOTES:
[49] Sawyer, _Jour. Amer. Med. a.s.soc._, LXIII (1914), 1537.
[50] _Eng. News_, LXX (1913), 322.
[51] Morse, _Report of State Board of Health of Ma.s.s._, 1899, p. 761.
[52] R. H. Creel, _Reprint from Public Health Reports, No. 72_, Washington, 1912.
[53] _Health Bull. No. 76, Pennsylvania State Department of Health_, December, 1915.
[54] _Amer. Jour. Public Health_, II (1912), 321.
[55] _Inst.i.tution Quarterly_, III (1912), 18.
[56] See also a similar instance reported by Lumsden, _Hyg. Lab., U.S.
Public Health and Marine Hosp. Service, Bull. 78_, p. 165.
[57] For a discussion of the oyster question see G. W. Fuller, _Jour. of Franklin Inst.i.tute_, August, 1905; _N.Y. City Dept. of Health, Monthly Bull._, November, 1913, and May, 1915; H. S. c.u.mming, _U.S. Public Health Service, Pub. Health Bull. 74_, March, 1916.
[58] _Lancet_, II (1895), 46.
[59] Park and Krumwiede, _Jour. Med. Research_, N.S., XVIII (1910), 363.
[60] _Ztschr. f. Hyg._, x.x.xV (1900), 265.
[61] _Centralbl. f. Bakt._, I, Orig., LXVI (1912), 194.
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. Hubener[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 a.s.sumed 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 cla.s.s comprising 67 girls between the ages of thirteen and seventeen. Out of 55 girls belonging to this cla.s.s 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 cla.s.ses, 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 carca.s.s 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 circ.u.mstances 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 a.s.sociated 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 a.s.sociated 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 pa.s.sed 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 a.s.sociated 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.
[Ill.u.s.tration: FIG. 6.--_Bacillus enteritidis_, Gartner; pure culture; Van Ermengem preparation. (Kolle and Wa.s.sermann.)]
The discovery of the connection of paratyphoid bacilli with meat poisoning dates from the investigation by Gartner,[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. Gartner 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 Gartner (_loc. cit._) and known as _B.
enteritidis_ or Gartner"s bacillus is commonly taken as the type of one of the agglutinative varieties. Bacilli with all the characters of Gartner"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_ Gartner. 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 Gartner bacillus, but refuses to agglutinate with the Gartner 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_ Gartner). It is still unsettled whether both types of food poisoning bacteria are always a.s.sociated 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" Gartner 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 Gartner 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 cla.s.sed with the so-called true toxins generated by the diphtheria and teta.n.u.s 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 quant.i.ty 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]