Fig. 11.—Bacillus botulinus with spores. Pure culture on sugar-gelatin. Van Ermengem preparation. (Kolle and Wassermann.)
Epidemiology.—The conditions under which B. botulinus occurs and is given opportunities for multiplying are not completely known. It is possible that there are localities where this bacillus is particularly abundant in the soil or in the intestinal contents of swine or other domestic animals, but on the whole it seems more probable that the organism is widely distributed, but that it does not often find suitable conditions for entrance into, and multiplication in, human food. Practically all the reported cases of botulism have been caused by food which has been given some sort of preliminary treatment, as smoking, pickling, or canning, then allowed to stand for a time, and eaten before cooking. Since both the bacillus, including the spore stage, and its toxin are destroyed by relatively slight heating, it is clear that a rather unusual set of factors must co-operate in order that botulism poisoning shall take place. These are evidently: (1) the presence of the bacilli in sufficient numbers in a suitable foodstuff; (2) the initial preparation of the food by a method that does not destroy the B. botulinus—inadequate smoking, too weak brine,[109] or insufficient cooking; (3) the holding of this inadequately preserved food for a sufficient length of time under the right conditions of temperature and lack of oxygen; (4) the use of this food, in which conditions have conspired to favor the production of toxin by B. botulinus, without final adequate cooking. It seems as reasonable to suppose that the infrequency with which these several factors coincide is responsible for the relative uncommonness of botulism as to suppose it due to the rarity of the specific bacillus. In the Belgian outbreak studied by Van Ermengem the poisonous ham had lain at the bottom of a cask of brine (anaërobic conditions) while the other ham of the same animal lay on top of it but was not covered with brine, and was eaten without producing any poisonous effect. In this instance the presence or absence of favorable conditions for anaërobic growth seemed to be the decisive factor.
Prevention and treatment.—The food in which B. botulinus has grown does not seem to be altered in a way that necessarily arouses suspicion. In the case described by Römer the incriminated ham showed bluish-gray areas from which B. botulinus could be isolated, but this condition does not seem to have attracted attention before the poisoning occurred and was an observation made only after the event. So far as can be learned the meat that has caused botulism has always come from perfectly sound animals. In some cases the accused article of food is said to have had a rancid or acrid taste (due to butyric acid?), but there is nothing definitely characteristic about this, as the majority of anaërobes produce butyric acid. If, as in the Darmstadt[110] and Stanford University[111] epidemics, the food (canned beans) is served with salad dressing, a sour taste might pass without notice or even add to the relish. In the instance reported by Sheppard the canned beans were good in appearance, taste, and smell.
The obvious precaution to take against poisoning of this sort is first the use of adequate methods of food preservation. To judge from the recorded outbreaks, domestically prepared vegetables and meats are more likely to give rise to botulism than those prepared commercially on a large scale. The general use of steam under pressure in the large canning factories affords a high degree of protection against the anaërobic bacteria and their resistant spores. Whatever the method of treatment, all canned or preserved food having an unnatural appearance, taste, or odor should be rejected. Reheating of all prepared foods immediately before use is an additional safeguard. Foods, such as salads, composed wholly or in part of uncooked materials should not be allowed to stand overnight before being served.
If symptoms of botulism, such as visual disturbances, become manifest, the stomach should be emptied with a stomach pump, cathartics administered, and strychnine and other stimulants given as required. Since one of the noteworthy features of this disease is the paralysis of the intestinal tract by the toxin absorbed, the guilty food may lie for a long time in the stomach (cf. Stiles, loc. cit.). Consequently, measures to empty the stomach should be taken even if the patient does not come under observation until several days after the poisonous food has been eaten.
An antitoxic serum has been prepared at the Koch Institute in Berlin. This serum has given successful results in animal experimentation, but has not been used, so far as I can learn, in any human outbreak. It is not available at any point in this country.
OTHER BACTERIAL POISONS
The interesting case reported by Barber[112] shows that there are other possibilities of food poisoning by formed bacterial poisons. Acute attacks of gastro-enteritis were produced in several individuals by the use of milk containing a poisonous substance elaborated by a white staphylococcus. This staphylococcus occurred in almost pure culture in the udder of the cow from which the milk was derived. The milk when used fresh was harmless and the poison was generated in effective quantities only when the milk stood some hours at room temperature before being used. The symptoms were similar to those usually ascribed to "ptomain poisoning."
SPOILED AND DECOMPOSED FOOD
There is a general belief that food is unwholesome whenever the evidence of the senses shows it to be more or less decomposed. This opinion finds expression in civilized countries in many legal enactments forbidding traffic in decomposed meats, vegetables, and fruits. There is unfortunately lack of evidence as to what kinds or degree of visible decomposition are most dangerous. In fact, some foods of high nutrient value, notably cheeses, are eaten only after somewhat extensive decomposition processes (termed ripening) have taken place. The characteristic flavors or aromas of the various hard and soft cheeses are due to the substances formed by certain species of molds and bacteria and are just as properly to be regarded as decomposition products as the unpleasant stenches generated by decomposing eggs or meat. Indeed, some of the decomposition products formed in the ripening of Brie, Camembert, or Limburger are similar to, if not identical with, those which are associated with spoiled foods. Sour milk, again, is recommended and commonly used as a food or beverage for persons in delicate health, and yet sour milk contains many millions of bacteria and their decomposition products. Some of the bacteria commonly concerned in the natural souring of milk are closely related to pathogenic types. The partial decomposition of meats and game birds is often considered to be advantageous rather than otherwise. Even eggs, a food whose "freshness" is marred for most persons by the initial stages of decomposition, are ripened in various ways by the Chinese and eaten as a delicacy after the lapse of months or years. The preserved ducks' eggs known as pidan are stored for months in a pasty mixture of tea, lime, salt, and wood ashes. "They are very different from fresh eggs. The somewhat darkened shell has numerous dark green dots on the inner membrane. Both the white and yolk are coagulated; the white is brown, more or less like coffee jelly...."[113] Increase of ammoniacal nitrogen has taken place to an extraordinary degree in these eggs, indicating much decomposition of the egg protein. The ammoniacal nitrogen in pidan is considerably higher than in the eggs known by egg candlers as black rots.