Experimental “Food-Poisoning” in Monkeys with Living Paratyphoid Bacilli.

Abstract

Previous experiments in this laboratory have shown: (1) that the symptoms of food-poisoning were not reproduced when enormous numbers of heat-killed paratyphoid bacilli were fed to monkeys and other animals; 1 (2) that similarly, no symptoms were produced when large amounts of heat-killed paratyphoid cultures were swallowed by human volunteers. 2 These results indicated that the thermostabile substance (or substances) long known to be toxic to animals on intraperitoneal inoculation, is not the substance (or substances) responsible for the gastro-intestinal outbreaks with which paratyphoid bacilli are commonly associated.

Experiments have accordingly been undertaken using massive doses of living paratyphoid bacilli taken from agar cultures grown in Kolle flasks. These have been carried out with rhesus monkeys, and have yielded positive results. Monkeys of about 31/2 to 41/2 kilos, fed with from 95 to 816 billions of viable organisms, have shown symptoms of illness, such as sluggishness, loss of appetite and marked watery diarrhea. There was in all instances some loss of weight, but as a rule this was quickly regained. The diarrhea usually lasts 1 or 2 days, but in one instance persisted over 4 days. In no case did death occur, and the organisms fed were in no instance isolated from the blood, although daily attempts at blood cultures were made. One strain used (411) was of the Aertrycke type and was isolated in 1923 in a food-poisoning outbreak in New York City. 3 Large doses of heat-killed cultures of this organism had been given in previous experiments without causing any symptoms in man, monkeys or other animals. 1 , 2 In the present series a saline suspension of organisms was prepared from several Kolle fiasks, and was divided into 2 equal portions, one portion consisting of living organisms, the other portion being boiled for 20 minutes before being fed. Symptoms of “food-poisoning” appeared in animals fed with living cells, not in the others. Similar positive results were obtained with an Enteritidis strain, but monkeys fed with a living Proteus strain and with living B. coli strains showed no signs of illness.