88 



STUDY AND IDENTIFICATION OF BACTERIA 



The best method of diagnosis is to inoculate the culture or material 



into the ear vein of a rabbit, kill it and 

 then incubate the body at 37C. Gas is 

 generated in the organs in a few hours. 

 While the organism is pathogenic for 

 guinea-pigs it has little effect on rabbits. 

 B. Perfringens. This is the name fre- 

 quently given to the organism which has 

 assumed such great importance on ac- 

 count of its causing the gas gangrene so 

 frequently observed in shell wounds re- 

 ceived in Belgium. It is considered to 

 be identical with B. aerogenes capsulatus 

 (Welch's gas bacillus) and B. phlegm onis 

 empysematosa. It is very abundant in 

 the soil of highly fertilized areas. 



In size the bacillus is large, 6X 2.5 microns with 

 square cut ends. It is strongly Gram-positive, 

 may or may not show a capsule and is nonmotile. 

 When sporing the spore occurs toward one end 

 with slight bulging of the rod. Grown in pure 

 culture spores are rarely found, but in symbiosis 

 with staphylococci they form abundantly. 

 Cultures from the clothing of men in the trenches 

 almost always show the Welch bacillus and less 

 frequently the tetanus bacillus. Streptococci 

 were rather frequent. When a shell wound oc- 

 curs we almost invariably have a gas bacillus 

 infection which during the first few days gives 

 rise to a foul-smelling reddish-brown discharge. 

 Smears from gas gangrene wounds, showing such 

 discharge, have chiefly the gas bacillus and 

 streptococci. In the second week the pus be- 

 comes more purulent and the gas bacillus is infre- 

 quent. Streptococci, staphylococci and coliform 

 bacilli are abundant. Glucose agar to which 

 about Ho c.c. of blood has been added makes 

 a very favorable medium for the gas bacillus. 

 It also grows well on milk or blood-serum. 

 Fleming prefers neutral red egg medium for its 

 culturing. Cultures of the gas bacillus from gas 



gangrene discharges when injected subcutaneously into guinea-pigs kill within 

 twenty-four hours causing emphysematous swellings. Chlorinated solutions seem 



FIG. 25. B. aerogenes capsu- 

 latus agar culture showing gas 

 formation. (Mac Neal.) 



