Bacillus Typhosus is a motile, flagellated, non-sporogenous, non-liquefying aerobic, facultative anaerobic bacillus, 0.5 to 0.8 µ broad by 1 to 3 µ long, with rounded ends. Seldom seen in chains. Is found in the urine and feces of infected individuals; also in the blood, gall-bladder, and internal organs. Is present in water and milk as a result of contamination.

Stains

Ordinary Methods, But Not By. Gram's. Culture

Ordinary Media

On potato there is formed a characteristic, thick, moist and shiny, invisible film. Must be distinguished from the Bacillus coli communis. The following are the chief differences between the two:

Bacillus TYPHOSUS

Bacillus COLI COMMUNIS

Colonies on gelatin plates:

On surface large, thin, and bluish, with notched border; yellowish brown in center. Deep colonies, brownish yellow and sharply circumscribed. Non-liquefying. Develop more slowly.

On surface large, yellow-brown, round or oval, with irregular border. Deep colonies, round, yellowish brown, homogeneous. Non-liquefying.

On potato:

Usually forms a thick, moist, and shiny invisible film. Sometimes yellowish or brownish.

Luxuriant growth. Yellowish brown and glistening.

Milk:

Slightly acidulated, but not coagulated. Diffuse cloudiness.

Rapid coagulating and marked acidulation. Turns blue litmus milk red, colors entire medium. Marked turbidity.

Peptone media:

No indol formation.

Indol formed within twenty-four to forty-eight hours.

Ferments:

No gas formed in media containing sugar.

Fermentation whenever sugar is present.

Potassium nitrate:

Not reduced.

Reduced to nitrites and then to ammonia.

Conradi-Drigalski medium:

Blue, transparent colonies.

Red, opaque colonies.

Endo agar:

Colorless colonies.

Red colonies.

Neutral red:

Color remains red.

Changed to yellow.

Agglutination test, Widal reaction:

Typhoid bacilli are clumped when acted upon by diluted serum from the blood of typhoid patients.

No clumping.

Bacillus Coli Communis

See typhoid. Structurally it resembles the Bacillus typhosus.

Bacillus Pestis

A minute non-flagellated, non-motile, non-sporogenous, non-liquefying aerobic bacillus. Is very short, 1.7 µ by 2 µ with rounded ends. Varies greatly in shape. Is found in the blood and in the enlarged lymphatic nodes.

Stains

Ordinary methods, but not by Gram's. The rounded ends stain more deeply than the middle, giving an appearance of a diplococcus.

Culture

Grows well on artificial media. Diffuse cloudiness in bouillon. Gelatin puncture growth scanty. On agar-agar forms white or bluish-white colonies with round, uneven edges. On agar-agar plus 2.5 per cent, salt forms marked involution forms. Best medium for culture is a 2 per cent, alkaline peptone solution containing 1 or 2 per cent, of gelatin.

Is the cause of bubonic plague in man. Is spread by means of rats and fleas.

Bacillus AėRogenes Capsulatus

A large non-motile, non-flagellate, sporogenous, purely anaerobic bacillus, 0.5 µ broad by 3 to 5 µ long, and with rounded or square ends. Occurs in groups and in pairs, but not in chains, in this way differing from the anthrax bacillus. Is found in the tissues in the necrotic areas.

Stains

Ordinary methods and by Gram's. The organisms obtained from the body show distinct capsules.

Culture

Ordinary media, but in glucose gelatin shows best the characteristic gas-production. Is no distinct liquefaction, but the gelatin becomes softer. In deep stabs forms small, knot-like, grayish-white colonies from which extend fine hair-like or feathery projections. Produces acid.

Causes emphysematous gangrene with necrosis of the tissue before death and the formation of gas post-mortem.