CHAPTER V.

TYPHOID FEVER.

THE bacillus of typhoid fever (Fig. 72) was discovered by Eberth in 1880, and was first secured in pure culture

FIG. 72.-Bacillus typhi, from a twenty-four-hours-old agar-agar culture; × 650 (Heim).

from the spleen and affected lymphatic glands by Gaffky four years later.

The organism is a small, short bacillus about 1-3 μ (2-4 Chantemesse, Widal) in length and 0.5-0.8 broad (Sternberg). The ends are rounded, and it is rather exceptional for the bacilli to be united in chains, though this arrangement is common in potato cultures. The size and morphology vary distinctly with the nature of the culture-medium and the age of the culture. Thoinot and Masselin in describing these morphological peculiarities mention that when grown in bouillon it is a very slender bacillus; in milk it is a large bacillus; upon agar-agar and potato it is very thick and short; and in old gelatin cultures it forms very long filaments.

The organisms are actively motile, the motility probably being caused by the numerous flagella with which

FIG. 73.-Bacillus coli communis, from an agar-agar culture; x 1000 (Itzerott and Niemann).

the bacilli are provided. The flagella stain well by Löffler's method, and, as they are numerous (eighteen

FIG. 74.-Bacillus typhi, from an agar-agar culture six hours old, showing the flagella stained by Löffler's method; x 1000 (Fränkel and Pfeiffer).

to twenty) and readily demonstrable, the typhoid bacillus is the favorite subject for their study.

The organism stains quite well by the ordinary methods, but loses the color entirely when stained by Gram's method. Its peculiarity of staining is the readiness with which the bacillus gives up its color in the presence of solvents, so that it is particularly difficult to stain it in tissue.

When sections are to be stained the best method is to allow the tissue to remain in Löffler's alkaline methylene blue for from fifteen minutes to twenty-four hours, then wash in water, dehydrate rapidly in alcohol, clear up in xylol, and mount in Canada balsam. Ziehl's method also gives good results. The sections are stained for fifteen minutes in a solution of distilled water 100, fuchsin 1, and phenol 5. After staining they are washed in distilled water containing 1 per cent. of acetic acid, dehydrated in alcohol, cleared, and mounted. In such preparations the bacilli may be found in little groups, which are easily discovered, under a low power of the microscope, as bluish specks, and readily resolved into bacilli with the high power of the oil-immersion lens.

In bacilli stained by this alkaline methylene-blue solution dark-colored dots may sometimes be observed near the ends of the rods. These dots were at first regarded as spores, but are now denominated polar granules, and are thought to be of no importance.

The typhoid bacillus is both saprophytic and parasitic. It finds abundant conditions in nature for its growth and development, and, enjoying strong resisting powers, can accommodate itself to environment much better than the majority of pathogenic bacteria, and can be found in water, air, soiled clothing, dust, sewage, milk, etc. contaminated directly or indirectly by the intestinal discharges of diseased persons.

The bacillus is also occasionally present upon green vegetables sprinkled with water containing it, and an epidemic is reported in which the infection was traced to oysters from a certain place where the water was infected

through sewage. The bacillus probably enters milk occasionally in water used to dilute it.

The resistant powers of the organisms have already been described as great. They can grow well at the room-temperature. The thermal death-point is given by Sternberg as 60° C. The bacilli can, according to Klemperer and Levy, remain vital for three months in distilled water, though in ordinary water the commoner and more vigorous saprophytes outgrow them and cause their disappearance in a few days. When buried in the upper layers of the soil the bacilli retain their vitality for nearly six months. Cold has no effect upon the typhoid bacilli, for freezing and thawing several times are without injury to them. They have been found to remain alive upon linen for from sixty to seventy-two days, and upon buckskin for from eighty to eighty-five days. Sternberg has succeeded in keeping hermetically-sealed bouillon cultures alive for more than a year. In the presence of chemical agents the bacillus is also able to retain its vitality, o.1 to 0.2 per cent. of carbolic acid added to the culture-media being without effect upon its growth. At one time the tolerance to carbolic acid was thought to be characteristic, but it is now known to be shared by other bacteria.

Cultures of the typhoid bacillus may be obtained, but with difficulty, from the alvine discharges of typhoid patients. In examining this material, however, it must be remembered that the bacilli are certain to be present only in the second and third weeks.

As numerous saprophytic bacteria are present in the feces, the resistance which the typhoid bacillus exhibits to carbolic acid can be made use of in obtaining the pure culture. To each of several tubes of melted gelatin 0.05 per cent. of carbolic acid is added. This addition is most easily calculated by supposing the average amount of gelatin contained in a tube to be 10 c. cm. To the average tubec.cm. of a 5 per cent. solution of carbolic acid is added, and gives very nearly the desired quantity. A

minute portion of the feces is broken up with a platinum loop and stirred in the tube of melted gelatin; a drop from this dilution is transferred to the second tube, a drop from it to a third, and then the contents of each tube are poured upon a sterile plate or into a Petri dish,

FIG. 75.-Bacillus typhi abdominalis: superficial colony two days old, as seen upon the surface of a gelatin plate; x 20 (Heim).

or rolled, according to Esmarch's plan, in the manner already described. The carbolic acid present in these cases prevents the great mass of saprophytes from developing, but allows the perfect development of the