Imágenes de páginas
PDF
EPUB
[graphic][ocr errors][subsumed][merged small]

Twenty-four hours' agar cultivation. Stained Gram. Washbourn and Goodall's "Infectious Diseases.")

[blocks in formation]
[graphic]

FIG. 40.-BACILLUS DIPHTHERIÆ.

Forty-eight hours' blood serum cultivation. Stained Gram.

× 1000.

Morphology.-Straight and slightly curved rods 3 to 4 μ long (twenty-four hours blood serum cultivation), often showing segmentation of the cell plasm by which the bacilli stain irregularly, especially with methylene blue.

By Neisser's method these bands are stained as blue dots, the rest of the organism brown. The bacillus usually lie grouped together with their long axes parallel, constantly the bacilli are of tapering wedge-shaped form, with the bases in apposition.

In older cultivations the ends of the bacilli become swollen and club shaped, forming the characteristic form. Various involution forms occur, the organisms becoming very much swollen, wedge shape, ovoid, &c. The segmentation of the cell plasm is usually well marked. In these older cultures red granules are often to be seen in specimens stained with carbol methylene blue. The organism retains the stain of Gram's method.

Various branched forms have been observed in old cultures as has been also observed with the tubercle bacillus, it is therefore suggested by Hueppe and others that these two organisms are really only a phase in the life cycle of some higher organism allied to the Streptotricheæ, such as S. actinomyces. Chester calls them myco-bacteria.

The diphtheria bacillus is not known to produce spores, although the condensation of the protoplasm and plasmolysis often gives the appearance of sporulation; still the death of the organism at the low temperature of 58° C. precludes the presence of true endogenous spores.

The diphtheria bacillus is not motile and is not known to possess flagella.

Biology.-Growth occurs on the ordinary laboratory media at 37-5° C., and at 22°, the optimum temperature being that of the body. The organism is facultative anäerobic and does not liquefy gelatin, and produces no pigment.

Gelatin Streak, 22° C.-In three days small discrete, raised white colonies, or confluent streak, edge indentate, no liquefaction. Gelatin Stab, 22° C.-Minute granular, discrete colonies to bottom of stab, no liquefaction.

Gelatin Plates, 22° C.-Minute white points, granular, irregular, under the "granular, irregular and yellowish-brown.

Agar Streak, 37.5° C.--In twenty-four hours does not grow luxuriantly at first, but does so after several transplantations.

Glycerine Agar, 37.5° C.-Delicate moist white to yellowish. Colonies.-Macroscopical (a) Superficial, delicate, grey-white, translucent.

(b) Deep, oval, grey, entire, amor

phous.

Microscopical (a) Superficial, round, entire, yellowish, translucent.

Blood Serum, 37.5° C.-Opaque white or grey raised colonies, or dull granular moist grey streak.

Potato, 22° C.-Glistening growth on alkaline potatoes which has the same colour as the medium. No growth on acid potato.

Litmus Milk, 37.5° C.-Twenty-four to forty-eight hours acid, no coagulation, later an alkaline reaction appears.

Broth, 27-5° C.-Twenty-four hours granular deposit with fine flocculi, often forming a surface film. Reaction at first acid, later alkaline.

Glucose Broth, 37-5° C.-Acid production. Acid is also formed from glycerine.

Peptone Water, 37·5° C.—Indol produced in seven days. In old cultures some nitrite is also formed, so that a cholera red reaction is given with pure sulphuric acid (nitrate free). A slight amount of sulphuretted hydrogen may be produced.

[ocr errors]

Pathogenesis. Inoculation of animals by the subcutaneous method with small quantities of the diphtheria bacilli causes death in from three to six days. Guinea-pigs are the most susceptible, rabbits being considerably more resistant. Subcutaneous inoculation of guinea-pigs with 0·1 to 0·3 cubic centimetres of broth culture results in death. The pathological changes observed at the autopsy are extensive ecchymosis and local oedema at the seat of inoculation, increase of fluid in the various serous cavities, pericardial, pleural and peritoneal; injected, enlarged and hæmorrhagic suprarenal capsules, with occasionally a slight swelling of liver and spleen. There may be a good deal of lymphatic enlargement and congestion, but it is not a constant symptom. Small dotted areas of necrosis and fatty degeneration are often found in the liver, kidney, and heart muscle, more particularly in those cases in which death is long delayed. The most typical lesions are the fibrous-gelatinous exudation at the seat of inoculation from which the diphtheria bacillus can be recovered in pure culture, and the hæmorrhagic suprarenal bodies.

[graphic][merged small]

Blood serum cultivation at thirty-six hours. (From Curtis' "Essentials of Practical Bacteriology.")

The bacillus is not found in the blood or in any of the organs. Roux and Yersin, who performed a large number of experimental inoculations in demonstrating the undeniable relation of the diphtheria bacillus to the disease of that name, found that rabbits, if inoculated subcutaneously with 2 cc. of virulent broth culture generally died in twenty to twenty-five days. Those animals which remained alive the longest often exhibited paralysis of the hind limbs, and other symptoms recalling the post-diphtherial paralysis of the human subject.

Pigeons generally recovered unless inoculated with 0.5 cc. or more of the broth culture. Rats and mice will withstand large

doses and are practically immune.

Toxine formation.-It is clear that a disease such as diphtheria, in which widespread pathological changes are followed by the injection of bacilli, and yet the organisms injected are only to be found subsequently at the site of inoculation, must owe its symptoms to a poison produced by the organisms rather than to the presence of the organisms themselves. That this is the case was first demonstrated by Roux and Yersin, who filtered broth cultivations of the diphtheria bacillus through porous porcelain. The fluid thus obtained is entirely free from bacteria, but contains any soluble poisons produced by the activity of the organism. It was found that the filtered culture, when injected into guinea-pigs and rabbits, produced all those symptoms described as caused by the injection of the bacilli themselves; no bacteria were found, however, at the site of inoculation, although the suprarenal glands showed the typical hæmorrhagic symptoms. The diphtheria bacillus therefore produces a poison or toxine.

The formation of the toxine goes on in the broth culture under certain conditions, an alkaline reaction favouring its production, little developing when the reaction is acid. The toxine is destroyed by exposure to the temperature of boiling water, and is much reduced in potency, although not actually destroyed, by a temperature of 58° C. for two hours. It is precipitated from the broth culture by the addition of three or four volumes of absolute alcohol to one of culture, and the white precipitate thrown down is soluble in distilled water. When injected it produces the same. symptoms as the injection of broth culture.

Sidney Martin has described a method of obtaining the toxine in quantity, using a solution of alkali albumin to grow the organisms

« AnteriorContinuar »