CHAPTER XXIX. GLANDERS. BACILLUS MALLEI (LÖFFLER AND SCHÜTZ).* General Characteristics.-A non-motile, non-flagellate, non-sporogenous, non-liquefying, non-chromogenic, non-aërogenic, aërobic and optionally anaerobic, acid-forming and milk coagulating bacillus, pathogenic for man and the lower animals, staining by ordinary methods, but not by Gram's method. Glanders is an infectious mycotic disease which, fortunately, is almost entirely confined to the lower animals. Only occasionally does it secure a victim among hostlers, drovers, soldiers, and others whose vocations bring them in contact with diseased horses. Several bacteriologists have succumbed to accidental laboratory infection. Glanders was first known to us as a disease of the horse and ass, characterized by the formation of discrete, cleanly cut ulcers upon the mucous membrane of the nose. The ulcers in the nose of the horse and ass are formed by the breaking down of inflammatory nodules which can be detected in all stages upon the diseased membranes. The ulcers, having once formed, show no tendency to recover, but slowly spread and persistently discharge a virulent pus. The edges of the ulcers are indurated and elevated, their surfaces often smooth. The disease does not progress to any great extent before the submaxillary lymphatic glands begin to enlarge, soften, open, and become discharging ulcers. The lungs may also become infected by inspiration of the infectious material from the nose and throat, and contain small foci of bronchopneumonia not unlike tubercles in their early appearance. The animals ultimately die of exhaustion. Specific Organism.-In 1882, shortly after the discovery of the tubercle bacillus, Löffler and Schütz discovered in the discharges and tissues of the disease the specific micro-organism, the glanders bacillus (Bacillus mallei). * "Deutsche med. Wochenschrift," 1882, 52. Distribution. The glanders bacillus does not seem to find conditions outside the animal body suitable for its growth, and probably lives a purely parasitic existence. Morphology.-The glanders bacillus is somewhat shorter and distinctly thicker than the tubercle bacillus, and has rounded ends. It measures about 0.25 to 0.4 X 1.5 to 3 μ, and is slightly bent; coccoid and branched forms sometimes occur. It usually occurs singly, though upon blood-serum, and especially upon potato, conjoined individuals may occasionally be found. Long threads are never formed. Fig. 253. Bacillus mallei, from a culture upon glycerin agar-agar. X 1000 (Fränkel and Pfeiffer). When stained with ordinary aqueous solutions of the aniline dyes, or with Löffler's alkaline methylene-blue, the bacillary substance does not usually appear homogeneous, but, like that of the diphtheria bacillus, shows marked inequalities, some area being deeply, some faintly, stained. The bacillus is non-motile, has no flagella, and does not form spores. Staining. The organism can be stained with the watery anilin-dye solutions, but not by Gram's method. The bacillus readily gives up the stain in the presence of decolorizing agents, so is difficult to stain in tissues. Löffler accomplished the staining by allowing the sections to lie for some time (five minutes) in the alkaline methylene-blue solution, then for five seconds, then to absolute alcohol, xylol, etc. The bacilli appear dark blue upon a paler ground. This method gives very good results, but has been largely superseded by the use of Kühne's carbol-methylene-blue: Kühne stains the section for about half an hour, washes it in water, decolorizes it carefully in hydrochloric acid (10 drops to 500 c.c. of water), immerses it at once in a solution of lithium carbonate (8 drops of a saturated solution of lithium carbonate in 10 c.c. of water), places it in a bath of distilled water for a few minutes, dips it into absolute alcohol colored with a little methylene-blue, dehydrates it in anilin oil containing a little methylene-blue in solution, washes it in pure anilin oil, not colored, then in a light ethereal oil, clears it in xylol, and finally mounts it in balsam. Vital Resistance. The organism grows only between 25° and 42° C. It is killed by exposure to 60° C. for two hours, or to 75° C. for one hour. Sunlight kills it after twenty-four hours' exposure. Thorough drying destroys it in a short time. When planted upon culture-media, sealed, and kept cool and in the dark, it may be kept alive for months and even years. Exposure to 1 per cent. carbolic acid destroys it in about half an hour; 1: 1000 bichlorid of mercury solution, in about fifteen minutes. According to Hiss and Zinsser, it may remain alive in the water of horse-troughs for seventy days. Isolation. Attempts at the isolation of the glanders bacillus from infectious discharges by the usual plate method are apt to fail, on account of the presence of other more rapidly growing organisms. The best method of isolation seems to be by infecting an animal and recovering the bacillus from its tissues. The guinea-pig, being a highly susceptible as well as a readily procurable animal, is appropriate for the detection. and isolation of the bacillus. When a subcutaneous inoculation of some of the infectious pus is made, a tumefaction can be observed in guinea-pigs in from four to five days. Somewhat later this tumefaction changes to a caseous nodule, which ruptures and leaves a chronic superficial ulcer with irregular margins. The lymph-glands speedily become invaded, and in four or five weeks signs of general infection appear. The lymph-glands, especially of the inguinal region, suppurate, and the testicles frequently undergo the same process. Later the joints are affected with a suppurative arthritis, the pus from which contains the bacilli. The animal eventually dies of exhaustion. No nasal ulcers form in guinea-pigs. In field-mice the disease is much more rapid, no local lesions being visible. For two or three days the animal seems unwell, its breathing is hurried, it sits with closed eyes in a corner of the cage, and finally, without any other preliminaries, tumbles over on its side, dead. From the tissues of the inoculated animals pure cultures are easily made. Perhaps the best places from which to secure a culture are the softened nodes which have not ruptured, or the joints. Diagnosis of Glanders.-Straus* has given us a method which is of great use, both for isolating pure cultures of the glanders bacillus and for making a diagnosis of the disease. But a short time is required. The material suspected to contain the glanders bacillus is injected into the peritoneal cavity of a male guinea-pig. In three or four days the disease becomes established and the testicles enlarge; the skin over them becomes red and shining; the testicles themselves begin to suppurate, and often evacuate through the skin. The animal dies in about two weeks. If, however, it be killed and its testicles examined, the tunica vaginalis testis will be found to contain pus, and sometimes to be partially obliterated by inflammatory exudation. The bacilli are present in this pus, and can be secured from it in pure cultures. The value of Straus' method has been somewhat lessened by the discovery by Kutcher, † that a new bacillus, which he has classed among the pseudo-tubercle bacilli, produces a similar testicular swelling when injected into the abdominal *"Compt. rendu Acad. d. Sciences," Paris, CVIII, 530. "Zeitschrift für Hygiene," Bd. xxi, Heft 1, Dec. 6, 1895. cavity; also by Levy and Steinmetz,* who found that Staphylococcus pyogenes aureus was also capable of provoking suppurative orchitis. However, the diagnosis is certain if a culture of the glanders bacillus be secured from the pus in the scrotum. As the purulent discharges from the noses of horses and other large animals commonly contain very few bacilli, their detection by the use of the guinea-pig inoculation is much simplified. For the diagnosis of the disease in living animals, subcutaneous injections of mallein (q. v.) are also employed. McFadyent was the first to recommend agglutination of the glanders bacillus by the serum of supposedly infected animals as a test of the existence of glanders. The subject has been somewhat extensively tried and officially adopted by the Prussian government. Moore and Taylor, ‡ in a recent review and examination of the test, conclude that it is easier and quite as accurate as the mallein method and is applicable in cases where fever exists. The maximum dilution of normal horse-serum that will macroscopically agglutinate glanders bacilli is 1: 500, but occurs in very few cases. The maximum agglutinative power of the serum of diseased horses not suffering from glanders is not higher than that of normal serum. The diagnosis is usually not difficult to make, but requires much care. Cultures of the glanders bacillus sometimes unexpectedly lose their ability to agglutinate. The diagnosis of glanders by means of the complementfixation method has been tried with glittering results by Mohler and Eichhorn. § Cultivation. The bacillus is an aërobic and optionally anaërobic organism, and can be grown in bouillon, upon agar-agar, better upon glycerin agar-agar, very well upon blood-serum, and quite characteristically upon potato. The optimum temperature is 37.5° C. Colonies. Upon 4 per cent. glycerin agar-agar plates the colonies appear upon the second day as whitish or pale yellow, shining, round dots. Under the microscope they are brownish yellow, thick and granular, with sharp borders. Bouillon. In broth cultures the glanders bacillus causes * "Berliner klin. Wochenschrift," March 18, 1895, No. 11. |