A culture medium for Haemophilus ducreyi. Some technical data related to this bacillus isolation.

Abstract

The author examines the technique used by Ducrey in obtaining pure cultures of Haemophilus ducreyi by the inoculation of infectious material in humans, and notes that the culture could be maintained pure from six to fifteen passages. He emphasizes the use of blood agar as proposed by Benzançon and associates, and describes some of the most important modification of this medium. The author then presents a new medium for the isolation of H. ducreyi, essentially a 2% glicerol in potato infusion, arrived at after considerable testing of a variety of substances. He gives detailed instructions for the preparation, use, and storage of the new medium. For the collection of clinical material, subsequent incubation, and isolation, he presents the following technique:

After throughly cleaning the lesion, disinfection is achieved by iodine diluted in alcohol. The lesion is then covered with a film of collodion or tape for 48 hours, after which, 3 to 4 loopfuls of pus (free of blood) are taken from the lesion and inoculated into tubes containing 1 ml of a solution of 0.01 % rosolic acid, (Rosolic acid Merck       1 gm.; alcohol 50 ml; distilled water to make 100 ml; 0.1 ml is diluted in 9.9 ml of saline.) In this preliminary processing the rosolic acid acts bacteriostatically on Gram-positive bacteria. After shaking, the tubes are incubated at 32° - 34° C, and at intervals of 4 - 8 and 24 hours, portions of the settled sediment are seeded in the new medium, the plates of which are kept humid by the use of a few drops of saline on the inside cover of the Petri dish. The plates are then inverted and incubated for 48 - 72 hours at 32 - 34° C. The author obtained a 41.6 % recovery of H. ducreyi on a series of 12 closed infected lymph-nodes, In all cases, he noted that on microscopic examination, the bacilli showed a distinct morphology, their size being three to four times larger and broader than the normal bacilli and that they characteristically stained heavier at their ends. The new medium described provides a very luxuriant growth of H. ducreyi, as seen in figures 4 and 5 and has proven an excellent medium for other species of the genus Haemophilus even Bordetella pertussis was easily isolated in the medium by the cough plate method.