Suitable thioglycolate media for the cultivation of Vibrio fetus.

Vibrio fetus is usually considered an organism difficult to grow on primary isolation. Even after adaptation to laboratory media growth remains scanty, and frequent transfers are required. However, we have found that excellent growth can be obtained on thioglycolate medium. (Brewer modified), which contains per liter: trypticase, 17.0 g; phytone, 3.0 g; glucose, 6.0 g; sodium chloride, 2.5 g; sodium thioglycolate, 0.5 g; agar, 0.7 g; L-cystine, 0.25 g; sodium sulfite, 0.1 g. A dehydrated medium having this composition is now available at Baltimore Biological Laboratory. This formula is highly satisfactory both for the primary isolation and the maintenance of Vibrio fetus cultures. Heavy growth is usually obtained in the tubes within 48 hours following inoculation of tissue fluids or stomach content of aborted fetuses. Incubation in an atmosphere of CO2 is not necessary when liquid thioglycolate medium is used. Cultures. will retain their viability for months when stored at room temperature following incubation at 37 C for 2 to 3 days. Of 35 stock cultures now being maintained in this medium, heavy growth is produced by 31 cultures in 48 hours at 37 C, while 96 hours' incubation is required for the other 4 cultures. It has been noted that thioglycolate broth which has been freshly autoclaved or steamed is less satisfactory than that which has been left at room temperature 4 or 5 days. This may possibly be due to an excessive oxygen reducing ability of fresh broth. In a medium which has been allowed to absorb oxygen prior to inoculation the zone of growth extends downward to a depth of one-half to three-quarters inch from the surface. Three-hundred ml Erlenmeyer flasks containing 100 ml of broth can be used very satisfactorily to obtain large quantities of organisms. A very turbid growth will be found throughout the flask in 2 to 3 days if a heavy inoculum is used. Solid thioglycolate medium, having the composition given above but with 3 per cent agar, is currently being used to prepare antigens for the vibrio agglutination test. The medium is dispensed in Kolle flasks and inoculated with 2 ml of a heavy suspension of organisms. A brownish mucoid growth covering the entire surface of the agar is obtained after 3 to 4 days' incubation at 37 C if 5 to 10 per cent of the air is replaced with CO2. The high concentration of agar gives a firm surface from which the organisms are easily washed. 772 [VOL. 64 NOTES