1972 Volume 41 Issue 3 Pages 113-117
The 1% egg yolk mediums1) is prepared as follows: The salt solution consists of KH2PO4, 1.0g; sodium glutamate, 1.0g; distilled water, 100ml. Added 6 ml glycerol, 6ml of a 2 per cent malachite green solution and 200ml egg yolk to the salt solution, mixed well, and distributed in sterile test tubes (170mm long, 18mm in diameter) in 5ml amounts. The medium is then coagulated in a slanting position at 90°C for 60 minutes. Reaction of the medium is about 6.1.
Despite the fact that only the egg yolk medium supports gross visible growth of the acid-fast organisms supposedly murine leprosy bacilli, the ability of the medium proved not so satisfactory. As previously described2), all of the ingredients in the medium appeared to be necessary for growth of the organism. This paper aimed for the improvement of the medium.
The following modified egg yolk media were prepared by varying the concentration of the salts and the glycerol or by varying the pH of the medium. The test media in Experiments I and II had the same composition as the original (standard) one except that the amount of monopotassium phosphate in the salt solution was varied to give concentrations ranging from 0.3 to 3 per cent. As a result, these slants possessed different pH values from that of the standard (Table 1). In Experiment III, similarly, the test media had the same formula as the standard one except the concentration of sodium glutamate in the salt solution was altered from 1 to 0.5 or 2 per cent (Table 2). The glycerol was decreased or increased to give final concentrations ranging from 0.5 to 16 per cent in the case of the test media in Experiments IV and V (Table 3).
In Experiments VI-IX, the pH of the medium was adjusted to 6.4 to 7.0 either by adding dibasic sodium phosphate to the salt solution (Table 4) or by adding an aqueous sodium hydroxide solution to the medium before inspissation (Table 5).
A total of 169 subcultures of the supposed Hawaiian strain was used for these growth experiments. Small portions of the growth were transferred by a loop lightly on the middle of the surface of media and then the tubes were incubated at 37°C for 3 months. Observations were repeated weekly or biweekly to compare the size of the gross visible growth on the standard and modified egg yolk media with that of the negative control growth on Ogawa's egg medium inoculated in parallel.
Evaluation of the modified media was made according to whether the frequency of the positive growth on them is higher or not than that of the positive growth on the standard egg yolk medium. The results showed, however, that none of the modified egg yolk media tested were supperior to the original one.
