Abstract
In Prévot's Manual (1966), gas production is one of the important characteristics for the identification of anaerobic cocci. No methods of examining gas production, however, were described in this manual.
Comparison was made on gas production among Rosenow cysteine medium (Buttiaux et al., 1966), GAM semisolid medium (Nissui) with vaselin seal, VF deep agar (Lebert et al., 1952), and VL deep agar (Buttiaux et al., 1966). Nineteen reference strains obtained from the ATCC, NCTC, and Pasteur Institute (Lille, France) and 133 strains isolated from clinical materials in the author's laboratory and the Juntendo University Hospital were used.
Ten of the 19 reference strains produced visible gas in GAM semisolid medium with vaselin seal at one day of incubation. The gas production of these 10 strains in other three media required incubation of two or three days.
The other nine strains produced no gas in four kinds of media by 14 days of incubation.
Of 133 strains isolated from clinical materials, 86 produced gas in Rosenow cysteine medium and GAM semisolid medium with vaselin seal, but 26 strains produced no gas in either medium by 14 days of incubation. Gas production of 21 strains was observed in the latter medium, but not in the former medium by 14 days of incubation. In VF deep agar, 12 of these 21 strains produced gas, but the other nine strains produced no gas by 14 days of incubation.
Thus the results of examination of gas production were influenced by the kind of media and the incubation time, so that confusion in the identification of the species was unavoidable. If the above 21 strains are considered to produce gas, 14 strains of them will be identified as Peptococcus asaccharolyticus, 1 strain as Peptostreptococcus anaerobius, and 6 strains as unidentified. On the other hand, if they are considered to produce no gas, they will consist of 6 strains of Peptococcus anaerobius and 15 unidentified strains.
