LITTLE is known about the epidemiology of infection with group-D streptococci. One reason for this may be that, to recognise members of the species that make up this group, several tests must be performed. A rapid and simple method is needed that can be applied in the diagnostic laboratory to identify members of the group and to distinguish clearly between the most important species, Streptococcus faecalis and S. faecium.The serological group diagnosis according to Lancefield remains the most accurate method for the classification of group-D streptococci; however, many difficulties have been met in the preparation of a potent group serum (Shattock, 1962), as well as in the extraction of the group-D antigen from the strains to be identiiied (Pleceaq, 1970). The cultural and biochemical tests used for the differentiation of species and varieties among the group-D streptococci were described by Deibel(1964), Hartman, Reinbold andSaraswat (1966), Facklam and Moody (1970) and Pleceaq (1970).In 1959 (Natkin, 1967; Herman and Hoch, 1971; Hoch and Hkrman, 1971). In the present note, we report the preliminary results of using mixtures of phages to give a group and a species diagnosis together in one test.
MATERIAL AND METHODS
Bacteriophages.Preparations of the following 20 enterococcal bacteriophages were used ; the routine test dilution (RTD) of each is given in brackets: (1) Romanian phages (Plecew, 1970), -nos. l(lO3), 2OO (lO3), 4(lO3), 5(103), 7(103), 41(102) (103). Three of the phages, namely nos. 8,670 and 867, are specific for S. faecium and the remainder for S. faecalis. The RTD of the phages was determined as the highest decimal dilution of the preparation that gave confluent lysis of the propagating strain of the phage.For the group diagnosis a mixture of equal quantities of the 20 undiluted phage preparations was used. It should be noted that the final strength of the individual phages in this pool varied between an RTD of 500,000 and 0.5, but was in most instances well in excess of 1.For the species diagnosis a mixture of the 17 phages specific for S. faecalis each diluted to a final strength of RTD x 1, and a mixture of the three phages specific for S. faecium similarly diluted, were applied. If no reactions were obtained, the tests were repeated with pools of phage at RTD x 10. Additionally, for the differentiation of S. faecalis, we used the following three pools of phages all at a final dilution of RTD x 1 : pool no. 1, phages no. 2OO,4, 5, 27E and 7; pool no. 2, phages no. 41,4D1,16D, 26D and 4D2; pool no. 3, phages no. 24D, 10,
