The previously reported sodium polyanethol sulfonate disk test for the identification of Peptostreptococcus anaerobius (Graves et al., 1974) was evaluated, with modifications. Three bands of brucella agar, three inoculum sizes, and two inoculum sources were compared. Nine stock cultures of P. anaerobius (eight normal flora isolates and ATCC 27337) and 16 fresh clinical isolates were used. All cultures of P. anaerobius showed inhibition zones of 12 to 30 mm in diameter, regardless of test conditions. Out of 103 clinical isolates of other species of anaerobic gram-positive cocci tested, only two had an inhibition zone size in this range (one P. micros of 11 studied had a zone of 12 mm and one P. prevotii of 14 studied had a zone of 16). The test had an overall accuracy of 98% in the identification of P. anaerobius from clinical specimens. Since P. anaerobius accounts for one-fifth to one-third of all anaerobic gram-positive cocci encountered in clinical specimens, this simple and rapid technique can be very useful for presumptive identification.
A simple and practical test for the identification of
Bacteroides fragilis
is described. It utilizes two well-known properties of this species, i.e., stimulation of growth by bile and resistance to kanamycin. The test media are a tryptic-soy bile agar plate and a supplemented blood agar plate on which a kanamycin 1,000-μg/ml disk is placed. Incubation is for 24 h at 37 C in GasPak. The results of screening 190 strains, mostly clinical isolates, indicate that
B. fragilis
can be easily and reliably distinguished from other
Bacteroides
and from
Fusobacterium
species by its growth on tryptic-soy bile agar and resistance to kanamycin.
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