The development and evaluation of a new selective medium (colistin-oxolinic acid-blood agar) for streptococci is described. Streptococci of medical and veterinary importance grew well on the medium. Gram-negative organisms, staphylococci, Bacillus spp., and coryneforms are all inhibited. It was concluded that the medium is valuable for the isolation of streptococci in pure culture from mixed flora and has advantages over other media previously described. Increased isolation rates were obtained together with earlier identification of the isolated strains. The isolation of streptococci is often complicated by the presence of other bacterial flora, which may either overgrow or restrict the growth of the streptococci. A number of media selective for streptococci have been described (1, 2, 5-7, 9, 10, 13, 14, 18, 19). In certain of these media, some of the selective agents have an adverse effect on some species of streptococci (3, 5, 6, 9, 11, 12, 14-16), including those for which the medium was developed. During the development of a selective broth medium for the rapid detection of streptococci (Petts, M.S. thesis,

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A commercial streptococcal grouping system was used to demonstrate streptococcal antigen in swabs before culture. The method detected 81% of the streptococci of groups A, B, C, and G subsequently isolated in culture. The method offers a sensitive and specific method for the early detection of beta-hemolytic streptococci.

A simple trivalent colour test, developed for the rapid detection and identification of streptococci belonging to Lancefield groups A, C and G, was evaluated for sensitivity and specificity with cultures and when directly used with wound and throat swabs. In tests performed on cultures, all of 94 group A, 78 group C and 94 group G cultures were correctly identified. In direct tests on wound swabs, 49 of 52 group A, 17 of 19 group C and 48 of 51 group G streptococci were detected and correctly identified; no false positives were observed. With throat swabs from pharyngitis patients 34 of 36 group A, 3 of 6 group C and 5 of 8 group G streptococci gave positive results. Almost 10% of these swabs gave false positive reactions with the group C component of the test system. Samples taken from uninfected individuals indicated that the false positives were probably associated with blood group A. The test system gives rapid and reliable results with streptococcal cultures, but when directly applied to clinical samples the results must be interpreted with caution, particularly if the patient's blood group is not known.

The use of oxolinic acid as a selective agent for the isolation of non‐sporing anaerobes from clinical material was investigated. At a concentration of 5 mg/l it compared favourably with nalidixic acid for this purpose and had the advantage of inhibiting the growth of staphylococci.