Definitive diagnosis of Johne’s disease in ruminants depends on confirming the presence of the causative bacterium, Mycobacterium avium subsp. paratuberculosis, in tissues of the host. This is readily achieved in most ruminant species by culture. However, culture of clinical specimens from sheep in many countries has been unrewarding. Such a culture from sheep was achieved recently in Australia by using a radiometric culture medium. The aims of the present study were to evaluate the culture of M. aviumsubsp. paratuberculosis from sheep by using modified BACTEC 12B radiometric medium, to determine the sensitivity of culture in relation to histopathology, and to evaluate a range of solid media. Culture of M. avium subsp. paratuberculosisfrom sheep with Johne’s disease is a sensitive method of diagnosis: intestinal tissues from all 43 animals with multibacillary disease and all 22 animals with paucibacillary disease were culture positive, while 98% of feces from 53 animals with multibacillary disease and 48% of feces from 31 animals with paucibacillary disease were culture positive. Of sheep without histological evidence of Johne’s disease from infected flocks, intestinal tissue from 32% of 41 were culture positive, while feces from 17% of 41 were culture positive. Consequently, culture is recommended as the “gold standard” test for detection of ovine Johne’s disease. Of the wide range of solid media that were evaluated, only modified Middlebrook 7H10 and 7H11 agars, which were very similar in composition to modified BACTEC 12B medium, yielded growth of ovine strains of M. avium subsp.paratuberculosis. The sensitivity of detection of M. avium subsp. paratuberculosis on solid media was slightly lower than that in modified BACTEC 12B radiometric medium. Both egg yolk and mycobactin J were essential additives for growth of ovine strains of M. avium subsp.paratuberculosis in both liquid and solid media.

SOME group-A streptococci cause the appearance of opacity in horse serum (Ward and Rudd, 1938). The production of the opacity factor (OF) is confined to members of certain serotypes (Keogh and Simmons, 1940;Gooder, 1961), and the OF of each serotype is antigenically specific (Top and Wannamaker, 1968a). Widdowson, Maxted and Grant (1970) confirmed the serological specificity of the OF and showed that it corresponded exactly to that of the M type of the streptococcus that produces it. The examination of a limited number of strains of each M type (Widdowson et al., 1970; and our unpublished observations) suggested that OF is produced by all members of 16 welldefined M types, and by a number of other types not so far established by international agreement.We have now made a more sytematic examination of the distribution of OF among strains of group-A streptococci sent to us for typing, and have investigated the use of the serum opacity reaction (SOR), and of its neutralisation by specific antisera, in routine typing and as a means of indentifying hitherto unrecognised streptococcal serotypes. MATERIALS AND METHODSStreptococci Strains used to produce antisera to OF in rabbits were the standard type strains used in the Streptococcus Reference Laboratory for the production of M antisera. Other strains sent to us for type identification from numerous laboratories were used in studies of the distribution of OF.Cultural methods Oxoid Todd-Hewitt Broth with the addition of 1 per cent. Neopeptone was seeded with a loopful of growth from solid medium and incubated overnight at 37°C. These cultures were used for the detection both of OF and of M antigen. Typing techniqueThe methods used in the Streptococcus Reference Laboratory for the preparation of typing sera and for M and T typing are those described by Williams (1958). M antigen was ~

Summary.A study of the morphotypes of 446 strains of Candida albicans, isolated from a variety of clinical specimens, is reported. The method was based on a morphotyping scheme that has recently been described, but not all of the potential characters were used in this analysis. By this limited code, 50 different morphotypes were distinguished, the largest group comprising 23% of the population. The simplicity and good discrimination of the method make it a useful typing scheme for C. albicans. Discontinuous colonial fringes were associated with strains from oral sites and deep infections. Significantly, 67% of strains from fatal infections were of the discontinuous fringe type, compared to only 11% of strains from other infections. Further associations between morphotype and anatomical source included narrow-coarse fringes in genitourinary isolates.

Strains of Candida albicans can be differentiated by the morphological features of streak colonies developed on malt agar. A morphotyping system is proposed, where numerical codes are assigned primarily on the basis of the nature and extent of marginal fringing and the surface topography of the streak colony. The system allows ready differentiation to be made of morphotypes, requires no specialized equipment or expertise and provides a simple and reproducible means for epidemiological studies of candida and candidosis.