Biotypes of the dermatophyte Microsporum distortum.

During a study of the epidemiology of Microsporum canis and closely related species, sub-specific variation was demonstrated within thirteen isolates of Microsporum distortum based on the pattern of carbohydrate utilization. Strains from three continents could be differentiated by their utilization of trehalose and erythritol. Isolates from New Zealand yielded the same patterns as M. canis (Arthroderma otae (-)); examination of 120 isolates indicated that M. canis could not be biotyped by carbohydrate utilization, although limited variation had been noted. Examination of total native protein patterns by gel electrophoresis showed that variations existed within the M. distortum group; the much larger number of M. canis (A. otae (-)) strains had appeared to be homogenous.

Polyacrylamide gel electrophoresis patterns of some Microsporum species.

The paper reports observations made of various Microsporum species during a PAGE pattern study of the epidemiology of Microsporum canis. It is shown that M. audouinii can readily be distinguished from M. canis but that M. equinum is more difficult to separate. M. rivalierii was distinguishable from M. audouinii, confirming previous reports. M. distortum could not be separated from M. canis by PAGE gels of total protein or by isozyme patterns generated. There are particular problems with studies of that type on dermatophyte protein in that the intrinsic proteases degrade the preparations.

The value of electrophoretic protein patterns for the study of Microsporum canis.

Whole-cell protein analysis of clinical isolates of Microsporum canis by polyacrylamide gel electrophoresis (PAGE) showed small but inconsistent differences in protein patterns. All clinical isolates closely resembled the (-) mating type of Arthroderma otae. A reference strain of A. otae (+) mating type from Japan gave a PAGE pattern which was distinct from those of the clinical isolates. Mating studies showed that the progeny of these reference (+) and (-) mating types had a variety of distinct protein patterns. Protein patterns can therefore distinguish between genetically different strains of M. canis (A. otae) suggesting that clinical isolates have a common clonal origin.

The dysgonic form of Microsporum canis in N.W. London.

An account is given of the occurrence in N.W. London of ringworm due to the dysgonic form of Microsporum canis in cats, dogs, and humans. The unusual morphology of the dysgonic strain is described as is the extraordinary lability of the fungus in culture. The distribution of cases in man and animals in the area is mapped. The clinical and epidemiological behaviour of the fungus, as illustrated by four family outbreaks, differs little from that of the typical strain. The origin of the dysgonic strain is unknown.

Atypical strains of Microsporum canis.

Four atypical isolates of Microsporum canis, three from humans and one from a cat, were obtained from North-West London. These and a further human isolate were compared with each other and with a typical isolate of the fungus. Immediately after isolation the atypical isolates were very labile, but were stabilised after a few subcultures from selected sectors. The stable forms differed from each other, but all had a tendency to brown rather than yellow pigmentation, to feathery submerged mycelium and to abnormal macroconidia. The macroscopic appearance and texture of the colonies depended on the density, orientation and branching pattern of the submerged mycelium. In recent years similar brown, feathery forms of M. canis have been reported from monkeys but not from cats. It is suggested that all such isolates may be culturally stable forms of a very unstable strains, probably feline in origin, which has yet to be described.