Mary P. English

Fungi in nails.

REPORTS from dermatological clinics of the incidence of various fungi in onychomycoses have appeared from many parts of the world. Surprisingly, many of them do not distinguish between fingerand toenails, and by no means all include yeasts and moulds as well as dermatophytes. There have been few studies of the incidence of onychomycosis in the general population (Grimmer, 1954; Langer, 1957). The present article combines a report of ca.ses of onychomycosis investigated in a routine mycological laboratory over a period of eight years with a detailed study of fungal infections of the toenail and their incidence in all new patients seen by one of us (M. M. W.) at dermatological clinics over a period of three years. In this way, it was hoped that a clearer picture than is at present available of the clinical features and epidemiology of onychomycosis due to different groups of fungi might be obtained.

The saprophytic growth of non-keratinophilic fungi on keratinized substrata, and a comparison with keratinophilic fungi

Of thirty-three species of non-keratinophilic fungi of twenty-five genera, all but two were able to utilize, as sole source of nutrient, at least some part of various keratinized substrata supplied to them. Invasion of these materials was by means of froncled mycelium produced by all the fungi; by boring hyphae produced by some of them; and by unspecialized mycelium. The means of invasion varied according to the physical nature of the substratum, and it was shown experimentally that those with a stratified and resistant physical structure induced the formation of fronds and borers. Digestion by the fungi in substrata containing hard keratin was apparently limited to the non-keratinized intercellular structures, but there was some evidence that medullary trichohyalin and soft keratin might undergo digestion. The fungi examined could be divided into five groups according to the type of substratum they were able to invade and the means by which they did so. The nature and mechanism of fronds and borers is discussed and it is suggested that the function of the former is primarily the absorption of nutrients, while that of the latter is the penetration of resistant and undigestible materials. The probable relationship between the fronded mycelium and borers of non-keratinophilic fungi and the eroding fronds and perforating organs of keratino-philic fungi is examined.

The saprophytic growth of Keratinophilic fungi on keratin

The growth of 9 species of keratinophilic fungi belonging to the genera Keratinomyces, Microsporum, Trichophyton and Epidermophyton was studied in vitro on hair, hedgehog spine, nail and callus. On hair digestion is carried out primarily by means of flat fronds of eroding mycelium which first life the cuticular scales and then erode the cortex. The well-known perforating organs arise from these fronds and in their turn may prouce further eroding mycelium which grows longitudinally through the cortex of the hair. The mechanism of penetration by perforating organs is discussed and a special study of T. rubrum showed that its method of attack on hair does not differ fundamentally from that of other keratinophilic fungi.It is also by means of fronds of eroding mycelium growing between the layers of keratinised cells that these fungi digest nail and hedgehog spine. Perforating organs are produced on both substrates by certain species. Eroding mycelium is uncommon in the softer keratin of callus.As frond-like m...

Onychomycosis in elderly chiropody patients

The thickened toe‐nails of 168 patients attending a chiropody clinic for old age pensioners were examined for onychomycosis by a suction drill sampling method. The nails of sixty‐eight (41%) of the patients were microscopically positive. Cultures from 12% of these were unsuccessful. Of the remainder, twenty (12%) were infected by dermatophytes and 42 (25%) by moulds. In addition, large quantities of several yeast species were grown from thirteen microscopically negative nails. A higher proportion of men than of women in the same age range were infected both by dermatophytes and moulds.

Invasion of the skin by filamentous non-dermatophyte fungi.

SUMMARY. —Four cases of invasion of the glabrous skin by filamentous, non‐dermatophyte fungi are described. Aspergillus niger was found in the toewebs of 1 patient and Allescheria boydii in those of another. Fusarium solani and F. oxysporum var. redolens were colonising necrotic skin in 2 diabetic patients.

THE FUNGAL FLORA OF ULCERATED LEGS

—The legs of patients with venous ulcers have been examined for funj*!, and the factors affecting the growth and spread of the organisms found have been studied. Candida parapsilosis, Fusaritun oxysporutn and F. solani were the most common species. Their headquarters was the moist skin surrounding the ulcers rather than the ulcers themselves, but such skin was regularly invaded by fungi only in patients from certain clinics: in these clinics there was evidence of cross-infection between patients during treatment. C. parap.iilosis was found to be less dependent on moisture than the Fusarlutn spp. and was associated with the less severe and drier ulcers as well as with the severe ones. The Fusaria were found only in legs with severe, moist ulcers. Experiments and observations to determine the origin of the fungi and the effect on them of various environmental conditions are reported, and the clinical and epidemiological significance of the results discussed. The unexpected rarity of C. albicuns, which was only found once, is also considered.

An improved method for the isolation of fungi in onychomycosis.

A description is given of the use of a drill for obtaining nail samples for fungal culture in cases of onychomycosis. The nail dust produced by the drill is collected by suction into a bag, and used to inoculate culture plates. Nail dust was found to be greatly superior to clippings for the successful culture of both dermatophytes and non‐dermatophytes. Possible reasons for this are discussed and it is suggested that in dermatological practice a drill should be used for sampling nails where attempts to culture from clippings have failed.

Trichophyton persicolor infection in a population of small wild mammals

A survey of Trichophyton persicolor infection in small wild mammals has been carried out on a Berkshire estate by means of Mackenzies hairbrush technique.Of 127 bank voles (Clethrionomys glareolus) examined, 53% were infected, of 113 field voles (Microtus agrestis) 25% were infected, and of 26 wood mice (Apodemus sylvaticus) 19% were infected, as was 1 of 6 common shrews (Sorex araneus). More than 1 in 2 infected bank voles were “colonized” by the fungus compared with only 1 in 5 infected field voles.The occurrence of T. persicolor in wood mice and common shrews is noted for the first time, but it is suggested that these species are not the normal hosts of the fungus.The infection rate in voles inhabiting woodland and old-established grassland was considerably higher than in those inhabiting an area of new plantation. Possible explanations for this are discussed.

THE EPIDEMIOLOGY OF ANIMAL RINGWORM IN MAN

Summary.— The epidemiology of animal ringworm in man is reviewed in the light of 7 factors affecting the incidence of the disease in man:

Variation in Trichophyton rubrum as seen in a routine diagnostic service.

A survey has been made of the strains of Trichophyton rubrum occurring in a mycological diagnostic service during the 9 years of its existence. The great majority of the 265 isolates investigated could be assigned to the type Trichophyton (Epidermophyton) rubrum (Castellani, 1910) but 3 other described strains were also found, together with 2 hitherto underscribed. In addition, 1 strain intermediate between T. rubrum and T. mentagrophytes (interdigitale type) is discussed.