THE fungi which can infect man are legion but we are concerned here with those common organisms which cause the various ringworm infections of the skin.
Candida albicans is normally a component of the flora of the human body, both cutaneous, oral, vaginal and intestinal and is in many cases transmitted to the child at birth. Alteration of the defense mechanisms by chronic diseases, immunological and hormonal abnormalities leads to the development of clinical forms of candidiasis.
Most of the ringworm fungi are transmitted from one person to another through direct or indirect contacts. Floors, duckboards, furniture, clothing, shoes and barbers’ instruments contaminated with infected fragments of skin and hair are sources of infection for ringworm of the feet, body and scalp. Such transmission in a closed community like a boarding school can result in a rise in the rate of infection with ringworm of the feet from 5 to 36 per cent within 2 years. The importance of these sources of infection is also shown by the reduction in in-cidence among susceptibles when areas such as swimming bath floors are adequately cleaned.
Other infections are acquired from animals; cats and dogs being a source of the organism microsporon canis which causes ringworm of the scalp. Cattle, and in particular calves, are the source of Trichophyton verrucosum, causing cattle ringworm.
While the sources of infection are known, virtually nothing is known of the factors which determine the susceptibility or resistance of the host. In some cases superficial fungus infections recur year after year, while in others infection is brief; in addition, only a minority of those exposed become infected. Infection is followed by the development of hypersensitivity to the fungus and as this reaches its peak, in primary infections the lesion clears. Waning of immunity coincides with reduction in the degree of hypersensitivity but on reinfection the defences react quickly producing a rapid destruction of both host and fungus tissue and a rapid casting off of the infection. Whether resistance to infection is dependent on the sensitivity is not fully established.
Candida infection may present in a variety of ways. In infants it is not uncommon in the first few weeks of life in the oral cavity, producing thrush in which milk white spots looking not unlike fungus cultures appear on the buccal mucosa and tongue; when scraped with a spatula these can be removed. In adults the same type of infection may follow antibiotic therapy, especially if oral and also may occur in patients taking corticosteroids. In both age groups nystatin oral suspension (100,000 units of nystatin per ml) applied as a paint 4-hourly usually controls the infection rapidly.
In infants such an oral infection may be followed by the appearance of a flexural intertrigo, usually first attacking the groins and gluteal cleft then axillae, fold? of the chin and neck. Unlike a napkin eruption it is worse in the apex of the skin folds and forms a bright red glazed erythema with a demarkated but undermined edge. If severe, scattered scaly macules may appear on the trunk and scalp giving an ultimate appearance resembling psoriasis. Candida can usually be grown from the flexural lesions and treatment with nystatin cream or antiseptic steroid ointment thrice daily heals the lesions rapidly.
A similar intertrigo, often exuding serum, may be seen in the groins, natal cleft and sometimes spreading to the submammary areas and axillae in obese women. In such patients diabetes mellitus is usually the alteration in the soil which has allowed Candida to become a pathogen. It is important to observe the demarkated but slightly undermined edge to the lesion which looks as though it could have been vesicular. In severe cases psoriasiform macules may appear on the trunk as a sensitisation reaction and make the differential diagnosis from flexural psoriasis or seborrhoeic eczema difficult until the urine is tested. One sugar-free urinary specimen should not be accepted and if there is any doubt a glucose tolerance test should be performed.
The equivalent eruption is seen as balanitis in the uncircumcised male diabetic. Candida balanitis in the male also occurs in the absence of diabetes when exposed to chronic Candida infection of the vagina in his partner, which has been shown to be more prevalent in women on the contraceptive pill. The prolonged use of potent corticosteroid applications, particularly in the flexures, causes overgrowth of Candida which often becomes the cause of chronicity of the lesion. Control of the diabetes is the most important measure and it is difficult to heal the eruption completely until this is achieved. Nystatin ointment or clotrimazole cream (Canesten) are specific local treatment; 1 per cent aqueous gentian violet is cheaper, effective but very messy.
The commonest area for Candida to cause trouble is the nail fold, producing chronic paronychia. Prolonged immersion of the hands in water frequently causes the quick to separate from the nail plate and the fungus becomes established in this area. Housewives, nurses, cooks, barmaids and bottle-washers are among those prone to develop this infection, the organism being acquired from the gastro-intestinal tract or sometimes associated with an active Candida vaginitis. Once established, recurrent painful swelling appears at the base of the nail producing a red bolstered appearance; a bead of pus can be squeezed from this when active and damage to the nail bed causes the nail plate to become ridged and distorted. Rarely the organism may invade the nail plate causing it to become opaque, thickened and broken. Once one nail fold is affected others soon succumb until in severe cases all fingers are invaded.
Treatment is simply a matter of persuading the patient to keep the hands dry by using rubber or polythene gloves over cotton gloves for all wet work and to apply nystatin ointment, clotrimazole cream (Canesten) or amphotericin B lotion to the nail folds at least 3 times daily so that there is constantly a film of medicament present. Other fungicides, such as Castellani’s paint, can be used but are less acceptable because of their colour. The nail should not be removed except in those very rare cases where there is actual infection of the plate; the base should not be incised; poultices and hot soaks are the worst possible treatment as they increase wet and warmth.
In a number of cases the infection is a mixture of Candida and Staph, pyogenes. If the pain and swelling do not subside rapidly with the treatment described, swabs should be taken for bacteriological examination and if Staph, pyogenes are found a course of oral erythromycin given.
Tinea pedis (Athlete’s foot)
Tinea pedis is the commonest manifestation of fungus infection of the skin and occurs in those who bath communally. It is therefore common among boys at boarding schools, coal miners using pithead baths, workers using industrial shower baths as well as athletes in sports clubs. Three organisms are commonly the cause and all are mycelium forming; Trichophyton mentagrophytes, Epidermophyton floccosum and Trichophyton rubrum. Differentiation of the first two is unimportant as they produce a similar clinical picture and response to treatment, but T. rubrum can be considered separately on both accounts.
The earliest sign of tinea pedis is maceration scaling and sometimes Assuring on the webs of the little toes, usually worse on one foot. Such lesions may settle in cool weather and recur in the summer. Not all are due to mycelial fungi, as yeasts or even bacterial infection such as Corynebacterium minutissimum (erythrasma) may cause similar changes, microscopic examination revealing mycelium in only about 25 per cent of cases. Under adverse conditions such as warmth or prolonged immersion the infection may spread, usually first producing maceration between all the toes of the affected foot, then desquamation on the flexor aspect of the toes and finally clear loculated vesicles or even bullae on the instep. Both feet may be affected but asymmetry is characteristic.
At this stage secondary bacterial infection may also occur, the vesicles becoming purulent and the interdigital spaces exuding odoriferous serum. If this progresses further, cellulitis may produce hot, red swelling of the foot, lymphangitis and tender enlargement of the inguinal lymph nodes accompanied by pyrexia and constitutional disturbance. In the more severe stages of eruption sensitisation to the organism may give rise to a vesicular eruption on the sides of the fingers, later spreading to the palms (cheiropompholyx); if one foot is uninfected this will also become covered with vesicles on the soles and if the reaction is particularly severe a scaly macular eruption may appear mainly on the limbs, the individual lesions of which resemble pityriasis rosea.
Differential diagnosis. Although often treated with fungicides, not every eruption on the foot is tinea pedis; shoe dermatitis may produce chronic scaly or acute lesions with vesiculation and exudation. The important features which differentiate this from tinea pedis are its symmetry, the involvement of the dorsum of the toes rather than the webs and the pattern of the shoe on the sides of the feet. If the soles only are involved, as may occur from wearing rubber soled slippers, the weight bearing areas are affected and the instep spared, in converse to tinea pedis. Pustular psoriasis also gives rise to difficulties but this is also often symmetrical, the pustules are uniform in size and evenly scattered over the red and scaly area of the sole involved; ringworm, by the nature of the activity of the fungus, being active at its edges.
Microscopic examination of the epidermis is desirable before treatment. The skin should be cleaned with methylated ether to remove debris and grease, then a scale taken from the active edge of the lesion or a vesicle snipped open and the roof removed to include the attached edge of the blister. Placed on a microscope slide, drops of 10 potassium hydroxide are added, the specimen covered with a coverslip and warmed slightly over a spirit lamp. If DMSO is used as a solvent, no warming is necessary. Microscopic examination reveals branching threads of mycelium crossing the paving of epithelial cells, and if profuse forming a loose network.
Treatment. Tinea pedis responds swiftly to the administration of griseofulvin 500 mg daily. This should be continued for 6 to 8 weeks to prevent a relapse. If the attack is acute with severe blistering the patient should be rested in bed and wet dressings of sodium hypochlorite solution applied. Secondary bacterial infection and cellulitis need systemic antibiotics but penicillin should be avoided owing to its antigenic relationship to the sensitising trichophyton. Castellani’s paint applied twice daily is useful in mildly vesicular cases and Whitfield’s ointment is both cheap and effective for the residual scaling or for scaling confined to toe webs. Of the numerous modern local applications miconazole cream (Daktarin) is most effective.
Trichophyton rubrum infection
T. rubrum infection produces scaling between the toes but a more chronic, less reactive eruption on the soles, consisting of erythema and a dry scaling which characteristically confines itself to the thickened keratin of the sole. In the majority of cases the nails are eventually involved producing opacity, yellow discoloration and subungual hyperkeratosis, starting at the distal end of the nail and progressing irregularly back down the nail plate. Eventually the plate becomes distorted and the condition spreads to involve other nails in an asymmetrical manner.
The hands usually eventually become involved, similar redness and scaling appearing on the palm and often remaining unilateral, the nail changes also produce a similar pattern. When both finger and toe nails are involved differentiation from psoriasis of the nails may be a problem, but in psoriasis the changes are usually symmetrical, pitting is a feature and finally, examination of cuttings from the nails in a potash preparation reveals whether fungus is present.
Extension of the T. rubrum infection to the legs produces a slightly scaly eruption dotted with follicular pustules, examination of a hair plucked from a pustule is more likely to reveal fungus than a skin scraping. When the groin is involved the condition spreads in an indolent fashion which may take months or even years to produce annular lesions extending often over the thighs and buttocks with a raised, slightly scaly edge. Locally applied fungicides have little effect on this organism and when this diagnosis is established Griseofulvin forte mg 500 daily is the treatment of choice. Lesions of skin are usually controlled in about 4 to 6 weeks but nail plates need time to grow out, which may mean continuous treatment for 6 months before the finger nails become normal. Great toenails may require treatment for a year or more and may still not fully recover. If they are sufficiently distorted to be troublesome on this account removal of the nail under local anaesthesia followed by griseofulvin therapy until the nail has regrown is justifiable. Even prolonged medication with griseofulvin does not eradicate the organism from the toe webs but miconazole cream (Daktarin) may be effective.
Tinea cruris and Corporis
Spread of fungus infections to the limbs and trunk produces the annular or ringed lesions which led to their name. Tinea cruris (tinea of the groins) is much commoner in men and is usually caused by T. men lagrophytes spread from infections of the feet. Symmetrical red lesions with a raised scaly edge extend over each upper inner thigh. In warm climates this infection may spread to produce ringed lesions with a slightly vesicular edge on the trunk or limbs. In Britain such ringed lesions are usually derived from animal contact, the commonest being cattle ringworm and less commonly a Microsporon canis infection from kittens or puppies. Treatment of flexural and other eruptions with potent corticosteroid applications without establishing a definite diagnosis has greatly increased the incidence of widespread fungus infections in recent years, as the fungus thrives in such conditions.
Solitary lesions may respond to local fungicides but severe tinea cruris and widespread tinea circinata is an indication for griseofulvin in full doses, given for at least 6 weeks to prevent a recurrence.
ringworm is found not only in farmers who may have been in contact with infected calves but may be acquired from contact with farm gates, lorries used for conveying cattle, in the cattle market or abattoir. On the limbs it characteristically starts on the wrist, whence is spreads asymmetrically to the trunk, producing initially mild looking scaly rings which progress to heaped up pustule-dotted plaques. On the beard area the follicular reaction is more pronounced, producing round pustule dotted granuloma-like nodules and plaques; while in the scalp, especially in children, a boggy swelling known as a kerion is produced which may erroneously be incised as an abscess.
Such is the discomfort produced by these lesions and so slow is spontaneous recovery, taking in the case of tinea barbae up to 3 months, that griseofulvin therapy should be started at once and may take several weeks to control the lesion. As a local application Castellani’s paint is the most useful as it also controls secondary sepsis.
Ringworm of the scalp, of the types which were once commonly encountered, occurs only in children below the age of puberty and is cast off at puberty. It was becoming rare even before griseofulvin therapy was introduced and now that an effective, safe treatment is available it seems to have become even more uncommon. The usual infections are Microsporon audouini, derived from humanvectors, or M. canis derived from cats, dogs or infected humans. An irregular bald area dotted with distorted broken stumps of hair appears, the degree to reaction in the underlying skin varying from very slight scaling in Audouini infections to erythema and scanty pustules in some Canis infections. Ringed lesions may also appear on the glabrous skin.
Examination of a hair stump in potash preparation reveals it to be packed with spores. Examination under Wood’s light (330 to 360 nm) produces a turquoise fluorescence of each infected hair. Such an examination is useful Doth in detecting fluorescent hairs for microscopy or culture and in detecting minor infections among contacts in a closed community such as a school or orphanage. If Wood’s light is not available, or when one of the rarer types of ringworm of the scalp which does not cause fluorescence is suspected, it may be necessary to collect material for culture of the fungus. This can be done with a round polythene scalp massager which has been sterilised by immersion in 10 per cent Teepol for 24 hours. The suspected scalp is massaged vigorously for a quarter of a minute. The polythene becomes electrostatically charged and picks up particles from the hair and scalp. The brush is then pressed into a dish of culture medium on which fungus cultues appear after incubation. Canis infections resolve spontaneously in about 3 months but before griseofulvin became available x-ray epilation was used for Audouini infections. Nowadays both infections respond to griseofulvin in the dose appropriate for the child’s age and can usually be cleared in about a month.
This is a trivial superficial infection with the organism Malassezia furfur. It is common in the tropics but also occurs in temperate climates. The lesions consists of faintly brown macules on the chest and back which may become confluent. The surface is very finely wrinkled. In pigmented skin partial depigmentation may occur. Examination with Wood’s light imparts a yellowish green fluorescence to the lesions.
Scrapings mounted in potash reveal profuse short crescentic mycelium and clustered small round spores.
Treatment with half strength Whitfield’s ointment rapidly clears the lesions, but unless persisted in for several weeks they soon recur.