British Journal of Dermatology (1975) 92, 413.
The areal extent of dermatophyte infection E.A.KNUDSEN Department of Dermato-Venereology, Rudolph Bergh Hospital, Copenhagen, Denmark Accepted for publication 7 August 1974
SUMMARY
After stripping with vinyl tape, dermatophytes may be cultured throughout the depth of the stratum corneum. In the present study skin strippings were used to investigate the horizontal spread of the dermatophyte infection. In five cases of tinea cruris and in twenty-two cases of tinea corporis, fungi could be cultured not only from the visible lesion, but in the majority of cases also from the normal-looking skin up to 6 cm from the margin of the lesion. No relationship could be found between the size and age of the lesion and the invasion of surrounding, normal-looking skin.
In dermatophyte infections of the skin the entire stratum corneum is invaded by fungal mycelia, as is demonstrable histologically. This vertical extent has been well demonstrated by Marks & Dawber (1972) by the so-called skin-surface biopsy; and by the vinyl tape stripping technique dermatophytes may be cultured from all parts of the stratum corneum (Knudsen, 1971). In the present study, culture of stratum corneum strippings was employed to investigate the horizontal extent of the fungous infection to decide whether the peripheral demarcation of the infection corresponds to the visible changes, or whether the fungous invasion affects also clinically normal skin.
MATERIAL AND METHOD
The material comprised five cases of tinea cruris and twenty-two cases of tinea corporis (two from the neck, nine from the trunk, and eleven from the limbs). The duration of the infection had been up to 2 weeks in sixteen cases, 3-4 weeks in three cases, 2-12 months in three cases, more than i year in one case, and unknown in four cases. The mean size of the lesions was 42 x 30 mm in the cases associated with T. mentagrophytes, 140 X 110 mm with T. rubrum^ 123 x 87 mm with E.fioccosum,and 15x11 mm with M. canis. Three cases had already been treated with antimycotics, three with a pure steroid cream, twelve had not had any treatment, and in nine cases no data concerning treatment were available. * Read in part at the 20th Meeting of the Scandinavian Dermatological Society, Stockholm, June 1974.
414
E.A.Kmidsen
Technical procedure
Using a I cm wide vinyl tape (Scotch brand tape 681, Minnesota Mining and Manufacturing Co., Los Angeles, California) the most superficial layer of the stratum corneum was stripped off from the marginal zone of the fungous lesion and radially 1-6 cm into the surrounding, normal-looking skin (Fig. l). Pieces of these strips 3 cm long were placed, adhesive side down, on the surface of Sabouraud's dextrose agar (with penicillin, streptomycin, and actidione added). The plate was then incubated at 26 C and studied for growth for up to 3 weeks.
FIGURE I. Stripping with vinyl tape from fungous lesion and 1-6 cm of the surrounding normallooking skin.
RESULTS
As is apparent from Table i, growth of fungi occurred not only from the lesion, but in the majority of cases also from normal-looking skin up to 6 cm from the marginal zone of the lesion. There was a tendency for growth from the visible fungous infection to appear earlier and with more vigour than from the surrounding skin (Fig. 2). DISCUSSION
Several authors have been able to isolate dermatophytes from normal-looking skin on the feet. Among patients with asymptomatic ringworm of the feet, Sylvest (1948) found a few having what he called latent infection. English (1969) considered such infections the precursor of symptomatic cases, and according to Marples (1965) dermatophytes may, under ideal conditions, be present as members of the normal cutaneous flora on the feet.
Area! extent of dermaiophyte infection TABLE 1. Numbers ol'isolations of dermatophytes obtained by vinyl stripping technique from tbo fungal lesion and at various distances from its border Distance trom edge of lesion (cm) Species of dermatophyte
No. of cases
Tricliophylon meiitagiophyies Trichophyton rubium Epidermophyton floccosum Aiicrosponim canis Total
5 4 3 15 27
4
I
2
3
3 3
3
2
2
I
I
I
12
II
II
10
22
16
16
16
FIGURE 2. Tape culture ol J1 ichophywu menta^rophyies on Sabouraud's dextrose agar from the lesion as well as i, 2, 4 and 6 cm of the surrounding skin.
4i6
E.A.Kniidsen
With the exception of palms and soles, asymptomatic infections of the glabrous skin do not occur, in Kligman's (1955) opinion, even in patients with widespread ringworm. However, the present srudy, which must be considered preliminary, has shown dermatophytes in cultures from normallooking skin for up to 6 cm from tinea corporis and tinea cruris lesions. Only further investigations can tell how far the latent infection can reach. New foci of infection may be imagined to arise by spread of spores from a plaque of fungus over the surface of the skin. These preliminary studies indicate, however, that spread around an existing plaque is due to direct outgrowth of mycelia from the fungous plaque throughout the depth of the stratum corneum. In his excellent study on tinea capitis, Kligman (1952) described a stage of spreading which he compared to the development of a circinate spot on glabrous skin. He found the growth of a spot in the scalp to continue until it reached a diameter of 3-5 cm, and thereafter the hyphae disappeared from the stratum corneum. In the present study it was not possible to demonstrate a corresponding relationship between the size or age of the spot and invasion of the surrounding, normal skin. According to Beare, Gentles & Mackenzie (1968), the incubation period for a dermatophyte infection is 1-3 weeks. The asymptomatic infection in the periphery of a fungous plaque, as described here, may be interpreted as an infection in the incubation stage. The practical consequence of the present study must be that in the treatment of ringworm a good portion of the surrounding, normal-looking skin must be included in the field of treatment. REFERENCES BEARE, J.M., GENTLES, J.C. & MACKENZIE, D . W . R . (1972) Mycology. In: Textbook of Dermatology (Ed. by A.J.
Rook, D.S.Wilkinson and F.J.Ebling), 2nd edn, Vol. i, p. 713. Blackwell Scientific Publications, Oxford. ENGLtSH, M.P. (1969) Tinea pedis as a public health problem. Comment, British Journal of Dermatology, 81, 705. KLIGMAN, A. (1955) Some Reflections on the Biology of Ringworm Infections. In: Therapy of fungus diseases (Sternberg & Newcomer), Little, Brown & Co., Boston. KLIGMAN, A. (t952) The Pathogenesis of Tinea Capitis due to Microsporum Audouini and Microsporum Canis. Journal of Investigative Dermatology, i8, 231. KNUDSEN, E.A. C1971) Fungal cultures from skin strippings. Sabouratddia, 9, 167. MAKKS, R.& DAWBER, R.P.R. (t972) In .sin* microbiology of the stratum corneum. Archives of Dermatology, 105, 216. MARPLES, M . J . (1965) The Ecology of the Human Skin. Thomas, Springfield. SYLVEST, B. (1948) Asymptomatic ringworm of the feet. Thesis, Munksgaard, Copenhagen.
The areal extent of dermatophyte infection E.A.KNUDSEN Department of Dermato-Venereology, Rudolph Bergh Hospital, Copenhagen, Denmark Accepted for publication 7 August 1974
SUMMARY
After stripping with vinyl tape, dermatophytes may be cultured throughout the depth of the stratum corneum. In the present study skin strippings were used to investigate the horizontal spread of the dermatophyte infection. In five cases of tinea cruris and in twenty-two cases of tinea corporis, fungi could be cultured not only from the visible lesion, but in the majority of cases also from the normal-looking skin up to 6 cm from the margin of the lesion. No relationship could be found between the size and age of the lesion and the invasion of surrounding, normal-looking skin.
In dermatophyte infections of the skin the entire stratum corneum is invaded by fungal mycelia, as is demonstrable histologically. This vertical extent has been well demonstrated by Marks & Dawber (1972) by the so-called skin-surface biopsy; and by the vinyl tape stripping technique dermatophytes may be cultured from all parts of the stratum corneum (Knudsen, 1971). In the present study, culture of stratum corneum strippings was employed to investigate the horizontal extent of the fungous infection to decide whether the peripheral demarcation of the infection corresponds to the visible changes, or whether the fungous invasion affects also clinically normal skin.
MATERIAL AND METHOD
The material comprised five cases of tinea cruris and twenty-two cases of tinea corporis (two from the neck, nine from the trunk, and eleven from the limbs). The duration of the infection had been up to 2 weeks in sixteen cases, 3-4 weeks in three cases, 2-12 months in three cases, more than i year in one case, and unknown in four cases. The mean size of the lesions was 42 x 30 mm in the cases associated with T. mentagrophytes, 140 X 110 mm with T. rubrum^ 123 x 87 mm with E.fioccosum,and 15x11 mm with M. canis. Three cases had already been treated with antimycotics, three with a pure steroid cream, twelve had not had any treatment, and in nine cases no data concerning treatment were available. * Read in part at the 20th Meeting of the Scandinavian Dermatological Society, Stockholm, June 1974.
414
E.A.Kmidsen
Technical procedure
Using a I cm wide vinyl tape (Scotch brand tape 681, Minnesota Mining and Manufacturing Co., Los Angeles, California) the most superficial layer of the stratum corneum was stripped off from the marginal zone of the fungous lesion and radially 1-6 cm into the surrounding, normal-looking skin (Fig. l). Pieces of these strips 3 cm long were placed, adhesive side down, on the surface of Sabouraud's dextrose agar (with penicillin, streptomycin, and actidione added). The plate was then incubated at 26 C and studied for growth for up to 3 weeks.
FIGURE I. Stripping with vinyl tape from fungous lesion and 1-6 cm of the surrounding normallooking skin.
RESULTS
As is apparent from Table i, growth of fungi occurred not only from the lesion, but in the majority of cases also from normal-looking skin up to 6 cm from the marginal zone of the lesion. There was a tendency for growth from the visible fungous infection to appear earlier and with more vigour than from the surrounding skin (Fig. 2). DISCUSSION
Several authors have been able to isolate dermatophytes from normal-looking skin on the feet. Among patients with asymptomatic ringworm of the feet, Sylvest (1948) found a few having what he called latent infection. English (1969) considered such infections the precursor of symptomatic cases, and according to Marples (1965) dermatophytes may, under ideal conditions, be present as members of the normal cutaneous flora on the feet.
Area! extent of dermaiophyte infection TABLE 1. Numbers ol'isolations of dermatophytes obtained by vinyl stripping technique from tbo fungal lesion and at various distances from its border Distance trom edge of lesion (cm) Species of dermatophyte
No. of cases
Tricliophylon meiitagiophyies Trichophyton rubium Epidermophyton floccosum Aiicrosponim canis Total
5 4 3 15 27
4
I
2
3
3 3
3
2
2
I
I
I
12
II
II
10
22
16
16
16
FIGURE 2. Tape culture ol J1 ichophywu menta^rophyies on Sabouraud's dextrose agar from the lesion as well as i, 2, 4 and 6 cm of the surrounding skin.
4i6
E.A.Kniidsen
With the exception of palms and soles, asymptomatic infections of the glabrous skin do not occur, in Kligman's (1955) opinion, even in patients with widespread ringworm. However, the present srudy, which must be considered preliminary, has shown dermatophytes in cultures from normallooking skin for up to 6 cm from tinea corporis and tinea cruris lesions. Only further investigations can tell how far the latent infection can reach. New foci of infection may be imagined to arise by spread of spores from a plaque of fungus over the surface of the skin. These preliminary studies indicate, however, that spread around an existing plaque is due to direct outgrowth of mycelia from the fungous plaque throughout the depth of the stratum corneum. In his excellent study on tinea capitis, Kligman (1952) described a stage of spreading which he compared to the development of a circinate spot on glabrous skin. He found the growth of a spot in the scalp to continue until it reached a diameter of 3-5 cm, and thereafter the hyphae disappeared from the stratum corneum. In the present study it was not possible to demonstrate a corresponding relationship between the size or age of the spot and invasion of the surrounding, normal skin. According to Beare, Gentles & Mackenzie (1968), the incubation period for a dermatophyte infection is 1-3 weeks. The asymptomatic infection in the periphery of a fungous plaque, as described here, may be interpreted as an infection in the incubation stage. The practical consequence of the present study must be that in the treatment of ringworm a good portion of the surrounding, normal-looking skin must be included in the field of treatment. REFERENCES BEARE, J.M., GENTLES, J.C. & MACKENZIE, D . W . R . (1972) Mycology. In: Textbook of Dermatology (Ed. by A.J.
Rook, D.S.Wilkinson and F.J.Ebling), 2nd edn, Vol. i, p. 713. Blackwell Scientific Publications, Oxford. ENGLtSH, M.P. (1969) Tinea pedis as a public health problem. Comment, British Journal of Dermatology, 81, 705. KLIGMAN, A. (1955) Some Reflections on the Biology of Ringworm Infections. In: Therapy of fungus diseases (Sternberg & Newcomer), Little, Brown & Co., Boston. KLIGMAN, A. (t952) The Pathogenesis of Tinea Capitis due to Microsporum Audouini and Microsporum Canis. Journal of Investigative Dermatology, i8, 231. KNUDSEN, E.A. C1971) Fungal cultures from skin strippings. Sabouratddia, 9, 167. MAKKS, R.& DAWBER, R.P.R. (t972) In .sin* microbiology of the stratum corneum. Archives of Dermatology, 105, 216. MARPLES, M . J . (1965) The Ecology of the Human Skin. Thomas, Springfield. SYLVEST, B. (1948) Asymptomatic ringworm of the feet. Thesis, Munksgaard, Copenhagen.
