8 - Dermatomycoses

1. Dermatomycoses are cutaneous mycoses caused by three genera of fungi namely microsporum, epidermophyton and trichophyton . these infections are called tinea or ringworm , a misnomer that has persisted from the days when they were thought to be caused by worms or lice .

2. tinea capitis ( ring worm of the scalp ) is due to an infection with MICROSPORUM CANIS or TRICHOPHYTON TONSURANS. It usuall occurs during childhood and heals spontaneously at puberty. Circular areas on the scalp with broken or no hair , are characteristic of this disorder.

3. Tinea corporis ( ring worm of the body ) is caused by MICROSPORUM CANIS or TRICHOPHYTON MENTAGROPHYTES . this disorder affects smooth skin and and produces circular pruritic rashes of redness and scaling .

4. Both tinea cruris ( ring worm of the groin , “ jock itch “ )and tinea pedis ( ring worm of the foot ) are caused by TRICHOPHYTON RUBRUM , TRICHOPHYTON MENTAGROPHYTES or EPIDERMOPHYTON FLOCCOSUM. These common conditions are pruritic and can cause scaling .

5. Tinea versicolor ( pityriasis versicolor ) is not a dermatophytic condition but, rather , a superficial mycosis now thought to be caused by MALASEZZIA FURFUR . the disorder is characterized by chronic but asymptomatic scaling on the trunk , arms or other parts of the body .

6 - dienes phenomenon

Proteus is a genus of bacteria in the family of Enterobacteriaceae. Proteus species are famous for their swarming on solid culture media.

When different Proteus species swarm towards each other, a line of inhibited growth results where strains meet. This was first observed in 1946 by Dienes and is referred to as the Dienes phenomenon. This line of inhibited growth results from the production of and sensitivity to different types of bacteriocins, namely, proticines, produced by different strains of Proteus species.

If two strains were able to detect different proticines produced by a neighbor, there would be growth inhibition and the formation of a Dienes line. Alternatively, if no proticine difference were detected, the neighboring swarmer would be recognized as "self" and the swarms would interact.

This phenomenon is of value in differentiating the two strains of Proteus for epidemiological purposes.