Piedraia hortae survives in the scalp is due to the slow rate of the keratin degradation near the cortex and the compact formation of the nodules and the hyphae are tightly packed in black piedra cases. The initial invasion of human hair by P. hortae is achieved by using an eroding hyphae, which force their way beneath or between the cuticular layer. The force applied between or beneath the hair cuticle arises from the growth of the fungus itself. The breakdown of keratin is mainly due to enzymatic processes and corresponds to the abundance of localized mitochondria. The breakdown of keratin begins with the cementing material and progresses to the cortex of the hair shaft. In the cortex two types of degradative patterns are produced which are either parallel or vertical to the axis hair shaft. The parallel pattern arises from hyphal separation of the external cortical layers. The vertical pattern is produced by direct hyphal penetration which creates channels that increase in size as the cortex degrades. Treatment
The infection cannot easily be removed mechanically, although further proliferation of infection can be achieved by avoidance of moisture. Removal generally involves cutting or shaving of the hair, but chemical treatments may be similarly useful. For women some individuals use a fine comb to remove as much of the infection as possible and then they cut or shave their hair. This is then followed by the application of a sublimate solution in 60% alcohol solution to the scalp.
Wash hands and forearms thoroughly with soap and running water after cleaning the tank, even if gloves were worn. Ensure regular and adequate chlorination of swimming pools to kill any bacteria that may be present. Treatment
Treatment involves the use of antibiotics. Since M. marinum has a high tendency for multi-drug resistance, treatment by one particular drug will not be effective. Often, up to six different antimicrobial regimes may be needed before the infection responds to a particular drug combination. This combination of antibiotics is based on the results of the culture and skin biopsy. The treatment can take up to several months.Surgery may also be needed to remove dead tissue if the lesions do not clear with antibiotics. This helps the wound to heal. Epidemiology
Mycobacterium marinum infection is not contagious; it is not spreading from person to person. It is also not transmitted in hospitals like other common bacteria. See also
Skin lesion
List of cutaneous conditions

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