[Infections of finger and toe nails due to fungi and bacteria]

Infections of the finger and the toe nails are most frequently caused by fungi, primarily dermatophytes. Causative agents of tinea unguium are mostly anthropophilic dermatophytes. Both in Germany, and worldwide, Trichophyton rubrum represents the main important causative agent of onychomycoses. Yeasts are isolated from fungal nail infections, both paronychia and onychomycosis far more often than generally expected. This can represent either saprophytic colonization as well as acute or chronic infection of the nail organ. The main yeasts causing nail infections are Candida parapsilosis, and Candida guilliermondii; Candida albicans is only in third place. Onychomycosis due to molds, or so called non-dermatophyte molds (NDM), are being increasingly detected. Molds as cause of an onychomycosis are considered as emerging pathogens. Fusarium species are the most common cause of NDM onychomycosis; however, rare molds like Onychocola canadensis may be found. Bacterial infections of the nails are caused by gram negative bacteria, usually Pseudomonas aeruginosa (recognizable because of green or black coloration of the nails) but also Klebsiella spp. and gram positive bacteria like Staphylococcus aureus. Treatment of onychomycosis includes application of topical antifungal agents (amorolfine, ciclopirox). If more than 50 % of the nail plate is affected or if more than three out of ten nails are affected by the fungal infection, oral treatment using terbinafine (in case of dermatophyte infection), fluconazole (for yeast infections), or alternatively itraconazole are recommended. Bacterial infections are treated topically with antiseptic agents (octenidine), and in some cases with topical antibiotics (nadifloxacin, gentamicin). Pseudomonas infections of the nail organ are treated by ciprofloxacin; other bacteria are treated according to the results of culture and sensitivity testing.