[Bacterial skin flora, host defense and skin infections]

Resident skin flora consists of coagulase-negative staphylococci, micrococci, aerobic and anaerobic coryneform organisms (i.e. propionibacterium acnes) as well as gram-negative rods (i.e. acinetobacter). Their growth is favoured by increased temperature and humidity and modified by body location, age, sex and chronic diseases (i.e. diabetes mellitus). Occupation, hospitalization, soaps and disinfectants as well as medications exert promoting and inhibiting influences, too. In addition, environment gains significant importance due to trauma and implants as well as contact with animals, infected persons and carriers. Whereas bacteria attach by adhesins and succeed other bacteria by factors of pathogeneity such as exotoxins, exoenzymes, bacteriocins and various interference mechanisms, skin exerts its resistance and defense by means of the intact horny layer, proliferation and desquamation, lipids and fatty acids as well as sweat, in addition, by means of IgA and the specific skin immune system with complex interactions between Langerhans-, TH-, TS- and cytotoxic T-cells, interleukins and cytokines. Furthermore the non-specific defense system (complement, NK-cells, granulocytes, mononuclear phagocytic system, inflammation) is involved. Finally, skin infections caused by resident bacterial flora are briefly discussed.