Susceptibility of brain and skin to bacterial challenge.

The brain is a uniquely protected organ. Once the protective barriers are overcome, the brain is susceptible to bacterial infection. Using a reproducible rat model, the susceptibility of brain tissue to challenge by S. aureus or E. coli was quantitatively compared to that of skin. Brain was significantly more susceptible to the presence of bacteria than was the skin of the scalp. The development of infection in skin required at least 10(5) organisms, while brain infection could be produced with as few as 100 organisms.