[Bacterial growth in the perfusion medium of the isolated rat brain and its inhibition by antibiotics].
In the perfusion medium of the isolated rat brain the bacterial content was examined. The perfusion medium used contained 30% bovine erythrocytes, 2 g% bovine serum albumin and about 13 mM glucose in Krebs-Henseleit-solution. Before the perfusion of the isolated rat brain was started the medium recirculated up to two hours in the perfusion apparatus. After this, the perfusion of the isolated rat brain was carried out for four hours. At various times and at different points of the circulating system samples of the perfusion medium were withdrawn and tested for their bacterial content. Using the plate count procedure, at the end of the perfusion 10(5) to 10(6) bacteria per ml medium were found. This order of magnitude of the bacterial content suggested that it is not necessary to add antibacterial substances to the medium when perfusions lasted up to 4 hours. Nevertheless, from each sample 10 bacteria species were isolated and their sensitivity against 15 different antibacterial substances was tested. The substances were ampicillin, carbenicillin, cephaloridine, chloramphenicol, cloxacillin, erythromycin, gentamycin, nalidixic acid, neomycin, nitrofurantoin, penicillin, polymyxin B, sulfadiazine, tetracycline and trimethoprim + sulfamethoxazole. Tetracycline was most active in inhibiting bacterial growth. 1 mg and 0.5 mg tetracycline added to 100 ml perfusion medium were able to prevent an increase of the bacterial count during the perfusion experiments.