Dr. Murai Éva szerk.: Parasitologia Hungarica 24. (Budapest, 1991)

tered intravenously at a dose of 20 million units proved to be effective both in neuroborreliosis and in arthritis (143, 146). None of the 132 ECM patients treated orally with 2x1 g Phenoxymethylpenicillin developed any complications, while 20% of the placebo-treated group produced progressive symptoms (6). Similar results have been published by others (14,110,136), but therapeutic failures have also been observed both in penicillin- and in tetracycline-treated patients (26, 33, 68, 70,120, 157). Penicillin treatment was highly effective in our ECM patients as well. A significantly faster improvement was seen in the penicillin- than in the tetracycline(usually doxycycline-) treated group. The rate of improvement, is even more influenced by the dosage of the antibiotic. Low-dose administration can hardly shorten the duration of erythema chronicum migrans, while high-dose treatment is significantly more effective. Residual symptoms were seen only in 10% of our cases. In contrast to the excellent clinical response seen by us, in vitro antibiotic susceptibility results show that Bb is almost resistant to penicillin (!) but sensitive to tetracycline and even more sensitive to erythromycin and ceftriaxone (60, 121). It seems to be absurd that an in vitro resistant microbe appears sensitive in vivo. How can that be?! Our preliminary results also support the opinion of others that traditional MIC and MBC values cannot be used in the case of very slowly multiplying microbes such as Bb (109). This is why erythromycin, a drug showing excellent efficacy in vitro, proves ineffective in vivo (58). Even in an animal model experiment in which erythromycin was administered at a dose 20 times the human dose, it was not able to kill Bb (61, 121). The in vitro results were virtually proved by Johnson's animal experiment. As much as 200 mg/kg penicillin was administered and 90% of the hamsters remained infected. However, the antibiotic was given only once a day and only for 5 days (60)! Hansen applied a treatment model similar to the human practice and treated infected gerbils with penicillin at a dose of 100 mg/kg t.i.d. for 10 days. All treated animals became free from borrelia (47)! To achieve an appropriate CSF level, doxycycline should be given at a dose of 200 mg b.i.d. (5,169), which is hardly tolerable. Because of its bacteriostatic effect, microbes are able to survive quite a long treatment and start to multiply again (91). Orally or intramuscularly administered penicillin does not get into the CSF but a high antibiotic level can be achieved in the serum (86). A minimum incubation time of 72 hours is needed to kill borrelia (91). For that reason, orally administered penicillin can be recommended only for the treatment of early ECM. In our experience, high doses (4x1 g per os) of penamecillinum are used. That is well tolerated and highly sufficient to prevent the development of further symptoms and to cause prompt improvement. At the later stages of Lb, only the intravenously administered antibiotics are effective. Intravenous administration of penicillin at a dose 3x6 g for 14 days seemed to be an effective treatment of systemic borrelia infection. Our opinion is also supported by the results of some other in vitro studies (15, 91). Laboratory and human clinical studies are agreed on that ceftriaxone is more effective than penicillin (27,28, 60, 89, 90, 159). Rocephin treatment is convenient because of the once-a-day administration. This antibiotic is usually well tolerated and results in a