Treatment of relapsing fever with antibiotics

Single Dose of Doxycycline for the Prevention of Tick-borne Relapsing Fever

The current postexposure prophylaxis regimen for tick-borne relapsing fever (TBRF) consists of 5 days' doxycycline. In this observational study of 77 spelunkers at high risk for TBRF, a single dose of 100 mg doxycycline taken up to 72 hours after exposure to ticks was 100% effective in preventing the disease.

Penicillin-binding proteins in Borrelia burgdorferi

Penicillin-binding proteins were identified in Borrelia burgdorferi membranes. A 94-kilodalton penicillin-binding protein was the first to be labeled with tritiated penicillin and was the first band to disappear in a competition experiment. Its binding ability was destroyed when membranes were preboiled. In addition, several of these penicillin-binding proteins comigrated with bands previously identified as surface proteins.

Action of penicillin on Borrelia hermsii

Borrelia hermsii, a spirochete and an etiological agent of relapsing fever, was cultivated in modified Kelly medium. Studies of the action of penicillin on B. hermsii strain HS1 revealed the following: (i) the in vitro minimum inhibitory concentration and minimum bactericidal concentration of benzylpenicillin for this strain were 0.4 and 3.1 nmol/ml (0.15 and 1.1 micrograms/ml), respectively; (ii) the primary morphological responses at the minimum bactericidal concentration of benzylpenicillin were the formation of spheroplast-like structures and an increased number of small, membranous blebs; (iii) radioactive benzylpenicillin bound to five penicillin-binding proteins in the whole cells of B. hermsii. The 50% binding concentrations of labeled penicillin for the five penicillin-binding proteins were within a factor of five of the minimum inhibitory concentration. More than one-half of the total bound labeled penicillin was associated with penicillin-binding protein 1, the penicillin-binding protein with the largest apparent molecular weight (90,000).