Susceptibility of Rickettsia rickettsii to Tigecycline in a Cell Culture Assay and Animal Model for Rocky Mountain Spotted Fever.

Susceptibility of Rickettsia rickettsii to Tigecycline in a Cell Culture Assay and Animal Model for Rocky Mountain Spotted Fever. Am J Trop Med Hyg. 2019 Sep 16;: Authors: Blanton LS, Wilson NM, Quade BR, Walker DH Abstract Rocky Mountain spotted fever (RMSF), caused by Rickettsia rickettsii, is a severe tick-borne infection endemic to the Americas. Oral doxycycline is effective, but during severe life-threatening disease, intravenous therapy is recommended. Unfortunately, intravenous formulations of doxycycline are not always available. Therefore, we aimed to determine the susceptibility of R. rickettsii to an alternative parenteral agent, tigecycline, in vitro and in vivo. To determine the minimum inhibitory concentration of tigecycline, R. rickettsii-inoculated Vero cells were incubated with medium containing tigecycline. At various time points, monolayers were collected and R. rickettsii was quantified via real-time PCR. The growth of R. rickettsii was inhibited in the presence of ≥ 0.5 µg/mL of tigecycline. To determine the effectiveness of tigecycline in vivo, guinea pigs were inoculated with R. rickettsii. Five days after inoculation, they were treated twice daily with subcutaneous tigecycline 3.75 mg/kg or subcutaneous doxycycline 5 mg/kg. Treated animals improved, whereas untreated controls remained ill. Tissues were collected for quantitative PCR-determined bacterial loads on day 8. Median bacterial loads in the tigecycl...
Source: The American Journal of Tropical Medicine and Hygiene - Category: Tropical Medicine Authors: Tags: Am J Trop Med Hyg Source Type: research