Evaluation of Combination Drug Therapy for Treatment of Antibiotic-Resistant Inhalation Anthrax in a Murine Model.

Bacillus anthracis is considered a likely agent to be used as a bioweapon, and the use of a strain resistant to the first-line antimicrobial treatments is a concern. We determined treatment efficacies against a ciprofloxacin-resistant strain of B. anthracis (Cipr Ames) in a murine inhalational anthrax model. Ten groups of 46 BALB/c mice were exposed by inhalation to 7 to 35 times the 50% lethal dose (LD50) of B. anthracis Cipr Ames spores. Commencing at 36 h postexposure, groups were administered intraperitoneal doses of sterile water for injections (SWI) and ciprofloxacin alone (control groups), or ciprofloxacin combined with two antimicrobials, including meropenem-linezolid, meropenem-clindamycin, meropenem-rifampin, meropenem-doxycycline, penicillin-linezolid, penicillin-doxycycline, rifampin-linezolid, and rifampin-clindamycin, at appropriate dosing intervals (6 or 12 h) for the respective antibiotics. Ten mice per group were treated for 14 days and observed until day 28. The remaining animals were euthanized every 6 to 12 h, and blood, lungs, and spleens were collected for lethal factor (LF) and/or bacterial load determinations. All combination groups showed significant survival over the SWI and ciprofloxacin controls: meropenem-linezolid (P = 0.004), meropenem-clindamycin (P = 0.005), meropenem-rifampin (P = 0.012), meropenem-doxycycline (P = 0.032), penicillin-doxycycline (P = 0.012), penicillin-linezolid (P = 0.026), rifampin-linezolid (P = 0.001), and rifampin-clindamycin (P = 0.032). In controls, blood, lung, and spleen bacterial counts increased to terminal endpoints. In combination treatment groups, blood and spleen bacterial counts showed low/no colonies after 24-h treatments. The LF fell below the detection limits for all combination groups yet remained elevated in control groups. Combinations with linezolid had the greatest inhibitory effect on mean LF levels.

Possible etiologic agents for toxic oil syndrome: fatty acid esters of 3-(N-phenylamino)-1,2-propanediol.

The etiologic agent(s) that was responsible for the 1981 toxic oil syndrome [TOS] epidemic in Spain has not been identified. Liquid chromatography combined with atmospheric pressure ionization tandem mass spectrometry was used for the analysis of oils associated with TOS. Analyses focused on measuring 3-(N-phenylamino)-1,2-propanediol [PAP], the 3-oleyl ester of PAP [MEPAP], and the 1,2-di-oleyl ester of PAP [DEPAP]. DEPAP and MEPAP were found more frequently and at higher concentrations in TOS case-associated oils than in control oils with odds ratios of 13.7 (95% CI 5.0-38) and 21.9 (95% 6.1-78), respectively. Other fatty acid esters of PAP are also likely to be present in the TOS case-associated oils. More significantly, DEPAP and MEPAP were found in aniline-denatured rapeseed oil refined at ITH, the oil refining company with the clearest link to TOS cases, yet these PAP esters were not detected in unrefined aniline-denatured samples of rapeseed oil delivered to ITH. These results show that the esters of PAP were products of the ITH refining process and were not formed spontaneously during storage. PAP esters were not detected in samples of other aniline-denatured rapeseed oils that were refined elsewhere, and which were not associated with illness. These findings provide strong support for the hypothesis that one or more of the fatty acid esters of PAP were the etiologic agents for TOS.