Comparison of clarithromycin and ciprofloxacin therapy for Bacillus anthracis Sterne infection in mice with or without 60Co gamma-photon irradiation

Postexposure Prophylaxis and Treatment of Bacillus anthracis Infections: A Systematic Review and Meta-analyses of Animal Models, 1947-2019

BACKGROUND

Anthrax is endemic to many countries, including the United States. The causative agent, Bacillus anthracis, poses a global bioterrorism threat. Without effective antimicrobial postexposure prophylaxis (PEPAbx) and treatment, the mortality of systemic anthrax is high. To inform clinical guidelines for PEPAbx and treatment of B. anthracis infections in humans, we systematically evaluated animal anthrax treatment model studies.

METHODS

We searched for survival outcome data in 9 scientific search engines for articles describing antimicrobial PEPAbx or treatment of anthrax in animals in any language through February 2019. We performed meta-analyses of efficacy of antimicrobial PEPAbx and treatment for each drug or drug combination using random-effects models. Pharmacokinetic/pharmacodynamic relationships were developed for 5 antimicrobials with available pharmacokinetic data. Monte Carlo simulations were used to predict unbound drug exposures in humans.

RESULTS

We synthesized data from 34 peer-reviewed studies with 3262 animals. For PEPAbx and treatment of infection by susceptible B. anthracis, effective monotherapy can be accomplished with fluoroquinolones, tetracyclines, β-lactams (including penicillin, amoxicillin-clavulanate, and imipenem-cilastatin), and lipopeptides or glycopeptides. For naturally occurring strains, unbound drug exposures in humans were predicted to adequately cover the minimal inhibitory concentrations (MICs; those required to inhibit the growth of 50% or 90% of organisms [MIC50 or MIC90]) for ciprofloxacin, levofloxacin, and doxycycline for both the PEPAbx and treatment targets. Dalbavancin covered its MIC50 for PEPAbx.

CONCLUSIONS

These animal studies show many reviewed antimicrobials are good choices for PEPAbx or treatment of susceptible B. anthracis strains, and some are also promising options for combating resistant strains. Monte Carlo simulations suggest that oral ciprofloxacin, levofloxacin, and doxycycline are particularly robust choices for PEPAbx or treatment.

In vivo pharmacodynamics of lascufloxacin and levofloxacin against Streptococcus pneumoniae and Prevotella intermedia in a pneumonia mixed-infection mouse model

This study aimed to evaluate the antimicrobial activity of a new quinolone, lascufloxacin, for the treatment of complicated pneumonia caused by Streptococcus pneumoniae and Prevotella intermedia using a neutropenic mice pneumonia mixed-infection model. In this study, one S. pneumoniae and four P. intermedia isolates were utilized. Antimicrobial efficacy was calculated for each isolate as the reduction of the bacterial count comparatively to the non-treated mice (log₁₀ colony forming units (cfu)/mL) obtained in the lungs of the treated mice after 24 h. Consequently, the bacterial densities of S. pneumoniae (KY-9) and P. intermedia (335) in the lungs of control animals were 8.20 ± 0.19 log₁₀ cfu/mL and 5.26 ± 1.50 log₁₀ cfu/mL, respectively. At human-simulated doses, lascufloxacin and levofloxacin showed high antimicrobial activities against not only S. pneumoniae (lascufloxacin: 1.88 ± 0.43 log₁₀ cfu/mL, p < 0.001; levofloxacin 4.30 ± 0.75 log₁₀ cfu/mL, p < 0.001), but also P. intermedia (lascufloxacin: 1.54 ± 0.57 log₁₀ cfu/mL, p < 0.001; levofloxacin: 2.79 ± 0.55 log₁₀ cfu/mL, p = 0.0102). Additionally, levofloxacin demonstrated attenuated antimicrobial efficacies against S. pneumoniae in the mixed-infection model compared with that in the single infection model. In contrast, lascufloxacin showed enhanced antimicrobial activities against S. pneumoniae and P. intermedia in the mixed-infection model. In conclusion, lascufloxacin resulted in enhanced efficacies against S. pneumoniae and P. intermedia, in both the single and mixed-infection models used. These data support the clinical utility of lascufloxacin for use against S. pneumoniae and P. intermedia in the treatment of pneumonia.