A Drug Combination Screen Identifies Drugs Active against Amoxicillin-Induced Round Bodies of In Vitro Borrelia burgdorferi Persisters from an FDA Drug Library
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http://journal.frontiersin.org/article/ ... 00743/full
Jie Feng1, Wanliang Shi1, Shuo Zhang1, David Sullivan1, Paul G. Auwaerter2 and Ying Zhang1*
1Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA
2Fisher Center for Environmental Infectious Diseases, School of Medicine, Johns Hopkins University, Baltimore, MD, USA
<snip from discussion section of full text>Although currently recommended antibiotics for Lyme disease such as doxycycline or amoxicillin cure the majority of the patients, about 10–20% of patients treated for Lyme disease may experience lingering symptoms including fatigue, pain, or joint and muscle aches. Under experimental stress conditions such as starvation or antibiotic exposure, Borrelia burgdorferi can develop round body forms, which are a type of persister bacteria that appear resistant in vitro to customary first-line antibiotics for Lyme disease. To identify more effective drugs with activity against the round body form of B. burgdorferi, we established a round body persister model induced by exposure to amoxicillin (50 μg/ml) and then screened the Food and Drug Administration drug library consisting of 1581 drug compounds and also 22 drug combinations using the SYBR Green I/propidium iodide viability assay. We identified 23 drug candidates that have higher activity against the round bodies of B. burgdorferi than either amoxicillin or doxycycline. Eleven individual drugs scored better than metronidazole and tinidazole which have been previously described to be active against round bodies. In this amoxicillin-induced round body model, some drug candidates such as daptomycin and clofazimine also displayed enhanced activity which was similar to a previous screen against stationary phase B. burgdorferi persisters not exposure to amoxicillin. Additional candidate drugs active against round bodies identified include artemisinin, ciprofloxacin, nifuroxime, fosfomycin, chlortetracycline, sulfacetamide, sulfamethoxypyridazine and sulfathiozole. Two triple drug combinations had the highest activity against amoxicillin-induced round bodies and stationary phase B. burgdorferi persisters: artemisinin/cefoperazone/doxycycline and sulfachlorpyridazine/daptomycin/doxycycline. These findings confirm and extend previous findings that certain drug combinations have superior activity against B. burgdorferi persisters in vitro, even when pre-treated with amoxicillin. These findings may have implications for improved treatment of Lyme disease.
Interestingly, this research group now includes Paul Auwaerter again and he is listed as a co-author on this paper.Despite the description of drug candidate’s active against the round body forms, their significance in improving the treatment remains to be determined. While evidence that round body form of persisters examined in this study may occur in vivo during infection remains to be confirmed, it is also unknown if antibiotics that target such potential persisters would lead to improved outcomes in human infection compared with standard Lyme disease treatment with doxycycline or amoxicillin that do not have good activity against the round body forms of B. burgdorferi (Brorson et al., 2009; Barthold et al., 2010) or if they even induce such forms in vivo. These studies indicate that it would be difficult to kill the round body form of B. burgdorferi using the current Lyme antibiotics if similar organisms exist in vivo or are incompletely eradicated in the human host under environmental stressors. The drug candidates identified in this study could allow the above possibility to be tested in animal models of persistence using the drug combinations that are active against round body forms of B. burgdorferi in the future.