Botanical Medicines with Activity Against Stationary Phase Bartonella henselae

Abstract

Bartonella henselae is a Gram-negative bacterium and is the causative agent of cat scratch disease. In humans, infections with B. henselae can result in acute or chronic systemic infections with diverse clinical symptoms. The current treatment for Bartonella infections with antibiotics such as doxycycline and rifampin is not always effective, presumably due in part to bacterial persistence. There are various anecdotal reports of herbal extracts used for treating patients with persistent Bartonella infections but their activity on B. henselae is unknown. In order to identify more effective therapies for persistent Bartonella infections, in this study, we tested the antimicrobial activity of botanical and herbal medicines and screened an herbal product collection against stationary phase B. henselae in vitro using a SYBR Green I/propidium iodide viability assay. We identified five herbal product extracts (at 1.67 mg/mL or 2.5 mg/mL), including Cryptolepis sanguinolenta, Juglans nigra, Polygonum cuspidatum, Scutellaria baicalensis, and Scutellaria barbata, that had high activity against stationary phase B. henselae. Among them, C. sanguinolenta, J. nigra, and P. cuspidatum could eradicate all stationary phase B. henselae cells within 7 days at 0.83 mg/mL or 1.25 mg/mL in drug exposure time-kill assays, whereas S. baicalensis and S. barbata showed relatively poor activity. These top hits were active against both stationary phase non-growing B. henselae and log phase growing B. henselae in minimum inhibitory concentration testing. These findings may have implications for improved treatment of persistent Bartonella infections.