Abstract
BackgroundNo animal model studies have been conducted in which the efficacy of herbal compounds has been tested against multidrug-resistant Acinetobacter baumannii infections. Very few antibiotics are available for the treatment of pulmonary infections caused by extensively drug-resistant Acinetobacter baumannii (XDRAB). To find alternative treatments, traditional Chinese herbs were screened for their antimicrobial potential.MethodsThe present study screened 30 herbs that are traditionally used in Taiwan and that are commonly prescribed for heat clearing and detoxification. The herbs with antibacterial activities were analysed by disc diffusion assays, time-kill assays and a murine lung infection model.ResultsOf the 30 herbs tested, only Scutellaria barbata demonstrated 100% in vitro activity against XDRAB. Furthermore, we compared the antibacterial effect of the S. barbata extract with that of colistin, and the S. barbata extract showed better antibacterial effect. In the XDRAB pneumonia murine model, we compared the antimicrobial effects of the orally administered S. barbata extract (200 mg/kg, every 24 h), the intratracheally administered colistin (75,000 U/kg, every 12 h), and the control group. The bacterial load in the lungs of the treatment group that received the oral S. barbata extract showed a significant decrease in comparison to that in the lungs of the control group. In addition, histopathological examinations also revealed better resolution of perivascular, peribronchial, and alveolar inflammation in the oral S. barbata extract-treated group.ConclusionsOur in vitro and in vivo data from the animal model support the use of S. barbata as an alternate drug to treat XDRAB pulmonary infections. However, detailed animal studies and clinical trials are necessary to establish the clinical utility of S. barbata in treating XDRAB pulmonary infections.
Highlights
No animal model studies have been conducted in which the efficacy of herbal compounds has been tested against multidrug-resistant Acinetobacter baumannii infections
We evaluated the antimicrobial effect of Chinese herbs against multidrug-resistant Acinetobacter baumannii (MDRAB) infection in a mouse model
The lungs were fixed immediately in 10% neutral buffered formalin and processed by Screening of antimicrobial activity Among the 30 Chinese herbs screened by the disc diffusion method, only the extract of Scutellaria barbata showed 100% antimicrobial activity against the 30 clinical isolates of A. baumannii, including the XDRAB strains with different pulsotypes (Table 1 and Fig. 1)
Summary
No animal model studies have been conducted in which the efficacy of herbal compounds has been tested against multidrug-resistant Acinetobacter baumannii infections. Tsai et al BMC Complementary and Alternative Medicine (2018) 18:96 emergence of drug resistance during the course of therapy limit the efficacy of tigecycline therapy for MDRAB when used as the single therapeutic agent [3, 6]. A study conducted by Savoia on the potential antimicrobial activity of plant-derived substances suggested that naturally bioactive plant compounds can be a source of new drugs in the future [7]. After screening sixty herbal extracts, Miyasaki et al reported that approximately 30% of the screened herbs displayed potential in vitro antimicrobial activity against MDRAB. One reason is that antibacterial compounds act more effectively in combination but show much lower efficacy when used in their isolated and purified forms [8]
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