Antibacterial and therapeutic effects of a combination of Sophora flavescens and Glycyrrhiza uralensis Fischer ethanol extracts on mice infected with Streptococcus pyogenes

Abstract

Abstract : This study evaluated the antibacterial effects of a mixture of Sophorae radix and Glycyrrhiza uralensisFischer (1 : 1) ethanol extracts (SGE) on mice infected with Streptococcus (S.) pyogenes. The minimum inhibitoryconcentration (MIC) and minimum bactericidal concentration of SGE necessary for antibacterial effects against S.pyogenes were 20µg/mL. Based on the time-kill curves for S. pyogenes, SGE was effective at 4× MIC after 16 h.On Day 12 after challenge, the survival rate of mice treated with 2.0 mg/kg SGE was 60%. In conclusion, SGE hadpotent in vitro and in vivo antibacterial activities against S. pyogenes.Keywords : crude extracts, medicinal plants, mice, Streptococcus pyogenes, treatment efficacy Streptococcus (S.) pyogenes, a group A streptococcus, is anaerobic, spherical, gram-positive extracellular bacterium thatis associated with a variety of mucosal and invasive humaninfections [3]. These bacteria cause various diseases rangingfrom mild and quite frequent non-invasive infections of theupper respiratory tract and skin to severe invasive infectionsthat include necrotizing fasciitis and streptococcal toxicshock syndrome [4]. The most important modes of S. pyogenes transmission arevia respiratory droplets, hand contact with nasal dischargeand skin contact with impetigo lesions [1]. In addition, S.pyogenes can be spread to cattle and then back to humansthrough raw milk as well as contaminated food sources suchas salads, milk and eggs [7]. In a previous study [16] that analyzed for antimicrobialsusceptibility against S. pyogenes isolates in scarlet feverpatients between 2003 and 2011 in China, 100, 97.0, and89.4% of the 74 S. pyogenes isolates were found to be resis-tant to erythromycin, clindamycin and tetracycline, respec-tively. The emergence of antibiotic resistance has led to thesearch for new, safe and effective antimicrobial agents fromalternative natural resources. Medicinal herbs as alternativesto antibiotics are attracting considerable attention by manyresearchers, and many such herbs have a long history ofmedicinal use in Asia [14]. Many of these herbs are oftenused in combination to increase their effects. These herbscontaining bioactive components have many potential clini-cal and therapeutic applications in modern medical care [11].In addition, antimicrobial agents can be derived from herbs,and more than 1,340 plants have been reported to have anti-microbial effects [15].Sophora (S.) flavescens which has antibacterial, antiinflam-matory, antipyretic, antiulcerative and antineoplastic effectshas been used traditionally as medicinal herbs in the treat-ment of jaundice, leucorrhea, carbuncles, pyogenic infec-tions of the skin, scabies, enteritis, and dysentery [8, 9].Glycyrrhiza (G.) uralensis Fischer is one of the most gener-ally used herbal medicines in the world and has been provedto possess antiinflammatory, liver protection, antibacterial,and anticancer activity, which are attributed to the containedtriterpenoid saponins and flavonoids [5]. This study evaluated the antibacterial activity of a combi-nation of ethanol extracts from the medicinal herbs, S. flave-scens and G. uralensis Fischer, against S. pyogenes. Inaddition, a preparation of the herbs was fed to mice infectedwith S. pyogenes in order to determine its therapeutic poten-