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Antibacterial activity of berberine (Ber) and 8-acetonyl-dihydroberberine (A-Ber) alone and combined uses with antibacterial agents ampicillin (AMP), azithromycin (AZM), cefazolin (CFZ) and levofloxacin (LEV) was studied on 10 clinical isolates of SCCmec III type methicillin-resistant Staphylococcus aureus (MRSA). Susceptibility to each agent alone was tested using a broth microdilution method and the chequerboard and time-kill tests for the combined evaluations, respectively. The alone MICs/MBCs (μg/mL) ranges were 32-128/64-256 (Ber) and 32-128/128-512 (A-Ber). Significant synergies were observed for the Ber (A-Ber)/AZM and Ber (A-Ber)/LEV combinations against 90% of the tested MRSA strains, with fractional inhibitory concentration indices (FICIs) values ranged from 0.188 to 0.500. An additivity result was also observed for the Ber/AZM combination by time-kill curves. These results demonstrated for the first time that Ber and A-Ber enhanced the in vitro inhibitory efficacy of AZM and LEV to a same extent, which had potential for further investigation in combinatory therapeutic applications of patients infected with MRSA. [ABSTRACT FROM AUTHOR]

Through bioassay-guided fractionation of the extracts from the aerial parts of the Chinese herb Hypericum japonicum Thunb. Murray, Isojacareubin (ISJ) was characterized as a potent antibacterial compound against the clinical methicillin-resistant Staphylococcus aureus (MRSA). The broth microdilution assay was used to determine the minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) of ISJ alone. The results showed that its MICs/MBCs ranged from 4/16 to 16/64 µg/mL, with the concentrations required to inhibit or kill 50% of the strains (MIC50/MBC50) at 8/16 µg/mL. Synergistic evaluations of this compound with four conventional antibacterial agents representing different types were performed by the chequerboard and time-kill tests. The chequerboard method showed significant synergy effects when ISJ was combined with Ceftazidime (CAZ), Levofloxacin (LEV) and Ampicillin (AMP), with the values of 50% of the fractional inhibitory concentration indices (FICI50) at 0.25, 0.37 and 0.37, respectively. Combined bactericidal activities were also observed in the time-kill dynamic assay. The results showed the ability of ISJ to reduce MRSA viable counts by log10CFU/mL at 24 h of incubation at a concentration of 1 × MIC were 1.5 (LEV, additivity), 0.92 (CAZ, indifference) and 0.82 (AMP, indifference), respectively. These in vitro anti-MRSA activities of ISJ alone and its synergy with conventional antibacterial agents demonstrated that ISJ enhanced their efficacy, which is of potential use for single and combinatory therapy of patients infected with MRSA. [ABSTRACT FROM AUTHOR]

The in vitro antimicrobial activities of 30 Chinese medicinal plants were evaluated with reference to the treatment record of infectious diseases in the Traditional Chinese Medicine (TCM) literature. The plant materials were extracted with 80% ethanol and the extracts were primarily screened against conventional clinical pathogens like Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans by the agar diffusion method. Their inhibition zone diameters (IZDs, mm, 50 mg/mL) ranged from <8 to 24. The 21 extracts which showed IZDs ⩾10 mm against MSSA were also active against methicillin-resistant S. aureus (MRSA) with lower IZDs of 9.0-18.8 mm. They were further subjected to minimal inhibitory concentration and minimal bactericidal concentration (MIC/MBC, μG/mL) assays, which were 8-2,048/32->2,048 by the standard broth microdilution method. The seven extracts from M. yunnanensis, S. sinensis, G. morella, E. daneillii, M. squamulata, S. arborescens and B. hancei were determined as the most active extracts, with MICs of 8-64 μg/mL. The results were in good agreement with their traditional applications in skin and other infections. [ABSTRACT FROM AUTHOR]

The antibacterial activity of two bisbenzylisoquinoline alkaloids, tetrandrine (Tet) and demethyltetrandrine (d-Tet), alone and in combination with the antibiotics ampicillin (AMP), azithromycin (AZM), cefazolin (CFZ) and levofloxacin (LEV) against 10 clinical isolates of staphylococcal chromosomal cassette mec (SCCmec) III type methicillin-resistant Staphylococcus aureus (MRSA) was studied. Susceptibility to each agent alone was tested using a broth microdilution method. The chequerboard and time-kill tests were used for the combined evaluations. The minimal inhibitory concentrations/minimal bactericidal concentrations (MICs/MBCs, μg/mL) ranges alone were 64-128/256-1,024 for both Tet and d-Tet. Significant synergies against 90% of the isolates were observed for the Tet/CFZ combination, with their MICs being reduced by 75-94% [fractional inhibitory concentration indices (FICIs) ranged from 0.188 to 0.625], respectively. An additive bactericidal result was also observed for the Tet (d-Tet)/CFZ combination in the time-kill experiments. These results demonstrated that Tet and d-Tet enhanced the in vitro inhibitory efficacy of CFZ. Their potential for combinatory therapy of patients infected with MRSA warrants further pharmacological investigation. [ABSTRACT FROM AUTHOR]

The antibacterial activity of 80% ethanol extracts of 10 medicinal plants collected in Yunnan (Southwest China), was tested against clinical isolates of extended-spectrum β-lactamase (ESBL)-producing strains. Their MIC values ranged between 1.56-12.50 mg/mL. The most active plant extract was Chelidonium majus L. (MIC = 1.56 mg/mL). Two potent isoquinoline alkaloids, 8-hydroxydihydrosanguinarine and 8-hydroxydihydrochelerythrine, were identified as the major active principles through bioassay-guided fractionation and identification of the active ethyl acetate fraction from C. majus, with minimum MIC/MBC values of 15.63/62.50 μg/mL. [ABSTRACT FROM AUTHOR]