Modulation of the norfloxacin resistance in Staphylococcus aureus by Cordia verbenaceae DC.

Background & objectives: Several chemical compounds isolated from natural sources have antibacterial activity and some enhance the antibacterial activity of antibiotics reversing the natural resistance of bacteria to certain antibiotics. In this study, the hexane and methanol extract of Cordia verbenaceae were assessed for antibacterial activity alone and combinated with norfloxacin against the Staphylococcus aureus strain SA1199B. Methods: The minimum inhibitory concentration (MIC) of extracts was assayed using microdilution assay and the modulatory activity was evaluated using plate diffusion assay. Results: The MIC observed varied between 256 to >1024 μg/ml. However, the antibiotic activity of norfloxacin was enhanced in the presence of subinhibitory concentrations of hexane extract of C. verbenaceae (HECV). Interpretations & conclusions: Our results indicate that Cordia verbenaceae DC. can be a source of plant derived products with antibiotic modifying activity.

Modulation of drug resistance in Staphylococcus aureus by extract of mango (Mangifera indica L., Anacardiaceae) peel

In an ongoing project to evaluate natural compounds isolated from by-products or wastes from vegetables and fruits (edible plants) as modulators of antibiotic resistance, ethanol extract from mango peel was investigated using Staphylococcus aureus strains possessing efflux mechanisms of resistance to norfloxacin, erythromycin and tetracycline. The minimum inhibitory concentrations (MIC) of the antibiotics were determined by the micro dilution assay in the absence and in the presence of sub-inhibitory mango peel extract concentration. Although the extract did not display relevant antibacterial activity (MIC>2048 µg/mL), it modulated the activity of antibiotics, i.e. in combination with antibiotics (at 512 µg/mL), a four-fold reduction in the MIC values for tetracycline and erythromycin was observed. The results presented here indicates that mango peel could serve as a source of potential adjuvant of antibiotics which add value to this mango by-product.

In vitro interference of Hyptis martiusii Benth. & chlorpromazine against an aminoglycoside - resistant Escherichia coli.

The antibacterial and synergistic activity of the ethanol extract from Hyptis martiusii Benth. was assayed by microdillution. The growth of two isolates of Escherichia coli tested was inhibited by the extract. The minimum inhibitory and minimum bactericidal concentrations (MIC and MBC) values ranged from 512 and >1024 μg/ml for the E. coli 27 and 1024 and > 1024 μg/ml for the E. coli ATCC8539, respectively. A synergism between this extract and all aminoglycosides assayed was demonstrated. In the same form synergism between chlorpromazine and kanamycin, amikacin and tobramycin was observed, indicating the involvement of an effl ux system. Extracts from H. martiusii could be used as a source of plant derived natural products with modifying antibiotic activity and these products may interact and affect multidrug resistance systems (MDR) as efflux pumps.

Composição química e modulação da resistência bacteriana a drogas do óleo essencial das folhas de Rollinia leptopetala R. E. Fries / Chemical composition and modulation of bacterial drug resistance of the essential oil from the leaves of Rollinia leptopetala R. E. Fries

O óleo essencial das folhasde Rollinia leptopetala foi obtido por hidrodestilação em aparelho de Clevenger e a sua composição química foi analisada através de CG-EM. Com essa técnica, foi possível identificar 22 constituintes em uma mistura complexa demonoterpenos (54,5 por cento) e sesquiterpenos (45,5 por cento). O principal componente encontradonas folhas foi o biciclogermacreno (22,47 por cento). O óleo essencial foi avaliado numa linhagem de Staphylococcus aureus portadora de bomba de efluxo responsável pela resistência norfloxacino. Embora o óleo essencial não tenha apresentado atividade antibacteriana relevante in vitro, ele apresentou atividade moduladora da resistência, ou seja, em combinação com o norfloxacino observou-se uma redução de 4x na concentração inibitória mínima do antibiótico, indicando inibição de bomba de efluxo.

The essential oil from the leaves of Rollinia leptopetala was obtained by hydrodistillation in Clevenger's apparatus and its chemical composition was analyzed by GC-MS. With this technique could be identified 22 constituents in a complex mixture of monoterpenes (54.5 percent) and sesquiterpenes (45.5 percent). The main component found in the leaves was the bicyclogermacrene (22.47 percent). The essential oil was assayed against a strain of Staphylococcus aureus possessing efflux mechanism of resistance to norfloxacin. Although the essential oil did not display relevant antibacterial activity in vitro, it modulated the activity of the norfloxacin, i.e. in combination with the antibiotic it was observed a fourfold reduction in the minimum inhibitory concentration for norfloxacin, indicating inhibition of efflux pump.