In vitro assessment of antibiotic-resistance reversal of a methanol extract from Rosa canina L.

The crude methanol extract of Rosa canina (RC) fruit was tested against multidrug-resistant (MDR) bacterial strains, including methicillin-resistant Staphylococcus aureus SA1199B, EMRSA16 and XU212 harbouring NorA, PBP2a and TetK resistance mechanisms, respectively, as well as S. aureus ATCC25923, a standard antimicrobial susceptible laboratory strain. The inhibition of the conjugal transfer of plasmid PKM101 and TP114 by the RC extract was also evaluated. The RC extract demonstrated a mild to poor antibacterial activity against the panel of bacteria having MIC values ranging from 256 to >512 μg/mL but strongly potentiated tetracycline activity (64-fold) against XU212, a tetracycline-effluxing and resistant strain. Furthermore, the extract showed moderate capacity to inhibit the conjugal transfer of TP114 and PKM101; transfer frequencies were between 40% and 45%. Cytotoxicity analysis of the RC extract against HepG2 cells line showed the IC50 > 500 mg/L and, thus, was considered non-toxic towards human cells. Phytochemical characterisation of the extracts was performed by the assessment of total phenolic content (RC: 60.86 mg TAE/g) and HPLC fingerprints with five main peaks at 360 nm. The results from this study provide new mechanistic evidence justifying, at least in part, the traditional use of this extract. However, the inhibition of bacterial plasmid conjugation opens the possibility of combination therapies to overcome antibiotic resistance

Seasonal and magnetic activity variations of nighttime ionospheric F-region vertical plasma drifts at Ibadan

14-19Nighttime F-region vertical electrodynamic drifts at Ibadan (lat. 7.4ºN, long. 3.9ºE; –6º dip) are obtained from the hourly-recorded ionosonde h′F data during 1957-58 International Geophysical Year (IGY) under geomagnetic quiet and disturbed conditions. The present results indicate strong seasonal variations in the drifts, even during quiet geomagnetic conditions. The downward nighttime average electrodynamic drift is found to be nearly 10 m/s. The drifts are consistently downward between ~2100 and 0500 hrs LT sector. The evening reversal time from upward daytime to downward nighttime does not vary much except during the June solstice months when it is found to be least, while it occurs early in December solstice and equinox. An equinoctial maximum in pre-reversal enhancements of the vertical drift is also noted. The present results are found to be completely consistent with some results obtained for some low latitude ionospheric stations, Jicamarca (lat. 11.9ºS, long. 76.8ºW; 1ºN dip), and Trivandrum (lat. 8.36ºN, long. 76.6ºE; 0.5ºN dip) that use different measurement techniques. Possible sources of the quiet-time variability in the electrodynamics can arise from changes in the global wind system and their resultant dynamo conditions, and changes in conductivity due to solar flux variability

Compositions and comparisons of antimicrobial potencies of some essential oils and antibiotics against selected bacteria

The antimicrobial activities of 10 essential oils extracted from various plant species were investigated and compared with the activities of 10 commercial antibiotics against 10 strains of bacteria using agar diffusion method. Although, all the essential oils were active at concentration ranging from 0.5 to 1.5 mg/ml, their activities were more lower than the commercial antibiotics. However, being natural products the oils have been reported to be much safer than the antibiotics. Another advantage of the essential oils used in this study was their broad spectrum activities against gram positive and gram negative bacteria. The oils were analyzed by GC and GC-MS techniques in order to determine their active compounds

The proposed mechanism of bactericidal action of eugenol,

The mechanism of antimicrobial activity of essential oils components; -terpineol, γ γ γ γ-terpinene and eugenol was studied to evaluate their effect on the bacterial membrane against four strains of bacteria: Listeria monocytogenes, Streptococcus pyogenes, Proteus vulgaris and Escherichia coli. The study was done to observe changes in membrane composition by assaying for the leakage of protein and lipid using Bradford and van Handel's method respectively. The oils components were capable of inducing cell lysis by the leakage of protein and lipid contents. Eugenol at 2 × MIC was highly effective toward protein content leakage after 120 min of exposure. Alpha terpineol and γ γ γ γ-terpinene showed similar effect at 2 × MIC under the same condition. Gamma terpinene displayed the highest activity toward lipid content leakage at 2 x MIC while -terpineol and eugenol showed similar effect after 120 min of exposure. The result revealed that both cell wall and membrane of the treated gram negative and gram positive bacteria were significantly damaged

Antibacterial and norfloxacin potentiation activities of Ocimum americanum L. against methicillin resistant Staphylococcus aureus

Staphylococcus species are among the most common resistant bacteria associated with the major cause of human ailments. The crude methanol extract from Ocimum americanum (OA) leaf was tested alone or in combination with norfloxacin (NOR) against strains of Staphylococcus aureus using the broth microdilution assay. The cytotoxicity of the OA extract was also evaluated using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) reagent assay on a HepG2 hepatocarcinomal cell line. While the plant extract exhibited a mild to poor antibacterial activity against our panel of bacteria, the antibiotic activity of norfloxacin at one-quarter MIC was enhanced by 2–4 fold in the presence of one-half MIC of OA extract against SA-1199B that over expresses the NorA efflux pump and MRSA-274829. These positive interactions were confirmed using a time-killing test; the combination therapy remarkably reduced the bacterial count of SA1199B and MRSA274829 ranging from a 6.0–4.2-log10-CFU/mL, after 24 h incubation. The OA extract strongly depleted DPPH* (IC50: 146.5 μg/mL), LOI (152 μg/mL), PGI (47.6 μg/mL) and FRAP (122.75 μmolFe(II)/g) possibly due to its richness in phenolic compounds. Furthermore, the OA extract showed a non-toxic effect on the HepG2 cells having an IC50 value of 378.0 μg/mL. These findings therefore support the folkloric use of Ocimum americanum at least in part for the treatment of infectious and free radical stress-related diseases

Chemical compound identification and antibacterial activity evaluation of cinnamon extracts obtained by subcritical n‐butane and ethanol extraction

Four important Cinnamomum species in China including C. cassia, C. loureiroi, C. wilsonii, and C. burmannii were chosen to be extracted by subcritical n‐butane and ethanol. The chemical compounds of extracts were identified by GC‐MS and HPLC‐MS, and the antibacterial activities were evaluated by agar‐well diffusion assay and twofold microdilution broth method. There were 47 compounds identified in n‐butane extracts and 11 compounds in ethanol extracts totally. The major compounds in n‐butane extracts varied significantly among different Cinnamomum species, and (E)‐cinnamaldehyde and coumarin were major compounds for C. cassia with area percentage of 74.32%; (E)‐cinnamaldehyde and α‐copaene for C. loureiroi with area percentage of 67.83%; linalool, (E)‐cinnamaldehyde, and citral for C. wilsonii with area percentage of 58.74%; and eugenol, (E)‐cinnamaldehyde, and coumarin for C. burmannii with area percentage of 76.43%. The maximum compounds in ethanol extracts were (E)‐cinnamaldehyde and (Z)‐cinnamaldehyde, and others varied among the Cinnamomum species. All cinnamon extracts showed antibacterial activities that n‐butane extracts were much more sensitive than ethanol extracts. The inhibition zone for N‐butane extracts against Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, and Salmonella anatum was from 18.98 to 37.45 mm while for ethanol extracts from 7.11 to 10.11 mm. The minimum bactericidal concentrations for n‐butane extracts were ranged from 0.31 to 2.50 mg/ml and for ethanol extracts ranged from 20.00 to 160.00 mg/ml. N‐butane extracts of C. cassia and C. loureiroi processed much higher antibacterial activities than C. wilsonii and C. burmannii. N‐butane extracts of C. cassia and C. loureiroi have the potential to be used as food biopreservative