In vitro time kill assessment of crude methanol extract of Helichrysum pedunculatum leaves

The in vitro antibacterial activities and time kill regimes of crude methanol extract of Helichrysum pedunculatum was assessed using standard microbiological procedures. The experiment wasconducted against a panel of bacterial species made up of clinical, environmental and reference strains. The extract was active against eleven of the twenty-one bacteria tested at a concentration of 10 mg/ml. Minimum Inhibitory Concentration (MIC) values for all the susceptible bacteria ranged between 0.1 – 5.0mg/ml. The average log reduction in viable cell count in time kill assay ranged between 0.17 Log10 to 6.37 Log10 cfu/ml after 6 h of interaction, and between 0.14 Log10 and 6.99 Log10 cfu/ml after 12 h interaction in 1×MIC and 2×MIC of the extract. The extract was bactericidal against 8 of the test bacteria at 1×MIC and against 9 of the test bacteria at 2×MIC from 12 h interaction period. At both MIC levels, the extract was bactericidal to all the reference strains and four of the six environmental strains at both MIC levels after 12 h of interaction. Also the extract was bactericidal to four of the six environmental strains at both MIC levels after 12 h of interaction and bacteriostatic during the first 6 h of interaction. Inhibitory levels of crude methanol extract of H. pedunculatum could be bacteriostatic or bactericidal independentof Gram’s characteristic

The proposed mechanism of bactericidal action of eugenol, &#8733-terpineol and g-terpinene against Listeria monocytogenes, Streptococcus pyogenes, Proteus vulgaris and Escherichia coli

The mechanism of antimicrobial activity of essential oils components; - terpineol, g-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 g-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

Studies on the in vitro time kill assessment of crude acetone and aqueous extracts of Helichrysum pedunculatum leaves

Helichrysum pedunculatum is used in folklore remedies to dress wound acquired after circumcision rite. This led to the study of in vitro antibacterial activities of this medicinal plant. Using standardmicrobiological procedures, six bacteria species made up of four gram positive and two gram negative bacteria were screened for susceptibility to crude acetone and aqueous extracts of this plant. Theminimum inhibitory concentrations (MICs) of the acetone extract against the susceptible bacteria was 5.0 mg/ml while that of the aqueous extract ranged between 0.5 - 35 mg/ml. Average log reduction in viable cell count in time kill assay of the acetone extract ranged between 0.64 Log10 and 5.99 Log10 cfu/ml after 6 h of interaction, and between 5.99 Log10 and 6.06 Log10 cfu/ml after 12 h interaction in 1 × MIC and 2 × MIC, and between 0.10 Log10 to 0.33 Log10 cfu/ml after 6 h of interaction, and 0.23 Log10 and 0.56 Log10 cfu/ml after 12 h interaction in 1 × MIC and 2 × MIC for the aqueous extract. The effect of the aqueous extract was only bacteriostatic on both reference and environmental strains and the clinical isolates were outrightly resistant to this extract (not reported here). This is worrisome and thiscould be one reason why, there is an incidence of high death rate resulting from circumcision wounds infection even after treating such wounds with H. pedunculatum leaf. Perhaps the plant could be ofmore relevance in combination therapy and a source of resistance modifying principles which is the subject of on going studies in our group

Assessment techniques of antimicrobial properties of natural compounds of plant origin: current methods and future trends

Medicinal plants have recently received the attention of the pharmaceutical and scientific communities and various publications have documented the therapeutic value of natural compounds in a bid tovalidate claims of their biological activity. Attention has been drawn to the antimicrobial activity of plants and their metabolites due to the challenge of growing incidences of drug-resistant pathogens.Some plants have shown the ability to overcome resistance in some organisms and this has led to researchers’ investigating their mechanisms of action and isolating active compounds. Particularfocus is on establishing the effect of the plant(s) extracts in terms of their microstatic and microcidal action and the spectrum of organisms affected. This has enabled exploitation of plants for the treatment of microbial infections and in the development of new antimicrobial agents. This requires rigorous research and it is therefore imperative to follow standard methods to authenticate claims of antimicrobial action. Results comparability is largely dependent on the techniques employed in the investigations and conclusive results can only be obtained if methods are standardized and universal. This paper reviews the current methods used in the investigations of the efficacy of plants asantimicrobial agents and points out some of the differences in techniques employed by different authors