Structural characterization and surface activities of biogenic rhamnolipid surfactants from Pseudomonas aeruginosa isolate MN1 and synergistic effects against methicillin-resistant Staphylococcus aureus.

The aim of present work was to study chemical structures and biological activities of rhamnolipid biosurfactants produced by Pseudomonas aeruginosa MN1 isolated from oil-contaminated soil. The results of liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis revealed that total rhamnolipids (RLs) contained 16 rhamnolipid homologues. Di-lipid RLs containing C(10)-C(10) moieties were by far the most predominant congeners among mono-rhamnose (53.29 %) and di-rhamnose (23.52 %) homologues. Mono-rhamnolipids form 68.35 % of the total congeners in the RLs. Two major fractions were revealed in the thin layer chromatogram of produced RLs which were then purified by column chromatography. The retardation factors (R (f)) of the two rhamnolipid purple spots were 0.71 for RL1 and 0.46 for RL2. LC-MS/MS analysis proved that RL1 was composed of mono-RLs and RL2 consisted of di-RLs. RL1 was more surface-active with the critical micelle concentration (CMC) value of 15 mg/L and the surface tension of 25 mN/m at CMC. The results of biological assay showed that RL1 is a more potent antibacterial agent than RL2. All methicillin-resistant Staphylococcus aureus (MRSA) strains were inhibited by RLs that were independent of their antibiotic susceptibility patterns. RLs remarkably enhanced the activity of oxacillin against MRSA strains and lowered the minimum inhibitory concentrations of oxacillin to the range of 3.12-6.25 µg/mL.

Chemical composition and antimicrobial activity of the essential oil of Anthemis altissima L. var. altissima.

The essential oil obtained from the flowering parts of Anthemis altissima L. var. altissima was analysed by gas chromatography and gas chromatography mass spectroscopy. In this study, 34 compounds representing 98.76% of the essential oil were identified. The main components were α-terpineol (26.42%), ß-pinene (9.23%), cis-chrysanthenyl acetate (6.30%), globulol (5.36%), n-tricosane (4.41%), terpinen-4-ol (4.08%) and 1,8 cineole (3.84%). Antibacterial activities of the essential oil and its two major components (α-terpineol and ß-pinene) were determined using microdilution method against both Gram-positive (Staphylococcus aureus, Bacillus subtilis, Staphylococcus epidermidis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae) bacteria. The essential oil showed a broad-spectrum antibacterial activity (MICs ranged from 3.13 to 6.25 µL mL(-1)). It was found that α-terpineol with minimum inhibitory concentration (MIC) values of the range 0.87-1.56 µL mL(-1) was a more potent antibacterial agent than ß-pinene with MIC values of the range 1.56-6.25 µL mL(-1). All of them, the essential oil, ß-pinene and α-terpineol, were more effective against Gram-positive bacteria than Gram-negative ones.

Efficacy of detergents and fresh produce disinfectants against microorganisms associated with mixed raw vegetables.

Efficacy of commercial detergent and disinfectants to eliminate microorganisms associated with fresh vegetables eaten raw in Iran, including radish, parsley, basil, coriander (cilantro), Allium porrum (leek), and peppermint were studied. The raw vegetables were subjected to a triple wash treatment of washing in tap water for mud removal, washing in water containing a detergent (dishwashing liquid) or disinfectant individually, and rinsing in tap water. The population of total mesophilic microbes on the surface of untreated vegetables ranged from 10(5) to 10(6) CFU/g. Washing in tap water or treatment with detergent (333 ppm for 10 min) or benzalkonium chloride (92 ppm for 15 min) reduced the total microbial count, most probable number (MPN) of coliforms, MPN of fecal coliforms, and MPN of fecal streptococci by about 1.2 to 2.3 log. No significant differences in microbial populations were found on vegetables after decontamination with tap water, detergent, or benzalkonium chloride (P > 0.05). Treatments with peracetic acid (100 ppm for 15 min) and hydrogen peroxide (133 ppm for 30 min) reduced the total mesophilic microbial counts by about 2.8 log. The microbial reductions with calcium hypochlorite (300 ppm for 15 min) and combined hydrogen peroxide and silver ion (133 ppm for 30 min) were significantly higher than those obtained after rinsing in tap water or after detergent or benzalkonium chloride wash (P < 0.05). Pretreatment with detergent slightly enhanced the efficacy of all decontamination treatments, but results were not significantly different from those obtained after individual application of disinfectants.