Antimicrobial effect and mode of action of terpeneless cold-pressed Valencia orange essential oil on methicillin-resistant Staphylococcus aureus.

AIMS: The objectives of this study were to evaluate the antistaphylococcal effect and elucidate the mechanism of action of orange essential oil against antibiotic-resistant Staphylococcus aureus strains. METHODS AND RESULTS: The inhibitory effect of commercial orange essential oil (EO) against six Staph. aureus strains was tested using disc diffusion and agar dilution methods. The mechanism of EO action on MRSA was analysed by transcriptional profiling. Morphological changes of EO-treated Staph. aureus were examined using transmission electron microscopy. Results showed that 0·1% of terpeneless cold-pressed Valencia orange oil (CPV) induced the cell wall stress stimulon consistent with the inhibition of cell wall synthesis. Transmission electron microscopic observation revealed cell lysis and suggested a cell wall lysis-related mechanism of CPV. CONCLUSIONS: CPV inhibits the growth of Staph. aureus, causes gene expression changes consistent with the inhibition of cell wall synthesis, and triggers cell lysis. SIGNIFICANCE AND IMPACT OF THE STUDY: Multiple antibiotics resistance is becoming a serious problem in the management of Staph. aureus infections. In this study, the altered expression of cell wall-associated genes and subsequent cell lysis in MRSA caused by CPV suggest that it may be a potential antimicrobial agent to control antibiotic-resistant Staph. aureus.

Modulatory effects of Crataeva nurvala bark against testosterone and N-methyl-N-nitrosourea-induced oxidative damage in prostate of male albino rats.

BACKGROUND: Antioxidant properties of Crataeva nurvala bark contains a variety of the bioactive phytochemical constituents in medicinal plants which include flavonoids, phenolic compounds, tannins, anthracene derivatives, and essential oils. Components from Crataeva nurvala bark have been accounted to play an important role in scavenging free radicals generated by mutagens and carcinogens. Androgens are the key factors in either the initiation or progression of prostate cancer by inducing oxidative stress. In the present set of investigations, the antioxidative potential of Crataeva nurvala bark extract against androgen-mediated oxidative stress in male Wistar rats has been studied. MATERIALS AND METHODS: Oxidative damage in prostate was induced in rats by the injection of testosterone (100 mg/kg body weight [bw]) for 3 days followed by injection of chemical carcinogen N-Methyl N-Nitroso Urea (50 mg/kg bw) for 1 week. The oxidative damage in prostate-induced rats were treated with the ethanolic extract of Crataeva nurvala bark (150 mg/kg bw) and testosterone injection (2 mg/ kg bw) was also continued through the experimental period of 4 months. The prostate tissue was dissected out for biochemical analysis of lipid peroxidation and enzymic-antioxidants viz. catalase, superoxide dismutase, glutathione peroxidase, glutathione-S-transferase, and glutathione reductase; the non-enzymic antioxidants viz. reduced glutathione, and Vitamin C. RESULTS: The results revealed that testosterone administration induced the oxidative stress in rat prostate; however, in drug (150 mg/kg bw) supplemented groups, a significant protective effect of Crataeva nurvala bark against testosterone-induced oxidative injury was recorded. CONCLUSION: Hence, the study reveals that constituents present in Crataeva nurvala bark impart protection against androgen-induced oxidative injury in prostate.

Genetic changes that correlate with the pine-oil disinfectant-reduced susceptibility mechanism of Staphylococcus aureus.

AIMS: To identify factors associated with the Staphylococcus aureus pine-oil disinfectant-reduced-susceptibility (PD(RS)) mechanism and to describe one possible PD(RS) model. METHODS AND RESULTS: Comparative genomic sequencing (CGS) and microarray analysis were utilized to detect mutations and transcriptome alterations that occur in a S. aureus PD(RS) mutant. Mutant analysis, antimicrobial gradient plates, growth studies and 3-hydroxy-3-methylglutaryl coenzyme A synthase assays were then performed to confirm the biological consequences of the 'omics' alterations detected in a PD(RS) mutant. CGS uncovered three mutations in a PD(RS) mutant in a(n): alcohol dehydrogenase (adh), catabolite control protein A (ccpA) and an NADPH-flavin oxidoreductase (frp). These mutations lead to increased growth rates; increased transcription of an NAD-dependent D-lactate dehydrogenase gene (ddh); and increased flux through the mevalonate pathway. PD(RS) mutants demonstrated reduced susceptibility to bacitracin and farnesol, and one PD(RS) mutant displayed upregulation of bacA, a bacitracin-resistance gene. Collectively, this evidence demonstrates altered undecaprenol metabolism in PD(RS) mutants. CONCLUSIONS: The PD(RS) mechanism proposed results from increased catabolic capabilities and increased flux through the mevalonate pathway as well as altered bactoprenol physiology. SIGNIFICANCE AND IMPACT OF THE STUDY: A novel mechanism that bacteria utilize to overcome the killing effects of PD formulations is proposed that is unique from the PD(RS) mechanism of the enterobacteraciae.