Litsea cubeba leaf essential oil from Vietnam: chemical diversity and its impacts on antibacterial activity.

The threat of bacterial resistance to antibiotics has created an urgent need to develop new antimicrobials. The aim of this study was to characterize the chemical diversity of Litsea cubeba leaf essential oil (EO) and its impacts on the antibacterial activity against pathogenic bacteria. Essential oils collected from seven provinces in North Vietnam (n = 25) were characterized by their high content in either 1,8-cineole or linalool. Linalool-type EOs were more effective against the eight bacterial strains tested than 1,8-cineole-type. Oil samples, LC19 (50% 1,8-cineole) and BV27 (94% linalool), were selected to investigate their antibacterial mechanisms against Escherichia coli. A strong bactericidal effect was observed after 4 and 2 h of exposure respectively. Microscopic analysis of treated E. coli cultures clearly showed that EOs caused changes in cell morphology, loss of integrity and permeability of the cell membrane, as well as DNA loss. However, the effects of both EOs were distinct. LC19 mostly affected cell membrane, led to a significant cell filamentation rate and altered cell width, whereas BV27 damaged cell membrane integrity leading to cell permeabilization and altered nucleoid morphology with the appearance of spot and visibly altered compaction. SIGNIFICANCE AND IMPACT OF THE STUDY: This study aimed to characterize the chemical diversity of Litsea cubeba leaf essential oil (EO) and its impacts on its antibacterial activity. Two major chemotypes (1,8-cineole or linalool rich) were identified in North Vietnam and both were bactericidal against several pathogenic bacteria. A distinct inhibitory effect of EO samples on Escherichia coli was observed. 1,8-cineole-rich sample (LC19) affected cell membrane, led to cell filamentation and perturbation of cell width, while the linalool-rich one (BV27) induced damages in the cell membrane and changes in the nucleoid morphology. The study demonstrates the importance of considering chemotype variations in terms of chemical composition as well as the mode of action.

Antibacterial activity of Litsea cubeba (Lauraceae, May Chang) and its effects on the biological response of common carp Cyprinus carpio challenged with Aeromonas hydrophila.

AIMS: The aims of this study were to characterize the antibacterial activity and the chemotype of Litsea cubeba leaf essential oil (EO) harvested in North Vietnam and to investigate the biological effects induced by the leaf powder on growth, nonspecific immunity and survival of common carp (Cyprinus carpio) challenged with Aeromonas hydrophila. METHODS AND RESULTS: The EO showed the prevalence of linalool (95%, n = 5). It was bactericidal against the majority of tested strains, with minimum inhibitory concentrations ranging from 0·72 to 2·89 mg ml(-1) (Aer. hydrophila, Edwarsiella tarda, Vibrio furnissii, Vibrio parahaemolyticus, Streptococcus garvieae, Escherichia coli, Salmonella Typhimurium). The fish was fed with 0 (control), 2, 4 and 8% leaf powder supplementation diets for 21 days. Nonspecific immunity parameters (lysozyme, haemolytic and bactericidal activities of plasma) were assessed 21 days after feeding period and before the experimental infection. Weight gain, specific growth rate and feed conversion ratio were improved by supplementation of L. cubeba in a dose-related manner, and a significant difference appeared at the highest dose (8%) when compared to the control. The increase in plasma lysozyme was significant for all the treated groups. Haemolysis activity was higher for the groups fed with 4 and 8% plant powder. Antibacterial activity increased significantly for the 8% dose only. CONCLUSIONS: Litsea cubeba leaf powder increased nonspecific immunity of carps in dose-related manner. After infection with Aer. hydrophila, survivals of fish fed with 4 and 8% L. cubeba doses were significantly higher than those fed with 2% dose and the control. SIGNIFICANCE AND IMPACT OF THE STUDY: A range of 4-8% L. cubeba leaf powder supplementation diet (from specific linalool-rich chemotype) can be used in aquaculture to reduce antibiotic burden and impacts of diseases caused by Aer. hydrophila.

Novel alternative to antibiotics in shrimp hatchery: effects of the essential oil of Cinnamosma fragrans on survival and bacterial concentration of Penaeus monodon larvae.

AIMS: The activity of two essential oils (EOs) of Cinnamosma fragrans, an endemic plant to Madagascar (B8: linalool-type and B143: 1,8-cineole-type), against bacterial isolates from a shrimp hatchery of Penaeus monodon and their effects on the survival and bacterial concentration of larvae were determined. METHODS AND RESULTS: Minimum inhibitory concentrations were determined using a broth dilution technique. The bacterial concentrations of both larvae and water tank were assessed on Marine agar and Thiosulfate Citrate Bile Sucrose agar. The assays took place in OSO Farming's shrimp hatchery in Madagascar. EOs were directly added to the water tank. Regarding the survival, the assays in larval culture (four replicates each of B8, B143, E and control) showed that B8 oil had a similar effect (P > 0.05) as the antibiotic (Erythromycin) and was more active than B143 (P < 0.05). A negative correlation was observed between the bacterial concentration and the survival of larvae for all assays. CONCLUSION: Both C. fragrans essential oils, as antibiotic, exhibited significantly higher survival rates and lower bacterial concentrations of the larvae than the control (oil and antibiotic free). SIGNIFICANCE AND IMPACTS OF THE STUDY: The potential of C. fragrans essential oil to control the bacterial load in in vivo conditions, thereby enhancing survival rate of P. monodon larvae, makes it a relevant option for developing a novel alternative to antibiotics in shrimp hatchery culture.

Decontamination of chicken skin surfaces inoculated with Listeria innocua, Salmonella enteritidis and Campylobacter jejuni by contact with a concentrated lactic acid solution.

1. The aim was to establish how poultry skin could be efficiently decontaminated without changing its organoleptic properties. 2. Chicken skins were surface inoculated with Listeria innocua and treated with different acid solutions (2 and 10% lactic acid for 1 and 30 min). Surviving bacteria were enumerated immediately after treatment and after 7 d storage at 4 degrees C. 3. Reductions of up to 2.6 log were reached immediately after treatment. The treatment effect persisted for 7 d storage, when the reduction exceeded 4.59 log for the strongest treatment. 4. Residual levels of lactic acid were not significantly higher than in untreated controls, except for the strongest treatment. A tasting panel found no significant difference between controls and samples. 5. After the initial results, an apparently optimal treatment (5% lactic acid for 1 min) was applied on chicken skins' surface inoculated with a mix of Listeria innocua, Salmonella enteritidis and Campylobacter jejuni. Treatment efficacy was assessed immediately after treatment and after 1, 4 and 7 d storage. 6. This treatment seems to be very promising from a food processing standpoint, being fast and allowing decimal reductions of 2.00 log for Listeria innocua and 2.38 log for Salmonella enteritidis after 7 d storage, neither significantly increasing skin lactic acid nor causing any organoleptic modifications to the product. The effect of the treatment is significant after one day storage for Listeria innocua and after 4 d storage for Salmonella enteritidis.

[Forrest 1b duodenal hemorrhage in previously undiagnosed primary hyperparathyroidism]. / Forrest 1b-Duodenalblutung bei vorher unbekanntem primärem Hyperparathyreoidismus.

We report on a female patient who was suffering from a duodenal ulcer with an oozing haemorrhage. It turned out to be the result of an adenoma of the parathyroid combined with the clinical picture of an 'osteodystrophia fibrosa cystica generalisata', which is rarely seen. The therapy consisted in a parathyroidectomy.