Increased ompW and ompA expression and higher virulence of Acinetobacter baumannii persister cells.

BACKGROUND: Acinetobacter baumannii is one of the main causes of healthcare-associated infections that threaten public health, and carbapenems, such as meropenem, have been a therapeutic option for these infections. Therapeutic failure is mainly due to the antimicrobial resistance of A. baumannii, as well as the presence of persister cells. Persisters constitute a fraction of the bacterial population that present a transient phenotype capable of tolerating supra-lethal concentrations of antibiotics. Some proteins have been suggested to be involved in the onset and/or maintenance of this phenotype. Thus, we investigated the mRNA levels of the adeB (AdeABC efflux pump component), ompA, and ompW (outer membrane proteins) in A. baumannii cells before and after exposure to meropenem. RESULTS: We found a significant increase (p-value < 0.05) in the expression of ompA (> 5.5-fold) and ompW (> 10.5-fold) in persisters. However, adeB did not show significantly different expression levels when comparing treated and untreated cells. Therefore, we suggest that these outer membrane proteins, especially OmpW, could be part of the mechanism of A. baumannii persisters to deal with the presence of high doses of meropenem. We also observed in the Galleria mellonella larvae model that persister cells are more virulent than regular ones, as evidenced by their LD50 values. CONCLUSIONS: Taken together, these data contribute to the understanding of the phenotypic features of A. baumannii persisters and their relation to virulence, as well as highlight OmpW and OmpA as potential targets for drug development against A. baumannii persisters.

Red pepper peptide coatings control Staphylococcus epidermidis adhesion and biofilm formation.

Medical devices (indwelling) have greatly improved healthcare. Nevertheless, infections related to the use of these apparatuses continue to be a major clinical concern. Biofilms form on surfaces after bacterial adhesion, and they function as bacterial reservoirs and as resistance and tolerance factors against antibiotics and the host immune response. Technological strategies to control biofilms and bacterial adhesion, such as the use of surface coatings, are being explored more frequently, and natural peptides may promote their development. In this study, we purified and identified antibiofilm peptides from Capsicum baccatum (red pepper) using chromatography-tandem mass spectrometry, MALDI-MS, MS/MS and bioinformatics. These peptides strongly controlled biofilm formation by Staphylococcus epidermidis, the most prevalent pathogen in device-related infections, without any antibiotic activity. Furthermore, natural peptide-coated surfaces dislayed effective antiadhesive proprieties and showed no cytotoxic effects against different representative human cell lines. Finally, we determined the lead peptide predicted by Mascot and identified CSP37, which may be useful as a prime structure for the design of new antibiofilm agents. Together, these results shed light on natural Capsicum peptides as a possible antiadhesive coat to prevent medical device colonization.

Kinetic characterization and gene expression of adenosine deaminase in intact trophozoites of Trichomonas vaginalis.

Trichomonas vaginalis is a parasite that resides in the human urogenital tract and causes trichomonosis, the most prevalent nonviral sexually transmitted disease. Nucleoside triphosphate diphosphohydrolase (NTPDase), which hydrolyzes extracellular di- and triphosphate nucleotides, and ecto-5'-nucleotidase, which hydrolyzes AMP, have been characterized in T. vaginalis. The aim of this study was to characterize the adenosine deaminase (ADA) activity in intact trophozoites of T. vaginalis. A strong inhibition in adenosine deamination was observed in the presence of calcium and magnesium, which was prevented by EDTA. The apparent K(M) value for adenosine was 1.13 ± 0.07mM. The calculated V(max) was 2.61 ± 0.054 nmol NH(3) min(-1) mg(-1) protein. Adenosine deamination was inhibited in the presence of erythro-9-(2-hydroxy-3-nonyl)adenine. Semi-quantitative reverse transcriptase-PCR experiments were performed and both ADA-related genes ada(125) and ada(231) mRNA were expressed, although ada(231) in higher quantity when compared with the ada(125) : α-tubulin ratio. Furthermore, a phylogenetic analysis showed that the T. vaginalis sequences formed a clade with Entamoeba histolytica and Dictyostelium discoideum sequences, and it strongly suggests homologous functions in the T. vaginalis genome. The presence of ADA activity in T. vaginalis may be important to modulate the adenosine/inosine levels during infection and, consequently, to maintain the anti-inflammatory properties through different nucleoside-signalling mechanisms.

Evaluation of antiulcer activity of the main phenolic acids found in Brazilian Green Propolis.

AIM OF THE STUDY: In a previous study, our group described the gastric protective effect of the hydroalcoholic extract of Brazilian green propolis. The main compounds found in Brazilian green propolis include phenolic acids, such as: caffeic, ferulic, p-coumaric and cinnamic acids. This study was therefore carried out to evaluate the antiulcerogenic property of the main phenolic acids found in Brazilian Green Propolis. MATERIAL AND METHODS: The anti-ulcer assays were performed using the following protocols: nonsteroidal-antiinflammatory drug (NSAID)-induced ulcer, ethanol-induced ulcer, and stress-induced ulcer. The effects of the phenolic acids on gastric content volume, pH and total acidity, using the pylorus ligated model, were also evaluated. RESULTS: It was observed that treatment using doses of 50 and 250 mg/kg of caffeic, ferulic, p-coumaric and cinnamic acids and positive controls (omeprazol or cimetidine) significantly diminished the lesion index, the total area of the lesion and the percentage of lesion in comparison with the negative control groups. In addition, the percentage of ulcer inhibition was significantly higher in the groups treated with the different phenolic acids, cimetidine or omeprazol, in all the protocols used, compared with the negative control groups. In the model to determine gastric secretion, using ligated pylorus, treatment with phenolic acids and cimetidine reduced the volume of gastric juice and total acidity and significantly increased the gastric pH (p<0.05), compared with the control group, with the exception of the group treated with 50mg/kg of p-coumaric acid, in which no significant difference was observed, compared with the control. In relation to the acute toxicity, none sign of toxicity was observed when phenolic acids, used in this study, were administered for rats in dose of 2,000 mg/kg. CONCLUSIONS: In conclusion, the results of this study show that caffeic, ferulic, p-coumaric and cinnamic acids display antiulcer activity.

Baccharis dracunculifolia, the main botanical source of Brazilian green propolis, displays antiulcer activity.

Baccharis dracunculifolia is the most important botanical source of Southeastern Brazilian propolis, known as green propolis for its colour. In a previous study, we described the gastric protective effect of the hydroalcoholic extract of Brazilian green propolis. We therefore wanted to investigate the possibility of using B. dracunculifolia extract for antiulcer treatment. This study was undertaken to evaluate the anti-ulcerogenic property of hydroalcoholic extract of B. dracunculifolia aerial parts. The HPLC analysis of the chemical composition of B. dracunculifolia extract used in this study revealed the presence mainly of cinnamic acid derivates and flavonoids. Doses of 50, 250 and 500 mg/kg of B. dracunculifolia crude extract and positive controls (omeprazole or cimetidine) significantly diminished the lesion index, the total lesion area and the percentage of lesion compared with negative control groups. The percentage of ulcer inhibition was significantly higher in groups treated with B. dracunculifolia, cimetidine or omeprazole, with all protocols used, compared with negative control groups. Regarding the model of gastric secretion, reductions in the volume of gastric juice and total acidity were observed, as well as an increase in the gastric pH. These results were similar to results from studies carried out with green propolis extract. Although more investigations are required, our results suggest that B. dracunculifolia has potential to be used as a phytotherapic preparation for the treatment of gastric ulcer.

Effect of Brazilian green propolis on experimental gastric ulcers in rats.

Propolis is a resinous hive product collected by honeybees from plants. The propolis produced in Southeastern of Brazil is known as green propolis because of its color. Modern herbalists recommend its use because it displays antibacterial, antifungal, antiviral, hepatoprotective, anti-inflammatory, immunomodulatory and anti-ulcer properties. The anti-ulcer activity of green propolis hydroalcoholic crude extract was evaluated by using models of acute gastric lesions induced by ethanol, indomethacin and stress in rats. Moreover, the effects of extract on gastric content volume, pH and total acidity, using pylorus ligated model were evaluated. Animals pretreated with propolis hydroalcoholic crude extract (50, 250 and 500 mg/kg) showed a significant reduction in lesion index, total affected area and percentage of lesion in comparison with control group (p<0.05) in the ethanol-induced ulcer model. Green propolis extract, at a higher dose (500 mg/kg), displayed a significant protection by reducing (p<0.05) the evaluated parameters in the gastric ulceration induced by indomethacin. In the stress-induced ulcer model it was observed a significant reduction (p<0.05) in those parameters in animals treated with green propolis extract (250 and 500 mg/kg). Regarding the pylorus ligated model it was observed that green propolis extract (250 and 500 mg/kg) displayed an anti-secretory activity, which lead to a reduction in the gastric juice volume, total acidity and pH. These findings indicate that Brazilian green propolis displays good anti-ulcer activity, corroborating the folk use of propolis preparations, and contributing for its pharmacological validation.