Antimicrobial, antitrypanosomal and antibiofilm activity of Equisetum hyemale.

This study evaluates, for the first time, the antibiofilm, antimicrobial and antiparasitic potential of crude extract and fractions of stems of Equisetum hyemale against several infectious agents (bacteria, fungi, Mycobacterium and Trypanosomes) by broth microdilution technique and investigates the phenolic composition of the plant by high performance liquid chromatography. The crude extract and fractions showed antimicrobial activity, as they were capable of inhibiting the growth of bacteria in minimal inhibitory concentrations (MICs) ranging from 52.4 mg/mL to 3.27 mg/mL. For Candida species, the MICs ranged from 52.4 mg/mL to 6.5 mg/mL, and for Mycobacterium species from 2.5 mg/mL to 0.625 mg/mL. The dichloromethane fraction was able to reduce 83% of Pseudomonas aeruginosa biofilm formation and 51% of Candida albicans biofilms. The n-butanol fraction presents an important protozoal effect, reducing 100% of Trypanosoma evansi trypomastigotes after 9 h of exposure. The HPLC analysis revealed that the major substances are rosmarinic acid in dichloromethane fraction (7.38 ± 0.08 mg/g FS) and chlorogenic acid in ethyl acetate fraction (8.4 ± 0.26 mg/g FS). The crude extract and fractions of E. hyemale can be both useful and effective agents as a sustainable alternative for the treatment and prevention of several infectious agents.

Antimicrobial activity of Amazonian oils against Paenibacillus species.

The Gram-positive, spore-forming bacterium Paenibacillus larvae is the primary bacterial pathogen of honeybee brood and the causative agent of American foulbrood disease (AFB). One of the feasible alternative treatments being used for their control of this disease is essential oils. In this study in vitro antimicrobial activity of Andiroba and Copaíba essential oils against Paenibacillus species, including P. larvae was evaluated. Minimal inhibitory concentration (MIC) in Mueller-Hinton broth by the microdilution method was assessed. Andiroba registered MIC values of 1.56-25%, while the MICs values obtained for Copaíba oil were of 1.56-12.5%. In order to determine the time-response effect of essential oils on P. larvae, this microorganism was exposed to the oils for up to 48 h. After 24 h treatment with Andiroba oil and after 48 h treatment with Copaíba oil no viable cells of P. larvae ATCC 9545 were observed. The possible toxic effect of essential oils were assessed by the spraying application method of the same concentrations of MICs. Bee mortality was evident only in treatment with Andiroba oil and the Copaíba oil shows no toxic effects after 10 days of observation. Taking together ours results showed for the first time that these oils presented a high activity against Paenibacillus species showing that Copaíba oil may be a candidate for the treatment or prevention of AFB.

Antimicrobial activity of Amazon Astrocaryum aculeatum extracts and its association to oxidative metabolism.

Several compounds present in fruits as polyphenols are able to kill or inhibit the growth of microorganisms. These proprieties are relevant mainly in tropical areas, as Amazonian region where infectious are highly prevalent. Therefore, this study investigated the antimicrobial activity of tucumã Amazonian fruit against 37 microorganisms. The potential role of oxidative metabolism imbalance was also studied as causal mechanism of antimicrobial activity. The results showed antibacterial effect of pulp and peel tucumã hydro-alcoholic extracts on three Gram-positive bacteria (Enterococcus faecalis, Bacillus cereus, Listeria monocytogenes) and antifungal effect against Candida albicans. The antimicrobial contribution of main chemical compounds (quercetin, rutin, ß-carotene and gallic, caffeic and chlorogenic acids) found in tucumã extracts was also investigated showing an inhibitory effect depending of the organism mainly by quercetin in bacteria and rutin in C. albicans. Analysis of kinetic of DNA releasing in extracellular medium by fluorescence using DNA Pico Green assay(®) and reactive oxygen species production (ROS) showed potential oxidative imbalance contribution on tucumã inhibitory effect. In B. cereus and C. albicans this effect was clear since after 24h the ROS levels were higher when compared to negative control group. In conclusion, tucumã extracts present antimicrobial activity to four microorganisms that have large problems of drug resistance, and the possible mechanism of action of this Amazon fruit is related to REDOX imbalance.

Chlorhexidine activity against bacterial biofilms.

BACKGROUND: A biofilm is a complex microbiological ecosystem deposited on surfaces. Microorganisms in form of biofilms are of particular clinical concern because of the poor response to antimicrobial treatments. This study aimed to determine whether bacterial and fungal biofilms are able to resist the antimicrobial activity of chlorhexidine, a powerful antiseptic widely used in the hospital environment. METHODS: Disk diffusion and susceptibility tests were conducted in accordance with Clinical and Laboratory Standards Institute standards for the determination of biofilm inhibitory concentration. Chlorhexidine was tested first at a minimum inhibitory concentration and then at higher concentrations when it was not able to destroy the biofilm. The plates were developed with a solution of 0.1% crystal violet, and readings were made at an optical density of 570 nm. RESULTS: Chlorhexidine demonstrated excellent antimicrobial activity for most microorganisms tested in their free form, but was less effective against biofilms of Acinetobacter baumannii, Escherichia coli, methicillin-resistant Staphylococcus aureus, and Pseudomonas aeruginosa. CONCLUSION: This study confirms that microorganisms in biofilms have greater resistance to chlorhexidine, likely owing to the mechanisms of resistance conferred to the structure of biofilms.