Polymers as advanced antibacterial and antibiofilm agents for direct and combination therapies

The growing prevalence of antimicrobial drug resistance in pathogenic bacteria is a critical threat to global health. Conventional antibiotics still play a crucial role in treating bacterial infections, but the...

Screening of Bioactive Metabolites Actinomycetes to Evaluate Potential Sources of Sustainable Marine Natural Products

This study aimed to screen the activity of methanol extract of sponge-derived actinomycetes as an anti-biofilm and antibacterial agent to Staphylococcus aureus. Nine actinomycetes isolates were selected from the UPT LTSIT deposit. S. aureus was obtained from the skin of patients at Abdul Moeloek General Hospital. An antibiotic susceptibility test was performed by the disk diffusion method. Biofilm formation of S. aureus was tested using the crystal violet method. The viability of pathogenic bacteria was measured using the indicator resazurin. The results of the biofilm formation test in vitro revealed that the organic extracts 33A1T2, 33A2T3, 21A1T11, and 38A1T12 inhibited bacterial growth at 0.5 mg/mL. Meanwhile, 50A2T9, 21A1T11, and 38A1T12 significantly inhibited the formation of staphylococcal biofilm on polystyrene at a concentration of 0.25 mg/mL. This information is very important as a basis for further understanding of the mechanism of action of antibiofilm agents.

Can yellow gentian (Gentiana lutea) be useful in protection against foodborne mutagens and food contaminants?

Gentiana lutea is a wellknown and respected medicinal plant that is used in many pharmacopoeias, mainly against different gastrointestinal disorders. The plant is under protection regimes in its natural habitats and for that reason is grown on plantations. In addition, it could be cultivated in vitro. The plants grown on plantation and in in vitro conditions were used to prepare methanolic and 50% ethanolic extracts of root and leaf/shoot, which were tested for antigenotoxic and antibacterial properties, against foodborne mutagens (heterocyclic aromatic amines PhIP and IQ) and food contaminants, respectively. The results obtained pointed out the excellent genoprotective effect (up to 78% inhibition of PhIP/IQ genotoxicity) based mostly on the antioxidative potential. The antibacterial effect was mainly weak; only the extracts of in vitro grown plant induced moderate activity against Listeria monocytogenes and Staphylococcus aureus (MICs ranged 0.15-5 mg/ml). In addition, the extracts’ potential to prevent biofilm formation by L. monocytogenes was very high (up to 90% inhibition). Taken together, the results obtained encourage further research that would be directed to the formulation of potent antigenotoxic and antibiofilm agents based on G. lutea.

Antibacterial Effect of Sodium Hypochlorite and EDTA in Combination with High-Purity Nisin on an Endodontic-like Biofilm Model

Antimicrobial peptides have been proposed as antibiofilm agents. Therefore, we evaluated the effect of endodontic irrigants combined or not with the antimicrobial peptide nisin against an endodontic biofilm model composed of eleven bacterial species. Biofilms were grown on hydroxyapatite discs for 3, 15 and 21 days and treated with 1.5% sodium hypochlorite (NaOCl) or 17% EDTA followed by high-purity nisin (nisin ZP) or saline for 5 min each. Differences between groups were tested by two-way ANOVA and Tukey’s multiple comparisons test (p < 0.05). Treatment with 1.5% NaOCl completely eliminated 3-d and 15-d biofilms but did not eradicate 21-d biofilms. Treatment with 1.5% NaOCl and 17% EDTA was equally effective against 21-d biofilms, showing 5-log and 4-log cell reduction, respectively, compared to the untreated control (9 log10, p < 0.05). No significant difference was found between 1.5% NaOCl + nisin ZP and 1.5% NaOCl in 21-d biofilms (p > 0.05). Likewise, no significant difference was found between 17% EDTA + nisin ZP and 17% EDTA treatments (p > 0.05). In conclusion, 1.5% NaOCl or 17% EDTA were effective strategies to combat mature biofilms. The additional use of nisin did not improve the activity of conventional irrigants against multispecies biofilms.

Anthraquinones as Potential Antibiofilm Agents Against Methicillin-Resistant Staphylococcus aureus

Biofilms formed by methicillin-resistant Staphylococcus aureus (MRSA) are one of the contributing factors to recurrent nosocomial infection in humans. There is currently no specific treatment targeting on biofilms in clinical trials approved by FDA, and antibiotics remain the primary therapeutic strategy. In this study, two anthraquinone compounds isolated from a rare actinobacterial strain Kitasatospora albolonga R62, 3,8-dihydroxy-l-methylanthraquinon-2-carboxylic acid (1) and 3,6,8-trihydroxy-1-methylanthraquinone-2-carboxylic acid (2), together with their 10 commercial analogs 3–12 were evaluated for antibacterial and antibiofilm activities against MRSA, which led to the discovery of two potential antibiofilm anthraquinone compounds anthraquinone-2-carboxlic acid (6) and rhein (12). The structure-activity relationship analysis of these anthraquinones indicated that the hydroxyl group at the C-2 position of the anthraquinone skeleton played an important role in inhibiting biofilm formation at high concentrations, while the carboxyl group at the same C-2 position had a great influence on the antibacterial activity and biofilm eradication activity. The results of crystal violet and methyl thiazolyl tetrazolium staining assays, as well as scanning electron microscope and confocal scanning laser microscopy imaging of compounds 6 and 12 treatment groups showed that both compounds could disrupt preformed MRSA biofilms possibly by killing or dispersing biofilm cells. RNA-Seq was subsequently used for the preliminary elucidation of the mechanism of biofilm eradication, and the results showed upregulation of phosphate transport-related genes in the overlapping differentially expressed genes of both compound treatment groups. Herein, we propose that anthraquinone compounds 6 and 12 could be considered promising candidates for the development of antibiofilm agents.