Molecular docking, quorum quenching effect, antibiofilm activity and safety profile of silver-complexed sulfonamide on Pseudomonas aeruginosa.

Microbial infections caused by sessile microorganisms are known to be a more challenging issue than infections caused by the same microorganisms in the planktonic state. Pseudomonas aeruginosa is an opportunistic pathogen and biofilm-forming agent. This species presents intense cellular communication mediated by signaling molecules. This process is known as quorum sensing (QS) and induces the transcription of specific genes that favors cell density growth and three-dimensional bacterial grouping. In this context, the discovery of compounds capable of inhibiting the action of the QS signaling molecules seems to be a promising strategy against biofilms. This work aimed to evaluate the anti-biofilm action and the in vitro safety profile of a sulfamethoxazole-Ag complex. The results obtained indicate potential anti-biofilm activity through QS inhibition. In silico tests showed that the compound acts on the las and pqs systems, which are the main regulators of biofilm formation in P. aeruginosa. Additionally, the molecule proved to be safe for human peripheral blood mononuclear cells.

Oxygen tension during biofilm growth influences the efficacy antimicrobial agents / Eficácia dos antimicrobianos em biofilme formado por diferentes tensões de oxigênio

Objective: To compare the antimicrobial efficacy of a 0.12% chlorhexidine (CHX) and herbal green tea (Camellia sinensis) solution on established biofilms formed at different oxygen tensions in an in situ model. Method: Twenty-five dental students were eligible for the study. In situ devices with standardized enamel specimens (ES) facing the palatal and buccal sides were inserted in the mouths of volunteers for a 7 day period. No agent was applied during the first four days. From the fifth day onward, both agents were applied to the test ES group and no agent was applied to the control ES group. After 7 days the ES fragments were removed from the devices, sonicated, plated on agar, and incubated for 24 h at 37 °C to determine and quantify the colony forming units (CFUs). Result: CHX had significantly higher efficacy compared to green tea on the buccal (1330 vs. 2170 CFU/µL) and palatal (2250 vs. 2520 CFU/µL) ES. In addition, intragroup comparisons showed significantly higher efficacy in buccal ES over palatal ES (1330 vs. 2250 CFU/µL for CHX and 2170 vs, 2520 CFU/µL for CV) for both solutions. Analysis of the ES controls showed significantly higher biofilm formation in palatal ES compared to buccal ES. Conclusion: CHX has higher efficacy than green tea on 4-day biofilms. The efficacy of both agents was reduced for biofilms grown in a low oxygen tension environment. Therefore, the oxygen tension environment seems to influence the efficacy of the tested agents.

Objetivo: Comparar a eficácia antimicrobiana de clorexidina 0,12% (CHX) e solução de chá verde (CV) (Camellia sinensis) em biofilmes formados em diferentes tensões de oxigênio em um modelo in situ. Método: Vinte e cinco estudantes de odontologia foram elegíveis. Um dispositivo com espécimes de esmalte (EE) padronizados, voltado para o palato e para vestibular foram inseridos nos voluntários por 7 dias. Durante os primeiros quatro dias nenhum agente foi aplicado. A partir do quinto dia, ambos os agentes foram aplicados nos EEs no grupo teste e nenhum agente foi aplicado no grupo EE controle. Após 7 dias, os fragmentos EEs foram removidos dos dispositivos, sonicados, plaqueados em ágar, e incubado durante 24 h a 37 °C para determinar unidades formadoras de colonias (UFCs). Resultado: CHX teve significativamente melhor eficácia em comparação com CV nos EEs para vestibular (1.330 vs. 2.170 UFC/mL) e EEs voltados para o palatal (2.250 vs. 2.520 UFC/mL). Comparações intragrupos mostraram maior eficácia em EEs vestibulares do que as EEs voltadas para o palato (1.330 vs. 2.250 UFC/mL para CHX e 2170 vs, 2520 UFC/mL para CV) em ambas as soluções. Análise dos controles, mostrou a formação de biofilme significativamente maior em comparação com EEs palatinas e bucais. Conclusão: CHX tem uma eficácia maior do que o chá verde em biofilmes formados por 4 dias. A eficácia dos agentes foi reduzida para os biofilmes em ambiente com baixa tensão de oxigênio. A tensão de oxigênio parece influenciar na eficácia dos agentes testados.

Antimicrobial activity of Scutia buxifolia against the honeybee pathogen Paenibacillus larvae.

The honeybee disease American foulbrood (AFB) is a serious problem since its causative agent (Paenibacillus larvae) has become increasingly resistant to conventional antibiotics. One of the feasible alternative treatments being used for control of this disease are plants extracts. The aim of the present work was to evaluate the effect of crude extract and fractions of Scutia buxifolia against six Paenibacillus species, including P. larvae, and its potential use for the control of AFB. In vitro activity of S. buxifolia samples against Paenibacillus species were evaluated by the disk diffusion and microdilution methods, and the minimal inhibitory concentration (MIC) were also determined. All Paenibacillus species were sensitive to crude extract and fractions of S. buxifolia. The dichloromethane (DC) fraction showed the better MIC (1.56 mg/mL), followed by ethyl acetate (EtAc) (6.25 mg/mL), n-butanol (BuOH) (25 mg/mL) and Crude extract (CE) (50 mg/mL). Toxic effect of S. buxifolia crude extracts and fractions against bees were also evaluated by the spraying application method of the same concentrations of MICs. The samples tested showed no toxic effects for the bees after 15 days of observation. These results are first time described for this species and showed that S. buxifolia presented a important activity against Paenibacillus species and proved to be a natural alternative for the prevention/control of AFB.