A mechanistic approach to the in-vitro resistance modulating effects of fluoxetine against meticillin resistant Staphylococcus aureus strains.

Emergence of methicilin resistant Staphylococcus aureus (MRSA) strains is a major cause of infirmity worldwide and has limited our therapeutic options against these pathogens. In this regard, the search for candidates with an antimicrobial activity, with a greater efficacy and a lower toxicity, is necessary. As a result, there is greater need to search for resistance modifying agents which, in combination with existing drugs, will restore the efficacy of these drugs. The antibacterial effect of fluoxetine was determined by a broth microdilution method (the M07-A9 method of the Clinical and Laboratory Standard Institute) and flow cytometry techniques in which the probable mechanism of action of the compound was also assessed. The isolates used in the study belonged to the Laboratory of Bioprospecting of Antimicrobial Molecules (LABIMAN) of the Federal University of Ceará. After 24 h, Methicillin-resistant Sthaphylococcus aureus (MRSA) strains showed fluoxetine MICs equal to 64 µg/mL and 128 µg/mL, respectively. Cytometric analysis showed that treatment with fluoxetine caused alterations to the integrity of the plasma membranes and DNA damage, which led to cell death, probably by apoptosis.

Biosurfactant complexed with arginine has antibiofilm activity against methicillin-resistant Staphylococcus aureus.

Aim: The present study investigated the antimicrobial effectiveness of a rhamnolipid complexed with arginine (RLMIX_Arg) against planktonic cells and biofilms of methicillin-resistant Staphylococcus aureus (MRSA). Methodology: Susceptibility testing was performed using the Clinical & Laboratory Standards Institute protocol: M07-A10, checkerboard test, biofilm in plates and catheters and flow cytometry were used. Result: RLMIX_Arg has bactericidal and synergistic activity with oxacillin. RLMIX_Arg inhibits the formation of MRSA biofilms on plates at sub-inhibitory concentrations and has antibiofilm action against MRSA in peripheral venous catheters. Catheters impregnated with RLMIX_Arg reduce the formation of MRSA biofilms. Conclusion: RLMIX_Arg exhibits potential for application in preventing infections related to methicillin-resistant S. aureus biofilms.

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Diazepam's antifungal activity in fluconazole-resistant Candida spp. and biofilm inhibition in C. albicans: evaluation of the relationship with the proteins ALS3 and SAP5.

The genus Candida spp. has been highlighted as one of the main etiological agents causing fungal infections, with Candida albicans being the most prominent, responsible for most cases of candidemia. Due to its capacity for invasion and tissue adhesion, it is associated with the formation of biofilms, mainly in the environment and hospital devices, decreasing the effectiveness of available treatments. The repositioning of drugs, which is characterized by the use of drugs already on the market for other purposes, together with molecular-docking methods can be used aiming at the faster development of new antifungals to combat micro-organisms. This study aimed to evaluate the antifungal effect of diazepam on mature C. albicans biofilms in vitro and its action on biofilm in formation, as well as its mechanism of action and interaction with structures related to the adhesion of C. albicans, ALS3 and SAP5. To determine the MIC, the broth microdilution test was used according to protocol M27-A3 (CLSI, 2008). In vitro biofilm formation tests were performed using 96-well plates, followed by molecular-docking protocols to analyse the binding agent interaction with ALS3 and SAP5 targets. The results indicate that diazepam has antimicrobial activity against planktonic cells of Candida spp. and C. albicans biofilms, interacting with important virulence factors related to biofilm formation (ALS3 and SAP5). In addition, treatment with diazepam triggered a series of events in C. albicans cells, such as loss of membrane integrity, mitochondrial depolarization and increased production of EROs, causing DNA damage and consequent cell apoptosis.