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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Antimicrobial activity of hydralazine against methicillin-resistant and methicillin-susceptible Staphylococcus aureus.

Background: Staphylococcus aureus is a human pathogen responsible for high mortality rates. The development of new antimicrobials is urgent. Materials & methods: The authors evaluated the activity of hydralazine along with its synergism with other drugs and action on biofilms. With regard to action mechanisms, the authors evaluated cell viability, DNA damage and molecular docking. Results: MIC and minimum bactericidal concentration values ranged from 128 to 2048 µg/ml. There was synergism with oxacillin (50%) and vancomycin (25%). Hydralazine reduced the viability of biofilms by 50%. After exposure to hydralazine 2× MIC, 58.78% of the cells were unviable, 62.07% were TUNEL positive and 27.03% presented damage in the comet assay (p < 0.05). Hydralazine showed affinity for DNA gyrase and TyrRS. Conclusion: Hydralazine is a potential antibacterial.

Staphylococcus aureus is a bacterium that can cause infection. Infections of S. aureus are becoming difficult to treat, but developing new drugs is a challenge. Repurposing them may be easier. This study looks at the possibility of using hydralazine, a type of medicine used to treat high blood pressure, against S. aureus. The authors found that hydralazine can kill S. aureus and can be used with other antibiotics, including oxacillin and vancomycin. Hydralazine interferes with important processes for the multiplication and survival of this bacterium. These results are preliminary but encouraging. Further studies are needed to confirm the use of hydralazine as a new treatment for S. aureus infections.

Antifungal activity of selective serotonin reuptake inhibitors against Cryptococcus spp. and their possible mechanism of action.

Fungal infections caused by Cryptococcus spp. pose a threat to health, especially in immunocompromised individuals. The available arsenal of drugs against cryptococcosis is limited, due to their toxicity and/or lack of accessibility in low-income countries, requiring more therapeutic alternatives. Selective serotonin reuptake inhibitors (SSRIs), through drug repositioning, are a promising alternative to broaden the range of new antifungals against Cryptococcus spp. This study evaluates the antifungal activity of three SSRIs, sertraline, paroxetine, and fluoxetine, against Cryptococcus spp. strains, as well as assesses their possible mechanism of action. Seven strains of Cryptococcus spp. were used. Sensitivity to SSRIs, fluconazole, and itraconazole was evaluated using the broth microdilution assay. The interactions resulting from combinations of SSRIs and azoles were investigated using the checkerboard assay. The possible action mechanism of SSRIs against Cryptococcus spp. was evaluated through flow cytometry assays. The SSRIs exhibited in vitro antifungal activity against Cryptococcus spp. strains, with minimum inhibitory concentrations ranging from 2 to 32 µg/mL, and had synergistic and additive interactions with azoles. The mechanism of action of SSRIs against Cryptococcus spp. involved damage to the mitochondrial membrane and increasing the production of reactive oxygen species, resulting in loss of cellular viability and apoptotic cell death. Fluoxetine also was able to cause significant damage to yeast DNA. These findings demonstrate the in vitro antifungal potential of SSRIs against Cryptococcus spp. strains.

Chia (Salvia hispanica L.) Seeds Contain a Highly Stable Trypsin Inhibitor with Potential for Bacterial Management Alone or in Drug Combination Therapy with Oxacillin.

The emergence of antibiotic resistance poses a serious and challenging threat to healthcare systems, making it imperative to discover novel therapeutic options. This work reports the isolation and characterization of a thermostable trypsin inhibitor from chia (Salvia hispanica L.) seeds, with antibacterial activity against Staphylococcus aureus sensitive and resistant to methicillin. The trypsin inhibitor ShTI was purified from chia seeds through crude extract heat treatment, followed by affinity and reversed-phase chromatography. Tricine-SDS-PAGE revealed a single glycoprotein band of ~ 11 kDa under nonreducing conditions, confirmed by mass spectrometry analysis (11.558 kDa). ShTI was remarkably stable under high temperatures (100 °C; 120 min) and a broad pH range (2-10; 30 min). Upon exposure to DTT (0.1 M; 120 min), ShTI antitrypsin activity was partially lost (~ 38%), indicating the participation of disulfide bridges in its structure. ShTI is a competitive inhibitor (Ki = 1.79 × 10-8 M; IC50 = 1.74 × 10-8 M) that forms a 1:1 stoichiometry ratio for the ShTI:trypsin complex. ShTI displayed antibacterial activity alone (MICs range from 15.83 to 19.03 µM) and in combination with oxacillin (FICI range from 0.20 to 0.33) against strains of S. aureus, including methicillin-resistant strains. Overproduction of reactive oxygen species and plasma membrane pore formation are involved in the antibacterial action mode of ShTI. Overall, ShTI represents a novel candidate for use as a therapeutic agent for the bacterial management of S. aureus infections.

Etomidate is devoid of genotoxicty and mutagenicity in human lymphocytes and in the Salmonella typhimurium/microsomal activation test.

No carcinogenesis or mutagenesis studies have been carried out with etomidate. The current study showed that etomidate has weak cytotoxic potential after 48 h exposure in human lymphocytes and has no hemolytic activity. The weak cytotoxicity seems to be related with redox imbalance of etomidate (40.9 and 81.9 µM) treated lymphocytes. At both etomidate concentrations, a slight decrease of the levels of GSH intracellular content and a significant increase in the amount of carbonylated proteins were observed after 48 h. The contribution of oxidative stress to genetic toxicity was only perceived when the enzyme Fpg was applied in the comet assay. Etomidate (40.9 and 81.9 µM) is a weak generator of oxidative DNA damage in lymphocytes. These damages to DNA probably were repaired, since no DNA strand breaks were detected in the standard alkaline comet assay (in the presence or absence of hepatic S9 microsomal fraction) without Fpg. Also, no micronucleated lymphocytes or carrying chromosomal aberrations were observed. Finally, etomidate (2046.8 and 4093.5 µM) was not mutagenic in the Salmonella/microsome mutagenicity assay, which used four Salmonella typhimurium strains (TA97a, TA98, TA100, and TA102) to detect frameshift and base-substitution mutations. In summary, etomidate is a weak oxidative DNA damaging anesthetic and is devoid of mutagenic properties in eukaryotic and prokaryotic models.

Synergistic effects of ketamine and azole derivatives on Candida spp. resistance to fluconazole.

The emergence of Candida spp. with resistance to antifungal molecules, mainly the azole class, is an increasing complication in hospitals around the globe. Aim: In the present research, we evaluated the synergistic effects of ketamine with two azole derivatives, itraconazole and fluconazole, on strains of Candida spp. to fluconazole. Materials & methods: The drug synergy was evaluated by quantifying the fractional inhibitory concentration index and by fluorescence microscopy and flow cytometry techniques. Results: Our achievements showed a synergistic effect between ketamine in addition to the two antifungal agents (fluconazole and itraconazole) against planktonic cells and biofilms of Candida spp. Conclusion: This combination promoted alteration of membrane integrity, generation of reactive oxygen species, damage to and DNA and externalization of phosphatidylserine.

Evaluation of Genotoxicity and Mutagenicity of Ketamine on Human Peripheral Blood Leukocytes and in Salmonella typhimurium.

Ketamine is a potent uncompetitive NMDA receptor antagonist that provides amnesia, analgesia, environmental dissociation and immobility, where it has its cytotoxic effect well described in the literature. However, the work on its genotoxic/mutagenic potentials are scarce and insufficient and does not allow a reasonable evaluation of its role. Thus, in the present work, we decided to evaluate the genotoxic and mutagenic effects of ketamine on human peripheral blood leukocytes (PBLs) and Salmonella typhimurium (TA98, TA97a, TA100, and TA102) through several well-established experimental protocols based on different parameters in the presence or not of exogenous metabolizing S9 fraction. Our data revealed that ketamine induces a weak cytotoxic effect on human PBLs after 24 h and is devoided of hemolytic effects. A small amount of DNA strand breaks levels were detected in the modified comet assay (employment of FPG enzyme) only at highest concentrations (500 and 700 µg/mL) of ketamine, highlighting our pro-oxidant data regarding ketamine. However, the oxidative DNA lesions were almost completely repaired which reflects in the lack of mutagenesis (micronuclei and chromosomal aberrations) on human PBLs and no increases in revertants numbers on S. typhimurium/microsome test (500 to 5000 µg/plate). In summary, ketamine is a weak oxidative DNA damaging agent and is devoid of mutagenic properties on eukaryotic and prokaryotic models.