Antibiotic Combined with Epitope-Specific Monoclonal Antibody Cocktail Protects Mice Against Bacteremia and Acute Pneumonia from Methicillin-Resistant Staphylococcus aureus Infection

The Combination of 3-Hydrazinoquinoxaline-2-Thiol with Thymoquinone Demonstrates Synergistic Activity Against Different Candida Strains

Introduction

Candida is the primary cause of invasive fungal disease, candidiasis, especially in developed nations. The increasing resistance observed in multiple antibiotics, coupled with the prolonged process of creating new antibiotics from the ground up, emphasizes the urgent requirement for innovative methods and new compounds to combat Candida infections. Employing a treatment strategy that combines antibiotics can improve efficacy, broaden the spectrum of targeted fungal, and reduce the chances of resistance emergence. This approach shows potential in tackling the escalating problem of antibiotic resistance. The objective of this research is to explore the potential synergistic effects of combining 3-hydrazinoquinoxaline-2-thiol and thymoquinone against a variety of Candida isolates. This investigation aims to offer an understanding of the collective antimicrobial action of these compounds.

Methods

Broth microdilution was utilized to assess the Minimum Inhibitory Concentrations (MICs) of 3-hydrazinoquinoxaline-2-thiol and thymoquinone for 22 clinical Candida isolates. Following this, a checkerboard assay was employed to analyze the interaction between 3-hydrazinoquinoxaline-2-thiol and thymoquinone, with a specific focus on the Fractional Inhibitory Concentration Index (FICI).

Results

The MICs of thymoquinone and 3-hydrazinoquinoxaline-2-thiol were determined for 22 clinical Candida strains, with thymoquinone exhibiting MICs ranging from 64 to 8 µg/mL, and 3-hydrazinoquinoxaline-2-thiol displaying MICs varying from 64 to 8 µg/mL. Notably, the combination of 3-hydrazinoquinoxaline-2-thiol and thymoquinone resulted in a synergistic effect, leading to a significant reduction in MICs, with reductions of up to 64-fold with FICI below 0.5 against tested strains.

Conclusion

The prospect of using 3-hydrazinoquinoxaline-2-thiol in combination with thymoquinone as an effective solution against Candida looks encouraging. Nevertheless, to validate its practical applicability, additional comprehensive testing and experiments are imperative.

Synergistic Activity of 3-Hydrazinoquinoxaline-2-Thiol in Combination with Penicillin Against MRSA

Background

The growing resistance seen in various antibiotics, including those considered as last-resort options, underscores the pressing need for novel approaches and new substances to address MRSA infections. Combining antibiotics as a treatment approach can enhance effectiveness, expand the range of targeted bacteria, and minimize the likelihood of resistance emergence. This approach holds promise in addressing the escalating issue of antibiotic resistance.

Purpose

This study seeks to investigate the potential synergy between 3-hydrazinoquinoxaline-2-thiol and penicillin against a diverse array of MRSA isolates, thereby providing insights into their combined antimicrobial action.

Methods

Twenty-two clinical MRSA isolates subjected to broth microdilution to determine the Minimum Inhibitory Concentrations (MICs) of 3-hydrazinoquinoxaline-2-thiol and penicillin. Subsequently, a checkerboard assay was employed to evaluate the interaction between 3-hydrazinoquinoxaline-2-thiol and penicillin, focusing on the Fractional Inhibitory Concentration Index (FICI).

Results

The MICs of penicillin and 3-hydrazinoquinoxaline-2-thiol were determined for 22 clinical MRSA strains. Penicillin exhibited MICs within a range of 1024 to 128 µg/mL, while 3-hydrazinoquinoxaline-2-thiol displayed MICs varying from 64 to 8 µg/mL. Remarkably, the combination of 3-hydrazinoquinoxaline-2-thiol and penicillin yielded a synergistic effect, resulting in a significant reduction of MICs by up to 64-fold.

Conclusion

The potential of 3-hydrazinoquinoxaline-2-thiol in combination with penicillin as a viable solution against MRSA appears promising. However, to establish its practical utility, further extensive testing and experiments are essential.

Inflammasome-mediated glucose limitation induces antibiotic tolerance in Staphylococcus aureus

Staphylococcus aureus is a leading human pathogen that frequently causes relapsing infections. The failure of antibiotics to eradicate infection contributes to infection relapse. Host-pathogen interactions have a substantial impact on antibiotic susceptibility and the formation of antibiotic tolerant cells. In this study, we interrogate how a major S. aureus virulence factor, α-toxin, interacts with macrophages to alter the microenvironment of the pathogen, thereby influencing its susceptibility to antibiotics. We find α-toxin-mediated activation of the NLRP3 inflammasome induces antibiotic tolerance. Induction of tolerance is driven by increased glycolysis in the host cells, resulting in glucose limitation and ATP depletion in S. aureus. Additionally, inhibition of NLRP3 activation improves antibiotic efficacy in vitro and in vivo, suggesting that this strategy has potential as a host-directed therapeutic to improve outcomes. Our findings identify interactions between S. aureus and the host that result in metabolic crosstalk that can determine the outcome of antimicrobial therapy.

Antibiotic Treatment of Staphylococcus aureus Infection Inhibits the Development of Protective Immunity

Recurrent Staphylococcus aureus infections are common, suggesting a failure to elicit protective immunity. Given the emergence of antibiotic resistance, a vaccine is urgently needed, but there is no approved vaccine for S. aureus. While antibiotics are routinely used to treat S. aureus infections, their impact on the development of protective immunity is not understood. Using an established mouse model of S. aureus skin and soft tissue infection (SSTI), we observed that antibiotic therapy effectively resolved infection but failed to elicit protection against secondary (2°) SSTI. Key contributors to protective immunity, toxin-specific antibodies and interleukin-17A (IL-17A)-producing T cells, were not strongly elicited in antibiotic-treated mice. Delaying antibiotic treatment failed to resolve skin lesions but resulted in higher antibody levels after infection and strong protection against 2° SSTI, suggesting that the development of protective immunity requires a longer period of antigen exposure. We next investigated if combining α-hemolysin (Hla) vaccination with antibiotics during primary infection would both treat infection and generate durable protective immunity. This "therapeutic vaccination" approach resulted in rapid resolution of primary infection and protection against recurrent infection, demonstrating that concurrent vaccination could circumvent the deleterious effects of antibiotic therapy on elicited immune responses. Collectively, these findings suggest that protective immunity is thwarted by the rapid elimination of antigen during antibiotic treatment. However, vaccination in conjunction with antibiotic treatment can retain the benefits of antibiotic treatment while also establishing protective immunity.