Circulating sex-steroids and Staphylococcus aureus nasal carriage in a general male population

Antimicrobial Susceptibility of Various MRSA Clinical Isolates and the Impact of Glycopeptide MICs on Clinical and Microbiological Outcomes

Objective

While vancomycin has remained the mainstay of the treatment for methicillin-resistant Staphylococcus aureus (MRSA) infections, there is growing evidence of the clinical impact of increased glycopeptide minimum inhibitory concentrations (MICs) in MRSA isolates. This study aimed to determine the susceptibility of various MRSA isolates to different antibiotics with antistaphylococcal activity and the impact of glycopeptide MICs on clinical and microbiological outcomes.

Materials and Methods

This retrospective cohort study, conducted between 2013 and 2017, evaluated the susceptibility of MRSA strains isolated from various clinical samples to antistaphylococcal antibiotics using the gradient strip method. The clinical and laboratory features of patients infected with MRSA isolates with elevated glycopeptide MICs (>1 mg/L) and with isolates that had low glycopeptide MICs (≤1 mg/L) were compared.

Results

A total of 104 patients infected with MRSA strains were included in this study. Male sex (odds ratio [OR]=2.48, 95% confidence interval [CI]=1.01-6.10, p=0.048), two or more comorbidities (OR=2.48, 95% CI=1.03-6.50, p=0.044), history of MRSA infection (OR=4.91, 95% CI=1.70-14.28, p=0.003) and a longer hospital stay prior to MRSA infection (OR=2.32, 95% CI=1.05-7.85, p=0.040) were independent risk factors for high glycopeptide MICs. In MRSA infections with a teicoplanin MIC of >0.75mg/L, the microbiological and treatment failures were 46.2% (p=0.044) and 60.6% (p=0.042), respectively.

Conclusion

This study showed that the critical MIC value, which suggested treatment failure as well as microbiological failure in the teicoplanin-treated MRSA infections, was >0.75 mg/L rather than >1 mg/L in our study cohort. The identification of high-risk patients;for treatment failures and mortality considering gradient strip method MIC values is crucial for the effective management of MRSA infections.

Adverse drug events associated with linezolid administration: a real-world pharmacovigilance study from 2004 to 2023 using the FAERS database

Introduction: Linezolid is an oxazolidinone antibiotic that is active against drug-resistant Gram-positive bacteria and multidrug-resistant Mycobacterium tuberculosis. Real-world studies on the safety of linezolid in large populations are lacking. This study aimed to determine the adverse events associated with linezolid in real-world settings by analyzing data from the US Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS). Methods: We retrospectively extracted reports on adverse drug events (ADEs) from the FAERS database from the first quarter of 2004 to that of 2023. By using disproportionality analysis including reporting odds ratio (ROR), proportional reporting ratio (PRR), Bayesian Confidence Propagation Neural Network (BCPNN), along with the multi-item gamma Poisson shrinker (MGPS), we evaluated whether there was a significant association between linezolid and ADE. The time to onset of ADE was further analyzed in the general population and within each age, weight, reporting population, and weight subgroups. Results: A total of 11,176 reports of linezolid as the "primary suspected" drug and 263 significant adverse events of linezolid were identified, including some common adverse events such as thrombocytopenia (n = 1,139, ROR 21.98), anaemia (n = 704, ROR 7.39), and unexpected signals that were not listed on the drug label such as rhabdomyolysis (n = 90, ROR 4.33), and electrocardiogram QT prolonged (n = 73, ROR 4.07). Linezolid-induced adverse reactions involved 27 System Organ Class (SOC). Gender differences existed in ADE signals related to linezolid. The median onset time of all ADEs was 6 days, and most ADEs (n = 3,778) occurred within the first month of linezolid use but some may continue to occur even after a year of treatment (n = 46). Conclusion: This study reports the time to onset of adverse effects in detail at the levels of SOC and specific preferred term (PT). The results of our study provide valuable insights for optimizing the use of linezolid and reducing potential side effects, expected to facilitate the safe use of linezolid in clinical settings.

Androgens at the skin surface regulate S. aureus pathogenesis through the activation of agr quorum sensing

Staphylococcus aureus, the most frequent cause of skin infections, is more common in men than women and selectively colonizes the skin during inflammation. Yet, the specific cues that drive infection in these settings remain unclear. Here we show that the host androgens testosterone and dihydrotestosterone promote S. aureus pathogenesis and skin infection. Without the secretion of these hormones, skin infection in vivo is limited. Testosterone activates S. aureus virulence in a concentration dependent manner through stimulation of the agr quorum sensing system, with the capacity to circumvent other inhibitory signals in the environment. Taken together, our work defines a previously uncharacterized inter-kingdom signal between the skin and the opportunistic pathogen S. aureus and identifies the mechanism of sex-dependent differences in S. aureus skin infection.

One-Sentence Summary

Testosterone promotes S. aureus pathogenesis through activation of the agr quorum sensing system.

Staphylococcus aureus adaptive evolution: Recent insights on how immune evasion, immunometabolic subversion and host genetics impact vaccine development

Despite meritorious attempts, a S. aureus vaccine that prevents infection or mitigates severity has not yet achieved efficacy endpoints in prospective, randomized clinical trials. This experience underscores the complexity of host-S. aureus interactions, which appear to be greater than many other bacterial pathogens against which successful vaccines have been developed. It is increasingly evident that S. aureus employs strategic countermeasures to evade or exploit human immune responses. From entering host cells to persist in stealthy intracellular reservoirs, to sensing the environmental milieu and leveraging bacterial or host metabolic products to reprogram host immune responses, S. aureus poses considerable challenges for the development of effective vaccines. The fact that this pathogen causes distinct types of infections and can undergo transient genetic, transcriptional or metabolic adaptations in vivo that do not occur in vitro compounds challenges in vaccine development. Notably, the metabolic versatility of both bacterial and host immune cells as they compete for available substrates within specific tissues inevitably impacts the variable repertoire of gene products that may or may not be vaccine antigens. In this respect, S. aureus has chameleon phenotypes that have alluded vaccine strategies thus far. Nonetheless, a number of recent studies have also revealed important new insights into pathogenesis vulnerabilities of S. aureus. A more detailed understanding of host protective immune defenses versus S. aureus adaptive immune evasion mechanisms may offer breakthroughs in the development of effective vaccines, but at present this goal remains a very high bar. Coupled with the recent advances in human genetics and epigenetics, newer vaccine technologies may enable such a goal. If so, future vaccines that protect against or mitigate the severity of S. aureus infections are likely to emerge at the intersection of precision and personalized medicine. For now, the development of S. aureus vaccines or alternative therapies that reduce mortality and morbidity must continue to be pursued.