Bacteremia due to Methicillin-Resistant Staphylococcus aureus: An Update on New Therapeutic Approaches

Evaluation of the efficacy of silymarin and dexmedetomidine on kidney and lung tissue in the treatment of sepsis in rats with cecal perforation

Sepsis is a systemic inflammatory response syndrome that develops in the host against microorganisms. This response develops away from the primary infection site and results in end-organ damage. The present study aimed to investigate the protective and therapeutic effects on lung and kidney tissue of silymarin (S) and dexmedetomidine (DEX) applied 1 h before and after sepsis induced by the cecal ligation and puncture (CLP) method in rats. A total of 62 rats was randomly divided into eight groups: i) Control (n=6); ii) cecal perforation (CLP; n=8); iii) S + CLP (n=8; S + CLP; S administered 1 h before CPL); iv) CLP + S (n=8; S administered 1 h after CLP); v) DEX + CLP (n=8; D + CLP; DEX administered 1 h before CLP); vi) CLP + D (n=8; DEX administered 1 h after CLP); vii) SD + CLP (n=8; S and DEX administered 1 h before CLP) and viii) CLP + SD (n=8; S and DEX administered 1 h after CLP). After the cecum filled with stool, it was tied with 3/0 silk under the ileocecal valve and the anterior surface of the cecum was punctured twice with an 18-gauge needle. A total of 100 mg/kg silymarin and 100 µg/kg DEX were administered intraperitoneally to the treatment groups. Lung and kidney tissue samples were collected to evaluate biochemical and histopathological parameters. In the histopathological examination, all parameters indicating kidney injury; interstitial edema, peritubular capillary dilatation, vacuolization, ablation of tubular epithelium from the basement membrane, loss of brush border in the proximal tubule epithelium, cell swelling and nuclear defragmentation; were increased in the CLP compared with the control group. Silymarin administration increased kidney damage, including ablation of tubular epithelium from the basement membrane, compared with that in the CLP group. DEX significantly reduced kidney damage compared with the CLP and silymarin groups. The co-administration of DEX + silymarin decreased kidney damage, although it was not as effective as DEX-alone. To conclude, intraperitoneal DEX ameliorated injury in CLP rats. DEX + silymarin partially ameliorated injury but silymarin administration increased damage. As a result, silymarin has a negative effects with this dosage and DEX has a protective effect. In the present study, it was determined that using the two drugs together had a greater therapeutic effect than silymarin and no differences in the effects were not observed any when the application times of the agents were changed.

Sparsely tethered bilayer lipid membranes formed by self-assembly of bicelles: Spectroelectrochemical characterization and incorporation of transmembrane protein

Many biochemical processes related to proper homeostasis take place in cell membranes. The key molecules involved in these processes are proteins, including transmembrane proteins. These macromolecules still challenge the understanding of their function within the membrane. Biomimetic models that mimic the properties of the cell membrane can help understand their functionality. Unfortunately, preserving the native protein structure in such systems is problematic. A possible solution to this problem involves the use of bicelles. Their unique properties make integrating bicelles with transmembrane proteins manageable while preserving their native structure. Hitherto, bicelles have not been used as precursors for protein-hosting lipid membranes deposited on solid substrates like pre-modified gold. Here, we demonstrated that bicelles can be self-assembled to form sparsely tethered bilayer lipid membranes and the properties of the resulting membrane satisfy the conditions suitable for transmembrane protein insertion. We showed that the incorporation of α-hemolysin toxin in the lipid membrane leads to a decrease in membrane resistance due to pore formation. Simultaneously, the insertion of the protein causes a drop in the capacitance of the membrane-modified electrode, which can be explained by the dehydration of the polar region of the lipid bilayer and the loss of water from the submembrane region.

Optimal drug therapy for Staphylococcus aureus bacteraemia in adults

PURPOSE OF REVIEW

Staphylococcus aureus is a significant human pathogen, causing a variety of infections, from skin and soft tissue infections to endocarditis, bone and joint infections and deep tissue abscesses. Mortality from S. aureus bacteraemia remains high, without major therapeutic advances in recent decades.

RECENT FINDINGS

In recent years, optimized dosing of antibiotics is increasingly being recognized as a cornerstone of management for severe infections including S. aureus bacteraemia. This comprehensive review details the pharmacokinetics/pharmacodynamics (PK/PD) targets for commonly used antistaphylococcal antibiotics and the doses predicted to achieve them in clinical practice. Recent advances in dosing of teicoplanin and use of cefazolin in CNS infections and findings from combination therapy studies are discussed. Drug exposure relationships related to toxicity are also detailed.

SUMMARY

This review details the different PK/PD targets for drugs used to treat S. aureus bacteraemia and how to apply them in various scenarios. The drug doses that achieve them, and the risks of toxicity are also provided.

Characteristics and calculations of paired vancomycin measurements for determination of 24-h area-under-curve (AUC)

Background

Current pharmacy practice guidelines recommend 24-h area-under-curve (AUC₂₄) targets for use of vancomycin against methicillin-resistant Staphylococcus aureus (MRSA). AUC protocol-specific vancomycin orders were begun recently (2022) at our institution. We reviewed initial AUC protocol-associated data and calculations.

Methods

AUC₂₄ calculations are derived from timed, paired measurements of vancomycin (V1,V2). We retrieved paired (V1,V2) measurements for a 90-day interval. Calculations to obtain AUC₂₄ were performed according to two accepted methods (A, B) that assume first-order kinetics for vancomycin elimination between V1 and V2.

Results

44 (V1,V2) measurement pairs were from among 27 patients. Dosing intervals were 8, 12, or 24 h. The first-order rate constant k was normally distributed (k = 0.096 ± 0.046 1/h); t_1/2 ranged from 3 to 30 h. For target AUC₂₄ = 400-600 h × μg/mL, 55% of calculated AUC₂₄ results were within target. Imprecision for calculated k was predicted to be least when V2 is a trough level. Method B results were greater than Method A results by a factor of 1.07.

Conclusions

45% of AUC₂₄ results indicated need for change in dosage. Recommendations are that average results from A and B methods of calculation should be used, and that V1 and V2 should be as widely separated as possible.

QKI degradation in macrophage by RNF6 protects mice from MRSA infection via enhancing PI3K p110β dependent autophagy

Background

Sepsis is a fatal condition commonly caused by Methicillin-resistant Staphylococcus aureus (MRSA) with a high death rate. Macrophages can protect the host from various microbial pathogens by recognizing and eliminating them. Earlier we found that Quaking (QKI), an RNA binding protein (RBP), was involved in differentiation and polarization of macrophages. However, the role of QKI in sepsis caused by pathogenic microbes, specifically MRSA, is unclear. This study aimed to investigate the role of QKI in regulation of host–pathogen interaction in MRSA-induced sepsis and explored the underlying mechanisms.

Methods

Transmission electron microscope and immunofluorescence were used to observe the autophagy level in macrophages. Real-time PCR and western blot were used to analyzed the expression of mRNA and protein respectively. The potential protein interaction was analyzed by iTRAQ mass spectrometry and Immunoprecipitation. RNA fluorescence in situ hybridization, dual-luciferase reporter assay and RNA immunoprecipitation were used to explore the mechanism of QKI regulating mRNA of PI3K-p110β.

Results

The mRNA level of QKI was aberrantly decreased in monocytes and PBMCs of septic patients with the increasing level of plasma procalcitonin (PCT). Then the mice with myeloid specific knockout of QKI was challenged with MRSA or Cecal Ligation and Puncture (CLP). Mice in these two models displayed higher survival rates and lower bacterial loads. Mechanistically, QKI deletion promoted phagocytosis and autophagic degradation of MRSA via activating p110β (a member of Class IA phosphoinositide 3-kinases) mediated autophagic response. QKI expression in macrophages led to the sequestration of p110β in mRNA processing (P) bodies and translational repression. Upon infection, the direct interaction of RNF6, a RING-type E3 ligase, mediated QKI ubiquitination degradation and facilitated PI3K-p110β related autophagic removal of pathogen. The administration of nanoparticles with QKI specific siRNA significantly protected mice from MRSA infection.

Conclusions

This study disclosed the novel function of QKI in the P body mRNA regulation during infection. QKI degradation in macrophage by RNF6 protects mice from MRSA infection via enhancing PI3K-p110β dependent autophagy. It suggested that QKI may serve as a potential theranostic marker in MRSA-induced sepsis.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00865-9.

Nephrotoxicity Related to Antibiotic-Loaded Spacers in a 2-Stage Revision for Periprosthetic Joint Infection

Antibiotic-loaded bone cement (ALBC) spacers are the mainstay in 2-stage revision, but antibiotics (vancomycin plus aminoglycosides) may undergo systemic absorption, resulting in acute kidney injury (AKI). Data on spacer antibiotics are heterogeneous. Our objective was to review risk factors for AKI and dosage of antibiotics. Significant AKI risk factors were antibiotic concentration greater than 3 or 3.6 g per cement batch, comorbidities, chronic kidney disease, and hypovolemia. Despite similar spacer antibiotic dosing, there was remarkable variability in serum concentrations. To err on the side of caution, it appears that antibiotic dose below 3 g per cement batch might be relatively safe until more evidence surfaces. Consideration of risk factors for AKI calls for appropriate antibiotic use in 2-stage revision. [Orthopedics. 20XX;XX(X):xx-xx.].

Pharmacokinetic/Pharmacodynamic Target Attainment of Vancomycin, at Three Reported Infusion Modes, for Methicillin-Resistant Staphylococcus aureus (MRSA) Bloodstream Infections in Critically Ill Patients: Focus on Novel Infusion Mode

Objective

The study aimed to evaluate and compare the pharmacokinetic/pharmacodynamic (PK/PD) exposure to vancomycin in the novel optimal two-step infusion (OTSI) vs. intermittent infusion (II) vs. continuous infusion (CI) mode, for MRSA bloodstream infections occurring in critical patients.

Methods

With PK/PD modeling and Monte Carlo simulations, the PK/PD exposure of 15 OTSI, 13 II, and 6 CI regimens for vancomycin, at 1, 2, 3, 4, 5, and 6 g daily dose, was evaluated. Using the Monte Carlo simulations, the vancomycin population PK parameters derived from critical patients, the PD parameter for MRSA isolates [i.e., minimum inhibitory concentration (MIC)], and the dosing parameters of these regimens were integrated into a robust mdel of vancomycin PK/PD index, defined as a ratio of the daily area under the curve (AUC0–24) to MIC (i.e., AUC0–24/MIC), to estimate the probability of target attainment (PTA) of these regimens against MRSA isolates with an MIC of 0.5, 1, 2, 4, and 8 mg/L in patients with varying renal function. The PTA at an AUC0–24/MIC ratio of >400, 400–600, and >600 was estimated. A regimen with a PTA of ≥90% at an AUC0–24/MIC ratio of 400–600, which is supposed to maximize both efficacy and safety, was considered optimal.

Results

At the same daily dose, almost only the OTSI regimens showed a PTA of ≥90% at an AUC0–24/MIC ratio of 400–600, and this profile seems evident especially in patients with creatinine clearance (CLcr) of ≥60 ml/min and for isolates with an MIC of ≤2 mg/L. However, for patients with CLcr of <60 ml/min and for isolates with an MIC of ≥4 mg/L, the II regimens often displayed a higher or even ≥90% PTA at an AUC0–24/MIC ratio of >400 and of >600. The CI regimens frequently afforded a reduced PTA at an AUC0–24/MIC ratio of >400 and of >600, regardless of CLcr and MIC.

Conclusions

The data indicated that the OTSI regimens allowed preferred PK/PD exposure in terms of both efficacy and safety, and thus should be focused more on, especially in patients with CLcr of ≥60 ml/min and for isolates with an MIC of ≤2 mg/L.

Vancomycin, Daptomycin, Antistaphylococcal β-Lactam, and Trimethoprim-Sulfamethoxazole Monotherapy and Combination Therapy in the Management of Methicillin-Resistant Staphylococcus aureus: A Network Meta-Analysis

Objective: The aim was to evaluate the efficacy and safety of vancomycin or daptomycin (VAN/DAP), antistaphylococcal β-lactam (ASBL), trimethoprim-sulfamethoxazole (TMP-SMX), and combination therapy of VAN/DAP + ASBL in the management of methicillin-resistant Staphylococcus aureus (MRSA). Methods: Databases including PubMed, Cochrane Library, Embase database, and google scholar were searched on 1 September 2021. The randomized control trials (RCTs) and comparable clinical studies of VAN/DAP, VAN/DAP + ASBL, ASBL, and TMP-SMX in the management of MRSA were identified. A network meta-analysis was conducted with STATA 14.0. Results: Seven RCTs and two matched cohorts with 1,048 patients were included in the analysis. The pooled results showed that VAN/DAP + ASBL had a significantly lower rate of persistent bacteremia >3 days than VAN/DAP alone [OR:0.46, 95%CI (0.26, 0.81), p < 0.001]. No obvious differences were observed in the outcomes of all-cause mortality, relapsed bacteremia, microbiological treatment failure, embolic or metastatic infection, and total adverse events. However, the ranking results showed that VAN/DAP + ASBL had slightly better efficacy (all-cause mortality, persistent bacteremia >3 days, duration of bacteremia, microbiological treatment failure, and relapsed bacteremia) but slightly higher adverse events than VAN/DAP alone. No obvious differences in the comparisons of VAN/DAP vs. ASBL, and VAN/DAP vs TMP-SMX in the analyzed outcomes. The ranking results revealed that ASBL and TMP-SMX did not have better efficacy or lower adverse events compared with the treatment of VAN/DAP. Conclusion: The efficacy of VAN/DAP + ASBL was slightly but not significantly better than VAN/DAP alone in the management of MRSA.

Rapid Monitoring of Vancomycin Concentration in Serum Using Europium (III) Chelate Nanoparticle-Based Lateral Flow Immunoassay

Establishing personalized medication plans for patients to maximize therapeutic efficacy and minimize the toxicity of vancomycin (VAN) requires rapid, simple, and accurate monitoring of VAN concentration in body fluid. In this study, we have developed a simple and rapid analytical method by integrating Eu (III) chelate nanoparticles (CN-EUs) and lateral flow immunoassay (LFIA) to achieve the real-time monitoring of VAN concentration in serum within 15 min. This approach was performed on nitrocellulose (NC) membrane assembled LFIA strips via indirect competitive immunoassay and exhibited a wide linear range of detection (0.1–80 μg*ml⁻¹) with a low limit of detection (69.2 ng*ml⁻¹). The coefficients of variation (CV) of the intra- and inter-assay in the detection of VAN were 7.12–8.53% and 8.46–11.82%, respectively. The dilution test and specificity indicated this method had a stability that was not affected by the serum matrix and some other antibiotics. Furthermore, the applicability of the proposed method was assessed by comparing the determined results with those measured by LC-MS/MS, showing a satisfactory correlation (R² = 0.9713). The proposed CN-EUs-based LFIA manifested promising analytical performance, which showed potential value in the real-time monitoring of VAN and could help optimize the clinical use of more antibiotics.

β-Lactams against the Fortress of the Gram-Positive Staphylococcus aureus Bacterium

The biological diversity of the unicellular bacteria-whether assessed by shape, food, metabolism, or ecological niche-surely rivals (if not exceeds) that of the multicellular eukaryotes. The relationship between bacteria whose ecological niche is the eukaryote, and the eukaryote, is often symbiosis or stasis. Some bacteria, however, seek advantage in this relationship. One of the most successful-to the disadvantage of the eukaryote-is the small (less than 1 μm diameter) and nearly spherical Staphylococcus aureus bacterium. For decades, successful clinical control of its infection has been accomplished using β-lactam antibiotics such as the penicillins and the cephalosporins. Over these same decades S. aureus has perfected resistance mechanisms against these antibiotics, which are then countered by new generations of β-lactam structure. This review addresses the current breadth of biochemical and microbiological efforts to preserve the future of the β-lactam antibiotics through a better understanding of how S. aureus protects the enzyme targets of the β-lactams, the penicillin-binding proteins. The penicillin-binding proteins are essential enzyme catalysts for the biosynthesis of the cell wall, and understanding how this cell wall is integrated into the protective cell envelope of the bacterium may identify new antibacterials and new adjuvants that preserve the efficacy of the β-lactams.

The Resistance to Host Antimicrobial Peptides in Infections Caused by Daptomycin-Resistant Staphylococcus aureus

Daptomycin is an important antibiotic for the treatment of infections caused by Staphylococcus aureus. The emergence of daptomycin resistance in S. aureus is associated with treatment failure and persistent infections with poor clinical outcomes. Here, we investigated host innate immune responses against clinically derived, daptomycin-resistant (DAP-R) and -susceptible S. aureus paired isolates using a zebrafish infection model. We showed that the control of DAP-R S. aureus infections was attenuated in vivo due to cross-resistance to host cationic antimicrobial peptides. These data provide mechanistic understanding into persistent infections caused by DAP-R S. aureus and provide crucial insights into the adaptive evolution of this troublesome pathogen.