Single- and Repeated-Dose Pharmacokinetics of Ceftaroline in Plasma and Soft Tissues of Healthy Volunteers for Two Different Dosing Regimens of Ceftaroline Fosamil

Penetration of Antibiotics into Subcutaneous and Intramuscular Interstitial Fluid: A Meta-Analysis of Microdialysis Studies in Adults

BACKGROUND AND OBJECTIVE

The interstitial fluid of tissues is the effect site for antibiotics targeting extracellular pathogens. Microdialysis studies investigating these concentrations in muscle and subcutaneous tissue have reported notable variability in tissue penetration. This study aimed to comprehensively summarise the existing data on interstitial fluid penetration in these tissues and to identify potential factors influencing antibiotic distribution.

METHODS

A literature review was conducted, focusing on subcutaneous and intramuscular microdialysis studies of antibiotics in both adult healthy volunteers and patients. Random-effect meta-analyses were used to aggregate effect size estimates of tissue penetration. The primary parameter of interest was the unbound penetration ratio, which represents the ratio of the area under the concentration-time curve in interstitial fluid relative to the area under the concentration-time curve in plasma, using unbound concentrations.

RESULTS

In total, 52 reports were incorporated into this analysis. The unbound antibiotic exposure in the interstitial fluid of healthy volunteers was, on average, 22% lower than in plasma. The unbound penetration ratio values were higher after multiple dosing but did not significantly differ between muscle and subcutaneous tissue. Unbound penetration ratio values were lower for acids and bases compared with neutral antibiotics. Neither the molecular weight nor the logP of the antibiotics accounted for the variations in the unbound penetration ratio. Obesity was associated with lower interstitial fluid penetration. Conditions such as sepsis, tissue inflammation and tissue ischaemia were not significantly associated with altered interstitial fluid penetration.

CONCLUSIONS

This study highlights the variability and generally lower exposure of unbound antibiotics in the subcutaneous and intramuscular interstitial fluid compared with exposure in plasma. Future research should focus on understanding the therapeutic relevance of these differences and identify key covariates that may influence them.

Integrative model-based comparison of target site-specific antimicrobial effects: A case study with ceftaroline and lefamulin

OBJECTIVE

Predictions of antimicrobial effects typically rely on plasma-based pharmacokinetic-pharmacodynamic (PK-PD) targets, ignoring target-site concentrations and potential differences in tissue penetration between antibiotics. In this study, we applied PK-PD modelling to compare target site-specific effects of antibiotics by integrating clinical microdialysis data, in vitro time-kill curves, and antimicrobial susceptibility distributions. As a case study, we compared the effect of lefamulin and ceftaroline against methicillin-resistant Staphylococcus aureus (MRSA) at soft-tissue concentrations.

METHODS

A population PK model describing lefamulin concentrations in plasma, subcutaneous adipose and muscle tissue was developed. For ceftaroline, a similar previously reported PK model was adopted. In vitro time-kill experiments were performed with six MRSA isolates and a PD model was developed to describe bacterial growth and antimicrobial effects. The clinical PK and in vitro PD models were linked to compare antimicrobial effects of ceftaroline and lefamulin at the different target sites.

RESULTS

Considering minimum inhibitory concentration (MIC) distributions and standard dosages, ceftaroline showed superior anti-MRSA effects compared to lefamulin both at plasma and soft-tissue concentrations. Looking at the individual antibiotics, lefamulin effects were highest at soft-tissue concentrations, while ceftaroline effects were highest at plasma concentrations, emphasising the importance of considering target-site PK-PD in antibiotic treatment optimisation.

CONCLUSION

Given standard dosing regimens, ceftaroline appeared more effective than lefamulin against MRSA at soft-tissue concentrations. The PK-PD model-based approach applied in this study could be used to compare or explore the potential of antibiotics for specific indications or in populations with unique target-site PK.

Safety and effectiveness of fifth generation cephalosporins for the treatment of methicillin-resistant staphylococcus aureus bloodstream infections: a narrative review exploring past, present, and future

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infection (BSI) is a major issue in healthcare, since it is often associated with endocarditis or deep site foci. Relevant morbidity and mortality associated with MRSA-BSIs forced the development of new antibiotic strategies; in particular, this review will focus the attention on fifth-generation cephalosporins (ceftaroline/ceftobiprole), that are the only ß-lactams active against MRSA.

AREAS COVERED

The review discusses the available randomized controlled trials and real-world observational studies conducted on safety and effectiveness of ceftaroline/ceftobiprole for the treatment of MRSA-BSIs. Finally, a proposal of MRSA-BSI treatment flowchart, based on fifth-generation cephalosporins, is described.

EXPERT OPINION

The use of anti-MRSA cephalosporins is an acceptable choice either in monotherapy or combination therapy for the treatment of MRSA-BSIs due to their relevant effectiveness and safety. Particularly, their use may be advisable in combination therapy in case of severe infections (including endocarditis or persistent bacteriemia) or in monotherapy in subjects at higher risk of drugs-induced toxicity with older regimens. On the contrary, caution should be taken in case of suspected/ascertained central nervous system infections due to inconsistent data regarding penetration of these drugs in cerebrospinal fluid and brain tissues.

Impact of Key Components of Intensified Ceftaroline Dosing on Pharmacokinetic/Pharmacodynamic Target Attainment

BACKGROUND AND OBJECTIVE

Ceftaroline fosamil is a β-lactam antibiotic approved as a 600 mg twice daily dose (≤1 h infusion, 'standard dosing') or a 600 mg thrice daily dose (2 h infusion) to treat complicated skin and soft tissue infections caused by Staphylococcus aureus (minimum inhibitory concentration [MIC] 2-4 mg/L). We sought to systematically evaluate the relative impact of the three key components of the intensified dosing regimen (i.e. shortened dosing interval, prolonged infusion duration and increased total daily dose [TDD]) on the pharmacokinetic/pharmacodynamic (PK/PD) target attainment given different grades of bacterial susceptibility.

METHODS

A population PK model was developed using data from 12 healthy volunteers (EudraCT-2012-005134-11) receiving standard or intensified dosing. PK/PD target attainment (ƒT>MIC = 35% and 100%) after 24 h was compared following systematically varied combinations of the (1) dosing interval (every 12 h [q12h]→ every 8 h [q8h]); (2) infusion duration (1 h→2 h); and (3) individual and total daily dose (400→900 mg, i.e. TDD 1200→1800 mg), as well as for varying susceptibility of S. aureus (MIC 0.032-8 mg/L).

RESULTS

A two-compartment model with linear elimination adequately described ceftaroline concentrations (n = 274). The relevance of the dosing components dosing interval/infusion duration/TDD for ƒT>MIC systematically changed with pathogen susceptibility. For susceptible pathogens with MIC ≤1 mg/L, shortened dosing intervals appeared as the main driver of the improved target attainment associated with the intensified dosing regimen, followed by increased TDD and infusion duration. For less susceptible pathogens, the advantage of q8h dosing and 2 h infusions declined, and increased TDD improved ƒT>MIC the most.

CONCLUSION

The analysis calls to mind consideration of dose increases when prolonging the infusion duration in the case of low bacterial susceptibility.

Real-world experience of therapeutic drug monitoring and PK/PD achievement of ceftaroline administered by different infusion regimens in patients with confirmed infections caused by Gram-positive bacteria

BACKGROUND

Ceftaroline is a novel cephalosporin active against MDR Gram-positive (GP) bacteria. For β-lactam antibiotics, such as ceftaroline, prolonged infusions and therapeutic drug monitoring (TDM) are used for dosage optimization based on their pharmacokinetics/pharmacodynamics (PK/PD).

OBJECTIVES

To describe our experience with TDM and PK/PD target attainment of ceftaroline administered by intermittent and prolonged infusion in a cohort of patients with MDR-GP bacterial infections.

METHODS

Patients treated with ceftaroline administered by continuous (24 h), extended (3 h/6 h) and intermittent infusion (1 h) and undergoing TDM of plasma concentrations were included. A 100%fT>4×MIC was the pre-specified PK/PD target and 100%fT>10×MIC was considered overexposure. Dose recommendations were made based on TDM results and each patient's clinical condition.

RESULTS

Twelve patients [83.3% male, median age of 73 (38-83) years] were included. Nine patients (75%) achieved 100%fT>4×MIC, all under prolonged infusions. In one patient, the 100%fT was >10×MIC but no toxicity was observed. Based on TDM results, initial doses were recommended to be maintained in eight patients, decreased in three and increased in one.

CONCLUSIONS

The administration of ceftaroline by prolonged infusion together with TDM may be a useful strategy for achieving the desired PK/PD target in these patients. However, more studies evaluating the relationship between PK/PD attainment and clinical outcomes are needed.

Development and validation of an LC-MS/MS method to quantify ceftaroline in microdialysate samples from plasma and brain: Application to a preclinical pharmacokinetic investigation

A bioanalytical LC-MS/MS method was developed and validated to determine ceftaroline in microdialysate samples from plasma and brain. Ceftaroline was separated using a C18 column and a mobile phase consisting of water and acetonitrile, both with 5 mM of ammonium formate and acid formic 0.1%, eluted as gradient. Ceftaroline was monitored using electrospray ionization operating on positive mode (ESI+) monitoring the transition 604.89 > 209.3 m/z. The method showed linearity in the concentration range of 0.5-500 ng/mL for brain microdialysate and 0.5-2500 ng/mL for plasma microdialysate with coefficients of determination ≥0.997. The inter-and intra-day precision, the accuracy, and the stability of the drug in different conditions were in accordance with the acceptable limits determined by international guidelines. Plasma pharmacokinetics and brain distribution of the drug were carried out after intravenous administration of 20 mg/kg of ceftaroline to male Wistar rats. The estimated geometric mean (geometric coefficient of variation) area under the curve (AUC_0-∞) was 4.68 (45.8%) mg·h/L and 1.20 (54.2%) mg·h/L for plasma and brain, respectively, resulting in a brain exposure of about 33% (AUC_{free brain}/AUC_{free plasma}). The results indicate that ceftaroline presents good penetration in the brain when considering free plasma and free brain concentrations.

Clinical evidence supporting ceftaroline fosamil and ceftobiprole for complicated skin and soft tissue infections

PURPOSE OF REVIEW

Ceftaroline and ceftobiprole are advanced generation cephalosporins with activity against methicillin-resistant Staphylococcus aureus (MRSA). This review summarizes their clinical efficacy for complicated skin and soft tissue infections (cSSTIs).

RECENT FINDINGS

Both these agents retain excellent in vitro activity against both MRSA and Gram-negative isolates from patients with CSSTIs. Both these agents are registered for the management of cSSTIs based on the results of large scale phase III noninferiority trials. Ceftaroline and ceftobiprole are noninferior to the combination of vancomycin and aztreonam as this was assessed by their clinical cure rate at the test-of-cure visits. Furthermore, ceftobiprole is noninferior to comparators for the achievement of early clinical success at 72 h. Ceftaroline achieves 81% clinical cure against diabetic foot infections.

SUMMARY

Ceftaroline and ceftobiprole can be used as monotherapy for the treatment of cSSTIs.

Penicillin-Binding Proteins and Alternative Dual-Beta-Lactam Combinations for Serious Enterococcus faecalis Infections with Elevated Penicillin MICs

Ampicillin-ceftriaxone has become a first-line therapy for Enterococcus faecalis endocarditis. We characterized the penicillin-binding protein (PBP) profiles of various E. faecalis strains and tested for synergy to better inform beta-lactam options for the treatment of E. faecalis infections. We assessed the affinity of PBP2B from elevated-MIC strain E. faecalis LS4828 compared to type strain JH2-2 using the fluorescent beta-lactam Bocillin FL. We also characterized pbp4 and pbpA structures and PBP4 and PBP2B expression and used deletion and complementation studies to assess the impact of PBP2B on the levels of resistance. We tested penicillin-susceptible and -resistant E. faecalis isolates against ceftriaxone or ceftaroline combinations with other beta-lactams in 24-h time-kill studies. Two penicillin-susceptible strains (JH2-2 and L2052) had identical pbp sequences and similar PBP expression levels. One reduced-penicillin-susceptibility strain (L2068) had pbp sequences identical to those of the susceptible strains but expressed more PBP4. The second decreased-penicillin-susceptibility strain (LS4828) had amino acid substitutions in both PBP4 and PBP2B and expressed increased quantities of both proteins. PBP2B did not appear to contribute significantly to the elevated beta-lactam MICs. No synergy was demonstrable against the strains with both mutated PBPs and increased expression (L2068 and LS4828). Meropenem plus ceftriaxone or ertapenem plus ceftriaxone demonstrated the most consistent synergistic activity. PBP2B of strain LS4828 does not contribute significantly to reduced penicillin susceptibility. Neither the MIC nor the level of PBP expression correlated directly with the identified synergistic combinations when tested at static subinhibitory concentrations.

Population Pharmacokinetic Modeling and Probability of Target Attainment of Ceftaroline in Brain and Soft Tissues

Ceftaroline, approved to treat skin infections and pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA), has been considered for the treatment of central nervous system (CNS) infections. A population pharmacokinetic (popPK) model was developed to describe ceftaroline soft tissue and cerebrospinal fluid (CSF) distributions and investigate the probability of target attainment (PTA) of the percentage of the dosing interval that the unbound drug concentration exceeded the MIC (%fT_>MIC) to treat MRSA infections. Healthy subjects' plasma and microdialysate concentrations from muscle and subcutaneous tissue following 600 mg every 12 h (q12h) and q8h and neurosurgical patients' plasma and CSF concentrations following single 600-mg dosing were used. Plasma concentrations were described by a two-compartment model, and tissue concentrations were incorporated as three independent compartments linked to the central compartment by bidirectional transport (clearance in [CL_in] and CL_out). Apparent volumes were fixed to physiological interstitial values. Healthy status and body weight were identified as covariates for the volume of the central compartment, and creatinine clearance was identified for clearance. The CSF glucose concentration (GLUC) was inversely correlated with CL_in,CSF. Simulations showed a PTA of >90% in plasma and soft tissues for both regimens assuming an MIC of 1 mg/L and a %fT_>MIC of 28.8%. Using the same target, patients with inflamed meninges (0.5 < GLUC ≤ 2 mmol/L) would reach PTAs of 99.8% and 97.2% for 600 mg q8h and q12h, respectively. For brain infection with mild inflammation (2 < GLUC ≤ 3.5 mmol/L), the PTAs would be reduced to 34.3% and 9.1%, respectively. Ceftaroline's penetration enhanced by meningeal inflammation suggests that the drug could be a candidate to treat MRSA CNS infections.

Population pharmacokinetic/pharmacodynamic study suggests continuous infusion of ceftaroline daily dose in ventilated critical care patients with early-onset pneumonia and augmented renal clearance

OBJECTIVES

Ceftaroline could be suitable to treat early-onset ventilator-associated pneumonia (VAP) because of its antibacterial spectrum. However, augmented renal clearance (ARC) is frequent in ICU patients and may affect ceftaroline pharmacokinetics and efficacy. The objective of the study was to explore the impact of ARC on ceftaroline pharmacokinetics and evaluate whether the currently recommended dosing regimen (600 mg every 12 h) is appropriate to treat VAP in ICU patients.

METHODS

A population pharmacokinetic model was developed using pharmacokinetic data from 18 patients with measured creatinine clearance (CLCR) ranging between 83 and 309 mL/min. Monte Carlo simulations were conducted to determine the PTA and the cumulative fraction of response (CFR) against Streptococcus pneumoniae and MRSA for five dosing regimens. Study registered at ClinicalTrials.gov (NCT03025841).

RESULTS

Ceftaroline clearance increased non-linearly with CLCR, with lower concentrations and lower probability of reaching pharmacokinetic/pharmacodynamic targets when CLCR increases. For the currently recommended dosing regimen, the probability of having unbound ceftaroline concentrations above the MIC over the entire dose range is greater than 90% for MICs below 0.125 mg/L. Considering the distribution of MICs, this regimen would not be effective against MRSA infections (CFR between 21% and 67% depending on CLCR), but would be effective against S. pneumoniae infections (CFR >86%).

CONCLUSIONS

The recommended dosing regimen of ceftaroline seems sufficient for covering S. pneumoniae in ICU patients with ARC, but not for MRSA. Among the dosing regimens tested it appears that a constant infusion (50 mg/h) after a loading dose of 600 mg could be more appropriate for MRSA infections.

Tissue Penetration of Antimicrobials in Intensive Care Unit Patients: A Systematic Review—Part I

The challenging severity of some infections, especially in critically ill patients, makes the diffusion of antimicrobial drugs within tissues one of the cornerstones of chemotherapy. The knowledge of how antibacterial agents penetrate tissues may come from different sources: preclinical studies in animal models, phase I–III clinical trials and post-registration studies. However, the particular physiopathology of critically ill patients may significantly alter drug pharmacokinetics. Indeed, changes in interstitial volumes (the third space) and/or in glomerular filtration ratio may influence the achievement of bactericidal concentrations in peripheral compartments, while inflammation can alter the systemic distribution of some drugs. On the contrary, other antibacterial agents may reach high and effective concentrations thanks to the increased tissue accumulation of macrophages and neutrophils. Therefore, the present review explores the tissue distribution of beta-lactams and other antimicrobials acting on the cell wall and cytoplasmic membrane of bacteria in critically ill patients. A systematic search of articles was performed according to PRISMA guidelines, and tissue/plasma penetration ratios were collected. Results showed a highly variable passage of drugs within tissues, while large interindividual variability may represent a hurdle which must be overcome to achieve therapeutic concentrations in some compartments. To solve that issue, off-label dosing regimens could represent an effective solution in particular conditions.

Microdosing as a Potential Tool to Enhance Clinical Development of Novel Antibiotics: A Tissue and Plasma PK Feasibility Study with Ciprofloxacin

Background and Objective

In microdose studies, drug pharmacokinetics is measured in humans after administration of subtherapeutic doses. While previous microdose studies focused primarily on plasma pharmacokinetics, we set out to evaluate the feasibility of microdosing for a pharmacokinetic assessment in subcutaneous tissue and epithelial lining fluid.

Methods

Healthy subjects received a single intravenous bolus injection of a microdose of [¹⁴C]ciprofloxacin (1.1 µg, 7 kBq) with (cohort A, n = 9) or without (cohort B, n = 9) a prior intravenous infusion of a therapeutic dose of unlabeled ciprofloxacin (400 mg). Microdialysis and bronchoalveolar lavage were applied for determination of subcutaneous and intrapulmonary drug concentrations. Microdose [¹⁴C]ciprofloxacin was quantified by accelerator mass spectrometry and therapeutic-dose ciprofloxacin by liquid chromatography–tandem mass spectrometry.

Results

The pharmacokinetics of therapeutic-dose ciprofloxacin (cohort A) in plasma, subcutaneous tissue, and epithelial lining fluid was in accordance with previous data. In plasma and subcutaneous tissue, the dose-adjusted area under the concentration–time curve of microdose ciprofloxacin was similar in cohorts A and B and within an 0.8-fold to 1.1-fold range of the area under the concentration–time curve of therapeutic-dose ciprofloxacin. Penetration of microdose ciprofloxacin into subcutaneous tissue was similar in cohorts A and B and comparable to that of therapeutic-dose ciprofloxacin with subcutaneous tissue-to-plasma area under the concentration–time curve ratios of 0.44, 0.44, and 0.38, respectively. Penetration of microdose ciprofloxacin into epithelial lining fluid was highly variable and failed to predict the epithelial lining fluid penetration of therapeutic-dose ciprofloxacin.

Conclusions

Our study confirms the feasibility of microdosing for pharmacokinetic measurements in plasma and subcutaneous tissue. Microdosing combined with microdialysis is a potentially useful tool in clinical antimicrobial drug development, but its applicability for the assessment of pulmonary pharmacokinetics with bronchoalveolar lavage requires further studies.

Clinical Trial Registration

ClinicalTrials.gov NCT03177720 (registered 6 June, 2017).

Supplementary Information

The online version contains supplementary material available at 10.1007/s40262-021-01091-1.

Impact of Underlying Comorbidities on Outcomes of Patients Treated with Ceftaroline Fosamil for Complicated Skin and Soft Tissue Infections: Pooled Results from Three Phase III Randomized Clinical Trials

Introduction

In three phase III randomized controlled trials, ceftaroline fosamil was shown to be non-inferior to vancomycin plus aztreonam for the treatment of complicated skin and soft tissue infections (cSSTIs). This exploratory analysis evaluated the impact of underlying comorbidities on clinical outcomes in patients with cSSTI pooled from these three studies.

Methods

CANVAS 1 and 2 and COVERS evaluated ceftaroline fosamil (600 mg every 12 h [q12h]; 600 mg every 8 h [q8h; COVERS]) versus vancomycin plus aztreonam (1 g q12h each [CANVAS 1 and 2]; vancomycin 15 mg/kg q12h and aztreonam 1 g q8h [COVERS]) in hospitalized adults with cSSTI. The primary efficacy variable in each trial was clinical response at the test-of-cure (TOC) visit. Subgroup analyses were performed on the pooled clinically evaluable (CE) population, exploring the impact of age and various baseline comorbidities.

Results

Overall, 1808 patients were included in the CE population (1005 ceftaroline fosamil; 803 vancomycin plus aztreonam). Clinical cure rates at TOC were 89.7% (ceftaroline fosamil) and 90.8% (vancomycin plus aztreonam) (difference [95% confidence interval] − 1.13 [− 3.87, 1.67]). Clinical response rates were similar between treatment groups, regardless of age (≤ 65 years or > 65 years), and in subgroups of patients with and without diabetes mellitus, peripheral vascular disease, cancer/malignancy, renal impairment, and obesity; within these subgroups, efficacy and safety results were generally consistent with those of the overall cSSTI population.

Conclusions

This analysis provides supportive evidence of the efficacy of ceftaroline fosamil in patients with cSSTI and underlying comorbidities.

Trial Registration

CANVAS 1, NCT00424190 and CANVAS 2, NCT00423657 (both trials first posted on ClinicalTrials.gov 18/01/2007); COVERS, NCT01499277 (first posted on ClinicalTrials.gov 26/12/2011).

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-021-00557-w.

Plasma and Lung Tissue Pharmacokinetics of Ceftaroline Fosamil in Patients Undergoing Cardiac Surgery with Cardiopulmonary Bypass: an In Vivo Microdialysis Study

Ceftaroline fosamil, a fifth-generation cephalosporin antibiotic with activity against methicillin-resistant Staphylococcus aureus (MRSA), is currently approved for the treatment of pneumonia and complicated skin and soft tissue infections. However, pharmacokinetics data on free lung tissue concentrations in critical patient populations are lacking. The aim of this study was to evaluate the pharmacokinetics of the high-dose regimen of ceftaroline in plasma and lung tissue in cardiac surgery patients during intermittent and continuous administration. Nine patients undergoing elective cardiac surgery on cardiopulmonary bypass were included in this study and randomly assigned to intermittent or continuous administration. Eighteen hundred milligrams of ceftaroline fosamil was administered intravenously as either 600 mg over 2 h every 8 h (q8h) (intermittent group) or 600 mg over 2 h (loading dose) plus 1,200 mg over 22 h (continuous group). Interstitial lung tissue concentrations were measured by in vivo microdialysis. Relevant pharmacokinetics parameters were calculated for each group. Plasma exposure levels during intermittent and continuous administration were comparable to those of previously published studies and did not differ significantly between the two groups. In vivo microdialysis demonstrated reliable and adequate penetration of ceftaroline into lung tissue during intermittent and continuous administration. The steady-state area under the concentration-time curve from 0 to 8 h (AUCss 0-8) and the ratio of AUCSS 0-8 in lung tissue and AUC in plasma (AUClung/plasma) were descriptively higher in the continuous group. Continuous administration of ceftaroline fosamil achieved a significantly higher proportion of time for which the free drug concentration remained above 4 times the minimal inhibitory concentration (MIC) during the dosing interval (% fT>4xMIC) than intermittent administration for pathogens with a MIC of 1 mg/liter. Ceftaroline showed adequate penetration into interstitial lung tissue of critically ill patients undergoing major cardiothoracic surgery, supporting its use for pneumonia caused by susceptible pathogens.

Treatment of severe pneumonia by hinokitiol in a murine antimicrobial-resistant pneumococcal pneumonia model

Streptococcus pneumoniae is often isolated from patients with community-acquired pneumonia. Antibiotics are the primary line of treatment for pneumococcal pneumonia; however, rising antimicrobial resistance is becoming more prevalent. Hinokitiol, which is isolated from trees in the cypress family, has been demonstrated to exert antibacterial activity against S. pneumoniae in vitro regardless of antimicrobial resistance. In this study, the efficacy of hinokitiol was investigated in a mouse pneumonia model. Male 8-week-old BALB/c mice were intratracheally infected with S. pneumoniae strains D39 (antimicrobial susceptible) and NU4471 (macrolide resistant). After 1 h, hinokitiol was injected via the tracheal route. Hinokitiol significantly decreased the number of S. pneumoniae in the bronchoalveolar lavage fluid (BALF) and the concentration of pneumococcal DNA in the serum, regardless of whether bacteria were resistant or susceptible to macrolides. In addition, hinokitiol decreased the infiltration of neutrophils in the lungs, as well as the concentration of inflammatory cytokines in the BALF and serum. Repeated hinokitiol injection at 18 h intervals showed downward trend in the number of S. pneumoniae in the BALF and the concentration of S. pneumoniae DNA in the serum with the number of hinokitiol administrations. These findings suggest that hinokitiol reduced bacterial load and suppressed excessive host immune response in the pneumonia mouse model. Accordingly, hinokitiol warrants further exploration as a potential candidate for the treatment of pneumococcal pneumonia.

Susceptibility of clinical isolates of meticillin-resistant Staphylococcus aureus and phenotypic non-extended-spectrum β-lactamase-producing Klebsiella pneumoniae to ceftaroline in Taiwan: Results from Antimicrobial Testing Leadership and Surveillance (ATLAS) in 2012-2018 and Surveillance of Multicentre Antimicrobial Resistance in Taiwan (SMART) in 2018-2019

Data on ceftaroline (CPT) susceptibility amongst clinical isolates of meticillin-resistant Staphylococcus aureus (MRSA, n=1284) and phenotypic non-extended-spectrum β-lactamase-producing (non-ESBL-P) Klebsiella pneumoniae (n=466), obtained from the Antimicrobial Testing Leadership and Surveillance (ATLAS) programme from 2012 to 2018, and selected MRSA isolates from patients with bloodstream infections (BSIs) (n=95) from the Surveillance of Multicentre Antimicrobial Resistance in Taiwan (SMART) programme from 2018 to 2019 were analysed. The minimum inhibitory concentrations (MICs) of ATLAS isolates were determined using the broth microdilution method, whereas the MICs of SMART BSI-MRSA isolates were determined using the Etest and MicroScan system. The pharmacokinetic profiles and pharmacodynamic parameters of CPT were applied to explore the optimal dosage against infections caused by Taiwanese MRSA and K. pneumoniae isolates. Approximately 7.1% of ATLAS MRSA isolates were susceptible-dose dependent (S-DD) to CPT, and 19.7% of the non-ESBL-P K. pneumoniae isolates were not susceptible to CPT. Amongst the ATLAS MRSA isolates, the S-DD rates to CPT amongst isolates causing lower respiratory tract infections were 11.9% and 8.5% for isolates from intensive care units (ICUs) and general wards (GWs), and those causing skin and soft tissue infections (SSTIs) were 20% and 5.3% for isolates from ICUs and GWs, respectively (P=0.015). Of the SSTI MRSA isolates from GWs, 22.7% displayed vancomycin MICs >1 mg/L. Amongst 95 SMART BSI MRSA isolates, 28 (46.7%) isolates exhibited lower CPT MICs by the Etest compared with 60 isolates with CPT MICs of 1-2 mg/L by the MicroScan system. CPT 600 mg as a 2-h intravenous infusion every 8 h is suggested for treatment of infections caused by MRSA and phenotypic non-ESBL-P K. pneumoniae in Taiwan.

A comparative assessment of clinical, pharmacological and antimicrobial profile of novel anti-methicillin-resistant Staphylococcus aureus agent levonadifloxacin: Therapeutic role in nosocomial and community infections

Staphylococcus aureus is of significant clinical concern in both community- and hospital-onset infections. The key to the success of S. aureus as a pathogen is its ability to swiftly develop antimicrobial resistance. Methicillin-resistant S. aureus (MRSA) is not only resistant to nearly all beta-lactams but also demonstrates resistance to several classes of antibiotics. A high prevalence of MRSA is seen across worldwide. For many decades, vancomycin remained as gold standard antibiotic for the treatment of MRSA infections. In the past decades, linezolid, daptomycin, ceftaroline and telavancin received regulatory approval for the treatment of infections caused by resistant Gram-positive pathogens. Although these drugs may offer some advantages over vancomycin, they also have significant limitations. These includes vancomycin's slow bactericidal activity, poor lung penetration and nephrotxicity;linezolid therapy induced myelosuppression and high cost of daptomycin greatly limits their clinical use. Moreover, daptomycin also gets inactivated by lung naturally occurring surfactants. Thus, currently available therapeutic options are unable to provide safe and efficacious treatment for those patients suffering from hospital-acquired pneumonia, bloodstream infections (BSIs), bone and joint infections and diabetic foot infections (DFI). An unmet need also exists for a safe and efficacious oral option for switch-over convenience and community treatment. Herein, the review is intended to describe the supporting role of anti-staphylococcal antibiotics used in the management of S. aureus infections with a special reference to levonadifloxacin. Levonadifloxacin and its prodrug alalevonadifloxacin are novel benzoquinolizine subclass of quinolone with broad-spectrum of anti-MRSA activity. It has been recently approved for the treatment of complicated skin and soft-tissue infection as well as concurrent bacteraemia and DFI in India.

Repeated determination of moxifloxacin concentrations in interstitial space fluid of muscle and subcutis in septic patients

BACKGROUND

For an effective antimicrobial treatment, it is crucial that antibiotics reach sufficient concentrations in plasma and tissue. Currently no data exist regarding moxifloxacin plasma concentrations and exposure levels in tissue under septic conditions.

OBJECTIVES

To determine the pharmacokinetics of moxifloxacin in plasma and interstitial space fluid over a prolonged period.

PATIENTS AND METHODS

Ten septic patients were treated with 400 mg of moxifloxacin once a day; on days 1, 3 and 5 of treatment plasma sampling and microdialysis in the subcutis and muscle of the upper thigh were performed to determine concentrations of moxifloxacin in different compartments. This trial was registered in the German Clinical Trials Register (DRKS, register number DRKS00012985).

RESULTS

Mean unbound fraction of moxifloxacin in plasma was 85.5±3.4%. On day 1, Cmax in subcutis and muscle was 2.8±1.8 and 2.5±1.3 mg/L, respectively, AUC was 24.8±15.1 and 21.3±10.5 mg·h/L, respectively, and fAUC0-24/MIC was 100.9±62.9 and 86.5±38.3 h, respectively. Cmax for unbound moxifloxacin in plasma was 3.5±0.9 mg/L, AUC was 23.5±7.5 mg·h/L and fAUC0-24/MIC was 91.6±24.8 h. Key pharmacokinetic parameters on days 3 and 5 showed no significant differences. Clearance was higher than in healthy adults, but tissue concentrations were comparable, most likely due to a lower protein binding.

CONCLUSIONS

Surprisingly, the first dose already achieved exposure comparable to steady-state conditions. The approved daily dose of 400 mg was adequate in our patient population. Thus, it seems that in septic patients a loading dose on the first day of treatment with moxifloxacin is not required.

Ceftaroline-Associated Neutropenia: Case Series and Literature Review of Incidence, Risk Factors, and Outcomes

Ceftaroline is increasingly prescribed for "off-label" indications involving longer durations and higher doses. There have been postmarketing case reports of neutropenia among patients who have received extended durations of ceftaroline, but limited published data currently exist on its incidence and risk factors. We review a total of 37 published cases of ceftaroline-associated neutropenia including cases (n = 4) identified in our health care system. The median time from ceftaroline initiation to development of neutropenia (range) was 25 (8-125) days, with a median duration of neutropenia (range) of 4 (1-16) days. Agranulocytosis (absolute neutrophil count [ANC] nadir < 100 cells/mm³) developed in 49% of cases (n = 18), and there was an ANC nadir of 0 in 27% (n = 10). The overall incidence of neutropenia among cases receiving ceftaroline for ≥7-14 days (range) was 12% (7%-18% per individual study), higher than for comparator antibiotics in the literature. Risk factors for ceftaroline-associated neutropenia varied among studies and remain poorly defined.

Cerebrospinal fluid pharmacokinetics of ceftaroline in neurosurgical patients with an external ventricular drain

BACKGROUND

Owing to its antibacterial properties, ceftaroline could be attractive for prevention or treatment of bacterial post-neurosurgical meningitis/ventriculitis. However, few data are available concerning its meningeal concentrations.

OBJECTIVES

To investigate ceftaroline CSF pharmacokinetics in ICU patients with an external ventricular drain (EVD).

METHODS

Patients received a single 600 mg dose of ceftaroline as a 1 h intravenous infusion. Blood and CSF samples were collected before and 0.5, 1, 3, 6, 12 and 24 h after the end of the infusion. Concentrations were assayed in plasma and CSF by LC-MS/MS. A two-step compartmental pharmacokinetic analysis was conducted. Ceftaroline plasma data were first analysed, and thereafter plasma parameters estimated and corrected for protein binding of 20% were fixed to fit unbound CSF concentrations. In the final model, parameters for both plasma and CSF data were simultaneously estimated.

RESULTS

Nine patients with an EVD were included. The Cmax was 18.29 ± 3.33 mg/L in plasma (total concentrations) and at 0.22 ± 0.17 mg/L in CSF (unbound concentration). The model-estimated CSF input/CSF output clearance ratio was 9.4%, attesting to extensive efflux transport at the blood-CSF barrier.

CONCLUSIONS

Ceftaroline CSF concentrations are too low to ensure prophylactic protection against most pathogens with MICs between 1 and 2 mg/L, owing to its limited central distribution.

Ceftaroline fosamil doses and breakpoints for Staphylococcus aureus in complicated skin and soft tissue infections

Objectives

To describe the pharmacokinetic/pharmacodynamic (PK/PD) modelling and microbiological data that were used to support the recent European approval of ceftaroline fosamil 600 mg q8h by 2 h intravenous (iv) infusion for patients with complicated skin and soft tissue infections (cSSTIs) caused by Staphylococcus aureus with ceftaroline MICs of 2 or 4 mg/L, and the associated EUCAST MIC breakpoint update for q8h dosing (intermediate = 2 mg/L and resistant >2 mg/L).

Methods

A population PK model for ceftaroline and ceftaroline fosamil was developed using PK data from 21 clinical studies. The final model was used to simulate PTA in patients with cSSTI receiving ceftaroline fosamil 600 mg q12h by 1 h iv infusion or 600 mg q8h by 2 h iv infusion. PTA was calculated by MIC for S. aureus PK/PD targets derived from preclinical studies (27% fT>MIC for stasis, 31% fT>MIC for 1 log10 kill and 35% fT>MIC for 2 log10 kill) and compared with S. aureus ceftaroline MIC distributions from a 2013 global surveillance study.

Results

The final population PK model based on 951 subjects adequately described ceftaroline and ceftaroline fosamil PK. High PTA (>90%) was predicted for the ceftaroline fosamil 600 mg q12h dosage regimen against S. aureus isolates with ceftaroline MICs ≤2 mg/L. Greater than 90% PTA was predicted for the ceftaroline fosamil 600 mg q8h dosage regimen against S. aureus with ceftaroline MICs ≤4 mg/L.

Conclusions

The approved ceftaroline fosamil dosage regimens for adults and adolescents with cSSTI achieve high PTA against S. aureus at the associated EUCAST breakpoints.

Ceftaroline pharmacokinetics and pharmacodynamics in patients with cystic fibrosis

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is a prevalent pathogen in patients with cystic fibrosis (CF) associated with increased morbidity. Ceftaroline fosamil is an intravenous (IV) cephalosporin with activity against MRSA. There are minimal data regarding dosing in the CF population. The objective of this study was to determine the pharmacokinetic and pharmacodynamic profile of IV ceftaroline in patients with CF.

METHODS

We conducted a single-center prospective study of children and young adults with CF receiving ceftaroline (15mg/kg IV up to 600mg every 8h) as part of treatment for a CF pulmonary exacerbation between June 2016 and April 2017. Seven patients were enrolled for a total of 10 treatment courses. For each treatment course, up to 8 plasma samples were assayed for ceftaroline using ultra-high performance liquid chromatography with mass spectrometry. Maximum plasma concentration, systemic clearance, and elimination half-life were calculated. The area under the curve (AUC) above the minimum inhibitory concentration (MIC) and the percent time above the MIC (%fT>MIC) were determined for each subject using MICs of 0.5, 1, and 2μg/mL and the measured MIC if available.

RESULTS

The mean (SD) age for the 7 patients was 20.3 (8.0) years. Mean (SD) maximum plasma concentration of ceftaroline was 22.7 (9.6) μg/mL, systemic clearance 7.9 (3.3) L/h, and half-life 1.1 (0.4) hours. Using a MIC of 1 μg/mL, accepted as the MIC 90 of MRSA isolates, AUC above MIC mean (SD) was 53.6 (19.5) μg·h/mL, mean (SD) %fT>MIC was 75.7 (10.4), and all subjects had >60%fT>MIC.

CONCLUSIONS

In this cohort of CF patients, mean ceftaroline half-life was 1.1h, which is notably lower than the general population. The dosing regimen studied, which exceeds the recommended dosing in the non-CF population, was adequate to achieve >60% time above the MIC in all patients.

The role of methicillin-resistant Staphylococcus aureus in skin and soft tissue infections

PURPOSE OF REVIEW

Methicillin-resistant Staphylococcus aureus (MRSA) has become a major public health issue worldwide over the last years. MRSA is frequently implicated in the development of skin and soft tissue infections, leading to significant increases in morbidity, mortality and overall healthcare costs.

RECENT FINDINGS

In order to face the threat of MRSA, major changes in clinical management of skin and soft tissue infections are required. The identification of populations at risk for the acquisition of infections due to MRSA, together with the improvement of the diagnostic techniques, is paramount. Moreover, a number of new antimicrobials with activity against MRSA have been recently developed and approved for the treatment of skin and soft tissue infections, however, the use of the new drugs in the wide clinical practice remains limited.

SUMMARY

We reviewed the current epidemiology of MRSA in skin and soft tissue infections, with particular focus on implications for clinical management. The potential role of new antibiotic options against MRSA infections is also discussed.

What is new in the management of skin and soft tissue infections in 2016?

PURPOSE OF REVIEW

Skin and soft tissue infections (SSTIs) are the most frequent infectious cause of referrals to emergency departments and hospital admissions in developed world, contributing to significant morbidity and healthcare expenditures. We sought to review recent literature covering epidemiology and management of SSTIs.

RECENT FINDINGS

Incidence trends of SSTIs were increasing worldwide with Staphylococcus aureus and streptococci predominating and methicillin-resistant S. aureus (MRSA) posing additional challenges, because of high rates of treatment failure and relapse. Development of new antimicrobials was associated with an appraisal of regulatory definitions and endpoints. Prediction of clinical response can be very tricky, because of variable risk factors for recurrence or treatment failure, depending mostly on the host. Precise indications for new antimicrobials should be established; their integration into clinical practice algorithms may serve reduction of unnecessary admissions, overtreatment and total costs.

SUMMARY

New antimicrobials with activity against MRSA have been recently launched. Long-acting agents, mainly oritavancin and dalbavancin, provide the opportunity of single-dose treatment and early discharge. Further outpatient treatment options include new per os antibiotics such as oxazolidinones. Validated assessment tools are urgently needed to support decision-making toward rational resource utilization and delivery of optimal treatment.

Ceftaroline efficacy against high-MIC clinical Staphylococcus aureus isolates in an in vitro hollow-fibre infection model

Objectives

The current CLSI and EUCAST clinical susceptible breakpoint for 600 mg q12h dosing of ceftaroline (active metabolite of ceftaroline fosamil) for Staphylococcus aureus is ≤1 mg/L. Efficacy data for S. aureus infections with ceftaroline MIC ≥2 mg/L are limited. This study was designed to generate in-depth pharmacokinetic/pharmacodynamics (PK/PD) understanding of S. aureus isolates inhibited by ≥ 2 mg/L ceftaroline using an in vitro hollow-fibre infection model (HFIM).

Methods

The PK/PD target of ceftaroline was investigated against 12 diverse characterized clinical MRSA isolates with ceftaroline MICs of 2 or 4 mg/L using q8h dosing for 24 h. These isolates carried substitutions in the penicillin-binding domain (PBD) and/or the non-PBD. Additionally, PD responses of mutants with ceftaroline MICs ranging from 2 to 32 mg/L were evaluated against the mean 600 mg q8h human-simulated dose over 72 h.

Results

The mean stasis, 1 log10-kill and 2 log10-kill PK/PD targets were 29%, 32% and 35% f T>MIC, respectively. In addition, these data suggest that the PK/PD target for MRSA is not impacted by the presence of substitutions in the non-PBD commonly found in isolates with ceftaroline MIC values of ≤ 2 mg/L. HFIM studies with 600 mg q8h dosing demonstrated a sustained long-term bacterial suppression for isolates with ceftaroline MICs of 2 and 4 mg/L.

Conclusions

Overall, efficacy was demonstrated against a diverse collection of clinical isolates using HFIM indicating the utility of 600 mg ceftaroline fosamil for S. aureus isolates with MIC ≤4 mg/L using q8h dosing.

Future trends in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infection: An in-depth review of newer antibiotics active against an enduring pathogen

Methicillin-resistant Staphylococcus aureus (MRSA) continues to be a major public health problem. Vancomycin and teicoplanin have been in clinical use for several decades but their drawbacks are well described. In the last 10 years, several antibiotics have been made available for clinical use. Daptomycin and linezolid have been extensively used during this period. Other agents such as ceftaroline, ceftobiprole, dalbavancin, oritavancin, tedizolid and telavancin have been approved by regulatory agencies since 2009. Many others, such as the newer tetracyclines, fluoroquinolones, oxazolidinones and pleuromutilins, are in various stages of development. In addition, an ongoing multicentre trial is investigating the role of combination of vancomycin or daptomycin with β-lactam antibiotics. This review discusses the role of the newer antibiotics, reflecting the views of the 6th MRSA Consensus Conference meeting of the International Society of Chemotherapy MRSA Working Group that took place in 2016.

Efficacy of Ceftaroline against Methicillin-Susceptible Staphylococcus aureus Exhibiting the Cefazolin High-Inoculum Effect in a Rat Model of Endocarditis

Certain Staphylococcus aureus strains exhibit an inoculum effect (InE) with cefazolin (CFZ) that has been associated with therapeutic failures in high-inoculum infections. We assessed the in vitro activities of ceftaroline (CPT), CFZ, and nafcillin (NAF) against 17 type A β-lactamase (βla)-producing, methicillin-susceptible S. aureus (MSSA) strains, including the previously reported TX0117, which exhibits the CFZ InE, and its βla-cured derivative, TX0117c. Additionally, we determined the pharmacokinetics of CPT in rats after single intramuscular doses of 20 and 40 mg/kg of body weight and evaluated the activities of CPT (40 mg/kg every 8 h [q8h]), CFZ, and NAF against TX0117 and TX0117c in a rat model of infective endocarditis. No InE was observed for CPT or NAF, whereas a marked InE was detected for CFZ (MIC, 8 to ≥128 μg/ml). CPT and NAF treatment against TX0117 resulted in mean bacterial counts of 2.3 and 2.1 log10 CFU/g in vegetations, respectively, compared to a mean of 5.9 log10 CFU/g in the CFZ-treated group (CPT and NAF versus CFZ, P = 0.001; CPT versus NAF, P = 0.9830). Both CFZ and CPT were efficacious against the βla-cured derivative, TX0117c, compared to time zero (t0) (P = <0.0001 and 0.0015, respectively). Our data reiterate the in vivo consequences of the CFZ InE and show that CPT is not affected by this phenomenon. CPT might be considered for high-inoculum infections caused by MSSA exhibiting the CFZ InE.

Dosing strategies to optimize currently available anti-MRSA treatment options (Part 1: IV options)

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) continues to be a predominant pathogen resulting in significant morbidity and mortality. Optimal dosing of anti-MRSA agents is needed to help prevent the development of antimicrobial resistance and to increase the likelihood of a favorable clinical outcome. Areas covered: This review summarizes the available data for antimicrobials routinely used for MRSA infections that are not administered orally or topically. We make recommendations and highlight the current gaps in the literature. A PubMed (1966 - Present) search was performed to identify relevant literature for this review. Expert commentary: Improvements in MIC determination and therapeutic drug monitoring are needed to fully implement individualized dosing that optimizes antimicrobial pharmacodynamics.Additional data will become available for these agents in regards to effectiveness for severe MRSA infections and pharmacokinetic data for special patient populations.