In vitro pharmacodynamics of human simulated exposures of ceftaroline and daptomycin against MRSA, hVISA, and VISA with and without prior vancomycin exposure

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.

Treatment strategies for persistent methicillin-resistant Staphylococcus aureus bacteraemia

WHAT IS KNOWN AND OBJECTIVE

Treatment of methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia is a long-standing challenge to health care, often complicated by metastatic infections, treatment failure and mortality. When MRSA bacteraemia persists despite adequate initial treatment, current Infectious Diseases Society of America guidelines recommend evaluation and removal of possible sources of infection. In addition, a change in therapy may be considered. The objective of this review was to explore the therapeutic options for the treatment of persistent MRSA bacteraemia.

METHODS

A literature search of PubMed, MEDLINE and Google Scholar was performed using the following search terms: [methicillin-resistant Staphylococcus aureus OR MRSA] AND [bacteraemia OR bloodstream infection] AND [persistent OR persistence OR refractory OR treatment failure OR salvage] AND treatment. We evaluated relevant, adult, English-language, peer-reviewed studies published between 1985 and May 2018. In vitro and animal studies were considered as supportive of in vivo data.

RESULTS AND DISCUSSION

Randomized, controlled trials are lacking. However, case series and case reports support multiple treatment options including high-dose daptomycin in combination with an antistaphylococcal β-lactam, ceftaroline, trimethoprim-sulfamethoxazole (TMP-SMX) or fosfomycin; ceftaroline alone or in combination with vancomycin or TMP-SMX; linezolid alone or in combination with a carbapenem, or telavancin.

WHAT IS NEW AND CONCLUSION

Given the heterogeneity of the data, a preferred regimen has not emerged. Prescribers must take into consideration recent exposure, source control, and available synergy and clinical data. Further comparative trials are needed to establish a preferred regimen and the creation of a universal treatment algorithm.

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.

Ceftaroline for the treatment of methicillin-resistant Staphylococcus aureus bacteremia

PURPOSE

The utility of ceftaroline for the treatment of methicillin-resistant Staphylococcus aureus bacteremia (MRSAB) is reviewed.

SUMMARY

Ceftaroline was originally approved for the treatment of community-acquired bacterial pneumonia (CABP) and acute bacterial skin and skin structure infections (ABSSSIs) but recently received an additional approval for the treatment of S. aureus bacteremia (SAB) associated with ABSSSIs. Ceftaroline has demonstrated efficacy for the treatment of MRSAB, including isolates with elevated minimum inhibitory concentrations to conventional therapy when used alone or in combination with other agents. In multiple studies, ceftaroline has displayed rapid bloodstream eradication, even in the setting of refractory MRSAB or infective endocarditis. The clinical resolution of MRSAB or SAB in patients who received ceftaroline ranged from 31.0% to 83.3%; studies used varying definitions for clinical resolution and included differing proportions of patients with endocarditis. The use of ceftaroline in treatment-refractory patients and assorted populations makes absolute effectiveness difficult to determine. Ceftaroline has been shown to be effective in patients who have not responded to other agents for MRSAB, making it an attractive option for such patients. Although the approved dosing regimen for ceftaroline fosamil is 600 mg every 12 hours for patients with normal renal function for the treatment of ABSSSIs and CABP, there is some debate about whether more frequent doses (i.e., every 8 hours) are needed for MRSAB.

CONCLUSION

Ceftaroline has been used to successfully treat SAB, including endocarditis. Therapy with ceftaroline may be considered when antibiotic resistance or previous treatment failure precludes the use of first-line agents.

Fosfomycin Enhances the Activity of Daptomycin against Vancomycin-Resistant Enterococci in an In Vitro Pharmacokinetic-Pharmacodynamic Model

Daptomycin (DAP) is being used more frequently to treat infections caused by vancomycin-resistant enterococcus (VRE). DAP tends to be less active against enterococci than staphylococci and may require high doses or combination therapy to be bactericidal. Fosfomycin (FOF) has activity against VRE and has demonstrated synergistic bactericidal activity with DAP in vitro The objective of this study was to evaluate the activity of DAP alone and in combination with FOF against VRE in an in vitro pharmacokinetic/pharmacodynamic (PK/PD) model. The activity of DAP at 8 and 12 mg/kg of body weight/day (DAP 8 and DAP 12, respectively) and FOF of 40 mg/kg intravenously every 8 h, alone and in combination, were evaluated against 2 vancomycin-resistant Enterococcus faecium strains (8019 and 5938) and 2 vancomycin-resistant E. faecalis strains (V583 and R7302) in an in vitro PK/PD model over 72 h. Cell surface charge in the presence and absence of FOF was evaluated by zeta potential analysis. Daptomycin-boron-dipyrromethene (bodipy) binding was assessed by fluorescence microscopy. The addition of FOF to DAP 8 and DAP 12 resulted in significantly increased killing over DAP alone at 72 h for 8019, V583, and R7302 (P < 0.05). Therapeutic enhancement was observed with DAP 12 plus FOF against 8019, V583, and R7302. Cell surface charge became more negative after exposure to FOF by ∼2 to 8mV in all 4 strains. Daptomycin-bodipy binding increased by 2.6 times in the presence of fosfomycin (P < 0.0001). The combination of DAP plus FOF may provide improved killing against VRE (including DAP-resistant strains) through modulation of cell surface charge. Further studies to clarify the role of intravenous FOF are warranted.

Predicting and preventing antimicrobial resistance utilizing pharmacodynamics: Part I gram positive bacteria

INTRODUCTION

Antimicrobial resistance is a potentially inevitable consequence of widespread use of antibiotics in the healthcare system. An enhanced understanding of pharmacodynamic (PD) targets that prevent antimicrobial resistance development will improve currently availably therapies and help to guide future drug development strategies. Current in vitro methods to predict bacterial resistance to antimicrobials consist of serial dilution experiments, determination of the mutant prevention concentration (MPC), mutant selection window (MSW), and human simulated pharmacodynamics studies. Clinical trial data and real -world surveillance studies can help validate or disprove in vitro modeling.

AREAS COVERED

This review will discuss methods of predicting development of resistance and how the use of pharmacodynamics can reduce or eliminate the emergence of resistance among Staphylococcus aureus, Streptococcus pneumoniae, and Enterococcus species.

EXPERT OPINION

Pharmacodynamic targets can be used successfully to guide antimicrobial therapy to prevent resistance development. Currently, PD targets do not take into consideration horizontal resistance gene transfer and various factors may lead to different PD targets based on sites of infection. Further research is necessary to guide future drug development strategies and optimize new drug therapies.

Daptomycin non-susceptible, vancomycin-intermediate Staphylococcus aureus endocarditis treated with ceftaroline and daptomycin: case report and brief review of the literature

We report a case of clearance of persistent bacteremia due to daptomycin non-susceptible, vancomycin-intermediate Staphylococcus aureus native mitral valve endocarditis with a combination of ceftaroline and daptomycin, in an 81-year-old medically complex patient who was not an operative candidate.

In Vitro Pharmacodynamics of Vancomycin against Methicillin-Susceptible and -Resistant Staphylococcus aureus: Considering the Variability in Observed Tissue Exposure

Vancomycin is considered a first-line antibiotic for complicated skin and skin structure infections (cSSSI) because of the risk of methicillin-resistant Staphylococcus aureus (MRSA). The vancomycin exposure of tissue can vary widely in patients with cSSSI, yet most models test only the average exposure. The in vitro pharmacodynamic model was used to simulate three tissue exposure levels attained by administering vancomycin at 1 g every 12 h (q12h), based on the median (50th), 25th, and 10th percentile tissue area under the concentration-time curve (AUC) values observed during an in vivo microdialysis study of diabetic patients. Four clinical isolates (two of MRSA [vancomycin MIC, 1 and 2 μg/ml] and two of methicillin-susceptible S. aureus [MSSA] [MIC, 1 and 2 μg/ml]) were evaluated. Experiments were performed over 72 h in duplicate. Time-kill curves were constructed, and the area under the bacterial killing and regrowth curve (AUBC) during the final 24-h dosing interval (48 to 72 h) (AUBC48-72) was calculated. Reductions in the 72-h number of CFU/ml and AUBC48-72 at the different exposure levels were compared. Target tissue vancomycin exposure levels for the 50th (AUC0-12, 102.0 ± 9.1 μg · h/ml), 25th (AUC0-12, 44.3 ± 1.8 μg · h/ml), and 10th (AUC0-12, 25.3 ± 3.1 μg · h/ml) percentiles were obtained in all studies. No differences in the 72-h number of CFU or AUBC were observed between exposure levels when all of the isolates were analyzed together. However, for the two MRSA isolates, the 10th percentile exposure level achieved a lower 72-h number of CFU/ml (-1.4 ± 0.4 log10 CFU/ml, P = 0.007) and a greater AUBC48-72 (97.1 ± 20.0 log10 CFU · h/ml, P = 0.011) than the higher exposure levels. The majority of the tissue exposure levels achieved with a vancomycin dosing regimen of 1 g q12h resulted in substantial killing of MSSA and MRSA; however, the lowest exposure levels observed in a minority of the population may explain the poor vancomycin response.

In Vitro Pharmacodynamics of Human Simulated Exposures of Telavancin against Methicillin-Susceptible and -Resistant Staphylococcus aureus with and without Prior Vancomycin Exposure

Telavancin is a lipoglycopeptide with potent activity against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S. aureus (MSSA). The activity of telavancin against MRSA and MSSA after prior vancomycin exposure was studied in an in vitro pharmacodynamic model. Two clinical MRSA and two MSSA isolates, all with vancomycin MICs of 2 μg/ml, were subjected to humanized free drug exposures of vancomycin at 1 g every 12 h (q12h) for 96 h, telavancin at 750 mg q24h for 96 h, and vancomycin at 1 g q12h for 72 h followed by telavancin at 750 mg q24h for 48 h (120 h total). The microbiological responses were measured by changes from 0 h in log10 CFU/ml at the end of experiments and area under the bacterial killing and regrowth curves over 96 h (AUBC0-96). The control isolates grew to 8.8 ± 0.3 log10 CFU/ml. Initially, all regimens caused -4.5 ± 0.9 reductions in log10 CFU/ml by 48 h followed by slight regrowth over the following 48 to 72 h. After 96 h, vancomycin and telavancin achieved -3.7 ± 0.9 and -3.8 ± 0.8 log10 CFU/ml changes from baseline, respectively (P = 0.74). Sequential exposure to telavancin after vancomycin did not result in additional CFU reductions or increases, with ultimate log10 CFU/ml reductions of -4.3 ± 1.1 at 96 h and -4.2 ± 1.3 at 120 h (P > 0.05 for all comparisons at 96 h). The AUBC0-96 was significantly smaller for the regimen of telavancin for 96 h than for the regimens of vancomycin for 96 h and vancomycin followed by telavancin (P ≤ 0.04). No resistance was observed throughout the experiment. Against these MRSA and MSSA isolates with vancomycin MICs of 2 μg/ml, telavancin was comparable with vancomycin and its activity was unaffected by prior vancomycin exposure.

Ventilator associated pneumonia in the ICU: where has it gone?

PURPOSE OF REVIEW

To highlight the clinical importance of ventilator-associated pneumonia (VAP) in an era of escalating antimicrobial resistance.

RECENT FINDINGS

VAP continues to be an important infection in the critically ill. The development of rapid microbiologic diagnostics and new antimicrobial agents offer opportunities for improved treatment strategies for VAP balancing the need to treat effectively in a timely manner and antimicrobial stewardship. Additionally, the new surveillance definitions for assessing the quality of care in critically ill patients (ventilator-associated events, ventilator-associated conditions, and infection-related ventilator-associated conditions) do not appear to be adequate surrogates for the identification of VAP.

SUMMARY

Clinicians caring for critically ill patients should be aware of the importance of correctly treating VAP. As new diagnostic technologies and antimicrobials become available for VAP, their incorporation into routine patient management should occur in a way that optimizes patient outcomes wherein minimizing further emergence of antimicrobial resistance.

Decreasing prevalence of isolates with vancomycin heteroresistance and vancomycin minimum inhibitory concentrations ≥2 mg/L in methicillin-resistant Staphylococcus aureus over 11 years: potential impact of vancomycin treatment guidelines

We evaluated vancomycin MIC (V-MIC) and the prevalence of intermediately susceptible (VISA) and heteroresistant (hVISA) isolates trends in methicillin-resistant Staphylococcus aureus bacteremia among 720 adults (≥ 18 years) inpatients over 4 study periods (2002-2003, 2005-2006, 2008-2009, and 2010-2012). V-MIC (Etest) and the prevalence of hVISA and VISA (determined by population analysis profile-area under the curve) were stratified according to the study period. Mean vancomycin MIC was 1.78 ± 0.39, 1.81 ± 0.47, 1.68 ± 0.26, and 1.54 ± 0.28 mg/L in 2002-2003, 2005-2006, 2008-2009, and 2010-2012, respectively (P < 0.0001). We noted a steadily decreasing prevalence of isolates with V-MIC ≥ 2 mg/L (50.0%, 45.2%, 35.4%, and 18.7%; P < 0.0001) and hVISA (9.7%, 6.6%, 3.0%, and 2.1%; P=0.0003). VISA prevalence remained low (0-2%). These changes coincided with steadily increasing vancomycin trough levels (9.9 ± 7.8, 11.1 ± 8.4, 16.6 ± 7.8, and 19.7 ± 5.9 mg/L in 2002-2003, 2005-2006, 2008-2009, and 2010-2012, respectively; P < 0.0001). These changes imply that adherence to vancomycin treatment guidelines may suppress the development of less susceptible isolates.

Ceftaroline fosamil salvage therapy: an option for reduced-vancomycin-susceptible MRSA bacteraemia

OBJECTIVES

To examine the activity of ceftaroline against reduced-vancomycin-susceptible MRSA isolates.

METHODS

One-hundred and three MRSA blood culture isolates (predominantly ST239-MRSA-III), with varying vancomycin phenotypes, had their ceftaroline MICs determined by broth microdilution and MIC Evaluator strip (Oxoid-Thermo Fisher). Statistical analyses were performed that examined relationships with vancomycin and daptomycin MICs. Mutations in mecA were also examined.

RESULTS

All 103 isolates (including 60 heteroresistant vancomycin-intermediate Staphylococcus aureus/vancomycin-intermediate S. aureus) were susceptible to ceftaroline, with one isolate displaying heteroresistance that may be related to a mecA mutation. Higher ceftaroline MICs were associated with vancomycin-susceptible S. aureus isolates.

CONCLUSIONS

This study highlights that ceftaroline fosamil is an option for salvage therapy based on in vitro activity.

In vitro activity of human-simulated epithelial lining fluid exposures of ceftaroline, ceftriaxone, and vancomycin against methicillin-susceptible and -resistant Staphylococcus aureus

Staphylococcus aureus, including methicillin-susceptible (MSSA) and -resistant (MRSA) strains, is an important pathogen of bacterial pneumonia. As antibiotic concentrations at the site of infection are responsible for killing, we investigated the activity of human-simulated epithelial lining fluid (ELF) exposures of three antibiotics (ceftaroline, ceftriaxone, and vancomycin) commonly used for treatment of S. aureus pneumonia. An in vitro pharmacodynamic model was used to simulate ELF exposures of vancomycin (1 g every 12 h [q12h]), ceftaroline (600 mg q12h and q8h), and ceftriaxone (2 g q24h and q12h). Four S. aureus isolates (2 MSSA and 2 MRSA) were evaluated over 72 h with a starting inoculum of ∼ 10(6) CFU/ml. Time-kill curves were constructed, and microbiological response (change in log10 CFU/ml from 0 h and the area under the bacterial killing and regrowth curve [AUBC]) was assessed in duplicate. The change in 72-h log10 CFU/ml was largest for ceftaroline q8h (reductions of >3 log10 CFU/ml against all strains). This regimen also achieved the lowest AUBC against all organisms (P < 0.05). Vancomycin produced reliable bacterial reductions of 0.9 to 3.3 log10 CFU/ml, while the activity of ceftaroline q12h was more variable (reductions of 0.2 to 2.3 log10 CFU/ml against 3 of 4 strains). Both regimens of ceftriaxone were poorly active against MSSA tested (0.1 reduction to a 1.8-log10 CFU/ml increase). Against these S. aureus isolates, ELF exposures of ceftaroline 600 mg q8h exhibited improved antibacterial activity compared with ceftaroline 600 mg q12h and vancomycin, and therefore, this q8h regimen deserves further evaluation for the treatment of bacterial pneumonia. These data also suggest that ceftriaxone should be avoided for S. aureus pneumonia.

Pharmacokinetic and pharmacodynamic evaluation of ceftaroline fosamil

INTRODUCTION

Ceftaroline fosamil is a 5th generation cephalosporin with an in vitro spectrum of activity including Streptococcus agalactiae, penicillin- and cephalosporin-resistant S. pneumoniae, S. pyogenes, methicillin-susceptible S. aureus and methicillin-resistant S. aureus, Haemophilus influenzae, Klebsiella oxytoca, K. pneumoniae and Moraxella catarrhalis. It is currently approved by the FDA for the treatment of acute bacterial skin and skin structure infections (ABSSSI) and community-acquired bacterial pneumonia (CABP) in adults.

AREAS COVERED

This review covers the mechanism of action; bacterial resistance; pharmacokinetic characteristics in various patient populations; pharmacodynamic data in animal and in vitro models as well as human studies; efficacy observed in clinical trials for ABSSSI and CABP; and adverse effects.

EXPERT OPINION

Ceftaroline provides in vitro bactericidal activity against methicillin-, vancomycin-, daptomycin-, and linezolid-resistant Gram-positive organisms and select Gram-negative pathogens. The pharmacodynamics of ceftaroline is similar to other β-lactam agents. Ceftaroline exhibits a favorable adverse effect profile and is generally well tolerated. There is little data on clinical success of ceftaroline in patients with bacteremia or endocarditis other than what has been published in a small series of case reports. Randomized-control studies are needed to establish clinical outcomes and safety in these patient populations.

Treatment of Gram-positive infections in critically ill patients

Gram-positive bacteria to include methicillin-resistant Staphylococcus aureus (MRSA), methicillin-susceptible Staphylococcus aureus (MSSA), and enterococci, to include vancomycin-resistant enterococci (VRE), display a remarkable array of resistance and virulence factors, which have contributed to their prominent role in infections of the critically ill. Over the last three decades infections with these pathogens has increased as has their overall resistance to available antimicrobial agents. This has led to the development of a number of new antibiotics for the treatment of Gram-positive bacteria. At present, it is important that clinicians recognize the changing resistance patterns and epidemiology of Gram-positive bacteria as these factors may impact patient outcomes. The increasing range of these pathogens, such as the emergence of community-associated MRSA clones, emphasizes that all specialties of physicians treating infections should have a good understanding of the infections caused by Gram-positive bacteria in their area of practice. When initiating empiric antibiotics, it is of vital importance that this therapy be timely and appropriate, as delays in treatment are associated with adverse outcomes. Although vancomycin has traditionally been considered a first-line therapy for serious MRSA infections, multiple concerns with this agent have opened the door for alternative agents demonstrating efficacy in this role. Similarly, the expansion of VRE as a pathogen in the ICU setting has required the development of agents targeting this important pathogen.

Comparison of in vivo and in vitro pharmacodynamics of a humanized regimen of 600 milligrams of Ceftaroline Fosamil every 12 hours against Staphylococcus aureus at initial inocula of 106 and 108 CFU per milliliter

In light of the in vivo/in vitro discordance among beta-lactams against Gram-negative pathogens, we compared the in vivo pharmacodynamics of humanized ceftaroline against 9 Staphylococcus aureus strains (MICs of 0.13 to 1 mg/liter) from published in vitro studies using standard and high inocula in the murine thigh infection model. Consistent with the in vitro findings, mean reductions of ≥1 log10 CFU were observed for ceftaroline against all strains using both standard and high inocula. These results suggest in vivo/in vitro concordance with no observed inoculum effect.