In vivo activity of a novel anti-methicillin-resistant Staphylococcus aureus cephalosporin, ceftaroline, against vancomycin-susceptible and -resistant Enterococcus faecalis strains in a rabbit endocarditis model: a comparative study with linezolid and vancomycin

New Antimicrobials and New Therapy Strategies for Endocarditis: Weapons That Should Be Defended

The overall low-quality evidence concerning the clinical benefits of different antibiotic regimens for the treatment of infective endocarditis (IE), which has made it difficult to strongly support or reject any regimen of antibiotic therapy, has led to a discrepancy between the available guidelines and clinical practice. In this complex scenario, very recently published guidelines have attempted to fill this gap. Indeed, in recent years several antimicrobials have entered the market, including ceftobiprole, ceftaroline, and the long-acting lipoglycopeptides dalbavancin and oritavancin. Despite being approved for different indications, real-world data on their use for the treatment of IE, alone or in combination, has accumulated over time. Furthermore, an old antibiotic, fosfomycin, has gained renewed interest for the treatment of complicated infections such as IE. In this narrative review, we focused on new antimicrobials and therapeutic strategies that we believe may provide important contributions to the advancement of Gram-positive IE treatment, providing a summary of the current in vitro, in vivo, and clinical evidence supporting their use in clinical practice.

Treatment of Enterococcus faecalis Infective Endocarditis: A Continuing Challenge

Today, Enterococcus faecalis is one of the main causes of infective endocarditis in the world, generally affecting an elderly and fragile population, with a high mortality rate. Enterococci are partially resistant to many commonly used antimicrobial agents such as penicillin and ampicillin, as well as high-level resistance to most cephalosporins and sometimes carbapenems, because of low-affinity penicillin-binding proteins, that lead to an unacceptable number of therapeutic failures with monotherapy. For many years, the synergistic combination of penicillins and aminoglycosides has been the cornerstone of treatment, but the emergence of strains with high resistance to aminoglycosides led to the search for new alternatives, like dual beta-lactam therapy. The development of multi-drug resistant strains of Enterococcus faecium is a matter of considerable concern due to its probable spread to E. faecalis and have necessitated the search of new guidelines with the combination of daptomycin, fosfomycin or tigecycline. Some of them have scarce clinical experience and others are still under investigation and will be analyzed in this review. In addition, the need for prolonged treatment (6–8 weeks) to avoid relapses has forced to the consideration of other viable options as outpatient parenteral strategies, long-acting administrations with the new lipoglycopeptides (dalbavancin or oritavancin), and sequential oral treatments, which will also be discussed.

Pharmacodynamics of Linezolid Plus Fosfomycin Against Vancomycin-Resistant Enterococcus faecium in a Hollow Fiber Infection Model

The optimal therapy for severe infections caused by vancomycin-resistant Enterococcus faecium (VREfm) remains unclear, but the combination of linezolid and fosfomycin may be a good choice. The 24-h static-concentration time-kill study (SCTK) was used to preliminarily explore the pharmacodynamics of linezolid combined with fosfomycin against three clinical isolates. Subsequently, a hollow-fibre infection model (HFIM) was used for the first time to further investigate the pharmacodynamic activity of the co-administration regimen against selected isolates over 72 h. To further quantify the relationship between fosfomycin resistance and bacterial virulence in VREfm, the Galleria mellonella infection model and virulence genes expression experiments were also performed. The results of SCTK showed that the combination of linezolid and fosfomycin had additive effect on all strains. In the HFIM, the dosage regimen of linezolid (12 mg/L, steady-state concentration) combined with fosfomycin (8 g administered intravenously every 8 h as a 1 h infusion) not only produced a sustained bactericidal effect of 3∼4 log₁₀ CFU/mL over 72 h, but also completely eradicated the resistant subpopulations. The expression of virulence genes was down-regulated to at least 0.222-fold in fosfomycin-resistant strains compared with baseline isolate, while survival rates of G. mellonella was increased (G. mellonella survival ≥45% at 72 h). For severe infections caused by VREfm, neither linezolid nor fosfomycin monotherapy regimens inhibited amplification of the resistant subpopulations, and the development of fosfomycin resistance was at the expense of the virulence of VREfm. The combination of linezolid with fosfomycin produced a sustained bactericidal effect and completely eradicated the resistant subpopulations. Linezolid plus Fosfomycin is a promising combination for therapy of severe infections caused by VREfm.

Dose Optimization of Combined Linezolid and Fosfomycin against Enterococcus by Using an In Vitro Pharmacokinetic/Pharmacodynamic Model

The rapid spread of antibiotic resistance among Enterococcus has prompted considerable interest in determining the dosage regimen of linezolid combined with fosfomycin. A checkerboard assay was employed to evaluate whether linezolid combined with fosfomycin had a synergistic effect on Enterococcus isolates from the hospital, including three drug-resistant strains (MIC of linezolid [MIC_LZD], ≥8 mg/L; MIC of fosfomycin [MIC_FOF], ≥256 mg/L). The in vitro static time-kill assay, dynamic pharmacokinetic (PK)/pharmacodynamic (PD) model, and semimechanistic PK/PD model were used to explore and predict effective combined dosage regimens. The checkerboard assay and in vitro static time-kill assay demonstrated that linezolid combined with fosfomycin has a synergistic effect on drug-resistant and sensitive Enterococcus. In the in vitro PK/PD model, the dosage regimen of linezolid (8 mg/L or 12 mg/L, steady-state concentration) combined with fosfomycin (6 g or 8 g) via a 0.5-h infusion every 8 h effectively suppressed bacterial growth at 24 h with a 3 log₁₀ CFU/mL decrease compared with the initial inocula against two resistant and one sensitive Enterococcus isolates. The semimechanistic PK/PD model predicted that linezolid (more than 16 mg/L) combined with fosfomycin (6 g or 10 g) via a 0.5-h infusion every 8 h was required to achieve a 4 log₁₀ CFU/mL decrease at 24 h against Enterococcus isolates (MIC_LZD ≥ 8 mg/L and MIC_FOF ≥ 256 mg/L). According to the prediction of the semimechanical PK/PD model, the effect of the combination was driven by linezolid, with fosfomycin enhancing the effect. Our study is the first to explore the synergistic effects of these two drugs from a qualitative and quantitative perspective and provides a simulation tool for future studies.

IMPORTANCE In this study, we found that linezolid combined with fosfomycin could kill Enterococcus in vitro and that the administered dose was significantly lower after the combination treatment, which could reduce adverse effects and the development of drug resistance. The potential mechanism of the two-drug combination against Enterococcus was revealed from a quantitative perspective, which is an important step toward dose optimization in simulated humans. We hope that our research will help build a better relationship between clinicians and patients as we work together to address the challenges of antibiotic resistance in the 21st century.

Human mecC-Carrying MRSA: Clinical Implications and Risk Factors

A new methicillin resistance gene, named mecC, was first described in 2011 in both humans and animals. Since then, this gene has been detected in different production and free-living animals and as an agent causing infections in some humans. The possible impact that these isolates can have in clinical settings remains unknown. The current available information about mecC-carrying methicillin resistant S. aureus (MRSA) isolates obtained from human samples was analyzed in order to establish its possible clinical implications as well as to determine the infection types associated with this resistance mechanism, the characteristics of these mecC-carrying isolates, their possible relation with animals and the presence of other risk factors. Until now, most human mecC-MRSA infections have been reported in Europe and mecC-MRSA isolates have been identified belonging to a small number of clonal complexes. Although the prevalence of mecC-MRSA human infections is very low and isolates usually contain few resistance (except for beta-lactams) and virulence genes, first isolates harboring important virulence genes or that are resistant to non-beta lactams have already been described. Moreover, severe and even fatal human infection cases have been detected. mecC-carrying MRSA should be taken into consideration in hospital, veterinary and food safety laboratories and in prevention strategies in order to avoid possible emerging health problems.

Ampicillin in Combination with Ceftaroline, Cefepime, or Ceftriaxone Demonstrates Equivalent Activities in a High-Inoculum Enterococcus faecalis Infection Model

Ampicillin-ceftriaxone combination therapy has become a predominant treatment for serious Enterococcus faecalis infections, such as endocarditis. Unfortunately, ceftriaxone use is associated with future vancomycin-resistant enterococcus colonization. We evaluated E. faecalis in an in vitro pharmacodynamic model against simulated human concentration-time profiles of ampicillin plus ceftaroline, cefepime, ceftriaxone, or gentamicin. Ampicillin-cefepime and ampicillin-ceftaroline demonstrated activities similar to those of ampicillin-ceftriaxone against E. faecalis.

Combination antibiotic therapy for the treatment of infective endocarditis due to enterococci. Infection. 2016;44:273-281. [PMID: 26324294 DOI: 10.1007/s15010-015-0836-0]

INTRODUCTION

Enterococci are common causes of infective endocarditis (IE) in both health care and community-based setting. Enterococcal IE requires bactericidal therapy for an optimal outcome. For decades, cell-wall-active antimicrobial agents (penicillins or vancomycin) in combination with aminoglycosides were the cornerstone of the treatment; however, the emergence of antibiotic resistance has significantly reduced the efficacy of these regimens.

MATERIALS AND METHODS

Data for this review were identified by searches of MEDLINE and references from relevant articles on antibiotic combination regimens for the treatment of enterococcal IE. Abstracts presented in scientific conferences were not searched for.

CONCLUSION

New effective and safe combination treatments, including double-β-lactam and daptomycin/β-lactam combination, are proving useful for the management of IE due to enterococci.

Enterococcal endocarditis revisited

The Enterococcus species is the third main cause of infective endocarditis (IE) worldwide, and it is gaining relevance, especially among healthcare-associated cases. Patients with enterococcal IE are older and have more comorbidities than other types of IE. Classical treatment options are limited due to the emergence of high-level aminoglycosides resistance (HLAR), vancomycin resistance and multidrug resistance in some cases. Besides, few new antimicrobial alternatives have shown real efficacy, despite some of them being recommended by major guidelines (including linezolid and daptomycin). Ampicillin plus ceftriaxone 2 g iv./12 h is a good option for Enterococcus faecalis IE caused by HLAR strains, but randomized clinical trials are essential to demonstrate its efficacy for non-HLAR EFIE and to compare it with ampicillin plus short-course gentamicin. The main mechanisms of resistance and treatment options are also reviewed for other enterococcal species.

Ceftaroline fosamil for the treatment of acute bacterial skin and skin structure infections

Skin infections have traditionally been classified by the US FDA as uncomplicated and complicated. In August 2010, the FDA released a new guidance document for the development of drugs to treat acute bacterial skin and skin structure infections (ABSSSI) and this was updated in 2013. Several new issues were addressed and henceforth skin infections in clinical trials were termed ABSSSI. In the USA, the annual prevalence of methicillin-resistant Staphylococcus aureus-related skin infections have continuously increased from 32.7% in 1998 to 53.8% in 2007. Ceftaroline fosamil is the only cephalosporin approved in the USA for monotherapy treatment of ABSSSI including infections caused by methicillin-resistant S. aureus. The efficacy of ceftaroline fosamil was shown in the CANVAS clinical trials. The CANVAS Day-3 analyses met an earlier, primary efficacy time point requested by the FDA. Ceftaroline has minimal drug-drug interactions, is well tolerated and possesses the safety profile associated with the cephalosporin class.

Treatment of infections due to resistant Staphylococcus aureus

This chapter reviews data on the treatment of infections caused by drug-resistant Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA). This review covers findings reported in the English language medical literature up to January of 2013. Despite the emergence of resistant and multidrug-resistant S. aureus, we have seven effective drugs in clinical use for which little resistance has been observed: vancomycin, quinupristin-dalfopristin, linezolid, tigecycline, telavancin, ceftaroline, and daptomycin. However, vancomycin is less effective for infections with MRSA isolates that have a higher MIC within the susceptible range. Linezolid is probably the drug of choice for the treatment of complicated MRSA skin and soft tissue infections (SSTIs); whether it is drug of choice in pneumonia remains debatable. Daptomycin has shown to be non-inferior to either vancomycin or β-lactams in the treatment of staphylococcal SSTIs, bacteremia, and right-sided endocarditis. Tigecycline was also non-inferior to comparator drugs in the treatment of SSTIs, but there is controversy about whether it is less effective than other therapeutic options in the treatment of more serious infections. Telavancin has been shown to be non-inferior to vancomycin in the treatment of SSTIs and pneumonia, but has greater nephrotoxicity. Ceftaroline is a broad-spectrum cephalosporin with activity against MRSA; it is non-inferior to vancomycin in the treatment of SSTIs. Clindamycin, trimethoprim-sulfamethoxazole, doxycycline, rifampin, moxifloxacin, and minocycline are oral anti-staphylococcal agents that may have utility in the treatment of SSTIs and osteomyelitis, but the clinical data for their efficacy is limited. There are also several drugs with broad-spectrum activity against Gm-positive organisms that have reached the phase II and III stages of clinical testing that will hopefully be approved for clinical use in the upcoming years: oritavancin, dalbavancin, omadacycline, tedizolid, delafloxacin, and JNJ-Q2. Thus, there are currently many effective drugs to treat resistant S. aureus infections and many promising agents in the pipeline. Nevertheless, S. aureus remains a formidable adversary, and despite our deep bullpen of potential therapies, there are still frequent treatment failures and unfortunate clinical outcomes. The following discussion summarizes the clinical challenges presented by MRSA, the clinical experience with our current anti-MRSA antibiotics, and the gaps in our knowledge on how to use these agents to most effectively combat MRSA infections.

Ceftaroline fosamil: a brief clinical review

Ceftaroline is a novel cephalosporin with a favorable tolerability profile and broad in vitro activity against many resistant Gram-positive and common Gram-negative organisms. Ceftaroline fosamil is the first cephalosporin to be approved by the United States Food and Drug Administration (FDA) for the treatment of adults with acute bacterial skin and soft tissue infections, including those caused by methicillin-resistant Staphylococcus aureus (MRSA). It is also approved by the FDA for the treatment of adults with community-acquired bacterial pneumonia, including cases caused by Streptococcus pneumoniae (with or without concurrent bacteremia), although there are no data at this time to support the use of ceftaroline fosamil for the treatment of pneumonia caused by MRSA. Ceftaroline fosamil is likewise approved by the European Commission for the treatment of adults with complicated skin and soft tissue infections or community-acquired pneumonia. This review summarizes the pharmacokinetic and microbiologic properties of ceftaroline, as well as the safety and efficacy data that led to its approval by the FDA in 2010 and the European Commission in 2012. Future directions to be addressed are also highlighted.

Ceftaroline fosamil: a review of its use in the treatment of complicated skin and soft tissue infections and community-acquired pneumonia

Ceftaroline, the active metabolite of the prodrug ceftaroline fosamil (Zinforo, Teflaro), is an advanced-generation, parenteral cephalosporin with broad-spectrum antibacterial activity in vitro against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and multidrug resistant Streptococcus pneumoniae and Gram-negative bacteria, including Haemophilus influenzae and Moraxella catarrhalis, but not Pseudomonas aeruginosa. Ceftaroline has demonstrated a low potential for the selection of resistance in vitro for drug-resistant Gram-positive organisms, including MRSA, as well as for Gram-negative respiratory pathogens. In pivotal phase III studies, intravenous ceftaroline fosamil demonstrated noninferiority to intravenous vancomycin plus aztreonam in patients hospitalized with complicated skin and soft tissue infections (cSSTIs) and intravenous ceftriaxone in patients hospitalized with community-acquired pneumonia (CAP) [Pneumonia Outcomes Research Team (PORT) risk class III or IV]; however, patients with CAP admitted to the intensive care unit were not evaluated. Ceftaroline fosamil was generally well tolerated in these trials, with an adverse event profile similar to that of other cephalosporins. Diarrhoea was the most commonly reported adverse event; however, the risk of Clostridium difficile-associated diarrhoea with ceftaroline fosamil appeared to be low. Potential limitations of the drug include the lack of an oral formulation and the requirement for twice-daily administration. Nonetheless, ceftaroline fosamil represents an attractive option (either alone or in combination with other agents) for the initial empirical treatment of patients hospitalized with cSSTIs (including those with suspected MRSA infection) or CAP (PORT risk class III or IV) who require intravenous antimicrobial therapy. As with all antibacterial agents, ceftaroline fosamil should be used in accordance with good antimicrobial stewardship.

Ceftaroline fosamil: a new cephalosporin active against resistant Gram-positive organisms including MRSA

The growing prevalence of resistant Gram-positive pathogens such as methicillin-resistant Staphylococcus aureus continues to pose a dilemma to clinicians. With strains developing reduced susceptibility to vancomycin, effective and well-tolerated antibiotics to combat these resistant pathogens are needed. Ceftaroline is a new parenteral cephalosporin that has been available in the USA for almost 2 years. Similar to other cephalosporins, it is well tolerated with mostly mild adverse events; however, compared with existing parenteral cephalosporins, ceftaroline has the unique attribute of being bactericidal against resistant Gram-positive aerobes including both hospital- and community-acquired methicillin-resistant S. aureus, S. aureus strains with reduced susceptibility or complete resistance to vancomycin, and resistant Streptococcus pneumoniae including multidrug-resistant strains. Current indications in the USA and Europe include treatment of adults with complicated skin, skin-structure infections and community-acquired pneumonia. This paper will review the properties of ceftaroline, its spectrum of activity, clinical use, safety profile and future role.

Intrinsic and acquired resistance mechanisms in enterococcus

Enterococci have the potential for resistance to virtually all clinically useful antibiotics. Their emergence as important nosocomial pathogens has coincided with increased expression of antimicrobial resistance by members of the genus. The mechanisms underlying antibiotic resistance in enterococci may be intrinsic to the species or acquired through mutation of intrinsic genes or horizontal exchange of genetic material encoding resistance determinants. This paper reviews the antibiotic resistance mechanisms in Enterococcus faecium and Enterococcus faecalis and discusses treatment options.

Ceftaroline fosamil in the treatment of community-acquired bacterial pneumonia and acute bacterial skin and skin structure infections

Ceftaroline fosamil is a cephalosporin antibacterial approved by the US Food and Drug Administration (FDA) for use in the treatment of acute bacterial skin and skin structure infections (ABSSSI) and community-acquired bacterial pneumonia (CABP). After intravenous administration, ceftaroline fosamil is rapidly converted to its bioactive metabolite, ceftaroline. Ceftaroline has broad-spectrum in vitro activity against Gram-positive and Gram-negative bacteria, including contemporary resistant Gram-positive phenotypes, such as methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant Streptococcus pneumoniae. Because of its unique spectrum of activity, the Clinical and Laboratory Standards Institute (CLSI) designated ceftaroline as a member of a new subclass of β-lactam antimicrobials, cephalosporins with anti-MRSA activity. The activity of ceftaroline against S. aureus extends to heteroresistant vancomycin-intermediate, vancomycin-intermediate, vancomycin-resistant and daptomycin-nonsusceptible isolates. Ceftaroline has low minimum inhibitory concentrations (MICs) for all tested species of streptococci, and has potent activity against S. pneumoniae isolates with varying degrees of penicillin resistance. The activity of ceftaroline is limited against Enterococcus faecalis and Enterococcus faecium and against anaerobes such as Bacteroides fragilis. The in vitro activity of ceftaroline includes many Gram-negative pathogens, but does not extend to bacteria that produce extended-spectrum β-lactamases, class B metallo-β-lactamases or AmpC cephalosporinases, or to most nonfermentative Gram-negative bacilli. Ceftaroline fosamil has been studied for the treatment of complicated skin and skin structure infections (cSSSI) and community-acquired pneumonia (CAP) in phase III randomized, double-blind, international, multicentre noninferiority clinical trials. Two identical trials (CANVAS 1 and CANVAS 2) compared the efficacy of ceftaroline fosamil with that of vancomycin plus aztreonam in 1378 adults with cSSSI. Results demonstrated that ceftaroline was noninferior to vancomycin plus aztreonam, with 91.6% in the ceftaroline fosamil group (pooled analysis) achieving clinical response compared with 92.7% in the vancomycin plus aztreonam group (difference -1.1%, 95% CI -4.2, 2.0). An additional analysis evaluated clinical cure in a subgroup of patients who met the FDA guidance definition of ABSSSI at treatment day 3. Clinical response, defined as cessation of lesion spread and absence of fever, was 74.0% in the ceftaroline fosamil group compared with 66.2% in the vancomycin plus aztreonam group (treatment difference 7.8%, 95% CI 1.3, 14.0). Clinical efficacy of ceftaroline fosamil in 1240 hospitalized adults with CAP was compared with that of ceftriaxone in two additional phase III trials (FOCUS 1 and FOCUS 2). Of note, because ceftriaxone does not have activity against MRSA, patients with confirmed or suspected MRSA CAP were excluded from the FOCUS trials. Results demonstrated that ceftaroline was noninferior to ceftriaxone, with 84.3% in the ceftaroline fosamil group achieving clinical cure compared with 77.7% in the ceftriaxone group (difference 6.7%, 95% CI 1.6, 11.8). An additional analysis of the trials was conducted in patients with moderate to severe CAP and at least one proven typical bacterial pathogen at baseline (i.e. CABP). Day 4 clinical response rates were 69.5% for ceftaroline and 59.4% for ceftriaxone (difference 10.1%, 95% CI -0.6, 20.6). In the phase III trials, adverse event rates were similar between groups. Overall, ceftaroline is well tolerated, which is consistent with the good safety and tolerability profile of the cephalosporin class. In summary, ceftaroline fosamil is a broad-spectrum parenteral cephalosporin with excellent in vitro activity against resistant Gram-positive pathogens, including MRSA, as well as many common Gram-negative organisms. It is a welcome treatment option for ABSSSI and CABP.

Ceftaroline in complicated skin and skin-structure infections

Ceftaroline is an advanced-generation cephalosporin antibiotic recently approved by the US Food and Drug Administration for the treatment of complicated skin and skin-structure infections (cSSSIs). This intravenous broad-spectrum antibiotic exerts potent bactericidal activity by inhibiting bacterial cell wall synthesis. A high affinity for the penicillin-binding protein 2a (PBP2a) of methicillin-resistant Staphylococcus aureus (MRSA) makes the drug especially beneficial to patients with MRSA cSSSIs. Ceftaroline has proved in multiple well-conducted clinical trials to have an excellent safety and efficacy profile. In adjusted doses it is also recommended for patients with renal or hepatic impairment. Furthermore, the clinical effectiveness and high cure rate demonstrated by ceftaroline in cSSSIs, including those caused by MRSA and other multidrug-resistant strains, warrants its consideration as a first-line treatment option for cSSSIs. This article reviews ceftaroline and its pharmacology, efficacy, and safety data to further elucidate its role in the treatment of cSSSIs.

Ceftaroline fosamil for treatment of community-acquired pneumonia: findings from FOCUS 1 and 2 and potential role in therapy

Cephalosporins have been widely used over the last few decades (often as first-line antibiotic therapy) for numerous infections, owing primarily to their broad spectrum of microbiologic activity and favorable safety profile. Current Infectious Diseases Society of America guidelines identify a third-generation cephalosporin in combination with a macrolide antibiotic as an option for treatment of hospitalized adult patients with community-acquired pneumonia (CAP) outside the intensive care unit setting. Although ceftriaxone is a frequently used agent for CAP, increasing incidence of multidrug-resistant Streptococcus pneumoniae and concerns regarding poor outcomes associated with ineffective therapy have prompted the search for a well-tolerated treatment alternative that is effective against bacteria that can cause CAP. Ceftaroline fosamil, the prodrug of ceftaroline, is a new extended-spectrum cephalosporin that exhibits time-dependant bactericidal activity against numerous Gram-negative and Gram-positive organisms, including methicillin-resistant Staphylococcus aureus and penicillin-resistant S. pneumoniae. Notable exceptions include Pseudomonas spp. and Gram-negative organisms that produce extended-spectrum β-lactamases or carbapenemases. Two large Phase III clinical trials (FOCUS 1 and 2) reported that ceftaroline fosamil was well tolerated, with a clinical cure rate of CAP that was noninferior to that with ceftriaxone in nonintensive care unit adult inpatients with moderately severe (Pneumonia Outcomes Research Team score of III or IV) community-acquired pneumonia.

Ceftaroline Fosamil

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Ceftaroline: a comprehensive update

Ceftaroline is a novel broad-spectrum cephalosporin antibiotic currently under US Food and Drug Administration (FDA) review for a new drug application (NDA), filed by Cerexa, Inc. (a wholly owned subsidiary of Forest Laboratories), for the treatment of complicated skin and skin-structure infections (cSSSIs) and community-associated pneumonia (CAP). The antibiotic acts by binding to penicillin-binding proteins in bacteria, consistent with other β-lactams. The antimicrobial spectrum of ceftaroline ranges from aerobic and anaerobic Gram-positive bacteria, including drug-resistant isolates of staphylococci, i.e. heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA), vancomycin-intermediate S. aureus (VISA) and vancomycin-resistant S. aureus (VRSA), to anaerobic Gram-negative pathogens such as Moraxella catarrhalis and Haemophilus influenzae (including β-lactamase-positive strains), as well as bacteria with multiple resistance phenotypes. Ceftaroline fosamil is the prodrug that is rapidly dephosphorylated by in vivo plasma phosphatases to the active drug ceftaroline, which follows a two-compartmental pharmacokinetic model and is eliminated primarily by renal excretion, with a plasma half-life of ca. 2.5 h. Ceftaroline is well tolerated, which is consistent with its good safety profile similar to other cephalosporins in clinical trials. Thus, it would be a promising drug to fight multidrug-resistant superbugs such as S. aureus and Streptococcus pneumoniae for the treatment of cSSSIs and CAP.

Ceftaroline: a novel cephalosporin with activity against methicillin-resistant Staphylococcus aureus

Ceftaroline (PPI 0903, formerly TAK-599), the active metabolite of a N-phosphono prodrug, ceftaroline fosamil, has been approved by the US Food and Drug Administration for the treatment of acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia. This antimicrobial agent binds to penicillin binding proteins (PBP) inhibiting cell wall synthesis and has a high affinity for PBP2a, which is associated with methicillin resistance. Ceftaroline is consistently active against multidrug-resistant Streptococcus pneumoniae and Staphylococcus aureus, including methicillin-resistant, vancomycin-intermediate, linezolid-resistant, and daptomycin-nonsusceptible strains. It possesses variable activity against Enterobacteriaceae and good activity against oral anaerobes. The drug is usually administrated intravenously at 600 mg every 12 h. Ceftaroline has low protein binding and is excreted by the kidneys and thus requires dose adjustments in individuals with renal failure. Clinical trials have demonstrated noninferiority when compared with vancomycin in the treatment of acute bacterial skin and skin structure infections and noninferiority when compared with ceftriaxone in the treatment of community-acquired bacterial pneumonia. Ceftaroline demonstrated a safety profile similar to that of comparator drugs in clinical trials.

Comparative ceftaroline activity tested against pathogens associated with community-acquired pneumonia: results from an international surveillance study

OBJECTIVES

To document the spectrum of activity of ceftaroline, the active form of the prodrug, ceftaroline fosamil, a new cephalosporin with anti-methicillin-resistant staphylococcal activity, against a surveillance collection of clinical isolates obtained from the USA and Europe during 2008-09.

METHODS

A selected group of species associated with community-acquired pneumonia (CAP; 6496 of 17 326 monitored strains) were tested for susceptibility in a central laboratory using CLSI broth microdilution methods. Organisms were sampled from 55 medical centres, 27 in the USA and 28 (12 countries) in Europe. Ceftaroline and comparator agents were tested and interpretations of MIC endpoints made by applying current CLSI (2010) and EUCAST (2010) breakpoint criteria.

RESULTS

Against 1340 Streptococcus pneumoniae, ceftaroline inhibited all isolates at ≤0.5 mg/L (MIC(50/90), ≤0.008/0.12 mg/L) and was 8-fold more active than ceftriaxone (MIC(90), 1 mg/L; only 79.2% coverage at EUCAST breakpoint). Haemophilus influenzae (n = 584; MIC(50/90), ≤0.008/0.015 mg/L), Moraxella catarrhalis (n = 377; MIC(50/90), 0.03-0.06/0.12 mg/L) and Staphylococcus aureus (n = 590; MIC(50/90), 0.5/1 mg/L) were very susceptible to ceftaroline, regardless of β-lactamase production or multidrug resistance (MDR) patterns. The potency of ceftaroline against three species of Enterobacteriaceae (Escherichia coli, Klebsiella pneumoniae and Enterobacter cloacae) was similar to that of ceftriaxone, ceftazidime and piperacillin/tazobactam. Only modest differences in rates of ceftaroline susceptibility (breakpoint ≤2 mg/L) were noted with extended-spectrum β-lactamase-negative Enterobacteriaceae strains between the USA and Europe (97.9% versus 97.0% for E. coli). Ceftaroline, like ceftriaxone, was not active against ceftazidime-resistant E. coli (10.2%-26.2% susceptible at ≤2 mg/L) or K. pneumoniae (5.3%-11.2%).

CONCLUSIONS

The ceftaroline surveillance for 2008-09 (USA and Europe) documented low MIC(50/90) values for S. aureus isolates at 0.5/1 and 0.25/1 mg/L, respectively. More importantly, ceftaroline MIC(90) results for S. pneumoniae (0.12 mg/L), H. influenzae (0.015 mg/L) and M. catarrhalis (0.12 mg/L) were very low, all MICs being ≤0.5 mg/L. Ceftaroline exhibited promising high potency and wide coverage against Gram-positive and -negative pathogens known to cause CAP, especially isolates of MDR pneumococci and methicillin-resistant S. aureus.

Ceftaroline: A New Cephalosporin with Activity against Methicillin-Resistant Staphylococcus aureus (MRSA)

Microbial resistance has reached alarming levels, threatening to outpace the ability to counter with more potent antimicrobial agents. In particular, methicillin-resistant Staphylococcus aureus (MRSA) has become a leading cause of skin and soft-tissue infections and PVL-positive strains have been associated with necrotizing pneumonia. Increasing reports of growing resistance to glycopeptides have been noted, further limiting the efficacy of standard antibiotics, such as vancomycin. Ceftaroline is a novel fifth-generation cephalosporin, which exhibits broad-spectrum activity against Gram-positive bacteria, including MRSA and extensively-resistant strains, such as vancomycin-intermediate S. aureus (VISA), heteroresistant VISA (hVISA), and vancomycin-resistant S. aureus (VRSA). In addition to being an exciting new agent in the anti-MRSA armamentarium, ceftaroline provides efficacy against many respiratory pathogens including Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. Ceftaroline (600 mg intravenously every 12 hours) has been shown effective in phase III studies in the treatment of complicated skin and soft tissue infections and community-acquired pneumonia. To date, this unique antibiotic exhibits a low propensity for inducing resistance and has a good safety profile, although further post-marketing data and clinical experience are needed. In summary, ceftaroline provides an additional option for the management of complex multidrug resistant infections, including MRSA.

Management of multidrug-resistant enterococcal infections

Enterococci are organisms with a remarkable ability to adapt to the environment and acquire antibiotic resistance determinants. The evolution of antimicrobial resistance in these organisms poses enormous challenges for clinicians when faced with patients affected with severe infections. The increased prevalence and dissemination of multidrug-resistant Enterococcus faecium worldwide has resulted in a major decrease in therapeutic options because the majority of E. faecium isolates are now resistant to ampicillin and vancomycin, and exhibit high-level resistance to aminoglycosides, which are three of the traditionally most useful anti-enterococcal antibiotics. Newer antibiotics such as linezolid, daptomycin and tigecycline have good in vitro activity against enterococcal isolates, although their clinical use may be limited in certain clinical scenarios as a result of reduced rates of success, possible underdosing for enterococci and low serum levels, respectively, and also by the emergence of resistance. The experimental agent oritavancin may offer some hope for the treatment of vancomycin-resistant enterococci but clinical data are still lacking. Thus, optimal therapies for the treatment of multidrug-resistant enterococcal infections continue to be based on empirical observations and extrapolations from in vitro and animal data. Clinical studies evaluating new strategies, including combination therapies, to treat severe vancomycin-resistant E. faecium infections are urgently needed.

Ceftaroline fosamil: drug profile and clinical data

Several studies have shown that the rates of resistant Gram-positive pathogens, such as methicillin-resistant Staphylococcus aureus, vancomycin-intermediate S. aureus (VISA), hetero-VISA, and penicillin-resistant Streptococcus pneumoniae have witnessed a substantial global increase. Ceftaroline fosamil is the prodrug form of ceftaroline, a new cephalosporin active against resistant Gram-positive pathogens and common Gram-negative organisms that do not produce extended-spectrum-β-lactamases and do not express AmpC. Ceftaroline fosamil was found to be effective and well-tolerated for the treatment of complicated skin and skin-structure infections and community-acquired bacterial pneumonia compared with standard therapy. The drug has recently been granted US FDA approval for both indications.