Tedizolid for 6 days versus linezolid for 10 days for acute bacterial skin and skin-structure infections (ESTABLISH-2): a randomised, double-blind, phase 3, non-inferiority trial

The role of tedizolid in skin and soft tissue infections

PURPOSE OF REVIEW

Tedizolid is a second-generation oxazolidinone with activity against Gram-positive bacteria, including MRSA isolates resistant to linezolid. Pivotal clinical trials showed that tedizolid at 200 mg once-daily for 6 days is not inferior to linezolid 600 mg twice daily for 10 days in patients with SSTI. The comparison of adverse events is favorable to tedizolid under the circumstances of the clinical trials. This is a review of recent literature on tedizolid, its use in special populations and potential adverse effects.

RECENT FINDINGS

Findings suggest that tedizolid can be used in SSTI in adolescents, those older than 65 years, obese individuals and patients with diabetic foot infections. Forthcoming research to determine the future uses of this drug in other clinical syndromes requires demonstration of tolerance whenever tedizolid is administered for longer than 6 days.We also speculate on missing data and potential future indications of tedizolid in the highly competitive field of the treatment of severe Gram-positive infections other than SSTI.

SUMMARY

Tedizolid is a second-generation oxazolidinone, very convenient for treatment of SSTI, in search for other indications including nosocomial pneumonia and bone and joint infections. VIDEO ABSTRACT.

Is there still a role for vancomycin in skin and soft-tissue infections?

PURPOSE OF REVIEW

Skin and soft-tissue infections (SSIs) are among the commonest infections encountered in clinical practice. Spread of methicillin-resistant Staphylococcus aureus SSIs continues to increase in both health care and community settings and presents a challenge for the best treatment choice. Vancomycin has been the mainstay of SSIs treatment, but recently its use has been questioned because of concerns about its efficacy, tolerability, and unfavorable pharmacokinetic/pharmacodynamic profile. The purpose of this review is to establish the current role for vancomycin in light of the literature published from January 2007 to September 2017 on comparison with both old and new alternatives.

RECENT FINDINGS

Meta-analyses show better clinical and microbiological outcomes for drugs approved for the treatment of SSI, including those sustained by methicillin-resistant S. aureus, in the last 10 years than for vancomycin. The newer glycopeptides and linezolid decrease the total treatment costs compared with vancomycin, by reducing the length of stay or avoiding the hospitalization.

SUMMARY

Vancomycin is noninferior in efficacy and safety to all comparator drugs, including the newest on the market. However, the SSI treatment evidence base presents several shortcomings limiting the clinical applicability of the results. High-level clinical trials should be performed to obtain results that can be generalized and applied effectively in clinical practice.

Tedizolid phosphate for the treatment of acute bacterial skin and skin-structure infections: an evidence-based review of its place in therapy

Introduction

Tedizolid phosphate is an oxazolidinone approved for the treatment of acute bacterial skin and skin-structure infections (ABSSSIs) and active against methicillin-resistant Staphylococcus aureus.

Aims

The objective of this article was to review the evidence for the efficacy and safety of tedizolid phosphate for the treatment of ABSSSI.

Evidence review

Approval of tedizolid phosphate for the treatment of ABSSSI was based on the results of two phase III randomized controlled trials, ESTABLISH-1 (NCT01170221) and ESTABLISH-2 (NCT01421511), comparing 6-day once-daily tedizolid vs 10-day twice-daily linezolid. In ESTABLISH-1, noninferiority was met with early clinical response rates of 79.5% and 79.4% in tedizolid and linezolid groups, respectively (difference 0.1%, 95% CI –6.1% to 6.2%, with a 10% noninferiority margin). In ESTABLISH-2, noninferiority was met with 85% and 83% rates of early clinical response in tedizolid and linezolid groups, respectively (difference 2.6%, 95% CI –3.0% to 8.2%). Pooled data from ESTABLISH-1 and ESTABLISH-2 indicated a lower frequency of thrombocytopenia in tedizolid-treated than in linezolid-treated patients.

Conclusion

Tedizolid offers the option of an intravenous to oral switch, allows once-daily administration, and presents lower risk of myelotoxicity when a 6-day course is used for the treatment of ABSSSI. Greater economic cost associated with this antibiotic could be offset by its shorter treatment duration and possibility of oral administration in routine clinical practice, although either sponsored or nonsponsored postmarketing observational experience remains essential for ultimately confirming the effectiveness and tolerability of tedizolid outside clinical trials.

Efficacy and Safety of Tedizolid Phosphate versus Linezolid in a Randomized Phase 3 Trial in Patients with Acute Bacterial Skin and Skin Structure Infection

Tedizolid phosphate is approved for the treatment of acute bacterial skin and skin structure infection (ABSSSI) caused by Gram-positive bacteria in the United States, Europe, and other countries. In this multicenter, double-blind, phase 3 study, 598 adult ABSSSI patients in China, Taiwan, the Philippines, and the United States were randomized to receive 200 mg of tedizolid, intravenously (i.v.)/orally (p.o.), once daily for 6 days or 600 mg of linezolid, i.v./p.o.

Tedizolid phosphate is approved for the treatment of acute bacterial skin and skin structure infection (ABSSSI) caused by Gram-positive bacteria in the United States, Europe, and other countries. In this multicenter, double-blind, phase 3 study, 598 adult ABSSSI patients in China, Taiwan, the Philippines, and the United States were randomized to receive 200 mg of tedizolid, intravenously (i.v.)/orally (p.o.), once daily for 6 days or 600 mg of linezolid, i.v./p.o. twice daily for 10 days. The primary endpoint was early clinical response rate at 48 to 72 h. Secondary endpoints included programmatic and investigator-assessed outcomes at end-of-therapy (EOT) and posttherapy evaluation (PTE) visits. Safety was also evaluated. In the intent-to-treat (ITT) population, 75.3% of tedizolid-treated patients and 79.9% of linezolid-treated patients were early responders (treatment difference, –4.6%; 95% confidence interval [CI], –11.2, 2.2). After exclusion of patients who never received the study drug (tedizolid, n = 8; linezolid, n = 1; modified ITT), comparable early response rates were observed (tedizolid, 77.4%; linezolid, 80.1%; treatment difference, –2.7%; 95% CI, –9.4, 3.9). Secondary endpoints showed high and similar clinical success rates in the ITT and clinically evaluable (CE) populations at EOT and PTE visits (e.g., CE-PTE for tedizolid, 90.4%; for linezolid, 93.5%). Both drugs were well tolerated, and no death occurred. Eight patients experienced phlebitis with tedizolid while none did with linezolid; hence, drug-related treatment-emergent adverse events were reported in a slightly higher proportion in the tedizolid (20.9%) arm than in the linezolid arm (15.8%). The study demonstrated that tedizolid in a primarily Asian population was an efficacious and well-tolerated treatment option for ABSSSI patients. (This study has been registered at ClinicalTrials.gov under registration no. NCT02066402.)

The safety of treatment options for acute bacterial skin and skin structure infections

INTRODUCTION

Acute bacterial skin and skin-structure infections (ABSSSI) may develop in both in-patients and out-patients, possibly with a severe clinical presentation. Since most phase 3 randomized clinical trials have shown non-inferiority in efficacy across different agents, considerations regarding their different safety profiles inevitably play a crucial role in the everyday choice about which of them should be employed for the treatment of ABSSSI.

AREAS COVERED

In this review, the authors discuss the safety profile of different treatment options for ABSSSI.

EXPERT OPINION

The spread of methicillin-resistant Staphylococcus aureus (MRSA) in the last decades has inevitably influenced the therapeutic approach to ABSSSI. Adequate knowledge of the peculiar toxicity profile of each drug active against MRSA is essential for guiding, monitoring and managing adverse events, in turn reducing any unfavorable impact of toxicity on patients' outcomes. In the next five years, potential toxicity will play a critical role in establishing the best available therapy for each specific patient, together with consideration regarding the possibility of avoiding hospitalization or allowing a switch from intravenous to oral therapy and early discharge.

Perspectives on synthetic pharmacotherapy for the treatment of nosocomial pneumonia

Introduction: Nosocomial pneumonia is the second most common infection in hospital settings, resulting in substantial increases in morbidity, mortality, and length of hospital stay. The rapid increase in resistance of nosocomial pathogens to many antibiotics and the high dissemination of resistance genes highlight the need for innovative approaches to combat difficult-to-treat nosocomial respiratory infections. Areas covered: This review summarizes the synthetic antimicrobials that are currently in development for the treatment of nosocomial pneumonia, focusing on antibiotics in the final phases of clinical development and on the strategies employed by novel synthetic antimicrobial peptides. Expert opinion: Several novel synthetic antimicrobials are currently in the pipeline, and it appears that new antimicrobial peptides or mimetics will soon be made available, expanding the opportunities to treat nosocomial pneumonia. However, the approval process for use in the treatment of nosocomial pneumonia is arduous. Given that significant investments by pharmaceutical companies have ended in failure to obtain the approval of regulatory agencies, novel platforms for antimicrobial discovery are needed. The identification of new and fully synthetic chemical structures with activity against nosocomial pathogens needs to be followed by preclinical studies in large animals and by pharmacokinetic and pharmacodynamic studies in specific critically ill populations to assess lung penetration.

Comparative In Vitro Activities of New Antibiotics for the Treatment of Skin Infections

Bacterial skin infections result in significant morbidity and have contributed to enhanced health-care resource utilization. The problem is heightened by emerging antimicrobial resistance. Multiple novel agents active against resistant pathogens that cause skin infections-including dalbavancin, tedizolid phosphate, oritavancin, and delafloxacin-have been approved over the past 5 years. Common features of these agents include gram-positive activity and favorable safety. Of these agents, delafloxacin is unique in being active against both gram-positive and gram-negative pathogens that cause skin infections, including those resistant to other antimicrobial agents. It is, therefore, an effective option for the treatment of skin infections.

Omadacycline for Acute Bacterial Skin and Skin-Structure Infections

BACKGROUND

Acute bacterial skin and skin-structure infections are associated with substantial morbidity and health care costs. Omadacycline, an aminomethylcycline antibiotic that can be administered once daily either orally or intravenously, is active against pathogens that commonly cause such infections, including antibiotic-resistant strains.

METHODS

In this double-blind trial, we randomly assigned adults with acute bacterial skin and skin-structure infections (in a 1:1 ratio) to receive omadacycline (100 mg given intravenously every 12 hours for two doses, then 100 mg given intravenously every 24 hours) or linezolid (600 mg given intravenously every 12 hours). A transition to oral omadacycline (300 mg every 24 hours) or oral linezolid (600 mg every 12 hours) was allowed after 3 days; the total treatment duration was 7 to 14 days. The primary end point was an early clinical response at 48 to 72 hours, defined as survival with a reduction in lesion size of at least 20% without rescue antibacterial therapy. A secondary end point was an investigator-assessed clinical response at the post-treatment evaluation 7 to 14 days after the last dose, with clinical response defined as survival with resolution or improvement in signs or symptoms of infection to the extent that further antibacterial therapy was unnecessary. For both end points, the noninferiority margin was 10 percentage points.

RESULTS

In the modified intention-to-treat population, omadacycline (316 patients) was noninferior to linezolid (311 patients) with respect to early clinical response (rate of response, 84.8% and 85.5%, respectively; difference, -0.7 percentage points; 95% confidence interval [CI], -6.3 to 4.9). Omadacycline also was noninferior to linezolid with respect to investigator-assessed clinical response at the post-treatment evaluation in the modified intention-to-treat population (rate of response, 86.1% and 83.6%, respectively; difference, 2.5 percentage points; 95% CI, -3.2 to 8.2) and in the clinical per-protocol population (96.3% and 93.5%, respectively; difference, 2.8 percentage points; 95% CI, -1.0 to 6.9). In both groups, the efficacy of the trial drug was similar for methicillin-susceptible and methicillin-resistant Staphylococcus aureus infections. Adverse events were reported in 48.3% of the patients in the omadacycline group and in 45.7% of those in the linezolid group; the most frequent adverse events in both groups were gastrointestinal (in 18.0% and 15.8% of the patients in the respective groups).

CONCLUSIONS

Omadacycline was noninferior to linezolid for the treatment of acute bacterial skin and skin-structure infections and had a similar safety profile. (Funded by Paratek Pharmaceuticals; OASIS-1 ClinicalTrials.gov number, NCT02378480 .).

Advances in pediatric antimicrobial agents development

PURPOSE OF REVIEW

Rising rates of multidrug-resistant organisms has necessitated the development of novel antimicrobials. In this review, we will highlight agents that have recently received licensure and those that are in clinical development.

RECENT FINDINGS

In recent years, development of novel antimicrobial agents has accelerated. Although most studies have targeted the adult population, studies in pediatric patients are underway. Adequately powered clinical trials are needed to establish the safety and role of these new drugs.

SUMMARY

The recent development of novel antimicrobials to combat multidrug-resistant organisms is encouraging; however, more studies in the pediatric population are needed.

Comparison of the microbiological efficacy of tedizolid and linezolid in acute bacterial skin and skin structure infections: pooled data from phase 3 clinical trials

We evaluated the microbiological efficacy of tedizolid compared with that of linezolid against common and emerging pathogens using pooled data from 2 phase 3 trials (NCT01170221 and NCT01421511) in patients with acute bacterial skin and skin structure infections. Patients received tedizolid 200 mg once daily for 6 days (n = 664) or linezolid 600 mg twice daily for 10 days (n = 669). Favorable microbiological outcome in both treatment groups, defined as eradication or presumed eradication at the end of treatment and at the posttherapy evaluation, exceeded 85% for most pathogens, including methicillin-resistant Staphylococcus aureus. Favorable microbiological response was observed for staphylococci and streptococci at tedizolid minimal inhibitory concentration values ≤0.5 mg/L and 0.25 mg/L, respectively. The studies demonstrated positive microbiological outcomes against common pathogens with a 6-day, once-daily regimen of tedizolid phosphate in patients with acute bacterial skin and skin structure infections.

Use of Translational Pharmacokinetic/Pharmacodynamic Infection Models To Understand the Impact of Neutropenia on the Efficacy of Tedizolid Phosphate

Tedizolid phosphate, the prodrug of the active antibiotic tedizolid, is an oxazolidinone for the treatment of acute bacterial skin and skin structure infections. Studies in a mouse thigh infection model demonstrated that tedizolid has improved potency and pharmacokinetics/pharmacodynamics (PK/PD) compared with those of linezolid. Subsequent studies showed that the efficacy of tedizolid was enhanced in immunocompetent (IC) mice compared with neutropenic (immunosuppressed [IS]) mice, with stasis at clinically relevant doses being achieved only in the presence of granulocytes. The tedizolid label therefore contains a warning about its use in neutropenic patients. This study reevaluated the PK/PD of tedizolid and linezolid in the mouse thigh infection model in IC and IS mice using a methicillin-resistant Staphylococcus aureus (MRSA) strain (ATCC 33591) and a methicillin-susceptible S. aureus (MSSA) strain (ATCC 29213). The antistaphylococcal effect of doses ranging from 1 to 150 mg/kg of body weight tedizolid (once daily) or linezolid (twice daily) was determined at 24, 48, and 72 h after initiating treatment. In IC mice, stasis was achieved in the absence of antibiotics, and both tedizolid and linezolid reduced the burden further beyond a static effect. In IS mice, tedizolid achieved stasis against MRSA ATCC 33591 and MSSA ATCC 29213 at 72 h at a human clinical dose of 200 mg, severalfold lower than that in earlier studies. Linezolid achieved a static effect against MRSA ATCC 33591 in IS mice at a dose lower than that used clinically. This study demonstrates that, with time, both tedizolid and linezolid at clinically relevant exposures achieve stasis in neutropenic mice with an MRSA or MSSA thigh infection.

Linezolid resistance genes and genetic elements enhancing their dissemination in enterococci and streptococci

Linezolid is considered a last resort drug in treatment of severe infections caused by Gram-positive pathogens, resistant to other antibiotics, such as vancomycin-resistant enterococci (VRE), methicillin-resistant staphylococci and multidrug resistant pneumococci. Although the vast majority of Gram-positive pathogenic bacteria remain susceptible to linezolid, resistant isolates of enterococci, staphylococci and streptococci have been reported worldwide. In these bacteria, apart from mutations, affecting mostly the 23S rRNA genes, acquisition of such genes as cfr, cfr(B), optrA and poxtA, often associated with mobile genetic elements (MGE), plays an important role for resistance. The purpose of this paper is to provide an overview on diversity and epidemiology of MGE carrying linezolid-resistance genes among clinically-relevant Gram-positive pathogens such as enterococci and streptococci.

Efficacy and Safety of Tedizolid and Linezolid for the Treatment of Acute Bacterial Skin and Skin Structure Infections in Injection Drug Users: Analysis of Two Clinical Trials

INTRODUCTION

Injection drug users (IDUs) often develop acute bacterial skin and skin structure infections (ABSSSI) and use emergency departments as their primary source for medical care.

METHODS

A post hoc subgroup analysis of two randomized trials examined the efficacy and safety of tedizolid in the treatment of ABSSSI in IDUs. IDUs (n = 389) were identified from two pooled phase 3 trials (NCT01170221, NCT01421511) in patients with ABSSSI (n = 1333). Patients were randomly assigned to tedizolid phosphate (200 mg once daily, 6 days) or linezolid (600 mg twice daily, 10 days). Primary endpoint was ≥ 20% reduction in lesion area from baseline at 48 -72 h. Secondary endpoints included investigator-assessed clinical and microbiological response at the post-therapy evaluation (PTE).

RESULTS

Wound infection was more common in IDUs (52.2%), while cellulitis/erysipelas was more common in non-IDUs (55.9%). Most infections were due to Staphylococcus aureus (IDUs, 75.2%; non-IDUs, 85.6%), while oral pathogens were more prevalent in IDUs. Early clinical success rates for tedizolid and linezolid were 82.5% and 79.6% in IDUs and 81.3% and 79.3% for non-IDUs, respectively; responses at PTE were similar. Microbiological response per pathogen was similar between treatment groups. Rates of treatment-emergent adverse events (AEs) in IDUs were comparable between tedizolid (46.2%) and linezolid (47.8%) arms, while lower incidence of gastrointestinal AEs was observed with tedizolid (20.3%) than with linezolid (25.1%).

CONCLUSION

Efficacy and safety of tedizolid and linezolid in the treatment of ABSSSI was similar in IDUs and non-IDUs, supporting the use of oxazolidinones in treating ABSSSIs in IDUs.

FUNDING

Merck & Co., Inc., Kenilworth, NJ, USA.

Tedizolid Activity Against Clinical Mycobacterium abscessus Complex Isolates-An in vitro Characterization Study

Mycobacterium abscessus complex consist of three rapidly growing subspecies: M. abscessus, M. massiliense, and M. bolletii. They are clinically important human pathogens responsible for opportunistic pulmonary and skin and soft tissue infections. Treatment of M. abscessus infections is difficult due to in vitro resistance to most antimicrobial agents. Tedizolid (TZD) is a next-generation oxazolidinone antimicrobial with a wide spectrum of activity even against multidrug resistant Gram-positive bacteria. In this study, the in vitro activity of TZD against the M. abscessus complex (n = 130) was investigated. Susceptibility testing by broth microdilution showed lower TZD minimum inhibitory concentrations (MICs) when compared to linezolid. The MIC₅₀ and MIC₉₀ was 1 mg/L and 4 mg/L, respectively across all M. abscessus complex members, reflecting no difference in subspecies response to TZD. Pre-exposure of M. abscessus complex to subinhibitory concentrations of TZD did not trigger any inducible drug resistance. Single-drug time kill assays and bactericidal activity assays demonstrated bacteriostatic activity of TZD in all three M. abscessus subspecies, even at high drug concentrations of 4 to 8x MIC. Combination testing of TZD with clarithromycin, doxycycline and amikacin using the checkerboard approach showed no antagonistic interactions. TZD may be an effective therapeutic antimicrobial agent for the treatment of M. abscessus infections.

Real-Life Evidence for Tedizolid Phosphate in the Treatment of Cellulitis and Wound Infections: A Case Series

Introduction

Tedizolid phosphate 200 mg, once daily for 6 days, has recently been approved for the treatment of patients with acute bacterial skin and skin structure infections (ABSSSIs) in several countries; however, clinical experience in real-life settings is currently limited. Here, we report on the use of tedizolid with an extended treatment duration for complex and severe ABSSSIs in real-world clinical settings.

Methods

Two patients with cellulitis and two patients with surgical site infection (SSI), aged 26–60 years, were treated with tedizolid phosphate 200 mg, intravenous/oral (IV/PO) or IV only, once daily at four different institutions.

Results

Two morbidly obese patients had non-necrotizing, non-purulent severe cellulitis, which were complicated by sepsis or systemic inflammatory response syndrome plus myositis. One female patient failed on first-line empiric therapy with IV cefalotin, clindamycin and imipenem (3–4 days), and was switched to IV/PO tedizolid (7 + 5 days). One male patient received IV clindamycin plus IV/PO tedizolid (5 + 5 days), but clindamycin was discontinued on Day 3 due to an adverse event. For both patients, clinical signs and symptoms improved within 72 h, and laboratory results were normalized by Days 7 and 8, respectively. Two other patients (one obese, diabetic female with chronic hepatitis and chronic obstructive pulmonary disease) had complicated SSIs occurring 10 days after hernia repair with mesh or 3 months after spinal fusion surgery with metal implant. First patient with previous methicillin-resistant Staphylococcus aureus (MRSA) bacteremia received a 7-day tedizolid IV course empirically. The second patient with culture-confirmed MRSA infection received a 14-day IV course. Both patients responded within 72 h, and local and systemic signs normalized by end of treatment. There were no reports of thrombocytopenia.

Conclusion

Tedizolid phosphate 200 mg for 7–14 days was a favored treatment option for patients with severe/complex ABSSSIs, and was effective following previous treatment failure or in late-onset infections.

Funding

Editorial assistance and the article processing charges were funded by Bayer AG, Berlin, Germany.

Pharmacokinetics of Tedizolid and Pseudoephedrine Administered Alone or in Combination in Healthy Volunteers

Therapeutic doses of tedizolid phosphate, an oxazolidinone antibiotic, lack monoamine oxidase inhibition in vivo, potentially resulting in an improved safety profile versus other oxazolidinones. This randomized, double-blind, placebo-controlled, 2-period, 2-sequence, crossover, phase 1 study (NCT01577459) assessed the potential for pharmacokinetic (PK) interactions between tedizolid and pseudoephedrine. Eighteen healthy volunteers (age: 18⁻45 years) were block-randomized to 1 of 2 treatment sequences containing 2 treatment periods (tedizolid phosphate or placebo once daily for 4 days; single dose of pseudoephedrine 60 mg on day 5) separated by a 2-day washout. Median time to maximum plasma concentration for tedizolid and pseudoephedrine ranged from 3 to 4 h, regardless of treatment coadministration. Steady-state tedizolid had no effect on the PK of pseudoephedrine; geometric mean ratio and 90% confidence interval remained within the no-effect 0.8 to 1.25 boundaries. The maximum observed concentration of tedizolid decreased by approximately 14% when pseudoephedrine was coadministered; no changes in the area under the plasma concentration-time curve or the minimum observed plasma concentration occurred. All adverse events (AEs) were mild, and there were no serious AEs or study drug discontinuations. No meaningful PK interactions occurred between tedizolid and pseudoephedrine, and tedizolid was well tolerated when administered in conjunction with pseudoephedrine.

Attitudes of physicians from 10 European countries on adherence and how treatment modalities in ABSSSI affect adherence: results from a Delphi survey

To explore the attitudes of European physicians on adherence and how treatment modalities impact adherence in complicated forms of soft skin and skin structure infections, now referred as acute bacterial skin and skin structures infections (ABSSSI). After literature review, a questionnaire was prepared. Topics focused on (1) the importance of adherence, (2) the importance of administration regimen on adherence, (3) the importance of drug selection on adherence, (4) the importance of complexity on choice of drug for treatment, (5) the role of adherence in drug resistance, and (6) the role of adherence in administration of long-acting antibiotics (ABs). The questionnaire was administered to 323 European infectious diseases specialists, of whom 74% responded. A modified Delphi method was used to obtain the highest consensus. Results varied by countries. We found a high degree of agreement of the importance of adherence in ABSSSI treatment. Experts agreed that complexity of patient’s conditions, drug selection, drug resistance, the type of regimen, and the number of infusions impact adherence. Two items linking oral switching and adherence did not reach consensus. Adherence for ABSSSI therapies appears a crucial factor for therapeutic management and reduces the risk of AB resistance. Among new treatment opportunities, long-acting agents, with their characteristics, may represent an interesting options.

Methicillin-resistant Staphylococcus aureus

Since the 1960s, methicillin-resistant Staphylococcus aureus (MRSA) has emerged, disseminated globally and become a leading cause of bacterial infections in both health-care and community settings. However, there is marked geographical variation in MRSA burden owing to several factors, including differences in local infection control practices and pathogen-specific characteristics of the circulating clones. Different MRSA clones have resulted from the independent acquisition of staphylococcal cassette chromosome mec (SCCmec), which contains genes encoding proteins that render the bacterium resistant to most β-lactam antibiotics (such as methicillin), by several S. aureus clones. The success of MRSA is a consequence of the extensive arsenal of virulence factors produced by S. aureus combined with β-lactam resistance and, for most clones, resistance to other antibiotic classes. Clinical manifestations of MRSA range from asymptomatic colonization of the nasal mucosa to mild skin and soft tissue infections to fulminant invasive disease with high mortality. Although treatment options for MRSA are limited, several new antimicrobials are under development. An understanding of colonization dynamics, routes of transmission, risk factors for progression to infection and conditions that promote the emergence of resistance will enable optimization of strategies to effectively control MRSA. Vaccine candidates are also under development and could become an effective prevention measure.

Management of drug-resistant tuberculosis in special sub-populations including those with HIV co-infection, pregnancy, diabetes, organ-specific dysfunction, and in the critically ill

Tuberculosis remains a major problem globally, and is the leading cause of death from an infectious agent. Drug-resistant tuberculosis threatens to marginalise the substantial gains that have recently been made in the fight against tuberculosis. Drug-resistant TB has significant associated morbidity and a high mortality, with only half of all multidrug-resistant TB patients achieving a successful treatment outcome. Patients with drug-resistant TB in resource-poor settings are now gaining access to newer and repurposed anti-tuberculosis drugs such as bedaquiline, delamanid and linezolid. However, with ever increasing rates of co-morbidity, there is little guidance on how to manage complex patients with drug-resistant TB. We address that knowledge gap, and outline principles underpinning the management of drug-resistant TB in special situations including HIV co-infection, pregnancy, renal disease, liver disease, diabetes, and in the critically ill.

Delafloxacin: Place in Therapy and Review of Microbiologic, Clinical and Pharmacologic Properties

Delafloxacin (formerly WQ-3034, ABT492, RX-3341) is a novel fluoroquinolone chemically distinct from currently marketed fluoroquinolones with the absence of a protonatable substituent conferring a weakly acidic character to the molecule. This property results in increased intracellular penetration and enhanced bactericidal activity under acidic conditions that characterize the infectious milieu at a number of sites. The enhanced potency and penetration in low pH environments contrast what has been observed for other zwitterionic fluoroquinolones, which tend to lose antibacterial potency under acidic conditions, and may be particularly advantageous against methicillin-resistant Staphylococcus aureus, for which the significance of the intracellular mode of survival is increasingly being recognized. Delafloxacin is also unique in its balanced target enzyme inhibition, a property that likely explains the very low frequencies of spontaneous mutations in vitro. Delafloxacin recently received US Food and Drug Administration approval for the treatment of acute bacterial skin and skin structure infections and is currently being evaluated in a phase 3 trial among patients with community-acquired pneumonia. In the current era of a heightened awareness pertaining to collateral ecologic damage, safety issues and antimicrobial stewardship principles, it is critical to describe the unique properties of delafloxacin and define its potential role in therapy. The purpose of this article is to review available data pertaining to delafloxacin’s biochemistry, pharmacokinetic/pharmacodynamics characteristics, in vitro activity and potential for resistance selection as well as current progress in clinical trials to ultimately assist clinicians in selecting patients who will benefit most from the distinctive properties of this agent.

In vitro activity of tedizolid and comparator agents against clinical Gram-positive isolates recovered from patients with cancer

A total of 248 Gram-positive isolates from cancer patients were tested for in-vitro susceptibility to tedizolid and 3 comparator agents using CLSI broth microdilution methodology. Tedizolid inhibited 97% of isolates at ≤0.5μg/ml. It was active against all Gram-positive species and consistently had 8 fold lower MICs than linezolid, although based on % susceptibility using CLSI breakpoints, most isolates were also susceptible to the comparators. Tedizolid was active against MRSA isolates with vancomycin MICs of ≥1.0μg/ml.

Efficacy and safety of linezolid compared with other treatments for skin and soft tissue infections: a meta-analysis

Linezolid with other treatments for skin and soft tissue infections (SSTIs) has been evaluated in several studies. However, the conclusions remain controversial. By searching PubMed, EMBASE, and Cochrane library databases, we conducted a meta-analysis to evaluate linezolid and other treatments for skin and soft tissue infections. The study was summarized, and the risk ratio (RR) and its 95% confidence interval (CI) were calculated. Eleven related articles were included in the meta-analysis. Our results revealed that linezolid was associated with a significantly better clinical (RR = 1.09, 95% CI: 1.02–1.16, P_{heterogeneity} = 0.326, I² = 13.0%) and microbiological cure rates (RR = 1.08, 95% CI: 1.01–1.16, P_{heterogeneity} = 0.089, I² = 41.7%) when comparing with vancomycin. There was no significant difference in the incidence of anemia, nausea, and mortality; however, the incidence of vomiting, diarrhea, and thrombocytopenia in patients treated with linezolid is significantly higher than that with other treatments. Our study confirmed that linezolid seems to be more effective than vancomycin for treating people with SSTIs. It is recommended that linezolid be monitored for thrombocytopenia, vomiting, and diarrhea. Further studies with larger dataset and well-designed models are required to validate our findings.

Tedizolid is highly bactericidal in the treatment of pulmonary Mycobacterium avium complex disease

Objectives

To determine if tedizolid is effective for pulmonary Mycobacterium avium complex (MAC) disease, and to use pharmacokinetics/pharmacodynamics to design optimal doses.

Methods

We performed an exposure-response experiment in the hollow-fibre system model of intracellular MAC (HFS-MAC). We mimicked the tedizolid concentration-time profiles achieved in the lungs of patients treated once daily for 28 days. The HFS-MAC was sampled at intervals to determine the tedizolid pharmacokinetics and MAC intracellular burden. We identified the 0-24 h area under the concentration-time curves to MIC (AUC0-24/MIC) ratios associated with the following targets: 80% of maximal kill (EC80), bacteriostasis, and 1.0 and 2.0 log10 cfu/mL kill. We then performed 10 000 patient Monte Carlo simulations to identify the optimal dose for each of the exposure targets.

Results

Tedizolid achieved the feat of 2.0 log10 cfu/mL kill below initial bacterial burden, an effect not seen before in this model with other antibiotics. The tedizolid exposure associated with 1.0 log10 cfu/mL kill was a non-protein bound AUC0-24/MIC ratio of 23.46, while that associated with 2.0 log10 cfu/mL kill was 37.50, and the EC80 was 21.71. The clinical dose of 200 mg achieved each of these targets in ∼100% of the 10 000 patients, except the 2.0 log10 cfu/mL kill which required 300 mg/day. A tedizolid susceptibility MIC breakpoint of 1 mg/L is proposed.

Conclusions

Tedizolid, at standard clinical doses, is expected to be bactericidal, and even achieved an unprecedented 2.0 log10 cfu/mL kill of MAC as monotherapy. We propose it as the backbone of short-course anti-MAC chemotherapy.

Are there any reasons to change our behavior in necrotizing fasciitis with the advent of new antibiotics?

PURPOSE OF REVIEW

The treatment of necrotizing fasciitis requires a multifaceted approach, consisting of surgical source control with immediate surgical debridement along with life support, clinical monitoring, and antimicrobial therapy. Many drugs are now available for the treatment of this life-threatening infectious disease, and the purpose of this review is to provide the reader with an updated overview of the newest therapeutic options.

RECENT FINDINGS

Because most necrotizing soft tissue infections are polymicrobial, broad-spectrum coverage is advisable. Acceptable monotherapy regimens include piperacillin-tazobactam or a carbapenem. However, drugs such as ceftolozane-tazobactam, ceftazidime-avibactam in association with an antianaerobic agent (metronidazole or clindamycin) are currently available as valuable alternatives. The new cephalosporins active against methicillin-resistant Staphylococcus aureus (MRSA), ceftaroline, and ceftobiprole share similar antibacterial activity against Gram-positive cocci, and they might be considered as an alternative to nonbetalactam anti-MRSA agents for necrotizing fasciitis management. Two new long-acting lypoglycopeptides - oritavancin and dalbavancin - share the indications for acute bacterial skin and skin structure infections and had similar activity against Gram-positive cocci including MRSA and streptococci.

SUMMARY

Carbapenem-sparing agents are particularly suitable for antimicrobial stewardship strategy. The new long-acting lypoglycopeptides are very effective in treating necrotizing fasciitis and are uttermost attractive for patients requiring short hospital stays and early discharge.

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.

Vancomycin-resistant enterococcus infection in the hematopoietic stem cell transplant recipient: an overview of epidemiology, management, and prevention

Vancomycin-resistant enterococcus (VRE) is now one of the leading causes of nosocomial infections in the United States. Hematopoietic stem cell transplantation (HSCT) recipients are at increased risk of VRE colonization and infection. VRE has emerged as a major cause of bacteremia in this population, raising important clinical questions regarding the role and impact of VRE colonization and infection in HSCT outcomes as well as the optimal means of prevention and treatment. We review here the published literature and scientific advances addressing these thorny issues and provide a rational framework for their approach.

Comparative Assessment of Tedizolid Pharmacokinetics and Tissue Penetration between Diabetic Patients with Wound Infections and Healthy Volunteers via In Vivo Microdialysis

Herein, we present pharmacokinetic and tissue penetration data for oral tedizolid in hospitalized patients with diabetic foot infections (DFI) compared with healthy volunteers. Participants received oral tedizolid phosphate 200 mg every 24 h for 3 doses to achieve steady state. A microdialysis catheter was inserted into the subcutaneous tissue near the margin of the wound for patients or into thigh tissue of volunteers. Following the third dose, 12 blood and 14 dialysate fluid samples were collected over 24 h to characterize tedizolid concentrations in plasma and interstitial extracellular fluid of soft tissue. Mean ± standard deviation (SD) tedizolid pharmacokinetic parameters in plasma for patients compared with volunteers, respectively, were as follows: maximum concentration (C_max), 1.5 ± 0.5 versus 2.7 ± 1.1 mg/liter (P = 0.005); time to C_max (T_max) (median [range]), 5.9 (1.2 to 8.0) versus 2.5 (2.0 to 3.0 h) (P = 0.003); half-life (t_1/2), 9.1 ± 3.6 versus 8.9 ± 2.2 h (P = 0.932); and plasma area under the concentration-time curve for the dosing interval (AUC _p ), 18.5 ± 9.7 versus 28.7 ± 9.6 mg · h/liter (P = 0.004). The tissue area under the concentration-time curve (AUC _t ) for the dosing interval was 3.4 ± 1.5 versus 5.2 ± 1.6 mg · h/liter (P = 0.075). Tissue penetration median (range) was 1.1 (0.3 to 1.6) versus 0.8 (0.7 to 1.0) (P = 0.351). Despite lower plasma C_max and delayed T_max values for patients with DFI relative to healthy volunteers, the penetration into and exposure to tissue were similar. Based on available pharmacodynamic thresholds for tedizolid, the plasma and tissue exposures using the oral 200 mg once-daily regimen are suitable for further study in treatment of DFI.

Thrombocytopenia with Tedizolid and Linezolid

Several studies have suggested the risk of thrombocytopenia with tedizolid, a second-in-class oxazolidinone antibiotic (approved June 2014), is less than that observed with linezolid (first-in-class oxazolidinone). Using data from the Food and Drug Administration adverse event reporting system (July 2014 through December 2016), we observed significantly increased risks of thrombocytopenia of similar magnitudes with both antibiotics: linezolid reporting odds ratio [ROR], 37.9 (95% confidence interval [CI], 20.78 to 69.17); tedizolid ROR, 34.0 (95% CI, 4.67 to 247.30).

Outpatient treatment of acute bacterial skin and skin structure infections (ABSSSI) with tedizolid phosphate and linezolid in patients in the United States: Subgroup analysis of 2 randomized phase 3 trials

BACKGROUND

Acute bacterial skin and skin structure infections (ABSSSI) are a frequent cause of hospital admissions in the United States. Safe and effective outpatient treatments may lower ABSSSI-associated health care costs by reducing unnecessary hospital admissions. Using data from 2 phase 3 trials (ESTABLISH-1, NCT01170221; ESTABLISH-2, NCT01421511), this post-hoc analysis explored the efficacy and safety of tedizolid in an outpatient setting.

METHODS

Subgroup analysis was performed on US outpatients (defined as patients who were not in hospital at the time of treatment initiation) with ABSSSI caused by presumed or proven gram-positive pathogens. Patients were randomly assigned to receive tedizolid phosphate 200 mg once daily for 6 days (n = 403) or linezolid 600 mg twice daily for 10 days (n = 410). The primary end point was early clinical response (48-72 hours after the start of treatment). Secondary end points included investigator-assessed clinical response at end of therapy (EOT) and post-therapy evaluation (PTE; 7-14 days after therapy). Additional assessments included the patient-reported level of pain using a visual analog scale (VAS) and the per-pathogen favorable microbiological response rate at the PTE visit. Compliance with treatment and safety outcomes was also recorded.

RESULTS

Early clinical response was similar between treatment groups (tedizolid, 82.4%; linezolid, 79.0%), as was investigator-assessed clinical response at EOT (tedizolid, 87.1%; linezolid, 86.1%) and PTE (tedizolid, 83.1%; linezolid, 83.7%). Mean changes from baseline to days 10 to 13 in VAS scores were identical between treatment groups (tedizolid, -51.9 mm; linezolid, -51.9 mm). Microbiological eradication rates were generally similar in both treatment groups for all key pathogens. Patients in both groups had favorable response at PTE. More tedizolid-treated patients (89.3%) than linezolid-treated patients (77.3%) were compliant with treatment. The most frequently reported drug-related treatment-emergent adverse events were nausea (tedizolid, 10.7%; linezolid, 13.8%), diarrhea (tedizolid, 4.5%; linezolid, 5.9%), and headache (tedizolid, 5.5%; linezolid, 4.4%). Treatment discontinuation rates were low for both treatment groups (tedizolid, 0.7%; linezolid, 1.0%).

CONCLUSION

Short-course therapy with tedizolid can successfully treat patients with ABSSSI caused by presumed or proven gram-positive pathogens in an outpatient setting.

Evaluating antibiotic therapies prescribed to adult patients in the emergency department

OBJECTIVES

The proper use of antibiotics is a public health priority to preserve their effectiveness. Little data is available on outpatient antibiotic prescriptions, especially in the emergency department. We aimed to assess the quality of outpatient antibiotic prescriptions in our hospital.

PATIENTS AND METHODS

Retrospective monocentric study of antibiotic prescriptions written to adult patients managed at the emergency department without hospitalization (November 15th, 2012-November 15th, 2013). Prescriptions were evaluated by an infectious disease specialist and an emergency physician on the basis of local recommendations compiled from national and international guidelines.

RESULTS

A total of 760 prescriptions were reviewed. The most frequent indications were urinary tract infections (n=263; 34.6%), cutaneous infections (n=198; 26.05%), respiratory tract infections (n=101; 13.28%), and ENT infections (n=62; 8.15%). The most frequently prescribed antibiotics were fluoroquinolones (n=314; 40.83%) and amoxicillin-clavulanic acid (n=245; 31.85%). Overall, 455 prescriptions (59.86%) did not comply with guidelines. The main reasons for inadequacy were the absence of an indication for antibiotic therapy (n=197; 40.7%), an inadequate spectrum of activity, i.e. too broad, (n=95; 19.62%), and excessive treatment duration (n=87; 17.97%). Rates of inadequate prescriptions were 82.26% for ENT infections, 71.2% for cutaneous infections, 46.53% for respiratory tract infections, and 38.4% for urinary tract infections.

CONCLUSION

Antibiotic prescriptions written to outpatients in the emergency department are often inadequate. Enhancing prescribers' training and handing out guidelines is therefore necessary. The quality of these prescriptions should then be re-assessed.

Linezolid-Associated Hypoglycemia

Our case describes a 77-year-old, African American male who was experiencing recurrent hypoglycemic episodes, which resulted in two emergency department (ED) visits and a subsequent inpatient admission during his second ED visit. He was prescribed linezolid 600 mg twice daily for 14 days for the treatment of a Staphylococcus hominis urinary tract infection. Nine and a half days into therapy, the patient began having recurrent hypoglycemic episodes. These episodes persisted despite repeated intravenous dextrose boluses. The patient’s linezolid was discontinued during the second day of his inpatient admission. After a brief lag period after the final linezolid administration, the patient’s blood glucose level stabilized within normal limits. He was later discharged home. The Naranjo scale scores the causality of this reaction between 4 and 8, indicating possible to probable causality. The patient had a follow-up appointment with his primary care physician 2 weeks after discharge, with no noted blood glucose complications. Two months after discharge, he entered hospice care for his advancing heart failure and later expired due to causes unrelated to blood glucose complications.

Determination of Tedizolid susceptibility interpretive criteria for gram-positive pathogens according to clinical and laboratory standards institute guidelines

For effective antibacterial therapy, physicians require qualitative test results using susceptibility breakpoints provided by clinical microbiology laboratories. This article summarizes the key components used to establish the Clinical Laboratory Standards Institute (CLSI) breakpoints for tedizolid. First, in vitro studies using recent surveillance and clinical trial isolates ascertained minimal inhibitory concentration (MIC) distributions against pertinent organisms, including staphylococci, streptococci, and enterococci. Studies in animal models of infection determined rates of antibacterial efficacy and survival following administration of tedizolid phosphate at doses equivalent to those in humans. Pharmacokinetic and pharmacodynamic analyses examined the relationship between plasma concentrations and MICs against the target organism. Finally, clinical trials assessed clinical and microbiologic outcomes by MIC. All these data were evaluated and combined to obtain the ratified CLSI susceptibility criteria for tedizolid of ≤0.5μg/mL for Staphylococcus aureus, Streptococcus pyogenes, Streptococcus agalactiae, and Enterococcus faecalis and ≤0.25μg/mL for Streptococcus anginosus group.