Antimicrobial agents for complicated skin and skin-structure infections: justification of noninferiority margins in the absence of placebo-controlled trials

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Target attainment of intravenous lefamulin for treatment of acute bacterial skin and skin structure infections

OBJECTIVES

Lefamulin is a pleuromutilin antibiotic approved for the treatment of community-acquired bacterial pneumonia (CABP). Its spectrum of activity, good penetration into soft tissues and low rates of cross-resistance also make lefamulin a potentially valuable option for treatment of acute bacterial skin and skin structure infections (ABSSSIs). A Phase 2 trial of lefamulin for ABSSSI indicated similar efficacy of 100 and 150 mg q12h IV dosing regimens. In the present study, the potential of lefamulin for this indication was further evaluated from a translational pharmacokinetic/pharmacodynamic perspective.

METHODS

PTA was determined for various dosages using Monte Carlo simulations of a population pharmacokinetic model of lefamulin in ABSSSI patients and preclinical exposure targets associated with bacteriostasis and a 1-log reduction in bacterial count. Overall target attainment against MSSA and MRSA was calculated using lefamulin MIC distributions.

RESULTS

Overall attainment of the bacteriostasis target was 94% against MSSA and 84% against MRSA for the IV dosage approved for CABP (150 mg q12h). Using the same target, for the 100 mg q12h regimen, overall target attainment dropped to 68% against MSSA and 50% against MRSA. Using the 1-log reduction target, overall target attainment for both regimens was <40%.

CONCLUSIONS

Lefamulin at the currently approved IV dosage covers most Staphylococcus aureus isolates when targeting drug exposure associated with bacteriostasis, suggesting potential of lefamulin for the treatment of ABSSSIs. Lefamulin may not be appropriate in ABSSSI when rapid bactericidal activity is warranted.

Cellulitis

Cellulitis is a common infection of the skin and subcutaneous tissue caused predominantly by gram-positive organisms. Risk factors include prior episodes of cellulitis, cutaneous lesions, tinea pedis, and chronic edema. Cellulitis is a clinical diagnosis and presents with localized skin erythema, edema, warmth, and tenderness. Uncomplicated cellulitis can be managed in the outpatient setting with oral antibiotics. Imaging often is not required but can be helpful. Recurrent cellulitis is common and predisposing conditions should be assessed for and treated at the time of initial diagnosis. For patients with frequent recurrences despite management of underlying conditions, antimicrobial prophylaxis can be effective.

Antibacterial activity of ruthenium polypyridyl complexes against Staphylococcus aureus and biofilms

There is clearly a need for the development of new classes of antimicrobials to fight against multidrug-resistant bacteria. Here, we designed and synthesized of three ruthenium polypyridyl complexes: [Ru(bpy)₂(BTPIP)](ClO₄)₂ (Ru(II)-1), [Ru(bpy)₂(ETPIP)](ClO₄)₂ (Ru(II)-2) and [Ru(bpy)₂(CAPIP)](ClO₄)₂ (Ru(II)-3) (N-N = bpy = 2,2'-bipyridine), their antimicrobial activities against S. aureus were assessed. The lead complexes of this set, Ru(II)-1(MIC = 0.016 mg/mL), was tested against biofilm. We also investigated whether bacteria can easily develop resistance to Ru(II)-1. The result demonstrated that S. aureus could not easily develop resistance to the ruthenium complexes. In addition, aimed to test whether ruthenium complexes treatment could increase the susceptibility of S. aureus to antibiotics, the synergism between Ru(II)-1 and common antibiotics against S. aureus were investigated using the checkerboard method. Interesting, Ru(II)-1 could increased the susceptibility of S. aureus to some aminoglycoside antibiotics(kanamycin and gentamicin). Finally, in vivo bacterial infection treatment studies were also conducted through murine skin infection model. These results confirmed ruthenium complexes have good antimicrobial activity in vitro and in vivo.

Shortening antibiotic duration in the treatment of acute cholangitis: rationale and study protocol for an open-label randomized controlled trial

BACKGROUND

Antimicrobial therapy with appropriate biliary drainage is considered the standard of care for acute cholangitis, but the optimal duration of antimicrobial therapy remains unknown. Seven to 10 days of antimicrobial therapy are common for the treatment of acute cholangitis, but a recent retrospective cohort study suggested a shorter duration might be effective. A shorter duration of antimicrobial therapy can be beneficial in decreasing the length of hospital stay, improving patients' quality of life, decreasing adverse effects, and even contributing to a decrease in the occurrence of antimicrobial resistance.

METHODS/DESIGN

We will conduct a multi-centre, open-label, randomized, non-inferiority trial to compare short-course therapy (SCT) with conventional long-course therapy (LCT) in treating patients with acute cholangitis. SCT consists of 5-day intravenous antimicrobial therapy if the patients had clinical improvement, while at least 7 days of intravenous antibiotics will be provided to the LCT group. The primary outcome is clinical cure at 30 days after onset. Patients will be randomly assigned in an open-label fashion. A total sample size of 150 was estimated to provide a power of 80% with a one-sided α level of 2.5% and a non-inferiority margin of 10%.

DISCUSSION

This trial is expected to reveal whether SCT is non-inferior to conventional LCT or not, and may provide evidence that one can shorten the treatment duration for acute cholangitis for the benefit of patients.

TRIAL REGISTRATION

University Hospital Medical Information Network, UMIN000028382. Registered on 30 August 2017.

Treatment of Necrotizing Soft Tissue Infections: Antibiotics

Necrotizing soft tissue infections (NSTIs) are severe, life-threatening infections, and early therapeutic intervention is essential. Prompt administration of potent antimicrobial agents is pivotal, but inadequate empirical therapy is unfortunately common. Optimization of the antibiotic treatment strategy in NSTIs requires consideration of local epidemiology of causative pathogens and antimicrobial resistance patterns, knowledge on common pathogenetic mechanisms in NSTIs, and adaptations to pharmacokinetic and pharmacodynamic physiological changes in critically ill patients. In the present article we address all these issues, as well as review and compare contemporary guidelines for antimicrobial treatment of NSTIs from around the world.

A look at clinical trial design for new antimicrobials for the adult population

Introduction: Antimicrobial resistance poses a substantial threat to global public health since it decreases the probability of effectively treating an infection and increases the risk of morbidity and mortality.Areas covered: In this review, the authors discuss the advantages and disadvantages of classical and novel trial designs for evaluating novel antibiotics for infections due to multidrug-resistant organisms (MDRO). An inductive literature search was performed using different keywords pertinent to the reviewed topics.Expert opinion: The need for active, effective compounds has strengthened regulatory, academic, and industry cooperation, leading to the recent approval of some novel anti-MDRO agents, with other promising compounds being also in the late phase of clinical development. Nonetheless, some important issues regarding the design of clinical trials have gained importance that are peculiar for novel anti-MDRO agents and should be addressed for continuing to guarantee the availability of effective treatments in the future. Very importantly, concerted cooperation with regulatory agencies will always be needed for continuously discussing and refining the acceptable level of evidence to be pursued through non-conventional and/or innovative trial designs or development strategies. Failure to do so would seriously pose the risk of perpetuating the unmet need for effective anti-MDRO agents.

Continuous cefazolin infusion versus cefazolin plus probenecid for the ambulatory treatment of uncomplicated cellulitis: A retrospective cohort study

BACKGROUND

The preferred ambulatory IV therapy for cellulitis is often once-daily cefazolin combined with once-daily oral probenecid (C+P). However, due to a national probenecid drug shortage in 2011, our centre developed a replacement protocol for the administration of cefazolin continuous infusion (CCI) using elastomeric infusers. Our goal was to compare treatment efficacy, duration of IV therapy, and recurrence associated with CCI and C+P using retrospective data from our centre.

METHODS

We conducted a non-inferiority single-centre retrospective cohort study of emergency department medical records. Patients received either C+P (cefazolin 2 g IV once daily plus probenecid 1 g PO once daily) or CCI (cefazolin 2 g IV loading dose, followed by cefazolin 6 g IV via continuous infusion over 24 hours, via an elastomeric infuser). We compared treatment efficacy, duration of IV therapy, and recurrence rates.

RESULTS

 total of 203 patients were analyzed, with 107 included in the CCI arm and 96 in the C+P arm. Overall, CCI users and C+P users were comparable in their sociodemographic and clinical variables measured at admission. We observed increased odds of achieving successful treatment among the CCI group, however it did not reach statistical significance (odds ratio [OR] 2.25; 95% CI 0.84 to 6.07). Recurrence rates were similar between both groups (OR 1.91; 95% CI 0.32 to 11.31). The average duration of IV therapy was similar between groups (p = 0.6).

CONCLUSIONS

ith results suggesting that CCI was non-inferior to C+P, and that both approaches required similar treatment durations, CCI could represent an acceptable alternative to C+P for the ambulatory IV treatment of cellulitis.

The Penicillin for the Emergency Department Outpatient treatment of CELLulitis (PEDOCELL) trial: update to the study protocol and detailed statistical analysis plan (SAP)

Background

Cellulitis is a painful, potentially serious, infectious process of the dermal and subdermal tissues and represents a significant disease burden. The statistical analysis plan (SAP) for the Penicillin for the Emergency Department Outpatient treatment of CELLulitis (PEDOCELL) trial is described here. The PEDOCELL trial is a multicentre, randomised, parallel-arm, double-blinded, non-inferiority clinical trial comparing the efficacy of flucloxacillin (monotherapy) with combination flucloxacillin/phenoxymethylpenicillin (dual therapy) for the outpatient treatment of cellulitis in the emergency department (ED) setting. To prevent outcome reporting bias, selective reporting and data-driven results, the a priori-defined, detailed SAP is presented here.

Methods/design

Patients will be randomised to either orally administered flucloxacillin 500 mg four times daily and placebo or orally administered 500 mg of flucloxacillin four times daily and phenoxymethylpenicillin 500 mg four times daily. The trial consists of a 7-day intervention period and a 2-week follow-up period. Study measurements will be taken at four specific time points: at patient enrolment, day 2–3 after enrolment and commencing treatment (early clinical response (ECR) visit), day 8–10 after enrolment (end-of-treatment (EOT) visit) and day 14–21 after enrolment (test-of-cure (TOC) visit). The primary outcome measure is investigator-determined clinical response measured at the TOC visit. The secondary outcomes are as follows: lesion size at ECR, clinical treatment failure at each follow-up visit, adherence and persistence of trial patients with orally administered antibiotic therapy at EOT, health-related quality of life (HRQoL) and pharmacoeconomic assessments. The plan for the presentation and comparison of baseline characteristics and outcomes is described in this paper.

Discussion

This trial aims to establish the non-inferiority of orally administered flucloxacillin monotherapy with orally administered flucloxacillin/phenoxymethylpenicillin dual therapy for the ED-directed outpatient treatment of cellulitis. In doing so, this trial will bridge a knowledge gap in this understudied and common condition and will be relevant to clinicians across several different disciplines. The SAP for the PEDOCELL trial was developed a priori in order to minimise analysis bias.

Trial registration

EU Clinical Trials Register (EudraCT number: 2016-001528-69). Registered on 5 April 2016.

ClinicalTrials.gov, ID: NCT02922686. Registered on 9 August 2016.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-2121-2) contains supplementary material, which is available to authorized users.

Aetiology and clinical features of facial cellulitis: a prospective study

BACKGROUND

In the early 20th century, the face was the predominant site of cellulitis. Despite a relative decrease in the incidence of facial cellulitis, it is still common. There are few studies on this condition during the last decades. The aim of this study was to describe contemporary aetiological and clinical characteristics of patients admitted to hospital with non-suppurative facial cellulitis.

METHODS

Patients were included prospectively. Clinical details, comorbidities and biochemistry results were recorded. Investigations included cultures of skin swab and blood and tests for streptococcal antibodies during the acute and convalescent stages.

RESULTS

Sixty-five patients were included. Serology, cultures and response to penicillin monotherapy identified probable or confirmed β-haemolytic streptococci (BHS) aetiology in 75% (49/65) of cases. Significant comorbidities were present in 54% (35/65). Fever, chills or rigors before or at admission was noted in 91% (59/65). Patients presented most often with sharply demarcated erythema and raised borders (54/64). Penicillin or penicillinase-resistant penicillin alone or in combination cured 68% (44/65) of the patients. Supplementary clindamycin was used in 28% (18/65), most often only for 1-3 days. Only four patients needed a second course of antibiotics. Clinical failure was more often seen in patients with non-BHS aetiology (p = .037). Few complications were noted; 14.5% (9/62) experienced transient diarrhoea, and only one had confirmed Clostridium difficile infection. No patients developed cerebral venous sinus thrombosis, and there were no fatalities.

CONCLUSIONS

Our findings indicate that BHS are the leading cause of facial cellulitis. Most patients exhibit sharply demarcated lesions and systemic symptoms. Narrow-spectrum β-lactam antibiotics and short hospital stay appear sufficient. Few complications and low recurrence rates were seen.

Effect of Cephalexin Plus Trimethoprim-Sulfamethoxazole vs Cephalexin Alone on Clinical Cure of Uncomplicated Cellulitis: A Randomized Clinical Trial

IMPORTANCE

Emergency department visits for skin infections in the United States have increased with the emergence of methicillin-resistant Staphylococcus aureus (MRSA). For cellulitis without purulent drainage, β-hemolytic streptococci are presumed to be the predominant pathogens. It is unknown if antimicrobial regimens possessing in vitro MRSA activity provide improved outcomes compared with treatments lacking MRSA activity.

OBJECTIVE

To determine whether cephalexin plus trimethoprim-sulfamethoxazole yields a higher clinical cure rate of uncomplicated cellulitis than cephalexin alone.

DESIGN, SETTING, AND PARTICIPANTS

Multicenter, double-blind, randomized superiority trial in 5 US emergency departments among outpatients older than 12 years with cellulitis and no wound, purulent drainage, or abscess enrolled from April 2009 through June 2012. All participants had soft tissue ultrasound performed at the time of enrollment to exclude abscess. Final follow-up was August 2012.

INTERVENTIONS

Cephalexin, 500 mg 4 times daily, plus trimethoprim-sulfamethoxazole, 320 mg/1600 mg twice daily, for 7 days (n = 248 participants) or cephalexin plus placebo for 7 days (n = 248 participants).

MAIN OUTCOMES AND MEASURES

The primary outcome determined a priori in the per-protocol group was clinical cure, defined as absence of these clinical failure criteria at follow-up visits: fever; increase in erythema (>25%), swelling, or tenderness (days 3-4); no decrease in erythema, swelling, or tenderness (days 8-10); and more than minimal erythema, swelling, or tenderness (days 14-21). A clinically significant difference was defined as greater than 10%.

RESULTS

Among 500 randomized participants, 496 (99%) were included in the modified intention-to-treat analysis and 411 (82.2%) in the per-protocol analysis (median age, 40 years [range, 15-78 years]; 58.4% male; 10.9% had diabetes). Median length and width of erythema were 13.0 cm and 10.0 cm. In the per-protocol population, clinical cure occurred in 182 (83.5%) of 218 participants in the cephalexin plus trimethoprim-sulfamethoxazole group vs 165 (85.5%) of 193 in the cephalexin group (difference, -2.0%; 95% CI, -9.7% to 5.7%; P = .50). In the modified intention-to-treat population, clinical cure occurred in 189 (76.2%) of 248 participants in the cephalexin plus trimethoprim-sulfamethoxazole group vs 171 (69.0%) of 248 in the cephalexin group (difference, 7.3%; 95% CI, -1.0% to 15.5%; P = .07). Between-group adverse event rates and secondary outcomes through 7 to 9 weeks, including overnight hospitalization, recurrent skin infections, and similar infection in household contacts, did not differ significantly.

CONCLUSIONS AND RELEVANCE

Among patients with uncomplicated cellulitis, the use of cephalexin plus trimethoprim-sulfamethoxazole compared to cephalexin alone did not result in higher rates of clinical resolution of cellulitis in the per-protocol analysis. However, because imprecision around the findings in the modified intention-to-treat analysis included a clinically important difference favoring cephalexin plus trimethoprim-sulfamethoxazole, further research may be needed.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00729937.

Early Response in Cellulitis: A Prospective Study of Dynamics and Predictors

In this prospective study of cellulitis, several nonpharmacological factors were associated with lack of early response. Such early nonresponse was rarely related to inappropriate therapy but strongly predictive of early treatment escalation, suggesting that broadening antibiotic treatment often may be premature.

Background. Skin and soft tissue infections are common reasons for medical care. Use of broad-spectrum therapy and costs have increased. Assessment of early treatment response has been given a central role both in clinical trials and everyday practice. However, there is a paucity of data on the dynamics of response, causes of early nonresponse, and how early nonresponse affects resource use and predicts outcome.

Methods. We prospectively enrolled 216 patients hospitalized with cellulitis. Clinical and biochemical response data during the first 3 days of treatment were analyzed in relation to baseline factors, antibiotic use, surgery, and outcome. Multivariable analysis included logistic lasso regression.

Results. Clinical or biochemical response was observed in the majority of patients the day after treatment initiation. Concordance between clinical and biochemical response was strongest at days 2 and 3. Female sex, cardiovascular disease, higher body mass index, shorter duration of symptoms, and cellulitis other than typical erysipelas were predictors of nonresponse at day 3. In contrast, baseline factors were not predictive of clinical failure assessed posttreatment. Among cases with antibiotic treatment escalation by day 2, 90% (37/41) had nonresponse at day 1, but only 5% (2/40) had inappropriate initial therapy. Nonresponse at day 3 was a predictor of treatment duration >14 days, but not of clinical failure.

Conclusions. Nonpharmacological factors had a major impact on early response dynamics. Delayed response was rarely related to inappropriate therapy but strongly predictive of early treatment escalation, suggesting that broadening antibiotic treatment may often be premature.

Failure of antibiotics in cellulitis trials: a systematic review and meta-analysis

OBJECTIVES

The objectives of the study are to quantify trial-to-trial variability in antibiotic failure rates, in randomized clinical trials of cellulitis treatment and to provide a point estimate for the treatment failure rate across trials.

METHODS

We conducted a structured search for clinical trials evaluating antibiotic treatment of cellulitis, indexed in PubMed by August 2015. We included studies published in English and excluded studies conducted wholly outside of developed countries because the pathophysiology of cellulitis is likely to be different in such settings. Two authors reviewed all abstracts identified for possible inclusion. Of studies identified initially, 5% met the selection criteria. Two reviewers extracted data independently, and data were pooled using the Freeman-Tukey transformation under a random-effects model. Our primary outcome was the summary estimate of treatment failure across intent-to-treat and clinically evaluable participants.

RESULTS

We included 19 articles reporting data from 20 studies, for a total of 3935 patients. Treatment failure was reported in 6% to 37% of participants in the 9 trials reporting intent-to-treat results, with a summary point estimate of 18% failing treatment (95% confidence interval, 15%-21%). In the 15 articles evaluating clinically evaluable participants, treatment failure rates ranged from 3% to 42%, and overall, 12% (95% confidence interval, 10%-14%) were designated treatment failures.

CONCLUSIONS

Treatment failure rates vary widely across cellulitis trials, from 6% to 37%. This may be due to confusion of cellulitis with its mimics and perhaps problems with construct validity of the diagnosis of cellulitis. Such factors bias trials toward equivalence and, in routine clinical care, impair quality and antibiotic stewardship. Objective diagnostic tools are needed.

Noninferior Antibiotics: When Is "Not Bad" "Good Enough"?

Novel treatment options are urgently needed for patients with serious multidrug-resistant infections seen increasingly in routine everyday clinical practice, both in the hospital and nursing home as well as in the clinic and office setting. Unfortunately, the problem is no longer confined to chronically ill, repeatedly hospitalized patients. This essay explores the role of noninferiorly studies in addressing the pressing need for new antimicrobial agents to combat the emerging “superbugs”, calling attention to the nuances of interpreting their sometimes less-than-straightforward results. The overriding aim is not to find better antibiotics for routinely treatable infections but to identify safe and efficacious treatment options where none presently exist.

Beyond Antibiotics: New Therapeutic Approaches for Bacterial Infections

The utility of conventional antibiotics for the treatment of bacterial infections has become increasingly strained due to increased rates of resistance coupled with reduced rates of development of new agents. As a result, multidrug-resistant, extensively drug-resistant, and pandrug-resistant bacterial strains are now frequently encountered. This has led to fears of a "postantibiotic era" in which many bacterial infections will be untreatable. Alternative nonantibiotic treatment strategies need to be explored to ensure that a robust pipeline of effective therapies is available to clinicians. In this review, we highlight some of the recent developments in this area, such as the targeting of bacterial virulence factors, utilization of bacteriophages to kill bacteria, and manipulation of the microbiome to combat infections.

Ertapenem versus piperacillin/tazobactam for diabetic foot infections in China: a Phase 3, multicentre, randomized, double-blind, active-controlled, non-inferiority trial

OBJECTIVES

Few randomized controlled studies have compared antibiotic regimens against diabetic foot infections (DFIs) in Chinese patients. We evaluated the efficacy and safety of ertapenem versus piperacillin/tazobactam for the treatment of DFIs in Chinese patients.

METHODS

Patients with moderate to severe DFIs requiring parenteral antibiotics were randomized in a 1 : 1 ratio to receive ertapenem (1.0 g once daily) or piperacillin/tazobactam (4.5 g every 8 h) by 30 min intravenous (iv) infusions for ≥5 days. The primary outcome was favourable clinical response at discontinuation of iv therapy (DCIV). An evaluable-patient population was identified for primary analysis of non-inferiority at -15%. Safety was assessed. ClinicalTrials.gov: NCT01370616.

RESULTS

Of 565 patients randomized, 443 patients (ertapenem = 219 and piperacillin/tazobactam = 224) were clinically evaluable for primary analysis. In the clinically evaluable population, the proportions of patients with favourable clinical response at DCIV were 93.6% (205/219) and 97.3% (218/224) in the ertapenem and piperacillin/tazobactam groups, respectively (difference: -3.8%, 95% CI: -8.3%, 0.0%). Ertapenem had a significantly lower favourable clinical response rate (91.5% versus 97.2%, 95% CI for difference: -12.1%, -0.3%) at DCIV in severe DFI patients. In the modified ITT population, 88.8% (237/267) and 90.6% (241/266) of patients in the ertapenem and piperacillin/tazobactam groups, respectively, had favourable clinical responses at DCIV (difference: -1.9%, 95% CI: -7.3%, 3.3%). Microbiological eradications of causative pathogens and adverse events were similar between treatment groups.

CONCLUSIONS

Treatment with ertapenem was non-inferior to piperacillin/tazobactam in Chinese patients with DFIs. Ertapenem treatment resulted in a markedly lower rate of clinical resolution in severe DFIs.

Systematic Review and Meta-Analysis To Estimate Antibacterial Treatment Effect in Acute Bacterial Skin and Skin Structure Infection

A systematic literature review and meta-analysis were conducted to estimate the antibacterial treatment effect for linezolid and ceftaroline to inform on the design of acute bacterial skin and skin structure infection (ABSSSI) noninferiority trials. The primary endpoints included an early clinical treatment response (ECTR) defined as cessation of lesion spread at 48 to 72 h postrandomization and the test-of-cure (TOC) response defined as total resolution of the infection at 7 to 14 days posttreatment. The systematic review identified no placebo-controlled trials in ABSSSI, 4 placebo-controlled trials in uncomplicated skin and soft tissue infection as a proxy for placebo in ABSSSI, 12 linezolid trials in ABSSSI, 3 ceftaroline trials in ABSSSI, and 2 trials for nonantibacterial treatment. The ECTR rates at 48 to 72 h and corresponding 95% confidence intervals (CI) were 78.7% (95% CI, 61.1 to 96.3%) for linezolid, 74.0% (95% CI, 69.7 to 78.3%) for ceftaroline, and 59.0% (95% CI, 52.8 to 65.3%) for nonantibacterial treatment. The early clinical treatment effect could not be estimated, given no available placebo or proxy for placebo data for this endpoint. Clinical, methodological, and statistical heterogeneity influenced the selection of trials for the meta-analysis of the TOC treatment effect estimation. The pooled estimates of the TOC treatment response were 31.0% (95% CI, 6.2 to 55.9%) for the proxy for placebo, 88.1% (95% CI, 81.0 to 95.1%) for linezolid, and 86.1% (95% CI, 83.7 to 88.6%) for ceftaroline. The TOC clinical treatment effect estimation was 25.1% for linezolid and 27.8% for ceftaroline. The antibacterial treatment effect estimation at TOC will inform on the design and analysis of future noninferiority ABSSSI clinical trials.

The large scale antibacterial, antifungal and anti-phage efficiency of Petamcin-A: new multicomponent preparation for skin diseases treatment

BACKGROUND

Human and animal skin diseases of bacterial, fungal and viral nature and their complications are widespread and globally cause a serious trouble. Their prevalence is increasing mainly due to drug resistance. Consequently, demand has increased for new effective antimicrobial drugs, which also should be less toxic, possess a wider spectrum of action and be economically more beneficial. The goal was to investigate antibacterial, antifungal and anti-phage activity of Petamcin-A-a new multicomponent preparation. It contains acetic acid and hexamethylenetetramine as main active antimicrobial components, as well as phosphatidylcholine, tocopheryl acetate and glycerol as excipients.

METHODS

Bacteriostatic activity and minimal inhibitory concentrations of the preparation against various test-organisms were determined by agar well diffusion assay. Antifungal activity was tested by agar dilution assay. To explore anti-phage activity double agar overlay plaque assay was used. Nystatin, chlorhexidine and acetic acid were used as control agents for comparative analysis. Statistical analysis was done with GraphPad Prism 5.03 or R 3.1.0 software.

RESULTS

The results showed a higher activity of Petamcin-A against all bacterial and fungal test strains compared with its components or control agents. The preparation was more effective against tested gram-positive bacteria than gram-negative ones. Petamcin-A expressed bactericidal activity against almost all test strains. In addition, the preparation demonstrated high activity against T4 phage of Escherichia coli C-T4 completely inhibiting its growth. 5-fold diluted Petamcin-A also exhibited considerable activity reducing phage concentration by 2.6 Log10.

CONCLUSIONS

Petamcin-A has a high antimicrobial activity against all tested strains of bacteria, yeasts and moulds. The preparation also exhibited high anti-phage activity. Moreover, taking into account that Petamcin-A has no observable toxicity on skin and its components are not expensive, it can be advantageous for management of various skin medical conditions.

Some current issues in the design of HIV noninferiority trials

Since the introduction of protease inhibitors and their combination with two nucleoside reverse transcriptase inhibitors in tri-therapy, there has been a continuous improvement in the efficacy of antiretroviral treatments. Such combinations have been rendered even more effective by the introduction of non-nucleoside reverse transcriptase inhibitors and, more recently, integrase inhibitors. This progress has led to a move away from superiority designs towards noninferiority designs for randomized clinical trials for HIV. Noninferiority trials aim to demonstrate that a new regimen is no worse than the current standard. The methodological issues associated with such designs have been discussed, but recent HIV trials provide us with an opportunity to consider the choice of hypotheses. Recent HIV trials have been overpowered, due to the assumption of lower success rates than observed and the enrollment of a large number of patients. The use of stratified statistical methods for primary endpoint analysis, with sample size calculated by classical methods (without stratification), also increases the statistical power. Some HIV trials have a statistical power close to 99%. Surprisingly, the results of some previous studies or phase II trials are not taken into account when designing the corresponding phase III trials. We discuss alternative hypotheses and designs.

Garenoxacin in Skin and Skin Structure Infections Sustained due to Road Traffic Accident

Skin and soft tissue infections represent a continuum of symptoms that range from uncomplicated cellulitis to the potentially lethal entity necrotizing fasciitis that is often considered to be microbial invasions of the epidermis, dermis and subcutaneous tissues. Garenoxacin, a newer oral des-fluoroquinolone having potent antimicrobial activity against wide variety of common pathogens involved in skin and skin structure infections (SSTIs), including the resistant strains offer the advantage of broad spectrum of coverage including gram positive, gram negative and anaerobic organisms. This case study indicates the utility of garenoxacin in treating skin and soft tissue infections caused by road traffic accidents.

FDA guidance for ABSSSI trials: implications for conducting and interpreting clinical trials

Recent guidance from the US Food and Drug Administration (FDA) on the conduct of clinical trials for acute bacterial skin and skin structure infection (ABSSSI) has changed the framework for clinical trial design and conduct. Notable changes included new disease state definitions, new primary endpoint definitions and the timing of assessments at these endpoints, and updated guidance on patient inclusion/exclusion criteria. Supportive evidence and statistical justification for the proposed noninferiority margins were described in detail. Although the updated guidelines are still considered drafts and have been adopted in some trials, they serve as the basis for study protocol discussions between pharmaceutical companies and the FDA in advancing the development of promising new agents. Not only will the new trial designs impact researchers and sponsors responsible for drug development programs, but they will also affect healthcare providers participating in clinical trials and the ways in which clinicians develop patient treatment plans based on the results of those trials. This review provides a summary of key changes that will impact future clinical trial design and outcomes.

Single-dose oritavancin in the treatment of acute bacterial skin infections

BACKGROUND

Oritavancin is a lipoglycopeptide with bactericidal activity against gram-positive bacteria. Its concentration-dependent activity and prolonged half-life allow for single-dose treatment.

METHODS

We conducted a randomized, double-blind trial in which adults with acute bacterial skin and skin-structure infections received either a single intravenous dose of 1200 mg of oritavancin or a regimen of intravenous vancomycin twice daily for 7 to 10 days. Three efficacy end points were tested for noninferiority. The primary composite end point was defined as cessation of spreading or reduction in lesion size, absence of fever, and no need for administration of a rescue antibiotic 48 to 72 hours after administration of oritavancin. Secondary end points were clinical cure 7 to 14 days after the end of treatment, as determined by a study investigator, and a reduction in lesion size of 20% or more 48 to 72 hours after administration of oritavancin.

RESULTS

The modified intention-to-treat population comprised 475 patients who received oritavancin and 479 patients who received vancomycin. All three efficacy end points met the prespecified noninferiority margin of 10 percentage points for oritavancin versus vancomycin: primary end point, 82.3% versus 78.9% (95% confidence interval [CI] for the difference, -1.6 to 8.4 percentage points); investigator-assessed clinical cure, 79.6% versus 80.0% (95% CI for the difference, -5.5 to 4.7 percentage points); and proportion of patients with a reduction in lesion area of 20% or more, 86.9% versus 82.9% (95% CI for the difference, -0.5 to 8.6 percentage points). Efficacy outcomes measured according to type of pathogen, including methicillin-resistant Staphylococcus aureus, were similar in the two treatment groups. The overall frequency of adverse events was also similar, although nausea was more common among those treated with oritavancin.

CONCLUSIONS

A single dose of oritavancin was noninferior to twice-daily vancomycin administered for 7 to 10 days for the treatment of acute bacterial skin and skin-structure infections caused by gram-positive pathogens. (Funded by the Medicines Company; SOLO I ClinicalTrials.gov number, NCT01252719.).

Phase 3 study comparing tigecycline and ertapenem in patients with diabetic foot infections with and without osteomyelitis

A phase 3, randomized, double-blind trial was conducted in subjects with diabetic foot infections without osteomyelitis (primary study) or with osteomyelitis (substudy) to determine the efficacy and safety of parenteral (intravenous [iv]) tigecycline (150 mg once-daily) versus 1 g once-daily iv ertapenem ± vancomycin. Among 944 subjects in the primary study who received ≥1 dose of study drug, >85% had type 2 diabetes; ~90% had Perfusion, Extent, Depth/tissue loss, Infection, and Sensation infection grade 2 or 3; and ~20% reported prior antibiotic failure. For the clinically evaluable population at test-of-cure, 77.5% of tigecycline- and 82.5% of ertapenem ± vancomycin-treated subjects were cured. Corresponding rates for the clinical modified intent-to-treat population were 71.4% and 77.9%, respectively. Clinical cure rates in the substudy were low (<36%) for a subset of tigecycline-treated subjects with osteomyelitis. Nausea and vomiting occurred significantly more often after tigecycline treatment (P = 0.003 and P < 0.001, respectively), resulting in significantly higher discontinuation rates in the primary study (nausea P = 0.007, vomiting P < 0.001). In the primary study, tigecycline did not meet criteria for noninferiority compared with ertapenem ± vancomycin in the treatment of subjects with diabetic foot infections.

A randomized trial of tigecycline versus ampicillin-sulbactam or amoxicillin-clavulanate for the treatment of complicated skin and skin structure infections

BACKGROUND

Complicated skin and skin structure infections (cSSSIs) frequently result in hospitalization with significant morbidity and mortality.

METHODS

In this phase 3b/4 parallel, randomized, open-label, comparative study, 531 subjects with cSSSI received tigecycline (100 mg initial dose, then 50 mg intravenously every 12 hrs) or ampicillin-sulbactam 1.5-3 g IV every 6 hrs or amoxicillin-clavulanate 1.2 g IV every 6-8 hrs. Vancomycin could be added at the discretion of the investigator to the comparator arm if methicillin-resistant Staphylococcus aureus (MRSA) was confirmed or suspected within 72 hrs of enrollment. The primary endpoint was clinical response in the clinically evaluable (CE) population at the test-of-cure (TOC) visit. Microbiologic response and safety were also assessed. The modified intent-to-treat (mITT) population comprised 531 subjects (tigecycline, n = 268; comparator, n = 263) and 405 were clinically evaluable (tigecycline, n = 209; comparator, n = 196).

RESULTS

In the CE population, 162/209 (77.5%) tigecycline-treated subjects and 152/196 (77.6%) comparator-treated subjects were clinically cured (difference 0.0; 95% confidence interval [CI]: -8.7, 8.6). The eradication rates at the subject level for the microbiologically evaluable (ME) population were 79.2% in the tigecycline treatment group and 76.8% in the comparator treatment group (difference 2.4; 95% CI: -9.6, 14.4) at the TOC assessment. Nausea, vomiting, and diarrhea rates were higher in the tigecycline group.

CONCLUSIONS

Tigecycline was generally safe and effective in the treatment of cSSSIs.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00368537.

Paradoxical interpretations of noninferiority studies: violating the excluded middle

Background: The noninferiority of a novel therapy compared with a standard of care is customarily defined by a noninferiority margin derived from an assessment of what would constitute a clinically relevant decrement in efficacy while preserving some of the treatment effect over placebo. Conundrum: If the one-sided 97.5% CI around the difference in the point estimates of efficacy between the two treatments (investigational drug minus comparator drug) does not extend below the prespecified threshold, noninferiority of the new agent to the comparator is typically concluded. In some cases, the corresponding two-sided 95% CI will fall entirely between zero and the noninferiority delta, technically implying inferiority and noninferiority concurrently. Solution: Stipulating that the upper bound of the two-sided confidence interval reach or exceed zero (as well as fall entirely above the noninferiority limit) to establish statistical noninferiority versus the comparator would avoid paradoxical interpretations.

Staphylococcus aureus bacteraemia at Alice Springs Hospital, Central Australia, 2003-2006

BACKGROUND

Infectious diseases remain the leading cause of death at Alice Springs Hospital (ASH) and Staphylococcus aureus bacteraemia (SAB) is the second most common bloodstream infection. Non-multidrug-resistant, methicillin-resistant S. aureus (nmMRSA) is endemic to the region.

AIMS

To determine whether differences exist between racial groups and resistance phenotypes in the clinical manifestations and outcomes of SAB at ASH.

METHODS

A retrospective review of medical and pathology records for inpatients with SAB between 1 January 2003 and 31 December 2006.

RESULTS

A total of 125 patients (indigenous, 111; non-indigenous, 14) presented with SAB during the study period. Among indigenous patients, there were 95 adults and 16 children. No non-indigenous child was admitted with SAB. The mean annual incidence rate was 160.7/100 000 indigenous population and 8.1/100 000 non-indigenous population (incidence rate ratio 19.9) (P = 0.010). Isolates were predominantly methicillin-susceptible S. aureus (indigenous, 85; non-indigenous, 13). Twenty of 27 MRSA isolates were non-multidrug-resistant. Indigenous adults were more likely to present with an infective focus (indigenous, 75; non-indigenous, 6) (P = 0.004). These were most often skin infections (skin abscesses, 31; scabies, 4). Twenty-seven indigenous adults self-discharged after receiving a median of only 5 days (inter-quartile range (IQR), 3-9) of antibiotic therapy. Ninety-day mortality rates for indigenous and non-indigenous adults were 14.7% and 14.3% respectively. The median age of death for indigenous adults was 50 years (IQR, 37-68).

CONCLUSIONS

Indigenous Australians have the highest reported incidence rate of SAB worldwide. This reflects the socioeconomic disadvantage experienced by indigenous Australians whose living conditions predispose to pathogen transmission and limits opportunities to maintain adequate skin hygiene.

CANVAS 1 and 2: analysis of clinical response at day 3 in two phase 3 trials of ceftaroline fosamil versus vancomycin plus aztreonam in treatment of acute bacterial skin and skin structure infections

Scientific and regulatory interest in assessing clinical endpoints after 48 to 72 h of treatment for acute bacterial skin and skin structure infections (ABSSSI) has increased. Historical, pre-antibiotic-era data suggest that a treatment effect relative to untreated controls can be discerned in this time interval. Ceftaroline fosamil, a broad-spectrum bactericidal cephalosporin with activity against Gram-positive organisms, including methicillin-resistant Staphylococcus aureus (MRSA), and Gram-negative organisms was efficacious in two phase 3 trials of complicated skin infections (CANVAS 1 and 2) using clinical cure rates at the test-of-cure visit. To assess an early clinical response in the CANVAS trials, a retrospective analysis using a day 3 clinical endpoint was conducted. Adults with ABSSSI received intravenous ceftaroline fosamil at 600 mg every 12 h (q12h) or vancomycin at 1 g plus aztreonam at 1 g (V/A) q12h for 5 to 14 days. Clinical response at day 3, defined as cessation of infection spread and absence of fever, was analyzed in patients with a lesion size of ≥ 75 cm(2) and either deep and/or extensive cellulitis, major abscess, or an infected wound. Day 3 integrated CANVAS clinical response rates were 74.0% (296/400) for ceftaroline and 66.2% (263/397) for V/A (difference, 7.8%; 95% confidence interval [CI], 1.3% to 14.0%). In the individual studies, absolute treatment differences of 9.4% (CANVAS 1) and 5.9% (CANVAS 2) favoring ceftaroline were observed. For ABSSSI due to MRSA, response rates were 81.7% and 77.4% in the ceftaroline and V/A groups, respectively. In this retrospective analysis, ceftaroline fosamil monotherapy had a numerically higher clinical response than V/A at day 3 in the treatment of ABSSSI.

Bactericidal kinetics of marine-derived napyradiomycins against contemporary methicillin-resistant Staphylococcus aureus

There is an urgent need for new antibiotics to treat hospital- and community-associated methicillin-resistant Staphylococcus aureus (MRSA) infections. Previous work has indicated that both terrestrial and marine-derived members of the napyradiomycin class possess potential anti-staphylococcal activities. These compounds are unique meroterpenoids with unusual levels of halogenation. In this paper we report the evaluation of two previously described napyradiomycin derivatives, A80915A (1) and A80915B (2) produced by the marine-derived actinomycete, Streptomyces sp. strain CNQ-525, for their specific activities against contemporary and clinically relevant MRSA. Reported are studies of the in vitro kinetics of these chemical scaffolds in time-kill MRSA assays. Both napyradiomycin derivatives demonstrate potent and rapid bactericidal activity against contemporary MRSA strains. These data may help guide future development and design of analogs of the napyradiomycins that could potentially serve as useful anti-MRSA therapeutics.

Design of clinical trials of antibacterial agents for community-acquired bacterial pneumonia

Standards for the conduct of clinical trials of antibacterial agents for community-acquired bacterial pneumonia (CABP) have changed dramatically in recent years. A draft guidance from the US FDA on the conduct of such trials was issued in March 2009. However, the guidance has already faced substantial criticism during the open public comment period, resulting in uncertainty regarding the appropriate design of such studies from a regulatory perspective. Controversies regarding the magnitude of the treatment effect associated with antibacterial therapy versus placebo/no therapy, the appropriate timing, nature and noninferiority margin for the primary efficacy end point, and other clinical and statistical issues have complicated efforts to reach consensus on appropriate trial design of antibacterial therapy for CABP. It is critical that studies of new drugs for CABP are designed to ensure that they are feasible to conduct and that their results are scientifically valid, statistically rigorous and clinically meaningful. Based on 3 years of active dialog between clinical, statistical, and regulatory experts, this article proposes an approach to enable a balance of clinical trial feasibility with appropriate scientific, statistical and clinical rigor.

Ceftaroline activity against pathogens associated with complicated skin and skin structure infections: results from an international surveillance study

OBJECTIVES

To assess the spectrum and potency of ceftaroline, a novel anti-methicillin-resistant staphylococcal cephalosporin, against a 2008 surveillance collection of clinical isolates from patients in the USA and Europe.

METHODS

A collection of 14 169 isolates of various bacterial species from complicated skin and skin structure infections (cSSSIs) was tested for susceptibility to ceftaroline and 19 comparator agents in a central reference laboratory using CLSI broth microdilution methods. Organisms were received from 55 medical centres; 27 in the USA and 28 in Europe (12 countries, including Israel). The clonality of isolates of Staphylococcus aureus with elevated ceftaroline MICs (4 mg/L) was determined by PFGE and single and multilocus sequence typing, and the mechanism of ceftaroline non-susceptibility was assessed by molecular methods (PCR amplification and sequencing).

RESULTS

Ceftaroline, the active component of the parenteral prodrug ceftaroline fosamil, was active against 2988 methicillin-resistant S. aureus (MRSA) isolates, with an MI₉₀ of 1 mg/L. The MIC₉₀ for methicillin-susceptible strains was 0.25-0.5 mg/L. Ceftaroline was additionally active against coagulase-negative staphylococci (MIC₉₀, 0.5-1 mg/L), Enterococcus faecalis (MIC₅₀, 2 mg/L), β-haemolytic and viridans group streptococci (MIC₉₀, 0.015-0.25 mg/L) and three commonly isolated Enterobacteriaceae (Escherichia coli, Klebsiella spp. and Proteus mirabilis; MIC₉₀ values of 0.25 to > 16 mg/L). All but four isolates of MRSA (0.13%) had ceftaroline MIC values of ≤ 2 mg/L. The isolates for which ceftaroline MICs were 4 mg/L were clonal (single Greek hospital) and had detectable mecA mutations (N146K, N204K, E150K and H351N).

CONCLUSIONS

The ceftaroline yearly (2008) surveillance for the USA and Europe documented low MIC₅₀/₉₀ values for MRSA isolates at 1/1 and 1/2 mg/L, respectively. Ceftaroline demonstrated promising potency and coverage against Gram-positive and -negative pathogens known to cause cSSSIs, including MRSA and β-haemolytic streptococci.

Severity assessment of skin and soft tissue infections: cohort study of management and outcomes for hospitalized patients

BACKGROUND

Skin and soft tissue infections (SSTIs) are caused by bacterial invasion of the skin and underlying soft tissues and can present with a wide spectrum of signs, symptoms and illness severity. They are a common indication for antimicrobial therapy. However, there are few data on treatment outcomes or the validity of clinical severity scores.

METHODS

Two hundred and five adult patients admitted to Ninewells Hospital, Scotland in 2005, and treated with antibiotics for SSTI, were identified. They were stratified into four classes of severity (class IV = most severe) based on sepsis, co-morbidity and their standardized early warning score (SEWS). Empirical antimicrobial therapy by severity class was compared with the recommendations of a UK guideline.

RESULTS

Thirty-five different empirical antimicrobial regimens were prescribed. Overall, 43% of patients were over-treated, this being particularly common in the lowest severity class I (65% patients). Thirty-day mortality was 9% (18/205) and 17 patients (8%) died during their index admission. Mortality (30 day) and inadequate therapy increased with severity class: I, no sepsis or co-morbidity (45% patients, 1% mortality, 14% therapy inadequate); II, significant co-morbidity but no sepsis (32% patients, 11% mortality, 39% therapy inadequate); III, sepsis but SEWS <4 (17% of patients, 17% mortality, 39% therapy inadequate); and IV, sepsis plus SEWS ≥ 4 (6% of patients, 33% mortality, 92% therapy inadequate).

CONCLUSIONS

SSTI in hospital is associated with significant mortality. Choice of empirical therapy is not evidence based, with significant under-treatment of severely ill patients.

Non-suppurative cellulitis: risk factors and its association with Staphylococcus aureus colonization in an area of endemic community-associated methicillin-resistant S. aureus infections

Suppurative methicillin-resistant Staphylococcus aureus (MRSA) skin infections are common and associated with MRSA colonization, but little is known about non-suppurative cellulitis and its relationship with MRSA colonization in areas endemic for community-associated MRSA. We prospectively enrolled patients hospitalized for non-suppurative cellulitis (n=50) and matched controls (n=100) and found S. aureus colonization was similar in cases and controls (30% vs. 25%, P=0·95). MRSA was uncommon in cases (6%) and controls (3%) (P=0·39). All MRSA isolates were USA300 by pulsed-field gel electrophoresis. Independent risk factors for non-suppurative cellulitis were diabetes (OR 3·5, 95% CI 1·4-8·9, P=0·01) and homelessness in the previous year (OR 6·4, 95% CI 1·9-20·9, P=0·002). These findings suggest that MRSA may only rarely be causative of non-suppurative cellulitis.