Comparative in vitro activity of oritavancin and other agents against methicillin-susceptible and methicillin-resistant Staphylococcus aureus

Oritavancin Versus Daptomycin for Osteomyelitis Treatment After Surgical Debridement

INTRODUCTION

Weekly intravenous (IV) oritavancin and daily daptomycin were compared in an outpatient setting following extensive surgical debridement for treating patients with osteomyelitis.

METHODS

This was a retrospective, observational study of patients diagnosed with acute osteomyelitis. Exclusion criteria were the use of Gram-negative antibiotic therapy, use of antibiotics for more than 48 h prior to oritavancin or daptomycin or prior use of > 2 doses of oritavancin or more than 4 weeks of daptomycin. Clinical success was resolution or improvement of symptoms and no further treatment. Data were analyzed with Chi-square test or Fisher's exact test.

RESULTS

Consecutive outpatients (n = 150) with acute osteomyelitis who were treated with oritavancin or daptomycin (1:1) following extensive surgical debridement were identified. Staphylococcus aureus was the most common pathogen (n = 117). No patient in either group received prior antibiotic therapy (previous 30 days) or was hospitalized within 90 days prior to surgical debridement. Twenty-one (28%) patients prescribed oritavancin had chronic kidney disease, seven of whom were receiving hemodialysis or peritoneal dialysis. Compared to oritavancin, patients prescribed daptomycin had higher rates of all-cause readmission [odds ratio (OR) 2.89; p < 0.001], more infection-related readmission (OR 3.19; p < 0.001), and greater likelihood of receiving antibiotics post-discontinuation of initial therapy (OR 2.13; p < 0.001). Repeat surgical debridement was required for 68.0% with daptomycin vs. 23.1% with oritavancin (p < 0.001).

CONCLUSIONS

Oritavancin demonstrated a significantly higher rate of clinical success compared to daptomycin, with lower all-cause and infection-related readmissions, reduced need for repeat surgical debridement, and fewer additional antibiotic requirements.

Oritavancin vs Standard of Care for Treatment of Nonendovascular Gram-Positive Bloodstream Infections

Background

Data is limited comparing oritavancin (ORT) to the standard-of-care (SOC) for the treatment gram-positive blood stream infections (BSI).

Methods

This was a retrospective study of all patients in the Veteran's Affairs Health Care System treated with at least 1 dose of oritavancin or at least 5 days of vancomycin, daptomycin, ceftaroline, ampicillin, ampicillin-sulbactam, nafcillin, oxacillin, or cefazolin for a documented gram-positive BSI from 1 January 2015 to 30 June 2021. Patients with polymicrobial blood cultures or positive cultures from other sites were included if the organisms were sensitive to the incident antimicrobial; no concomitant antimicrobials could be used once the incident agent was started. Individuals were also excluded if they were diagnosed with endocarditis, had a neutrophil count 96-hours of treatment before the incident antimicrobial was started.The primary composite outcome was clinical failure, defined as all-cause mortality within 30-days from the end of therapy, or blood cultures positive for the incident organisms ≥72 hours after administration of the first dose and ≤30 days after the administration of the final dose of the study antimicrobial, or any drug or line-related readmissions within 30-days of hospital discharge.

Results

Two hundred-forty patients were identified for screening with 96 meeting criteria (27 in ORT and 69 in SOC groups). Baseline characteristics were generally balanced between groups except more patients in the ORT group received >96-hours of treatment before the incident antimicrobial was started (70.3% (19/27) vs 13.04% 9/69); P < .001). The pathogen most prevalent was methicillin susceptible Staphylococcus aureus (MSSA) (ORT 33.3% (9/27) vs SOC 46.4% (32/69)). Clinical failure occurred in 7.4% (2/27) in the ORT group and 17.4% (12/69) in SOC (P = .34). No components of the primary outcome were significantly different between groups, but AKI did occur more commonly in the SOC group (27.5% (19/69) vs 3.7% (1/27); P = .01).

Conclusions

ORT appears to be a safe and effective option when directly compared to the SOC for non-endocarditis BSIs.

Parenteral Vancomycin in the Treatment of MRSA-Associated Diabetic Foot Infections: An Unnecessary Risk

Diabetic foot infections (DFIs) are a common and costly complication of diabetes. Soft tissue and bone infections in DFIs frequently lead to amputation and/or sepsis which can be costly for both the patient and the healthcare system. Staphylococcus aureus is the most commonly identified causative agent in DFIs, and people with diabetes may have an increased risk of infection with methicillin-resistant Staphylococcus aureus (MRSA). In addition to increased susceptibility to severe infection, MRSA in DFIs is associated with high rates of treatment failure, morbidity, and hospitalization costs meaning appropriate treatment is a high priority. While hospitalized patients are usually treated with intravenous (IV) vancomycin, this can be costly in terms of inpatient stays, staffing costs, and adverse events. For example, vancomycin-associated acute kidney injury not only delays hospital discharge and increases costs but is also a particular concern for patients with diabetes who already have an increased risk of kidney problems. Vancomycin-resistant strains of S. aureus have also been identified, which means that alternative treatment options may need to be explored. Treatment alternatives to IV vancomycin, including oral antibiotics, have been shown to provide similar efficacy, with reduced costs, outpatient or home-based administration, and with fewer serious adverse effects. Although infectious disease specialists often use IV vancomycin alone, or in combination, as a first-line therapeutic option, they are increasingly seeing the value of outpatient or at-home oral antibiotics as an alternative. This manuscript reviews the evidence for true costs of vancomycin therapy for MRSA-associated DFIs and examines the alternatives.

Comparative In Vitro Activity of New Lipoglycopeptides and Vancomycin Against Ocular Staphylococci and Their Toxicity on the Human Corneal Epithelium

PURPOSE

The purpose of this study was to assess the potential of new lipoglycopeptides as novel topical therapies for improved treatment of recalcitrant ocular infections. We evaluated the in vitro antimicrobial activity of oritavancin, dalbavancin, and telavancin compared with vancomycin (VAN) against a large collection of ocular staphylococcal isolates and their cytotoxicity on human corneal epithelial cells (HCECs).

METHODS

Antimicrobial susceptibility testing was performed by broth microdilution against 223 Staphylococcus spp. clinical isolates. Time-kill kinetics were determined for methicillin-resistant strains of Staphylococcus aureus (MRSA) (n = 2) and Staphylococcus epidermidis (MRSE) (n = 1). In vitro cytotoxicity assays were performed with AlamarBlue and live/dead staining on HCECs.

RESULTS

All new lipoglycopeptides showed strong in vitro potency against ocular staphylococci, including multidrug-resistant MRSA strains, with dalbavancin showing a slightly higher potency overall [minimum inhibitory concentration (MIC) 90 0.06 μg/mL] compared with telavancin and oritavancin (MIC 90 0.12 μg/mL), whereas VAN had the lowest potency (MIC 90 2 μg/mL). Oritavancin exerted rapid bactericidal activity within 1 h for MRSA and 2 h for MRSE. All other drugs were bactericidal within 24 h. At a concentration commonly used for topical preparations (25 mg/mL), cytotoxicity was observed for VAN after 5 min of incubation, whereas reduction in HCEC viability was not seen for telavancin and was less affected by oritavancin and dalbavancin. Cytotoxicity at 25 mg/mL was seen for all drugs at 30 and 60 min but was significantly reduced or undetected for lower concentrations.

CONCLUSIONS

Our study demonstrates that new lipoglycopeptides have substantially better in vitro antimicrobial activity against ocular staphylococcal isolates compared with VAN, with a similar or improved toxicity profile on HCECs.

Evaluation of Dilution Susceptibility Testing Methods for Aztreonam in Combination with Avibactam against Enterobacterales

As multidrug and pan-resistance among Enterobacterales continue to increase, there is an urgent need for more therapeutic options to treat these infections. New β-lactam and β-lactam inhibitor (BLI) combinations have a broad spectrum of activity, but those currently approved do not provide coverage against isolates harboring metallo-β-lactamases (MBL). Aztreonam (ATM) and avibactam (AVI) in combination (ATM/AVI; AVI at 4 μg/mL fixed concentration) provides a similarly broad range of activity while maintaining activity against MBL-producing isolates. The in vitro susceptibility testing of ATM/AVI by standard methods was evaluated during development. This study investigated the impact of nonstandard testing conditions on the activity of ATM/AVI as observed during broth microdilution testing as well as the equivalency between agar dilution and broth microdilution MIC values when testing a diverse panel of Enterobacterales (N = 201). Nonstandard test conditions evaluated included inoculum density, atmosphere of incubation, media pH, varied medium cation concentrations, incubation time, varied serum concentrations, testing in pooled urine instead of media, addition of blood to the media, and the presence of surfactant. Generally, apart from low pH and high inoculum density, nonstandard testing parameters did not affect ATM/AVI broth microdilution MIC values. Correlation of MIC values obtained by agar dilution and broth microdilution resulted in an essential agreement of 97.0% for all tested Enterobacterales. Variation of standard testing conditions had little impact on broth microdilution MIC values for ATM/AVI. The correlation between broth microdilution and agar dilution MICs suggests both methods are reliable for determination of ATM/AVI MIC values. IMPORTANCE Increasing antibiotic resistance and emergence of pan-resistant isolates threaten the ability to control infections and to provide many other medical interventions such as surgery and chemotherapy, among others. New therapies are required to control emerging resistance mechanisms, including the increase in metallo-β-lactamases. Some new antibiotic combinations provide coverage against highly resistant isolates but are unable to target organisms that produce metallo-β-lactamases. Aztreonam in combination with avibactam provides a broad spectrum of activity against highly resistant isolates that also targets metallo-β-lactamase-producing organisms. An important part of drug development is the ability for clinical labs to determine the susceptibility of isolates to the antimicrobial. This manuscript investigates the in vitro susceptibility testing of aztreonam/avibactam with nonstandard testing conditions and a correlation study between broth microdilution and agar dilution against clinical isolates encoding a variety of resistance mechanisms. Overall, aztreonam/avibactam was generally unaffected by changes in testing conditions and showed strong agar/broth correlation.

Antibacterial activity of recently approved antibiotics against methicillin-resistant Staphylococcus aureus (MRSA) strains: A systematic review and meta-analysis

Background

Methicillin-resistant Staphylococcus aureus (MRSA) infections are considered an important public health problem, and treatment options are limited. Accordingly, in this meta-analysis, we analyzed published studies to survey in vitro activity of recently approved antibiotics against MRSA isolates.

Methods

We searched electronic databases; PubMed, Scopus, and Web of Science to identify relevant studies (until November 30, 2020) that have focused on the in vitro activity of telavancin, dalbavancin, oritavancin, and tedizolid against MRSA isolates. Statistical analyses were conducted using STATA software (version 14.0).

Results

Thirty-eight studies were included in this meta-analysis. Overall in vitro activity of tedizolid on 12,204 MRSA isolates was 0.250 and 0.5 µg/mL for MIC₅₀ and MIC₉₀, (minimum inhibitory concentration at which 50% and 90% of isolates were inhibited, respectively), respectively. The overall antibacterial activity of dalbavancin on 28539 MRSA isolates was 0.060 and 0.120 µg/mL for MIC₅₀ and MIC₉₀, respectively. The overall antibacterial activity of oritavancin on 420 MRSA isolates was 0.045 and 0.120 µg/mL for MIC₅₀ and MIC₉₀, respectively. The overall antibacterial activity of telavancin on 7353 MRSA isolates was 0.032 and 0.060 µg/mL for MIC₅₀ and MIC₉₀, respectively. The pooled prevalence of tedizolid, telavancin, and dalbavancin susceptibility was 100% (95% CI: 100–100).

Conclusion

Telavancin, dalbavancin, oritavancin, and tedizolid had potent in vitro activity against MRSA isolates. The low MICs and high susceptibility rates of these antibiotics recommend a hopeful direction to introduce useful antibiotics in treating MRSA infections in the future.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12941-022-00529-z.

Development and Preclinical Evaluation of New Inhaled Lipoglycopeptides for the Treatment of Persistent Pulmonary Methicillin-Resistant Staphylococcus aureus Infections

Chronic pulmonary methicillin-resistant Staphylococcus aureus (MRSA) disease in cystic fibrosis (CF) has a high probability of recurrence following treatment with standard-of-care antibiotics and represents an area of unmet need associated with reduced life expectancy. We developed a lipoglycopeptide therapy customized for pulmonary delivery that not only demonstrates potent activity against planktonic MRSA, but also against protected colonies of MRSA in biofilms and within cells, the latter of which have been linked to clinical antibiotic failure. A library of next-generation potent lipoglycopeptides was synthesized with an emphasis on attaining superior pharmacokinetics (PK) and pharmacodynamics to similar compounds of their class. Our strategy focused on hydrophobic modification of vancomycin, where ester and amide functionality were included with carbonyl configuration and alkyl length as key variables. Candidates representative of each carbonyl attachment chemistry demonstrated potent activity in vitro, with several compounds being 30 to 60 times more potent than vancomycin. Selected compounds were advanced into in vivo nose-only inhalation PK evaluations in rats, where RV94, a potent lipoglycopeptide that utilizes an inverted amide linker to attach a 10-carbon chain to vancomycin, demonstrated the most favorable lung residence time after inhalation. Further in vitro evaluation of RV94 showed superior activity to vancomycin against an expanded panel of Gram-positive organisms, cellular accumulation and efficacy against intracellular MRSA, and MRSA biofilm killing. Moreover, in vivo efficacy of inhaled nebulized RV94 in a 48 h acute model of pulmonary MRSA (USA300) infection in neutropenic rats demonstrated statistically significant antibacterial activity that was superior to inhaled vancomycin.

Importance of beta-lactam pharmacokinetics and pharmacodynamics on the recovery of microbial diversity in the airway of persons with cystic fibrosis

Cystic fibrosis (CF) is a chronic lung disease characterized by acute pulmonary exacerbations (PExs) that are frequently treated with antibiotics. The impact of antibiotics on airway microbial diversity remains a critical knowledge gap. We sought to define the association between beta-lactam pharmacokinetic (PK) and pharmacodynamic target attainment on richness and alpha diversity. Twenty-seven children <18 years of age with CF participated in the prospective study. Airway samples were collected at hospital admission for PEx, end of antibiotic treatment (Tr), and >1 month in follow-up (FU). Metagenomic sequencing was performed to determine richness, alpha diversity, and the presence of antibiotic resistance genes. Free plasma beta-lactam levels were measured, and PK modeling was performed to determine time above the minimum inhibitory concentration (fT>MIC). 52% of study subjects had sufficient fT>MIC for optimal bacterial killing. There were no significant differences in demographics or PEx characteristics, except for F508del homozygosity. No significant differences were noted in richness or alpha diversity at individual time points, and both groups experienced a decrease in richness and alpha diversity at Tr compared with PEx. However, alpha diversity remained decreased at FU compared with PEx in those with sufficient fT>MIC but increased in those with insufficient fT>MIC (Shannon -0.222 vs +0.452, p=0.031, and inverse Simpson -1.376 vs +1.388, p=0.032). Fluoroquinolone resistance was also more frequently detected in those with insufficient fT>MIC (log2 fold change (log2FC) 2.29, p=0.025). These findings suggest sufficient beta-lactam fT>MIC is associated with suppressed recovery of alpha diversity following the antibiotic exposure period.

In Vitro Activity of Vancapticin MCC5145 against Methicillin-Resistant Staphylococcus aureus from Periprosthetic Joint Infection

MRSA periprosthetic 1 joint infection (PJI) can be challenging to treat due to biofilm formation, alongside sometimes limited vancomycin activity (1-3).….

Tedizolid is a promising antimicrobial option for the treatment of Staphylococcus aureus infections in cystic fibrosis patients

BACKGROUND

Tedizolid is a protein synthesis inhibitor in clinical use for the treatment of Gram-positive infections. Pulmonary MRSA infections are a growing problem in patients with cystic fibrosis (CF) and the efficacy of tedizolid-based therapy in CF pulmonary infections is unknown.

OBJECTIVES

To evaluate the in vitro and in vivo activity of tedizolid and predict the likelihood of tedizolid resistance selection in CF-background Staphylococcus aureus strains.

METHODS

A collection of 330 S. aureus strains (from adult and paediatric patients), either of normal or small colony variant (SCV) phenotypes, gathered at three CF centres in the USA was used. Tedizolid activity was assessed by broth microdilution, Etest and time-kill analysis. In vivo tedizolid efficacy was tested in a murine pneumonia model. Tedizolid in vitro mutants were obtained by 40 days of exposure and progressive passages. Whole genome sequencing of clinical S. aureus strains with reduced susceptibility to tedizolid was performed.

RESULTS

MRSA strain MIC90s were tedizolid 0.12-0.25 mg/L and linezolid 1-2 mg/L; for MSSA strains, MIC90s were tedizolid 0.12 mg/L and linezolid 1-2 mg/L. Two strains, WIS 441 and Seattle 106, with tedizolid MICs of 2 mg/L and 1 mg/L, respectively, had MICs above the FDA tedizolid breakpoint (0.5 mg/L). Tedizolid at free serum concentrations exhibited a bacteriostatic effect. Mean bacterial burdens in lungs (log10 cfu/g) for WIS 423-infected mice were: control, 11.2±0.5; tedizolid-treated (10 mg/kg), 3.40±1.87; linezolid-treated (40 mg/kg), 4.51±2.1; and vancomycin-treated (30 mg/kg), 5.21±1.93. For WIS 441-infected mice the (log10 cfu/g) values were: control, 9.66±0.8; tedizolid-treated, 3.18±1.35; linezolid-treated 5.94±2.19; and vancomycin-treated, 4.35±1.7.

CONCLUSIONS

These results suggest that tedizolid represents a promising therapeutic option for the treatment of CF-associated MRSA/MSSA infections, having potent in vivo activity and low resistance potential.

Interplay between ESKAPE Pathogens and Immunity in Skin Infections: An Overview of the Major Determinants of Virulence and Antibiotic Resistance

The skin is the largest organ in the human body, acting as a physical and immunological barrier against pathogenic microorganisms. The cutaneous lesions constitute a gateway for microbial contamination that can lead to chronic wounds and other invasive infections. Chronic wounds are considered as serious public health problems due the related social, psychological and economic consequences. The group of bacteria known as ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter sp.) are among the most prevalent bacteria in cutaneous infections. These pathogens have a high level of incidence in hospital environments and several strains present phenotypes of multidrug resistance. In this review, we discuss some important aspects of skin immunology and the involvement of ESKAPE in wound infections. First, we introduce some fundamental aspects of skin physiology and immunology related to cutaneous infections. Following this, the major virulence factors involved in colonization and tissue damage are highlighted, as well as the most frequently detected antimicrobial resistance genes. ESKAPE pathogens express several virulence determinants that overcome the skin's physical and immunological barriers, enabling them to cause severe wound infections. The high ability these bacteria to acquire resistance is alarming, particularly in the hospital settings where immunocompromised individuals are exposed to these pathogens. Knowledge about the virulence and resistance markers of these species is important in order to develop new strategies to detect and treat their associated infections.

Fabrication and characterization of mucoadhesive bioplastic patch via coaxial polylactic acid (PLA) based electrospun nanofibers with antimicrobial and wound healing application

Polylactic acid (PLA) is the second-highest consumed bioplastic in the world. PVP/PLA-PEO complex nanofibers encapsulating collagen and cefazolin dressing scaffold were fabricated using a coaxial electrospinning method to target the release of the encapsulated compounds. It was observed that in collagen doses of 10 and 20%, the speed of healing showed a significant difference with the control sample, but the dose of 40% caused a decrease in wound healing rate in mice. The nanofibers' morphology and surface roughness were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. The mechanical properties and adhesion strength of the scaffolds were investigated. The scaffolds' antimicrobial activity was evaluated by disk diffusion method against the E. coli, S. aureus, and P. aeruginosa. The results indicated a positive effect on the antimicrobial activity of the samples. In this study, we were able to prolong the effect of scaffolds by changing the pattern of release of cefazolin from inside the nanofibers. Possible interactions between the polymers and the encapsulated compounds were investigated using Fourier-transform infrared spectroscopy (FTIR). Finally, in-vivo and histological tests were performed to evaluate the efficacy of the scaffolds in accelerating wound healing.

Emerging drugs for treating methicillin-resistant Staphylococcus aureus

Introduction: In clinical practice, methicillin-resistant Staphylococcus aureus (MRSA) represents a major threat and has been associated with high rates of inadequate antibiotic treatment and significant increases in morbidity, mortality, and overall healthcare costs. The association between the prescription of an inappropriate or delayed antibiotic and impaired clinical outcomes has been widely described. Areas covered: To address the threat of MRSA, many new therapeutic options with a peculiar activity against MRSA have been recently developed and approved. New agents are characterized by specific issues in terms of spectrum of activity, pharmacokinetics, risk of drug-drug interactions, and toxicity, with potential advantages that should be considered in everyday clinical practice. Expert opinion: The most attractive characteristic of new drugs is represented by the broad spectrum of activity against multidrug-resistant pathogens; moreover, new compounds in most cases are characterized by favorable toxicity profiles compared with old drugs currently used in clinical practice. Some of the new antimicrobials will be also available as oral formulations, with the potential for oral switch, even in infections due to resistant pathogens. In particular conditions/populations (e.g. liver failure, renal disease, pregnancy, diabetic, children, and elderly), novel antibiotics with reduced toxicity could be an important option, including after hospital discharge.

Clinical Pharmacokinetics and Pharmacodynamics of Telavancin Compared with the Other Glycopeptides

Telavancin was discovered by modifying the chemical structure of vancomycin and belongs to the group of lipoglycopeptides. It employs its antimicrobial potential through two distinct mechanisms of action: inhibition of bacterial cell wall synthesis and induction of bacterial membrane depolarization and permeabilization. In this article we review the clinically relevant pharmacokinetic and pharmacodynamic data of telavancin. For comparison, the pharmacokinetic and pharmacodynamic data of the other glycopeptides are presented. Although, in contrast to the newer lipoglycopeptides, telavancin demonstrates a relatively short half-life and rapid total clearance, its apparent volume of distribution (V_d) is almost identical to that of dalbavancin. The accumulation of telavancin after repeated dosing is only marginal, whereas the pharmacokinetic values of the other glycopeptides show much greater differences after administration of multiple doses. Despite its high plasma-protein binding of 90% and relatively low V_d of approximately 11 L, telavancin shows near complete equilibration of the free fraction in plasma with soft tissue. The ratio of the area under the plasma concentration-time curve from time zero to 24 h (AUC₂₄) of unbound plasma concentrations to the minimal inhibitory concentration (MIC) required to inhibit growth of 90% of organisms (MIC₉₀) of Staphylococcus aureus and S. epidermidis of telavancin are sufficiently high to achieve pharmacokinetic/pharmacodynamic targets indicative for optimal bacterial killing. Considering both the AUC₂₄/MIC ratios of telavancin and the near complete equilibration of the free fraction in plasma with soft tissue, telavancin is an appropriate antimicrobial agent to treat soft tissue infections caused by Gram-positive pathogens. Although the penetration of telavancin into epithelial lining fluid (ELF) requires further investigations, the AUC₂₄/MIC ratio for S. aureus indicates that bactericidal activity in the ELF could be expected.

Activity of Telavancin against Staphylococcus aureus Isolates, Including Those with Decreased Susceptibility to Ceftaroline, from Cystic Fibrosis Patients

Methicillin-resistant Staphylococcus aureus (MRSA) acquisition in cystic fibrosis (CF) patients confers a clinical outcome worse than that in non-CF patients with an increased rate of declined lung function. Telavancin, an approved lipoglycopeptide used to treat infections due to S. aureus, has a dual mode of action causing inhibition of peptidoglycan synthesis and membrane depolarization. MRSA infections in CF patients remain an important problem with no foreseeable decline in prevalence rates. Although telavancin is currently in clinical use for the treatment of complicated skin infections and hospital-acquired pneumonia, the activity against S. aureus infections in CF patients has not been investigated. In this work, we studied the activity of telavancin against CF patient-derived S. aureus strains collected from geographically diverse CF centers in the United States. We found that the telavancin MIC90 was 0.06 μg/ml, 8-fold lower than the ceftaroline or daptomycin MIC90 and 25-fold lower than the linezolid and vancomycin MIC90 We demonstrate that telavancin at serum free concentrations has rapid bactericidal activity, with a decrease of more than 3 log10 CFU/ml being achieved during the first 4 to 6 h of treatment, performing better in this assay than vancomycin and ceftaroline, including against S. aureus strains resistant to ceftaroline. Telavancin resistance was infrequent (0.3%), although we found that it can occur in vitro in both CF- and non-CF patient-derived S. aureus strains by progressive passages with subinhibitory concentrations. Genetic analysis of telavancin-resistant in vitro mutants showed gene polymorphisms in cell wall and virulence genes and increased survival in a Galleria mellonella infection model. Thus, we conclude that telavancin represents a promising therapeutic option for infections in CF patients with potent in vitro activity and a low resistance development potential.

Relationship of Pulmonary Outcomes, Microbiology, and Serum Antibiotic Concentrations in Cystic Fibrosis Patients

OBJECTIVES

To determine the frequency of subtherapeutic exposure to intravenously administered β-lactam antibiotics in a cohort of cystic fibrosis (CF) patients who were treated for a pulmonary exacerbation, and its impact on pulmonary function.

METHODS

Nineteen CF patients between the ages of 5 and 21 years treated at Children's National Health System for a pulmonary exacerbation were followed between March 2015 and August 2016 in a prospective, longitudinal study. Pharmacokinetic modeling and minimum inhibitory concentrations (MICs) of the involved pathogens were used to determine therapeutic or subtherapeutic β-lactam antibiotic exposure based on the time the antibiotic concentration was above the MIC. Clinical outcomes were measured by spirometry values.

RESULTS

The 19 participants were treated with a total of 29 courses of antibiotics. The most common β-lactam antibiotics used in a treatment course were ceftazidime (62%) and meropenem (45%). There was no difference in age, CF genotype, or creatinine clearance between the 9 participants (47%) who reached therapeutic concentrations versus the 10 (53%) who did not. Those who achieved sufficiently high antibiotic exposure had more significant improvement of their pulmonary function tests.

CONCLUSIONS

We found that sufficient antibiotic exposure during treatment of CF pulmonary exacerbations was associated with improved pulmonary function. Moreover, it was impossible to predict, solely from the dosing regimen used, which patients were going to reach therapeutic β-lactam antibiotic serum concentrations. This suggests that CF patients may benefit from closer monitoring of their β-lactam exposure and bacterial MIC for optimal clinical outcomes.

In vitro activity of oritavancin against biofilms of staphylococci isolated from prosthetic joint infection

We tested the in vitro activity of oritavancin against 185 staphylococci associated with prosthetic joint infection, including 37 methicillin-resistant S. aureus, 67 methicillin-susceptible S. aureus, 59 methicillin-resistant S. epidermidis (MRSE), and 22 methicillin-susceptible S. epidermidis (MSSE) isolates. The oritavancin MIC₅₀ for S. aureus and MSSE was 0.03 μg/mL, and for MRSE, it was 0.06 μg/mL; MIC₉₀ for S. aureus and S. epidermidis was 0.12 μg/mL for both the methicillin-resistant and -susceptible subgroups. The oritavancin MBBC₅₀ for S. aureus and S. epidermidis was 2 μg/mL for both the methicillin-resistant and -susceptible subgroups; the MBBC₉₀ for S. aureus and MSSE was 4 μg/mL, and for MRSE, it was 8 μg/mL.

Morbidity, mortality, and management of methicillin-resistant S. aureus bacteremia in the USA: update on antibacterial choices and understanding

Methicillin-resistant Staphylococcus aureus (MRSA) bacteremia is associated with significant healthcare costs, morbidity, and mortality in the United States. Complications of MRSA bacteremia include infective endocarditis, osteomyelitis, and sepsis, all of which are difficult to treat. Time to effective therapy and antibacterial choice greatly affect patient outcomes. Vancomycin and daptomycin remain first-line therapies; however, reports of vancomycin-associated treatment failure and reduced daptomycin susceptibility highlight the need to define alternative strategies for MRSA bacteremia treatment. In addition, several patient- and pathogen-specific factors influence the outcomes of MRSA bacteremia. It is, therefore, critical to explore the interaction between host- and pathogen-specific factors and its effect on MRSA bacteremia pathogenesis and mortality. This review discusses the factors that drive the development of MRSA bacteremia and examines alternative treatment strategies.

Single Intravenous Dose of Oritavancin for Treatment of Acute Skin and Skin Structure Infections Caused by Gram-Positive Bacteria: Summary of Safety Analysis from the Phase 3 SOLO Studies

Oritavancin is a lipoglycopeptide with bactericidal activity against Gram-positive organisms. Its rapid concentration-dependent bactericidal activity and long elimination half-life allow single-dose treatment of acute bacterial skin and skin structure infections (ABSSSI). SOLO I and SOLO II were randomized, double-blind studies evaluating the efficacy and safety of a single 1,200-mg intravenous (i.v.) dose of oritavancin versus twice-daily i.v. vancomycin for 7 to 10 days in ABSSSI patients. Safety data from both studies were pooled for safety analysis. The database comprised pooled safety data for 976 oritavancin-treated patients and 983 vancomycin-treated patients. The incidences of adverse events, serious adverse events, and discontinuations due to adverse events were similar for oritavancin (55.3, 5.8, and 3.7%, respectively) and vancomycin (56.9, 5.9, and 4.2%, respectively). The median time to onset (3.8 days versus 3.1 days, respectively) and the duration (3.0 days for both groups) of adverse events were also similar between the two groups. The most frequently reported events were nausea, headache, and vomiting. Greater than 90% of all events were mild or moderate in severity. There were slightly more infections and infestations, abscesses or cellulitis, and hepatic and cardiac adverse events in the oritavancin group; however, more than 80% of these events were mild or moderate. Subgroup analyses did not identify clinically meaningful differences in the incidence of adverse events attributed to oritavancin. A single 1,200-mg dose of oritavancin was well tolerated and had a safety profile similar to that of twice-daily vancomycin. The long elimination half-life of oritavancin compared to that of vancomycin did not result in a clinically meaningful delay to the onset or prolongation of adverse events. (This study has been registered at ClinicalTrials.gov under registration no. NCT01252719 and NCT01252732.).

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.

New Antimicrobial Agents for the Treatment of Staphylococcal Infections in Children

Several new antimicrobial agents-daptomycin, ceftaroline, telavancin, dalbavancin, and-tedizolid have been approved for the treatment of staphylococcal infections, including methicillin-resistant Staphylococcus aureus (MRSA), in adults. Ceftaroline and daptomycin have been approved by the US Food and Drug Administration for use in children. Ceftaroline, a beta-lactam antibiotic with activity against MRSA, has been approved for treatment of community-acquired bacterial pneumonia and complicated skin and skin structure infections. Daptomycin has been approved for treatment of complicated skin and skin structure infections. In this article, we review the pharmacokinetics and pharmacodynamics of these antibiotics and available data on use in children.