Dalbavancin: A New Option for the Treatment of Gram-Positive Infections

Clinical Pharmacokinetics and Pharmacodynamics of Dalbavancin

Dalbavancin is a synthetic lipoglycopeptide that exerts its antimicrobial activity through two distinct modes of action, inhibition of cell wall synthesis and an anchoring mechanism. Compared with previous glycopeptide antibiotics, dalbavancin demonstrates improved antibacterial potency against Gram-positive organisms and a long half-life of approximately 1 week, which is longer in tissues (e.g., skin, bone) than plasma. These factors facilitated the development of single-dose or once-weekly dosing regimens to treat acute bacterial skin and skin structure infections (ABSSSI). Dalbavancin exhibits dose-proportional pharmacokinetics and is highly protein bound (93%). Despite being highly protein bound, it has a steady-state volume of distribution >10 L and distributes widely into the skin, bone, peritoneal space, and epithelial lining fluid, but not cerebrospinal fluid. Dalbavancin elimination occurs via a combination of renal (approximately 45%) and non-renal clearance, with dose adjustments recommended only in patients with a creatinine clearance <30 mL/min not receiving any form of dialysis. The established pharmacokinetic/pharmacodynamic index associated with bacterial kill is free area under the concentration-time curve over the minimum inhibitory concentration (fAUC/MIC), with a goal 24-h fAUC/MIC of at least 27.1 for Staphylococcus aureus infections. Recent data suggest usefulness in the treatment of infections beyond ABSSSI, with convenient dosing and redosing strategies for complicated infections requiring extended treatment durations. Additional studies are needed to confirm these preliminary findings.

N-Terminal guanidine derivatives of teicoplanin antibiotics strongly active against glycopeptide resistant Enterococcus faecium

Antibiotic resistance is one of the major challenges in healthcare of our time. To meet this challenge, we designed and prepared guanidine and lipophilic guanidine derivatives of the glycopeptide antibiotic teicoplanin to armed them with activity against the most threatening nosocomial bacteria, multiresistant enterococci. From teicoplanin and its pseudoaglycone, a series of N-terminal guanidine derivatives have been prepared with free and amide C-terminal parts. Six aliphatic and aromatic lipophilic carbodiimides were prepared and used for the synthesis of lipophilic guanidine teicoplanin conjugates. All new N-terminal guanidine antibiotics showed high activity against a standard panel of Gram-positive bacteria. Four selected derivatives displayed excellent antibacterial activity against a series of nosocomial VanA Enterococcus faecium strains.

Antibiotics for gram-positive bacterial infections: vancomycin, teicoplanin, quinupristin/dalfopristin, oxazolidinones, daptomycin, dalbavancin, and telavancin

An overview of the mechanism of action, dosing, clinical indications, and toxicities of the glycopeptide vancomycin is provided. The emerging gram-positive bacterial resistance to antimicrobials and its mechanisms are reviewed. Strategies to control this emergence of resistance are expected to be proposed. Newer antimicrobial agents that have activity against vancomycin-resistant organisms are now available and play a critical role in the treatment of life-threatening infections.

New antimicrobial agents for use in the intensive care unit

Timely provision of adequate antimicrobial coverage in an initial anti-infective treatment regimen results in optimal outcomes for bacterial and fungal infections. However, selection of appropriate antimicrobial regimens for treatment of infections in the intensive care unit (ICU) can be challenging due to expansion of resistance, which typically requires use of multidrug anti-infective regimens to provide adequate coverage of important pathogens commonly seen in the ICU setting. Indeed, a recent additional call to action by the Infectious Diseases Society of America (IDSA) has enforced the impact that antimicrobial-resistant pathogens can have on patient care. The term ESKAPE has been coined by this IDSA group to refer to Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumanii, Pseudomonas aeruginosa, and Enterobacter species, the etiologic causes of the majority of hospital-acquired infections in the United States that are able to effectively "escape" our antibiotic arsenal and that also mandate discovery of new antimicrobial agents. This article reviews select antibacterial agents and an antifungal agent in late stages of clinical development that appear to have potential for treatment of infections in the ICU.

Management of complicated infections in the era of antimicrobial resistance: the role of tigecycline

BACKGROUND

Increasing antimicrobial resistance and infection complications pose challenges to optimal antibiotic therapy. Paucity of new antibiotics (and the eventual bacterial resistance they face) highlights the critical need for more appropriate use of broadly effective agents, which may help to thwart the dramatic rise in global resistance. Single agents that can be combined effectively with others, if needed, promise the simplest overall utility. Approved in 2005 to treat complicated skin and intra-abdominal infections, tigecycline is a novel extended-spectrum minocycline derivative that circumvents bacterial resistance, as it is unaffected by efflux pumps and ribosomal protection. However, tigecycline should not be used as empiric monotherapy for treatment of health-care associated infections known or suspected to be owing to Pseudomonas aeruginosa or Proteus spp.

OBJECTIVE

This article summarizes the demonstrated clinical utility of tigecycline so far.

METHODS

A MEDLINE search examined authoritative published clinical studies, reviews and case reports detailing the clinical record of tigecycline since 2004.

RESULTS/CONCLUSION

Tigecycline continues to maintain satisfactory profiles of safety, efficacy and antimicrobial resistance avoidance. Regardless, continued surveillance is needed to detect reduced susceptibility and resistance against both community and nosocomial pathogens. Judicious use of agents reserved for multidrug resistant pathogens is vital to preserve their effectiveness.

Multicenter evaluation of the in vitro activity of dalbavancin tested against staphylococci and streptococci in 5 European countries: results from the DECIDE Surveillance Program (2007)

Dalbavancin is an antimicrobial lipoglycopeptide agent that has proven activity against Gram-positive pathogens and a once weekly dosing advantage compared with other agents in the glycopeptide class. The most common pathogens isolated from skin and skin structure infections (SSSIs) include Staphylococcus aureus and beta-hemolytic streptococci (betaHS), and dalbavancin has demonstrated excellent activity against these species. This study used 18 medical center laboratories in 5 European countries to assess the activity of dalbavancin, vancomycin, and teicoplanin against S. aureus, coagulase-negative staphylococci (CoNS), and betaHS. The rank order of potency was dalbavancin (MIC(50), 0.06 microg/mL) > teicoplanin (MIC(50), 0.5 microg/mL) > vancomycin (MIC(50), 2 microg/mL) and dalbavancin (MIC(50), 0.06 microg/mL) > teicoplanin and vancomycin (MIC(50), 2 microg/mL) against S. aureus and CoNS, respectively. Dalbavancin was the most active glycopeptide tested against betaHS with all strains inhibited by < or = 0.12 microg/mL. Susceptibility to other antimicrobial classes was also evaluated with noticeable differences demonstrated between countries. Higher methicillin-resistant S. aureus (MRSA) rates were observed in Italy (44.2%) and the United Kingdom (36.8%) compared with other countries, but resistance to erythromycin (51.6-83.1%) and clindamycin (5.7-68.4%) among MRSA also varied significantly between countries. The excellent contemporary activity of dalbavancin against common Gram-positive pathogens collected in European countries suggests that dalbavancin could have a role in the treatment of various types of SSSIs.

Activities of dalbavancin against a worldwide collection of 81,673 gram-positive bacterial isolates

Dalbavancin, a long-acting lipoglycopeptide, was evaluated against 81,673 isolates of staphylococci, enterococci, and streptococci collected from 33 countries during worldwide resistance surveillance (2002 to 2007). Regardless of susceptibility to oxacillin, comparable potencies for dalbavancin against Staphylococcus aureus and coagulase-negative staphylococci from all countries were noted (MIC(90), 0.06 to 0.12 microg/ml). Vancomycin-susceptible Enterococcus spp. had dalbavancin MIC(90)s comparable to those for staphylococci, whereas vancomycin-resistant strains were more resistant (MIC(50), >4 microg/ml). beta-Hemolytic and viridians group streptococci were very susceptible to dalbavancin (MIC(90), <or=0.03 microg/ml). Overall, dalbavancin was >or=16-fold more active than vancomycin against the monitored gram-positive species.

Approaches to serious methicillin-resistant Staphylococcus aureus infections with decreased susceptibility to vancomycin: clinical significance and options for management

PURPOSE OF REVIEW

This review addresses therapeutic approaches to Staphylococcus aureus infections with diminished susceptibility to vancomycin, focusing on recently published data in English language medical literature between June 2006 and July 2007.

RECENT FINDINGS

Knowledge regarding the potential limitations of vancomycin therapy for S. aureus infections continues to emerge. Recent changes include alteration of the Clinical Laboratory and Standards Institute vancomycin breakpoint for S. aureus and questions regarding the utility of the lower breakpoint of 2.0 mg/l. Interest continues in the accessory gene regulator (agr) locus and its impact on the activity of vancomycin. Newer options for drug therapy progress, with strengths and limitations becoming more apparent for each.

SUMMARY

Newer antimicrobial agents active against methicillin-resistant S. aureus such as daptomycin and linezolid continue to show value. Older antimicrobial agents may play an important therapeutic role and warrant further examination. Work is needed to evaluate current agents against methicillin-resistant S. aureus in the setting of elevated vancomycin minimum inhibitory concentrations or clinical failure. Antimicrobial selection for methicillin-resistant S. aureus infections with reduced susceptibility to vancomycin should be governed by disease severity, susceptibility patterns, knowledge of the limitations of current susceptibility testing, and strengths and weaknesses of the agents being considered.

Superbugs in the coming new decade; multidrug resistance and prospects for treatment of Staphylococcus aureus, Enterococcus spp. and Pseudomonas aeruginosa in 2010

New resistance problems have emerged recently among hospital and community-acquired pathogens such as in Staphylococcus aureus, Enterococcus faecium and Pseudomonas aeruginosa. Hospital-acquired and now community-acquired methicillin-resistant S. aureus are emerging worldwide whereas vancomycin-resistant S. aureus remain extremely rare. Hospital-acquired outbreaks of vancomycin-resistant enterococci and multidrug resistant Pseudomonas aeruginosa infections are increasingly reported worldwide. Whereas novel molecules are being developed for treating Gram-positive infections, difficult to non possible-to-treat pandrug-resistant P. aeruginosa infections may become a therapeutic challenge soon.

Investigational treatments for postoperative surgical site infections

Surgical site infections rank third among nosocomial infections, representing a global threat, associated with the emergence of multi-drug-resistant bacteria. The pharmaceutical industry has recently curtailed developmental programmes; however, the need for new compounds is extremely important. This article reviews new antimicrobials and immunointerventional targets for their potential to treat surgical site infections in comparison with recently licensed compounds. Daptomycin, dalbavancin, oritavancin, telavancin, iclaprim and ranbezolid seem to be promising agents against infections caused by Gram-positive pathogens and effectively address the present problems of multi-resistance in Gram-positive infections. Peptide deformylase inhibitors and immunostimulating agents open new perspectives in this field; however, very few compounds targeting Gram-negative problematic pathogens are in the pipeline of the future. Tigecycline (recently marketed) ceftobiprole, ceftaroline and doripenem seem to possess an extended anti-Gram-positive and -negative spectrum. Among these compounds, only doripenem demonstrates activity against Pseudomonas aeruginosa, for which there is a clear unmet need for new compounds, focusing on new targets.

Activity of dalbavancin tested against Staphylococcus spp. and beta-hemolytic Streptococcus spp. isolated from 52 geographically diverse medical centers in the United States

Dalbavancin is a lipoglycopeptide antimicrobial agent with a potency significantly better than that of vancomycin when tested against staphylococci and streptococci. These two pathogens are common causes of skin and skin structure infections (SSSIs), and dalbavancin has been approved for the treatment of moderate to severe SSSIs. This study generated susceptibility data for staphylococci and beta-hemolytic streptococci from 52 U.S. medical centers that locally tested dalbavancin, vancomycin, and other antimicrobial class representatives to assess the potency of dalbavancin and the overall contemporary activities of commonly prescribed agents. Locally generated data showed that oxacillin-resistant staphylococci (57.0% overall) had slightly higher dalbavancin MIC(90) values (0.19 microg/ml) than oxacillin-susceptible strains (0.125 microg/ml). This potency was 8- to 16-fold greater than that for vancomycin. beta-Hemolytic streptococci had MIC(90) values ranging between <or=0.016 and 0.064 microg/ml (highest for group B isolates). Levofloxacin, gentamicin, and tetracycline were active against oxacillin-susceptible staphylococci (82 to 99% susceptible), with lower susceptibility rates seen for the oxacillin-resistant strains. Linezolid coverage was >98% against staphylococci. Erythromycin resistance was high for staphylococci (30.6 to 94.1%) with inducible clindamycin resistance rates of 26.0% and 55.0% for oxacillin-susceptible and -resistant Staphylococcus aureus, respectively. Beta-hemolytic streptococci had a 20.2% erythromycin resistance rate and a 60% inducible clindamycin resistance rate but were highly susceptible to other tested agents. Etest reading errors were apparent and skewed results towards slightly higher dalbavancin MICs, requiring further education on how to interpret Etest method results for this compound. Current disk diffusion breakpoint criteria for oxacillin susceptibility for S. aureus showed a very-major-error rate of 2.3% and only a 0.9% minor-error rate when cefoxitin was used to predict oxacillin susceptibility. Dalbavancin demonstrated excellent potency and activity (100% susceptibility at proposed breakpoints) against common causes of SSSI pathogens in this U.S. multicenter study sample.