Influence of human serum on pharmacodynamic properties of an investigational glycopeptide, LY333328, and comparator agents against Staphylococcus aureus

Optical Screening and Classification of Drug Binding to Proteins in Human Blood Serum

Protein-drug interactions in the human bloodstream are important factors in applications ranging from drug design, where protein binding influences efficacy and dose delivery, to biomedical diagnostics, where rapid, quantitative measurements could guide optimized treatment regimes. Current measurement approaches use multistep assays, which probe the protein-bound drug fraction indirectly and do not provide fundamental structural or dynamic information about the in vivo protein-drug interaction. We demonstrate that ultrafast 2D-IR spectroscopy can overcome these issues by providing a direct, label-free optical measurement of protein-drug binding in blood serum samples. Four commonly prescribed drugs, known to bind to human serum albumin (HSA), were added to pooled human serum at physiologically relevant concentrations. In each case, spectral changes to the amide I band of the serum sample were observed, consistent with binding to HSA, but were distinct for each of the four drugs. A machine-learning-based classification of the serum samples achieved a total cross-validation prediction accuracy of 92% when differentiating serum-only samples from those with a drug present. Identification on a per-drug basis achieved correct drug identification in 75% of cases. These unique spectroscopic signatures of the drug-protein interaction thus enable the detection and differentiation of drug containing samples and give structural insight into the binding process as well as quantitative information on protein-drug binding. Using currently available instrumentation, the 2D-IR data acquisition required just 1 min and 10 μL of serum per sample, and so these results pave the way to fast, specific, and quantitative measurements of protein-drug binding in vivo with potentially invaluable applications for the development of novel therapies and personalized medicine.

Protein Binding in Translational Antimicrobial Development-Focus on Interspecies Differences

Background/Introduction: Plasma protein binding (PPB) continues to be a key aspect of antibiotic development and clinical use. PPB is essential to understand several properties of drug candidates, including antimicrobial activity, drug-drug interaction, drug clearance, volume of distribution, and therapeutic index. Focus areas of the review: In this review, we discuss the basics of PPB, including the main drug binding proteins i.e., Albumin and α-1-acid glycoprotein (AAG). Furthermore, we present the effects of PPB on the antimicrobial activity of antibiotics and the current role of PPB in in vitro pharmacodynamic (PD) models of antibiotics. Moreover, the effect of PPB on the PK/PD of antibiotics has been discussed in this review. A key aspect of this paper is a concise evaluation of PPB between animal species (dog, rat, mouse, rabbit and monkey) and humans. Our statistical analysis of the data available in the literature suggests a significant difference between antibiotic binding in humans and that of dogs or mice, with the majority of measurements from the pre-clinical species falling within five-fold of the human plasma value. Conversely, no significant difference in binding was found between humans and rats, rabbits, or monkeys. This information may be helpful for drug researchers to select the most relevant animal species in which the metabolism of a compound can be studied for extrapolating the results to humans. Furthermore, state-of-the-art methods for determining PPB such as equilibrium dialysis, ultracentrifugation, microdialysis, gel filtration, chromatographic methods and fluorescence spectroscopy are highlighted with their advantages and disadvantages.

PEGylated Oligothioetheramide Prodrugs Activated by Host Serum Proteases

Due to the increasing prominence of antibiotic resistance, novel drug discovery and delivery approaches targeting bacteria are essential. In this work we evaluate a prodrug design to improve the cytotoxic profile of polycationic oligothioetheramides (oligoTEAs), which are promising antimicrobials. Herein we chemically modify the oligoTEA, PDT-4G, with a polyethylene glycol (PEG) and show that 1, 2, and 5 kDa PEGs mitigate cytotoxicity. As PEGylation reduces antibacterial activity, we evaluate two peptide linkers which, unlike oligoTEAs, are susceptible to proteolytic cleavage in serum. To gain insight into the prodrug reactivation, two linkers were tested, the 5-residue peptide sequence LMPTG, and the dipeptide sequence VC-PABC. In the presence of 20 % serum, prodrugs made with the VC-PABC linker successfully inhibited bacterial growth. Overall, we observed reactivation of oligoTEAs facilitated by serum protease cleavage of the peptide linkers. This work opens the door to the future design of antimicrobial prodrugs with tunable release profiles.

A Pharmacoepidemiologic Study of the Safety and Effectiveness of Clindamycin in Infants

BACKGROUND

Despite the absence of adequate safety or efficacy data, clindamycin is widely prescribed in the neonatal intensive care unit. We evaluated the association between clindamycin exposure and adverse events, as well as antibiotic effectiveness in infants.

METHODS

This was a retrospective cohort study of infants receiving clindamycin before postnatal day 121 who were discharged from a Pediatrix Medical Group neonatal intensive care unit (1997-2015). Using a previously developed pharmacokinetic model, we performed simulations to predict clindamycin exposure based on available dosing data. We used multivariable logistic regression to evaluate the association between clindamycin exposure and safety outcomes during and after clindamycin therapy. We reported the proportion of infants with methicillin-resistant Staphylococcus aureus (MRSA) bacteremia and clearance of MRSA bacteremia.

RESULTS

A total of 4089 infants received clindamycin at a median (25th-75th percentile) dose of 15 mg/kg/d (12-16). Clearance increased with older gestational age. Infants with the highest total clindamycin exposure had marginally increased odds of necrotizing enterocolitis within 7 days (adjusted odds ratio = 1.95 [1.04-3.63]), but exposure was not associated with death, sepsis, seizures, intestinal perforation or intestinal strictures. Of 25 infants who had MRSA bacteremia, 19 (76%) cleared the infection by the end of the clindamycin course.

CONCLUSIONS

Higher clindamycin exposure was not associated with increased odds of death or nonlaboratory adverse events. The use of pharmacokinetic models combined with available electronic health record data offers a valuable, cost-effective approach to analyzing the safety and effectiveness of drugs in infants when large-scale trials are not feasible.

Decoding the human serum interactome of snake-derived antimicrobial peptide Ctn[15-34]: Toward an explanation for unusually long half-life

The inherent propensity to enzymatic degradation of most peptides remains a bottleneck in their therapeutic development. Efficient, early screening methods are necessary for in vitro characterization of the molecular events occurring when peptides get in contact with biological fluids such us plasma. Herein we present an affinity purification/MS approach for mapping peptide serum interactors. We have applied this methodology to identify the serum partners of antibiotic peptide Ctn [15-34], aiming to ascertain the molecular interactions underlying its unusually long half-life (~ 12 h) in human serum. From 42 proteins captured in pull-downs with biotinylated Ctn [15-34] as bait, five are of special interest for their transport/binding properties hence alleged peptide arresting potential. The subset contains two members of the albumin superfamily, two apolipoproteins and a globulin. All five share a binding ability for hydrophobic species, and also bind Ctn [15-34], presumably via its C-terminal hydrophobic section, with affinities in the μM range as shown by surface plasmon resonance. Additionally, our functional enrichment reveals several significant immune-related processes suggesting an immunomodulatory role of Ctn [15-34]. Taken together, this study exemplifies how pharmacoproteomics can be used to analyze bioavailability issues and shed light on the serum interactors ultimately conferring protection to Ctn [15-34] against proteolytic events. SIGNIFICANCE: The affinity purification/MS identification methodology reported here can be viewed as a routine pharmacoproteomic approach to investigate the serum interactome of peptide drugs, identifying proteins affecting bioavailability and thus assisting the peptide drug development process. The specific results described here enlighten the serum stability issues of peptide Ctn [15-34] and ratify its promising future as an anti-infective lead.

Sensitivity of Antibacterial Activity to Backbone Sequence in Constitutionally Isomeric OligoTEAs

Antimicrobial peptides are promising alternatives to traditional antibiotics but their translational potential is limited due to rapid degradation by serum proteases. Recently, a number of peptidomimetics with backbones resistant to proteolysis have been synthesized and their antimicrobial potential evaluated as a function of their hydrophobic to cationic ratio. However, these mimetics also have a fixed backbone thus making it difficult to isolate the effect of backbone hydrophobic composition and sequence. In this work, advantage is taken of the oligothioetheramide (oligoTEA) synthetic strategy that allows for precise control over backbone and pendant group placement to systematically study the effect of backbone hydrophobic sequence while keeping pendant group constant. Biophysical data acquired with a set of constitutional oligoTEA isomers show that backbone hydrophobic sequence, that is, local hydrophobicity, affects the mode of oligoTEA interaction with lipid bilayers. This differential interaction among the constitutionally isomeric oligoTEAs is manifested in their antibacterial activities and points to the possibility of using backbone hydrophobic sequence to tune antibacterial potency and selectivity.

Effect of Composition on Antibacterial Activity of Sequence-Defined Cationic Oligothioetheramides

In response to the urgent need for new antibiotic development strategies, antimicrobial peptides and their synthetic mimetics are being investigated as promising alternatives to traditional antibiotics. To facilitate their development into clinically viable candidates, we need to understand what molecular features and physicochemical properties are needed to induce cell death. Within the context of sequence-defined oligothioetheramides (oligoTEAs), we explore the impact of the cationic pendant group and backbone hydrophobicity on the potency and selectivity of antibacterial oligoTEAs. Through antibacterial, cytotoxicity, membrane destabilization, and membrane depolarization assays, we find a strong dependency on the nature of the cationic group and improved selectivity toward bacteria by tuning backbone hydrophobicity. In particular, compounds with the guanidinium headgroup are more potent than those with amines. Finally, we identify a promising oligoTEA, PDT-4G, with enhanced activity in vitro (minimum inhibitory concentration (MIC) ∼ 0.78 μM) and moderate activity in a mouse thigh infection model of methicillin-resistant Staphylococcus aureus. The studies outlined in this work provide insights into the effect of macromolecular physicochemical properties on antibacterial potency. This knowledge base will be vital for researchers engaged in the ongoing development of clinically viable antibacterial agents.

Pharmacodynamic studies of voriconazole: informing the clinical management of invasive fungal infections

INTRODUCTION

Voriconazole is a broad-spectrum antifungal agent commonly used to treat invasive fungal infections (IFI), including aspergillosis, candidiasis, Scedosporium infection, and Fusarium infection. IFI often occur in immunocompromised patients, leading to increased morbidity and mortality.

AREAS COVERED

The objective of this review is to summarize the pharmacodynamic properties of voriconazole and to provide considerations for potential optimal dosing strategies. Studies have demonstrated superior clinical response when an AUC/MIC >25 or Cmin/MIC >1 is attained in adult patients, correlating to a trough concentration range as narrow as 2-4.5 mg/L; however, these targets are poorly established in the pediatric population. Topics in this discussion include voriconazole use in multiple age groups, predisposing patient factors for IFI, and considerations for clinicians managing IFI. Expert commentary: The relationship between voriconazole dosing and exposure is not well defined due to the large inter- and intra-subject variability. Development of comprehensive decision support tools for individualizing dosing, particularly in children who require higher dosing, will help to increase the probability of achieving therapeutic efficacy and decrease sub-therapeutic dosing and adverse events.

Clindamycin Pharmacokinetics and Safety in Preterm and Term Infants

Clindamycin may be active against methicillin-resistant Staphylococcus aureus, a common pathogen causing sepsis in infants, but optimal dosing in this population is unknown. We performed a multicenter, prospective pharmacokinetic (PK) and safety study of clindamycin in infants. We analyzed the data using a population PK analysis approach and included samples from two additional pediatric trials. Intravenous data were collected from 62 infants (135 plasma PK samples) with postnatal ages of <121 days (median [range] gestational age of 28 weeks [23 to 42] and postnatal age of 17 days [1 to 115]). In addition to body weight, postmenstrual age (PMA) and plasma protein concentrations (albumin and alpha-1 acid glycoprotein) were found to be significantly associated with clearance and volume of distribution, respectively. Clearance reached 50% of the adult value at PMA of 39.5 weeks. Simulated PMA-based intravenous dosing regimens administered every 8 h (≤32 weeks PMA, 5 mg/kg; 32 to 40 weeks PMA, 7 mg/kg; >40 to 60 weeks PMA, 9 mg/kg) resulted in an unbound, steady-state concentration at half the dosing interval greater than a MIC for S. aureus of 0.12 μg/ml in >90% of infants. There were no adverse events related to clindamycin use. (This study has been registered at ClinicalTrials.gov under registration no. NCT01728363.).

Determination of compound kill kinetics against Mycobacterium tuberculosis

In this chapter, we describe how to determine the kill kinetics and minimum bactericidal concentration (MBC) of a compound against Mycobacterium tuberculosis. Techniques are described for three conditions: actively growing aerobic bacteria, and non-replicating bacteria induced by nutrient starvation and/or low pH. Each technique involves determining the number of viable bacteria in the presence of several concentrations of compound over 3 weeks. Guidelines for how to interpret the results, to determine if growth-inhibitory compounds are bactericidal or bacteriostatic and also whether compounds exhibit time-dependent or concentration-dependent kill are provided.

Amphotericin B- and voriconazole-echinocandin combinations against Aspergillus spp.: Effect of serum on inhibitory and fungicidal interactions

Antifungal combination therapy with voriconazole or amphotericin B and an echinocandin is often employed as primary or salvage therapy for management particularly of refractory aspergillosis. The pharmacodynamic interactions of amphotericin B- and voriconazole-based combinations with the three echinocandins caspofungin, micafungin, and anidulafungin in the presence of serum were tested against 15 Aspergillus fumigatus complex, A. flavus complex, and A. terreus complex isolates to assess both their growth-inhibitory and fungicidal activities. The in vitro activity of each drug alone and in combination at a 1:1 fixed concentration ratio was tested with a broth microdilution colorimetric method, and interactions were assessed by isobolographic analysis. Synergy was found for all amphotericin B- and voriconazole-based combinations, with amphotericin B-based combinations showing strong inhibitory synergistic interactions (interaction indices of 0.20 to 0.52) and with voriconazole-based combinations demonstrating strong fungicidal synergistic interactions (interaction indices of 0.10 to 0.29) (P < 0.001). Drug- and species-specific differences were found, with caspofungin and the A. fumigatus complex exhibiting the weakest synergistic interactions. In the presence of serum, the synergistic interactions were reduced in the order (from largest to smallest decrease) micafungin > anidulafungin > caspofungin, and A. flavus complex > A. fumigatus complex > A. terreus complex, resulting in additive interactions, particularly for inhibitory activities of amphotericin B-echinocandin combinations and fungicidal activities of voriconazole-echinocandin combinations. Drug- and species-specific differences were found in the presence of serum for inhibitory activities of antifungal drugs, with the lowest interaction indices being observed for amphotericin B-caspofungin (median, 0.77) and for the A. terreus complex (median, 0.56). The present in vitro data showed that serum had a major impact on synergistic interactions of amphotericin B-echinocandin and voriconazole-echinocandin combinations, resulting in additive interactions and explaining the indifferent outcomes usually observed in vivo.

Human serum binding and its effect on the pharmacodynamics of the lantibiotic MU1140

The degree of MU1140 binding to human serum was measured and the effect of serum on MU1140 pharmacodynamics against Streptococcus pneumoniae and Staphylococcus aureus was investigated. 92.7% ± 2.0% of total MU1140 was bound to serum components as determined by ultrafiltration when tested in the concentration range 6.25-200 μg/ml. MIC and time-kill studies were used to study the effect of serum on the dynamics of MU1140. Serum inhibited MU1140 activity against S. pneumoniae but was found to enhance its activity against S. aureus. This phenomenon has not been reported for any other lantibiotic. Time-kill studies of MU1140 against S. aureus in various concentrations of serum revealed that the greatest bactericidal effect was observed at the lowest serum concentration. Mathematical modeling was used to quantify serum augmentation of MU1140 activity against S. aureus. Serum, at the lowest concentration, was shown to decrease MU1140 EC(50) against S. aureus by an order of magnitude. The data suggests that unbound MU1140 comprise the pharmacologically active fraction. Further, these findings suggest the possible existence of a complex dual inhibition and augmentation effect of serum on MU1140's activity against S. aureus. The molecular mechanism responsible for the synergistic action of human serum on MU1140's activity against S. aureus remains to be elucidated.

Assessment of oritavancin serum protein binding across species

Biophysical methods to study the binding of oritavancin, a lipoglycopeptide, to serum protein are confounded by nonspecific drug adsorption to labware surfaces. We assessed oritavancin binding to serum from mouse, rat, dog, and human by a microbiological growth-based method under conditions that allow near-quantitative drug recovery. Protein binding was similar across species, ranging from 81.9% in human serum to 87.1% in dog serum. These estimates support the translation of oritavancin exposure from nonclinical studies to humans.

Impact of human serum albumin on oritavancin in vitro activity against enterococci

Oritavancin is a lipoglycopeptide with activity against gram-positive pathogens including vancomycin-resistant enterococci. The impact of human serum albumin (HSA) on oritavancin activity against enterococci was compared to those of vancomycin, daptomycin, teicoplanin, and linezolid in vitro using MIC and time-kill methods. Oritavancin MICs increased between 0- and 8-fold in the presence of HSA. In time-kill assays with HSA, oritavancin retained activity, killing or inhibiting enterococci more rapidly than did comparators when peak concentrations were simulated.

Intracellular activity of antibiotics in a model of human THP-1 macrophages infected by a Staphylococcus aureus small-colony variant strain isolated from a cystic fibrosis patient: study of antibiotic combinations

In a companion paper (H. A. Nguyen et al., Antimicrob. Agents Chemother. 53:1434-1442, 2009), we showed that vancomycin, oxacillin, fusidic acid, clindamycin, linezolid, and daptomycin are poorly active against the intracellular form of a thymidine-dependent small-colony variant (SCV) strain isolated from a cystic fibrosis patient and that the activity of quinupristin-dalfopristin, moxifloxacin, rifampin, and oritavancin remains limited (2- to 3-log CFU reduction) compared to their extracellular activity. Antibiotic combination is a well-known strategy to improve antibacterial activity, which was examined here against an intracellular SCV strain using combinations with either rifampin or oritavancin. Time-kill curve analysis using either concentrations that caused a static effect for each antibiotic individually or concentrations corresponding to the maximum concentration in human serum showed largely divergent effects that were favorable when antibiotics were combined with rifampin at low concentrations only and with oritavancin at both low and high concentrations. The nature of the interaction between rifampin, oritavancin, and moxifloxacin was further examined using the fractional maximal effect method, which allows categorization of the effects of combinations when dose-effect relationships are not linear. Rifampin and oritavancin were synergistic at all concentration ratios investigated. Oritavancin and moxifloxacin were also synergistic but at high oritavancin concentrations only. Rifampin and moxifloxacin were additive. This approach may help in better assessing and improving the activity of antibiotics against intracellular SCV strains.

Urinary bactericidal activity of extended-release ciprofloxacin (1,000 milligrams) versus levofloxacin (500 milligrams) in healthy volunteers receiving a single oral dose

Twelve volunteers received a single oral dose of 1,000 mg extended-release (XR) ciprofloxacin versus 500 mg levofloxacin to assess urinary bactericidal titers (UBTs) against common uropathogens. Areas under UBT-time curves were significantly larger for Proteus mirabilis with XR ciprofloxacin and for staphylococci with levofloxacin.

Pharmacokinetics, safety, and tolerability of ascending single intravenous doses of oritavancin administered to healthy human subjects

Oritavancin (LY333328 diphosphate) is a novel glycopeptide antimicrobial agent with potent microbiological activity in vitro against Gram-positive bacteria. A single-dose, open-label, noncontrolled, dose-escalation study in 11 healthy human subjects was carried out to evaluate the safety and pharmacokinetics of oritavancin. One subject at each dose level received a single intravenous dose of 0.02, 0.03, 0.05, 0.08, 0.125, 0.20, and 0.325 mg/kg infused over 1 hour and four subjects each received a single-dose of 0.5 mg/kg. Safety and tolerability were evaluated by monitoring adverse events and laboratory parameters. Oritavancin pharmacokinetics were assessed by blood, urine, and fecal sampling. The plasma concentrations of oritavancin after the end of infusion followed a multiexponential decline over a 2-week period. Median (range) C(max) for the 0.5 mg/kg dose group was 6.5 (4.7-7.6) microg/mL. In every subject, plasma concentrations declined to < or =10% of the C(max) within 24 hours. Following a short, constant-rate infusion, the pharmacokinetics of oritavancin were linear across a total dose range from 3.66-44.6 mg. Renal clearance was approximately 0.457 mL/min. The mean (range) plasma terminal half-life of oritavancin was 195.4 (135.8-273.8) hours across all dose levels from 0.05-0.5 mg/kg. Less than 5% and 1% of administered drug were recovered in the urine and feces, respectively, after 7 days. This first time in man evaluation of oritavancin revealed that single doses of oritavancin of up to and including 0.5 mg/kg were safe and well tolerated. Although no clinically relevant changes in renal, hepatic and hematologic indices from baseline were observed, five subjects did manifest asymptomatic and transient elevations of hepatic transaminase concentrations. Because this study was not placebo-controlled and enrolled a small number of subjects, the safety and pharmacokinetic profiles of oritavancin need to be confirmed in additional studies.

Glycopeptide Antibiotics

Vancomycin and teicoplanin are still the only glycopeptide antibiotics available for use in humans. Emergence of resistance in enterococci and staphylococci has led to restriction of their use to severe infections caused by Gram-positive bacteria for which no other alternative is acceptable (because of resistance or allergy). In parallel, considerable efforts have been made to produce semisynthetic glycopeptides with improved pharmacokinetic and pharmacodynamic properties, and with activity towards resistant strains. Several molecules have now been obtained, helping to better delineate structure-activity relationships. Two are being currently evaluated for skin and soft tissue infections and are in phases II/III. The first, oritavancin (LY333328), is the 4'-chlorobiphenylmethyl derivative of chloroeremomycin, an analogue to vancomycin. It is characterised by: i) a spectrum covering vancomycin-resistant enterococci (VRE), methicillin-resistant Staphylococcus aureus (MRSA) and to some extent glycopeptide-intermediate S. aureus (GISA); ii) rapid bactericidal activity including against the intracellular forms of enterococci and staphylococci; and iii) a prolonged half-life, allowing for daily administration. The second molecule is dalbavancin (BI397), a derivative of the teicoplanin analogue A40926. Dalbavancin has a spectrum of activity similar to that of oritavancin against vancomycin-sensitive strains, but is not active against VRE. It can be administered once a week, based on its prolonged retention in the organism. Despite these remarkable properties, the use of these potent agents should be restricted to severe infections, as should the older glycopeptides, with an extension towards resistant or poorly sensitive bacteria, to limit the risk of potential selection of resistance.

Influence of human serum on antifungal pharmacodynamics with Candida albicans

Antifungal susceptibilities (NCCLS, approved standard M27-A, 1997) were determined for the reference strain ATCC 90028 and 21 clinical isolates of Candida albicans with varying levels of fluconazole susceptibility using RPMI 1640 (RPMI) and 80% fresh human serum-20% RPMI (serum). Sixty-four percent (14 of 22) of the isolates tested demonstrated significant decreases (> or = 4-fold) in fluconazole MICs in the presence of serum, and the remaining eight isolates exhibited no change. Itraconazole and ketoconazole, two highly protein-bound antifungal agents, had MICs in serum that were increased or unchanged for 46% (10 of 22) and 41% (9 of 22) of the isolates, respectively. All 10 isolates tested against an investigational antifungal agent, LY303366, demonstrated significant increases in the MIC required in serum, while differences in amphotericin B MICs in the two media were not observed. Four of 10 isolates tested demonstrated fourfold higher flucytosine MICs in serum than in RPMI. Postantifungal effects (PAFEs) and 24-h kill curves were determined by standard methods for selected isolates. At the MIC, fluconazole, itraconazole, ketoconazole, flucytosine, and LY303366 kill curves and PAFEs in RPMI were similar to those in serum. Isolates of fluconazole-resistant C. albicans required lower MICs in serum than in RPMI, without relative increases in fungal killing or PAFEs. Isolates tested against amphotericin B demonstrated significantly reduced killing and shorter PAFEs in serum than in RPMI without observable changes in MIC. In conclusion, antifungal pharmacodynamics in RPMI did not consistently predict antifungal activity in serum for azoles and amphotericin B. Generally speaking, antifungal agents with high protein binding exhibited some form of reduced activity (MIC, killing, or PAFE) in the presence of serum compared to those with low protein binding.

Activity of oritavancin (LY333328), an investigational glycopeptide, compared to that of vancomycin against multidrug-resistant Streptococcus pneumoniae in an in vitro pharmacodynamic model

In the past 2 decades, multidrug-resistant Streptococcus pneumoniae has been encountered with increasing frequency around the world. This has led to the need for newer agents in the treatment of S. pneumoniae infections. Oritavancin (LY333328) is a new glycopeptide antibiotic with activity against gram-positive organisms; however, there is limited information on the pharmacodynamics of oritavancin with respect to the treatment of S. pneumoniae. We utilized an in vitro pharmacodynamic model to compare the activity of oritavancin to that of vancomycin against two penicillin-, macrolide-, and ciprofloxacin-resistant S. pneumoniae isolates (R919 and R921) over a 48-h period. Both oritavancin and vancomycin achieved 99.9% (3-log) kill, with oritavancin achieving the limit of detection (10(2) CFU/ml) within 1 h and vancomycin achieving this limit at 24 h for both isolates. Detection of resistance was not observed for oritavancin or vancomycin during the 48-h experiments. The key pharmacodynamic parameter for oritavancin has not been well defined. In our experiment, the ratios of the area under the curve from 0 to 24 h to the MIC of oritavancin, oritavancin plus albumin, and vancomycin for both isolates were greater than 944.5, and the ratios of the maximum concentration of drug in serum to the MIC ranged from 73.7 to 7188.5. T>MIC was 100% for oritavancin and vancomycin for both isolates. Oritavancin is a unique and potent antimicrobial that warrants further investigation against multidrug-resistant S. pneumoniae.

[Glycopeptides]

OBJECTIVES

To review pharmacology, pharmacokinetic and therapeutic use of glycopeptides in intensive care units.

DATA SOURCES

Extraction from Medline database of French and English articles on glycopeptides and search along with major review articles.

DATA SELECTION

The collected articles were reviewed and selected according to their quality and originality. The more recent data were selected.

DATA SYNTHESIS

Glycopeptides are bactericidal antibiotics which are only active against Gram positive species acting by inhibiting peptidoglycan synthesis. They had been in clinical use for almost 30 years without high-level resistance underlining. For ten years, there have been disturbing reports of first, resistance to vancomycin in enterococcal species and more recently in strains of Staphylococcus aureus by complex and large mechanisms of action. This new resistances may lead to a therapeutic impasse and a fatal issue for infected patients. The only response to this situation is the respect of prescription rules and the careful use of antibiotics.

CONCLUSION

Considering their spectrum, glycopeptides are an antibiotic family which importance is fundamental to treat infected patients of intensive care units. Staff members of intensive care units are responsible for their good use.

New developments in the treatment of infective endocarditis infective cardiovasculitis

The natural history of infective endocarditis has undergone remarkable changes over the past 100 years as regards both the demographic characteristics of the disease and changes in the incidence of the so-called diagnostic signs. Alongside these changes and the development of new and better diagnostic tools and criteria, we are also facing new problems with the precise definition of cardiovascular infections and calculation of the incidence of the disease. Nosocomial endocarditis presents an emerging problem of diagnosis and treatment after heart valve surgery, with pace-maker catheters, defibrillators and a very large variety of foreign materials used in connection with heart valve surgery. New technological progress including new types of prosthetic valves and use of homografts or the Ross operation will give a greater possibility of choosing the best solution in a particular case. Antimicrobial chemotherapy is mainly based on our understanding of the pathophysiology of the disease and efficacy of the antibiotics achieved in an experimental animal model of endocarditis. Important recommendations of single or combined drug therapy or the dosing regimens of antibiotics are still an expression of expert opinion not always supported by experimental or clinical proof. A typical example is the recommendation of two divided doses of gentamicin for treatment of streptococcal endocarditis. Nevertheless, it is the author's opinion that the development of uncomplicated, easy to handle diagnostic and treatment regimens are justified in order to achieve better compliance with these recommendations.