Activity of a new glycopeptide antibiotic (LY333328) against enterococci and other resistant gram-positive organisms

Lipophilic teicoplanin pseudoaglycon derivatives are active against vancomycin- and teicoplanin-resistant enterococci

A selection of nine derivatives of teicoplanin pseudoaglycon were tested in vitro against clinical vancomycin-resistant Enterococcus strains possessing vanA, vanB or both genes. The bacteria were characterized by PCR for the identification of their resistance genes. The tested compounds contain lipoic acid, different carbohydrates and aryl groups as lipophilic moieties. About one-third of the teicoplanin-resistant strains were shown to be susceptible to one or more of the glycopeptide derivatives.

Oritavancin diphosphate

Each month, subscribers to The Formulary Monograph Service receive 5 to 6 well-documented monographs on drugs that are newly released or are in late phase 3 trials. The monographs are targeted to Pharmacy & Therapeutics Committees. Subscribers also receive monthly 1-page summary monographs on agents that are useful for agendas and pharmacy/nursing in-services. A comprehensive target drug utilization evaluation/medication use evaluation (DUE/MUE) is also provided each month. With a subscription, the monographs are sent in print and are also available on-line. Monographs can be customized to meet the needs of a facility. A drug class review is now published monthly with The Formulary Monograph Service. Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. For more information about The Formulary Monograph Service, call The Formulary at 800-322-4349. The December 2014 monograph topics are olodaterol, peginterferon beta-1a, testosterone nasal gel, ferric citrate corredination complex, and safinamide. The Safety MUE is on olodaterol.

Oritavancin diphosphate

Each month, subscribers to The Formulary Monograph Service receive 5 to 6 well-documented monographs on drugs that are newly released or are in late phase 3 trials. The monographs are targeted to Pharmacy & Therapeutics Committees. Subscribers also receive monthly 1-page summary monographs on agents that are useful for agendas and pharmacy/nursing in-services. A comprehensive target drug utilization evaluation/medication use evaluation (DUE/MUE) is also provided each month. With a subscription, the monographs are sent in print and are also available on-line. Monographs can be customized to meet the needs of a facility. A drug class review is now published monthly with The Formulary Monograph Service. Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. For more information about The Formulary Monograph Service, call The Formulary at 800-322-4349. The December 2014 monograph topics are olodaterol, peginterferon beta-1a, testosterone nasal gel, ferric citrate corredination complex, and safinamide. The Safety MUE is on olodaterol.

Oritavancin: a new avenue for resistant Gram-positive bacteria

Oritavancin, a new semisynthetic glycopeptide has a spectrum of activity similar to vancomycin, although it exhibits potent antimicrobial activity against vancomycin-resistant staphylococci and enterococci species. It has a long-terminal half-life of 360 h, is highly protein bound and has been dosed once-daily in clinical trials. Oritavancin has been studied in complicated skin and skin structure infections where it was noninferior to the comparator group of vancomycin/cephalexin. Thus far, oritavancin has a favorable side-effect profile and appears promising in the treatment of multidrug resistant Gram-positive bacteria.

Gram-positive resistance: pathogens, implications, and treatment options: insights from the Society of Infectious Diseases Pharmacists

Despite the advent of new antibiotics, resistance in gram-positive pathogens, including staphylococci and enterococci, continues to increase. This is evident with the recent emergence of vancomycin-resistant Staphylococcus aureus . Newer treatment agents are available, including quinupristin-dalfopristin, linezolid, and daptomycin. In addition, investigational agents are being explored. Clinical trials have been conducted for various infections, such as skin and skin structure infections, pneumonia, and bloodstream infections. Antibacterial activity, site of infection, and potential for adverse effects must be taken into account when making decisions regarding therapy.

In vitro activity of oritavancin (LY333328), vancomycin, clindamycin, and metronidazole against Clostridium perfringens, Propionibacterium acnes, and anaerobic Gram-positive cocci

Using an agar dilution method, we determined the in vitro activity of oritavancin, vancomycin, clindamycin and metronidazole against 114 unique clinical isolates of Gram-positive anaerobes. MIC(90)s (microg/mL) for oritavancin were as follows: Clostridium perfringens 1.0, Propionibacterium acnes 0.25, Peptostreptococcus anaerobius 0.25, Peptoniphilus asaccharolyticus 0.5, Finegoldia magna 0.25, Micromonas. micros 0.25, and Anaerococcus prevotii 0.25. On a weight basis, oritavancin is slightly more active than vancomycin against the strains tested. The oritavancin MICs are comparable to those previously reported against staphylococci and enterococci. Oritavancin shows excellent potential for treatment of infections containing Gram-positive anaerobes such as these.

Oritavancin and Tigecycline: Investigational Antimicrobials for Multidrug-Resistant Bacteria

The advent of multidrug-resistant gram-positive aerobes such as Staphylococcus aureus, Streptococcus pneumoniae, and the enterococci, which are resistant to beta-lactams, vancomycin, and a host of other commonly used antimicrobials, has complicated our approach to antibiotic therapy. Despite marketing of the first oxazolidinone, linezolid, and the streptogramin combination, quinupristin-dalfopristin, an urgent need exists for more agents to combat these pathogens. Two such agents, the glycopeptide oritavancin (LY333328) and the glycylcycline tigecycline (GAR-936), are in phase III clinical trials. These agents, which require parenteral administration, exhibit substantial in vitro activity against a variety of gram-positive aerobes and anaerobes, including the multidrug-resistant organisms listed previously. Only tigecycline demonstrates useful activity against gram-negative organisms. Combination therapy of these agents with ampicillin or aminoglycosides frequently leads to synergistic in vitro activity against multidrug-resistant staphylococci and streptococci. These agents are also active in a variety of animal models of systemic and localized infections. Few published efficacy and tolerability data are available in humans. If controlled clinical trial data verify these agents' efficacy and tolerability, both drugs should become welcome additions to the available antimicrobials. However, restricting their use to the treatment of infections caused by bacteria resistant to other antimicrobials, especially multidrug-resistant staphylococci and streptococci, may prolong their clinical utility by retarding the development of resistance. Careful surveillance of bacterial sensitivity to these agents should be undertaken to assist clinicians in the decision whether or not to use these agents empirically to treat infections caused by suspected multidrug-resistant gram-positive pathogens.

Recent developments in antibiotic treatment

Antibiotic resistance of gram-positive and gram-negative bacteria remains a major challenge for clinicians treating HAP. Since the recent release of linezolid and QD, treatment options for resistant gram-positive bacteria have improved. The development of new substances continues and it is hoped that some of them will be available soon. Investigation has centered on gram-positive bacteria, although multiresistant gram-negative pathogens, such as A haumanii, S maltophilia, and resistant P aeruginosa, are of major clinical relevance. New treatment options are unfortunately not in sight. No antibiotic, however, is a miraculous magic wand against resistant bacteria. The bugs are smart; they have been on this world far longer than humans. Regardless of how innovative the mechanism of action of new substances is, resistance will emerge. The solution is certainly not a nihilistic approach leading to a fearful restriction in the use of new substances. No antibiotic, regardless of its potency, can free the clinician from keeping the difficult balance between individual undertreatment and general overtreatment.

Novel agents for the treatment of resistant Gram-positive infections

Bacteria have proved themselves able to develop resistance to every antibiotic used clinically. Traditional agents used for treatment of serious infections caused by Gram-positive species have recently been supplemented with the introduction of linezolid, quinupristin-dalfopristin, several new quinolones and telithromycin. However, resistance to many of these agents has already been reported and, although each currently retains activity against the vast majority of clinical isolates of its target species, their long-term efficacy is uncertain. We must look to develop other compounds to replace and hopefully improve upon existing anti-Gram-positive agents. Daptomycin (a lipopeptide), oritavancin and dalbavancin (both second-generation glycopeptides) and ramoplanin (a glycolipodepsipeptide) are among the agents in advanced stages of development and, at present, many seem likely to proceed to licensing. In addition, it is encouraging that many agents active against novel bacterial targets have been discovered and are in earlier stages of development. In the next two decades, we should be optimistic that a regular flow of new anti-Gram-positive agents will enable us to offset the constant spectre of bacterial resistance.

Mechanism of action of oritavancin and related glycopeptide antibiotics

Oritavancin (LY333328) is a semisynthetic glycopeptide antibiotic having excellent bactericidal activity against glycopeptide-susceptible and -resistant Gram-positive bacteria. Oritavancin is the N-alkyl-p-chlorophenylbenzyl derivative of chloroeremomycin (LY264826) and is currently in phase III clinical trials for use in Gram-positive infections. Studies show that oritavancin and related alkyl glycopeptides inhibit bacterial cell wall formation by blocking the transglycosylation step in peptidoglycan biosynthesis in a substrate-dependent manner. As with other glycopeptide antibiotics, including vancomycin, the effects of oritavancin on cell wall synthesis are attributable to interactions with dipeptidyl residues of peptidoglycan precursors. Unlike vancomycin, however, oritavancin is strongly dimerized and can anchor to the cytoplasmic membrane, the latter facilitated by its alkyl side chain. Cooperative interactions derived from dimerization and membrane anchoring in situ can be of sufficient strength to enable binding to either dipeptidyl or didepsipeptidyl peptidoglycan residues of vancomycin-susceptible and -resistant enterococci, respectively. This review describes the antibacterial activity of oritavancin, and examines the evidence supporting the proposed mechanism of action for this agent and related analogs.

Coagulase-negative staphylococci as a cause of infections related to intravascular prosthetic devices: limitations of present therapy

Coagulase-negative staphylococci (CNS) are an important cause of catheter-related bloodstream infections. This review will shed light on the pathogenesis related to biofilm formation, and will discuss antimicrobial susceptibility of CNS to older and newer antibiotics, as well as therapeutic options.

Novel agents for resistant Gram-positive infections--a review

Gram-positive infections have increased in recent years, particularly those that are of nosocomial origin, leading to a broad use of agents with activity against these pathogens. Concomitantly, antimicrobial resistance of these pathogens also became widespread. Among the most common Gram-positive resistant pathogens are: Streptococcus pneumoniae, resistant to penicillin and macrolides, methicillin-resistant Staphylococcus aureus (MRSA), glycopeptide-intermediately-resistant S. aureus (GISA), methicillin-resistant S. epidermidis, glycopeptide-resistant enterococci and vancomycin-resistant enterococci (VRE). The response of the pharmaceutical industry to this challenge was the development of new antibiotics active against these pathogens. Among these antibiotics, this review will focus on: linezolid, an oxazolidinone; GAR-936, a tetracycline derivative; daptomycin, a lipopeptide; and ortivancin (LY-333328), a glycopeptide related to vancomycin. Except for linezolid, which has been recently launched in many countries, all other agents referred to in this review are still at various developmental stages. It is hoped that in the near future most of these agents will be approved and thus the grim outlook of patients infected with resistant Gram-positive bacteria may improve.

In vitro activities of LY333328 and comparative agents against nosocomial gram-positive pathogens collected in a 1997 global surveillance study

The in vitro activity of LY333328 was evaluated for 1,479 nosocomial gram-positive pathogens isolated in 12 countries during 1997. LY333328 MICs at which 90% of the isolates tested were inhibited for Enterococcus faecalis (n = 351), Enterococcus faecium (n = 100), Staphylococcus aureus (n = 593), coagulase-negative Staphylococcus species (n = 325), and Streptococcus pneumoniae (n = 110) were 1, 1, 2, 2, and 0.015 microg/ml, respectively. LY333328 demonstrated potent activity against isolates of vancomycin-resistant enterococci, oxacillin-resistant staphylococci, and penicillin-resistant pneumococci.

Antimicrobial susceptibility patterns of enterococci causing infections in Europe. The European VRE Study Group

In vitro susceptibilities of 4,208 enterococci (83% Enterococcus faecalis isolates, 13.6% Enterococcus faecium isolates, and 3.4% isolates of other species) from patients in 27 European countries towards 16 antibiotics were determined. High-level resistance to gentamicin varied by country (range, 1 to 49%; mean, 22.6% +/- 12. 3%) and per species (19.7% E. faecalis isolates, 13.6% E. faecium isolates, 3.4% by other species). Vancomycin resistance was detected in 0.06% E. faecalis, 3.8% E. faecium, and 19.1% isolates of other species. All enterococci were susceptible to LY 333328 and everninomicin, and 25% of E. faecalis isolates and 85% of other enterococci were susceptible to quinupristin-dalfopristin. The MIC of moxifloxacin and trovafloxacin for ciprofloxacin-susceptible E. faecalis at which 90% of the isolates were inhibited was 0.25 to 0.5 microg/ml.

MIC distribution and inoculum effect of LY333328: a study of vancomycin-susceptible and VanA-type and VanC-type enterococci obtained from intensive care unit patient surveillance cultures

OBJECTIVE: To determine the in vitro activity and inoculum effect of LY333328, a semisynthetic glycopeptide, against vancomycin-susceptible and vancomycin-resistant enterococcal isolates. METHODS: One hundred and seventy-six enterococcal isolates (117 vancomycin-susceptible, 29 VanA-type and 30 VanC-type isolates) obtained from surveillance cultures of 139 intensive care unit patients were studied by the standard agar dilution method. Vancomycin resistance determinants were characterized by PCR. RESULTS: The activity of LY333328 was comparable (MIC range, 0.1-2 mg/L) to those of vancomycin (0.1-4 mg/L) and teicoplanin (0.06-1 mg/L) for vancomycin-susceptible isolates. LY333328 was more active (0.1-8 mg/L) than vancomycin (256 to >1024 mg/L) and teicoplanin (32-512 mg/L) against VanA-type isolates, and similar (0.2-1 mg/L) to teicoplanin (0.1-0.5 mg/L) against VanC-type isolates. The MIC distribution of LY333328 displayed a narrower range than that of vancomycin, with no clear distinction between susceptible and resistant populations. The increment in the inoculum size, from 104 to 106 CFU/spot, of susceptible isolates increased the MIC values of LY333328, vancomycin and teicoplanin by factors of 11.4, 1.6 and 3.8, respectively. The corresponding factors for LY333328 for VanA-type and VanC-type isolates were 3.5 and 6.4, respectively. CONCLUSIONS: LY333328 displays an excellent in vitro activity against vancomycin-susceptible and -resistant enterococci. Nevertheless, the inoculum size used in susceptibility tests should be carefully controlled.

Vancomycin-Resistant Enterococcus: Infectious Endocarditis Treatment

Vancomycin-resistant Enterococcus species represent serious gram-positive pathogens for which there is currently no recommended therapy. There are a number of new antibiotics with activity against these pathogens in development. Although there is a great deal of experience with some of these agents for skin and soft tissue infections, bacteremia, pneumonia, and intra-abdominal infections, there is currently little information available for the treatment of endocarditis. Animal and limited human data thus far suggest that new agents such as quinuprisitin-dalfopristin, LY333328 (a new glycopeptide antibiotic), and daptomycin (a lipopeptide antibiotic) may prove useful for this indication. Additional information, and especially combination treatment, are warranted to improve success and limit the emergence of resistance to these new antibiotics.

Activity and diffusion of LY333328 in experimental endocarditis due to vancomycin-resistant Enterococcus faecalis

The activity of LY333328 against Enterococcus faecalis JH2-2, which is susceptible to glycopeptides, and against its transconjugants E. faecalis BM4281 and BM4316, with VanB and VanA phenotypes, respectively, was investigated. LY333328 was active in vitro against the three strains, for which MICs were 2 microg/ml on agar and 0.25 microg/ml in broth. LY333328 was bactericidal in broth against E. faecalis JH2-2 and BM4281 at a concentration of 8 microg/ml and against BM4316 at a concentration of 30 microg/ml. The protein binding of LY333328 to rabbit serum was >99%, and the bactericidal activity of LY333328 in broth was reduced when it was tested in the presence of 90% rabbit serum. Autoradiographic studies performed in rabbits with enterococcal endocarditis showed that 14[C]LY333328 was distributed heterogeneously throughout cardiac vegetations. In rabbits with aortic endocarditis, a regimen of 20 mg of LY333328 per kg of body weight administered intramuscularly twice a day for 5 days after a loading dose of 40 mg/kg was active against the three strains in vivo (P < 0.01), whereas vancomycin was not active against the VanB-type strain and teicoplanin was not active against the VanA-type strain. We conclude that the activity of LY333328 is not significantly modified by acquired resistance to glycopeptides in E. faecalis either in vitro or in experimental endocarditis.

Comparison of inhibitory and bactericidal activities and postantibiotic effects of LY333328 and ampicillin used singly and in combination against vancomycin-resistant Enterococcus faecium

One hundred ninety-five individual vancomycin-resistant Enterococcus faecium (VRE) isolates from five upstate New York hospitals were studied for antimicrobial susceptibilities to LY333328, quinupristin-dalfopristin, teicoplanin, ampicillin, and gentamicin. LY333328 was the most active antibiotic against VRE. The effect of media and methods on the antibacterial activity of LY333328, its synergy with ampicillin, and the postantibiotic effects (PAE) of LY333328 and ampicillin were evaluated. In microdilution tests, the MIC of LY333328 at which 90% of the isolates were inhibited (MIC90) was 2 microg/ml in Mueller-Hinton II (MH II) broth and 1 microg/ml in brain heart infusion (BHI) broth. In contrast, on MH II agar the MIC90 was 4 microg/ml and on BHI agar it was >16 microg/ml. Bactericidal activity was observed for most strains at concentrations from 8 to >/=133 times the MIC of the tube macrodilution in MH II broth. A bactericidal effect of LY333328 plus ampicillin was demonstrated in time-kill studies, but there was great strain-to-strain variability. By the MH II agar dilution method, bacteristatic synergy (defined as a fractional inhibitory concentration of <0.5) with LY333328 and ampicillin was demonstrated for 61% of the strains tested. Under similar conditions, there was synergy with LY333328 and quinupristin-dalfopristin or gentamicin for 27 and 15% of the strains tested, respectively. The PAE of LY333328 was prolonged (23.0 h at 10 times the MIC). However, 50% normal pooled human serum decreased the PAE to 12.2 h at 10 times the MIC. Test conditions and media had a considerable effect on VRE susceptibilities to LY333328. The prolonged PAE of LY333328, a potent new bactericidal glycopeptide, and its synergy with ampicillin in a large proportion of strains suggest that further evaluation of this drug in pharmacokinetic studies and experimental infections, including those with VRE, is warranted.

Novel approaches to the discovery of antimicrobial agents

With the completion of numerous bacterial genome sequences, the discovery of antibacterial drugs has fully entered the genomic era. The strategies for effectively using genomic information for target identification, target characterization, screen development and compound evaluation are emerging, and have greatly increased the number of antibacterial targets available for screening. Fortunately, simultaneous efforts in improving miniaturization, robotics and database tools are underway so that the potential of genomics can be realized.