Kevin M. Krause

Telavancin, a Multifunctional Lipoglycopeptide, Disrupts both Cell Wall Synthesis and Cell Membrane Integrity in Methicillin-Resistant Staphylococcus aureus

ABSTRACT The emergence and spread of multidrug-resistant gram-positive bacteria represent a serious clinical problem. Telavancin is a novel lipoglycopeptide antibiotic that possesses rapid in vitro bactericidal activity against a broad spectrum of clinically relevant gram-positive pathogens. Here we demonstrate that telavancins antibacterial activity derives from at least two mechanisms. As observed with vancomycin, telavancin inhibited late-stage peptidoglycan biosynthesis in a substrate-dependent fashion and bound the cell wall, as it did the lipid II surrogate tripeptide N,N′-diacetyl-l-lysinyl-d-alanyl-d-alanine, with high affinity. Telavancin also perturbed bacterial cell membrane potential and permeability. In methicillin-resistant Staphylococcus aureus, telavancin caused rapid, concentration-dependent depolarization of the plasma membrane, increases in permeability, and leakage of cellular ATP and K+. The timing of these changes correlated with rapid , concentration-dependent loss of bacterial viability, suggesting that the early bactericidal activity of telavancin results from dissipation of cell membrane potential and an increase in membrane permeability. Binding and cell fractionation studies provided direct evidence for an interaction of telavancin with the bacterial cell membrane; stronger binding interactions were observed with the bacterial cell wall and cell membrane relative to vancomycin. We suggest that this multifunctional mechanism of action confers advantageous antibacterial properties.

In Vitro Activity of TD-6424 against Staphylococcus aureus

ABSTRACT TD-6424, a rapidly bactericidal agent with multiple mechanisms of action, is more potent in vitro and more rapidly bactericidal than currently available agents against methicillin-susceptible and methicillin-resistant Staphylococcus aureus. TD-6424 produces a postantibiotic effect with a duration of 4 to 6 h against these organisms. The results suggest potential efficacy against susceptible and resistant strains of S. aureus.

Contemporary Diversity of β-Lactamases among Enterobacteriaceae in the Nine U.S. Census Regions and Ceftazidime-Avibactam Activity Tested against Isolates Producing the Most Prevalent β-Lactamase Groups

ABSTRACT Escherichia coli (328 isolates), Klebsiella pneumoniae (296), Klebsiella oxytoca (44), and Proteus mirabilis (33) isolates collected during 2012 from the nine U.S. census regions and displaying extended-spectrum-β-lactamase (ESBL) phenotypes were evaluated for the presence of β-lactamase genes, and antimicrobial susceptibility profiles were analyzed. The highest ESBL rates were noted for K. pneumoniae (16.0%, versus 4.8 to 11.9% for the other species) and in the Mid-Atlantic and West South Central census regions. CTX-M group 1 (including CTX-M-15) was detected in 303 strains and was widespread throughout the United States but was more prevalent in the West South Central, Mid-Atlantic, and East North Central regions. KPC producers (118 strains [112 K. pneumoniae strains]) were detected in all regions and were most frequent in the Mid-Atlantic region (58 strains). Thirteen KPC producers also carried blaCTX-M. SHV genes encoding ESBL activity were detected among 176 isolates. Other β-lactamase genes observed were CTX-M group 9 (72 isolates), FOX (10), TEM ESBL (9), DHA (7), CTX-M group 2 (3), NDM-1 (2 [Colorado]), and CTX-M groups 8 and 25 (1). Additionally, 62.9% of isolates carried ≥2 β-lactamase genes. KPC producers were highly resistant to multiple agents, but ceftazidime-avibactam (MIC50/90, 0.5/2 μg/ml) and tigecycline (MIC50/90, 0.5/1 μg/ml) were the most active agents tested. Overall, meropenem (MIC50, ≤0.06 μg/ml), ceftazidime-avibactam (MIC50, 0.12 to 0.5 μg/ml), and tigecycline (MIC50, 0.12 to 2 μg/ml) were the most active antimicrobials when tested against this collection. NDM-1 producers were resistant to all β-lactams tested. The diversity and increasing prevalence of β-lactamase-producing Enterobacteriaceae have been documented, and ceftazidime-avibactam was very active against the vast majority of β-lactamase-producing strains isolated from U.S. hospitals.

In Vitro Activity of Telavancin against Resistant Gram-Positive Bacteria

ABSTRACT The in vitro activity of telavancin was tested against 743 predominantly antimicrobial-resistant, gram-positive isolates. Telavancin was highly active against methicillin-resistant staphylococci (MIC90, 0.5 to 1 μg/ml), streptococci (all MICs, ≤0.12 μg/ml), and VanB-type enterococci (all MICs, ≤2 μg/ml). Time-kill studies demonstrated the potent bactericidal activity of telavancin.

Comparative surveillance study of telavancin activity against recently collected gram-positive clinical isolates from across the United States.

ABSTRACT Telavancin is an investigational, rapidly bactericidal lipoglycopeptide antibiotic that is being developed to treat serious infections caused by gram-positive bacteria. A baseline prospective surveillance study was conducted to assess telavancin activity, in comparison with other agents, against contemporary clinical isolates collected from 2004 to 2005 from across the United States. Nearly 4,000 isolates were collected, including staphylococci, enterococci, and streptococci (pneumococci, beta-hemolytic, and viridans). Telavancin had potent activity against Staphylococcus aureus and coagulase-negative staphylococci (MIC range, 0.03 to 1.0 μg/ml), independent of resistance to methicillin or to multiple agents. Telavancin activity was particularly potent against all streptococcal groups (MIC90s, 0.03 to 0.12 μg/ml). Telavancin had excellent activity against vancomycin-susceptible enterococci (MIC90, 1 μg/ml) and was active against VanB strains of vancomycin-resistant enterococci (MIC90, 2 μg/ml) but less active against VanA strains (MIC90, 8 to 16 μg/ml). Telavancin also demonstrated activity against vancomycin-intermediate S. aureus and vancomycin-resistant S. aureus strains (MICs, 0.5 μg/ml to 1.0 μg/ml and 1.0 μg/ml to 4.0 μg/ml, respectively). These data may support the efficacy of telavancin for treatment of serious infections with a wide range of gram-positive organisms.

Efficacy of telavancin (TD-6424), a rapidly bactericidal lipoglycopeptide with multiple mechanisms of action, in a murine model of pneumonia induced by methicillin-resistant Staphylococcus aureus.

ABSTRACT The efficacy of telavancin, a bactericidal lipoglycopeptide, was compared to that of vancomycin and linezolid against methicillin-resistant Staphylococcus aureus (MRSA) in a murine pneumonia model. Telavancin produced greater reductions in lung bacterial titer and mortality than did vancomycin and linezolid at human doses equivalent to those described by the area under the concentration-time curve. These results suggest the potential utility of telavancin for treatment of MRSA pneumonia.

Intrapulmonary Distribution of Intravenous Telavancin in Healthy Subjects and Effect of Pulmonary Surfactant on In Vitro Activities of Telavancin and Other Antibiotics

ABSTRACT Steady-state concentrations of telavancin, a novel, bactericidal lipoglycopeptide, were determined in the plasma, pulmonary epithelial lining fluid (ELF), and alveolar macrophages (AMs) of 20 healthy subjects. Telavancin at 10 mg of drug/kg of body weight/day was administered as a 1-h intravenous infusion on three successive days, with bronchoalveolar lavage performed on five subjects, each at 4, 8, 12, and 24 h after the last dose. Plasma samples were collected before the first and third infusions and at 1, 2, 3, 4, 8, 12, and 24 h after the third infusion. The plasma telavancin concentration-time profile was as reported previously. Telavancin (mean ± standard deviation) penetrated well into ELF (3.73 ± 1.28 μg/ml at 8 h and 0.89 ± 1.03 μg/ml at 24 h) and extensively into AMs (19.0 ± 16.8 μg/ml at 8 h, 45.0 ± 22.4 μg/ml at 12 h, and 42.0 ± 31.4 μg/ml at 24 h). Mean concentrations in AMs and plasma at 12 h were 45.0 μg/ml and 22.9 μg/ml (mean AM/plasma ratio, 1.93), respectively, and at 24 h were 42.0 μg/ml and 7.28 μg/ml (mean AM/plasma ratio, 6.67), respectively. Over the entire dosing interval, telavancin was present in ELF and AMs at concentrations up to 8-fold and 85-fold, respectively, above its MIC90 for methicillin-resistant Staphylococcus aureus (0.5 μg/ml). Pulmonary surfactant did not affect telavancins in vitro antibacterial activity. Telavancin was well tolerated. These results support the proposal for further clinical evaluation of telavancin for treating gram-positive respiratory infections.

In vitro activity of telavancin against recent Gram-positive clinical isolates: results of the 2004-05 Prospective European Surveillance Initiative.

OBJECTIVES Telavancin is a novel semi-synthetic lipoglycopeptide currently in late-stage clinical development for the treatment of serious infections due to Gram-positive bacteria. The objective of this study was to provide a baseline prospective assessment of its in vitro activity against a large and diverse collection of Gram-positive clinical isolates from Europe and Israel. METHODS Gram-positive clinical isolates, collected between October 2004 and December 2005 from 36 hospital laboratories in 15 countries, were tested by broth microdilution using CLSI methodology. RESULTS In total, 3206 isolates were collected. Telavancin had potent activity against Staphylococcus aureus and coagulase-negative staphylococci (MIC range < or =0.015 to 2 mg/L), independent of resistance to methicillin or to multiple drugs. Telavancin had particularly strong activity against streptococcal isolates (MIC range < or =0.001 to 0.5 mg/L), including penicillin-resistant and multiple drug-resistant Streptococcus pneumoniae and erythromycin non-susceptible beta-haemolytic and viridans group streptococci. Telavancin also had excellent activity against vancomycin-susceptible enterococci (MIC(90) 0.5 mg/L), and although its MICs were elevated against VanA strains (Enterococcus faecalis MIC(90) 8 mg/L and Enterococcus faecium MIC(90) 4 mg/L), its MIC(90) was substantially lower than observed with available glycopeptides. CONCLUSIONS Telavancin has potent in vitro activity against contemporary Gram-positive clinical isolates from diverse geographic areas in Europe and Israel.

Bactericidal Activity, Absence of Serum Effect, and Time-Kill Kinetics of Ceftazidime-Avibactam against β-Lactamase-Producing Enterobacteriaceae and Pseudomonas aeruginosa

ABSTRACT Avibactam, a non-β-lactam β-lactamase inhibitor with activity against extended-spectrum β-lactamases (ESBLs), KPC, AmpC, and some OXA enzymes, extends the antibacterial activity of ceftazidime against most ceftazidime-resistant organisms producing these enzymes. In this study, the bactericidal activity of ceftazidime-avibactam against 18 Pseudomonas aeruginosa isolates and 15 Enterobacteriaceae isolates, including wild-type isolates and ESBL, KPC, and/or AmpC producers, was evaluated. Ceftazidime-avibactam MICs (0.016 to 32 μg/ml) were lower than those for ceftazidime alone (0.06 to ≥256 μg/ml) against all isolates except for 2 P. aeruginosa isolates (1 blaVIM-positive isolate and 1 blaOXA-23-positive isolate). The minimum bactericidal concentration/MIC ratios of ceftazidime-avibactam were ≤4 for all isolates, indicating bactericidal activity. Human serum and human serum albumin had a minimal effect on ceftazidime-avibactam MICs. Ceftazidime-avibactam time-kill kinetics were evaluated at low MIC multiples and showed time-dependent reductions in the number of CFU/ml from 0 to 6 h for all strains tested. A ≥3-log10 decrease in the number of CFU/ml was observed at 6 h for all Enterobacteriaceae, and a 2-log10 reduction in the number of CFU/ml was observed at 6 h for 3 of the 6 P. aeruginosa isolates. Regrowth was noted at 24 h for some of the isolates tested in time-kill assays. These data demonstrate the potent bactericidal activity of ceftazidime-avibactam and support the continued clinical development of ceftazidime-avibactam as a new treatment option for infections caused by Enterobacteriaceae and P. aeruginosa, including isolates resistant to ceftazidime by mechanisms dependent on avibactam-sensitive β-lactamases.

In Vitro Activities of Ceftazidime-Avibactam, Aztreonam-Avibactam, and a Panel of Older and Contemporary Antimicrobial Agents against Carbapenemase-Producing Gram-Negative Bacilli

ABSTRACT Among 177 carbapenemase-producing Gram-negative bacilli (108 KPC, 32 NDM, 11 IMP, 8 OXA-48, 4 OXA-181, 2 OXA-232, 5 IMI, 4 VIM, and 3 SME producers), aztreonam-avibactam was active against all isolates except two NDM producers with elevated MICs of 8/4 and 16/4 mg/liter; ceftazidime-avibactam was active against all KPC-, IMI-, SME-, and most OXA-48 group-producing isolates (93%) but not metallo-β-lactamase producers. Among older and contemporary antimicrobials, the most active were colistin, tigecycline, and fosfomycin, with overall susceptibilities of 88%, 79%, and 78%, respectively.