Cellular pharmacokinetics of telavancin, a novel lipoglycopeptide antibiotic, and analysis of lysosomal changes in cultured eukaryotic cells (J774 mouse macrophages and rat embryonic fibroblasts)

Background Telavancin is a lipoglycopeptide with multiple mechanisms of action that include membrane-destabilizing effects towards bacterial cells. It shows bactericidal activity against forms of Staphylococcus aureus (phagolysosomal infection) with different resistance phenotypes [methicillin-resistant S. aureus, vancomycin-intermediate S. aureus or vancomycin-resistant S. aureus]. We examine here the uptake, efflux and intracellular distribution of telavancin in eukaryotic cells as well as its potential to induce lysosomal changes (in comparison with vancomycin and oritavancin). Methods J774 macrophages and rat embryo fibroblasts were exposed for up to 24 and 72 h to telavancin (5-90 mg/L). The following studies were performed: measurement of (14)C-labelled telavancin cellular uptake and subcellular distribution (cell fractionation), determination of pericellular membrane integrity (lactate dehydrogenase release), electron microscopy with morphometric analysis of changes in lysosome size and determination of total phospholipid and cholesterol content. Results The uptake of telavancin proceeded linearly as a function of time and concentration in both cell types (clearance rate of approximately 10 mL/g of protein/h). Efflux (macrophages) was approximately 5.7-fold slower. Telavancin subcellular distribution was superimposable on that of a lysosomal marker (N-acetyl-beta-hexosaminidase). It did not cause an increase in the release of lactate dehydrogenase and did not induce significant increases in total phospholipid or cholesterol content. It caused only mild morphological lysosomal alterations (similar to vancomycin and much less than oritavancin by morphometric analysis). Conclusions Telavancin is taken up by eukaryotic cells and localizes in lysosomes, causing mild morphological alterations without evidence of lipid metabolism alterations. These data support our observations that telavancin is active against intracellular S. aureus

Cellular pharmacodynamics and pharmacokinetics of antibiotics: current views and perspectives.

The treatment of intracellular infections requires the use of antibiotics presenting appropriate cellular pharmacokinetic and pharmacodynamic properties. These properties, however, cannot be predicted on the simple basis of cellular drug accumulation and minimum inhibitory concentration in broth. In most cases, intracellular activity is actually lower than extracellular activity, despite the fact that all antibiotics reach intracellular concentrations that are at least equal to, and more often higher than the extracellular concentrations. This discrepancy may result from impairment of the expression of antibiotic activity or a change in bacterial responsiveness inside the cells. It therefore appears important to evaluate the intracellular activity of antibiotics in appropriate models

Comparative activity of quinolones (ciprofloxacin, levofloxacin, moxifloxacin and garenoxacin) against extracellular and intracellular infection by Listeria monocytogenes and Staphylococcus aureus in J774 macrophages

OBJECTIVES: Quinolones accumulate in eukaryotic cells and show activity against a large array of intracellular organisms, but systematic studies aimed at examining their pharmacodynamic profile against intracellular bacteria are scarce. The present work aims at comparing intracellular-to-extracellular activities in this context. METHODS: We assessed the activities of ciprofloxacin, levofloxacin, moxifloxacin and garenoxacin against the extracellular (broth) and intracellular (infected J774 macrophages) forms of Listeria monocytogenes (cytosolic infection) and Staphylococcus aureus (phagolysosomal infection) using a range of clinically meaningful extracellular concentrations (0.06-4 mg/L). RESULTS: All four quinolones displayed concentration-dependent bactericidal activity against extracellular and intracellular L. monocytogenes and S. aureus for extracellular concentrations in the range 1-4-fold their MIC. Compared at equipotent extracellular concentrations, intracellular activities against L. monocytogenes were roughly equal to those that were extracellular, but were 50-100 times lower against S. aureus. Because quinolones accumulate in cells (ciprofloxacin, approximately 3 times; levofloxacin, approximately 5 times; garenoxacin, approximately 10 times, moxifloxacin, approximately 13 times), these data show that, intracellularly, quinolones are 5-10 times less potent against L. monocytogenes (P=0.065 [ANCOVA]), and at least 100 times less potent (P < 0.0001) against S. aureus. Because of their lower MICs and higher accumulation levels, garenoxacin and moxifloxacin were, however, more active than ciprofloxacin and levofloxacin when compared at similar extracellular concentrations. CONCLUSIONS: Quinolone activity is reduced intracellulary. This suggests that either only a fraction of cell-associated quinolones exert an antibacterial effect, or that intracellular activity is defeated by the local environment, or that intracellular bacteria only poorly respond to the action of quinolones

Pharmacodynamic evaluation of the intracellular activities of antibiotics against Staphylococcus aureus in a model of THP-1 macrophages

The pharmacodynamic properties governing the activities of antibiotics against intracellular Staphylococcus aureus are still largely undetermined. Sixteen antibiotics of seven different pharmacological classes (azithromycin and telithromycin [macrolides]; gentamicin [an aminoglycoside]; linezolid [an oxazolidinone]; penicillin V, nafcillin, ampicillin, and oxacillin [beta-lactams]; teicoplanin, vancomycin, and oritavancin [glycopeptides]; rifampin [an ansamycin]; and ciprofloxacin, levofloxacin, garenoxacin, and moxifloxacin [quinolones]) have been examined for their activities against S. aureus (ATCC 25923) in human THP-1 macrophages (intracellular) versus that in culture medium (extracellular) by using a 0- to 24-h exposure time and a wide range of extracellular concentrations (including the range of the MIC to the maximum concentration in serum [C(max); total drug] of humans). All molecules except the macrolides caused a net reduction in bacterial counts that was time and concentration/MIC ratio dependent (four molecules tested in detail [gentamicin, oxacillin, moxifloxacin, and oritavancin] showed typical sigmoidal dose-response curves at 24 h). Maximal intracellular activities remained consistently lower than extracellular activities, irrespective of the level of drug accumulation and of the pharmacological class. Relative potencies (50% effective concentration or at a fixed extracellular concentration/MIC ratio) were also decreased, but to different extents. At an extracellular concentration corresponding to their C(max)s (total drug) in humans, only oxacillin, levofloxacin, garenoxacin, moxifloxacin, and oritavancin had truly intracellular bactericidal effects (2-log decrease or more, as defined by the Clinical and Laboratory Standards Institute guidelines). The intracellular activities of antibiotics against S. aureus (i) are critically dependent upon their extracellular concentrations and the duration of cell exposure (within the 0- to 24-h time frame) to antibiotics and (ii) are always lower than those that can be observed extracellularly. This model may help in rationalizing the choice of antibiotic for the treatment of S. aureus intracellular infections

Evaluation of the extracellular and intracellular activities (human THP-1 macrophages) of telavancin versus vancomycin against methicillin-susceptible, methicillin-resistant, vancomycin-intermediate and vancomycin-resistant Staphylococcus aureus

OBJECTIVES: To compare extracellular and intracellular activities of telavancin (versus vancomycin) against Staphylococcus aureus (MSSA, MRSA, VISA and VRSA). METHODS: Determination of cfu changes (3-24 h) in culture medium and in macrophages at concentrations ranging from 0.01 to 1000x MIC. RESULTS: Extracellularly, telavancin displayed a fast, concentration-dependent bactericidal activity against all strains. The concentration-effect relationship was bimodal for MSSA and MRSA [two successive sharp drops in bacterial counts (0.3-1x MIC and 100-1000x MIC) separated by a zone of low concentration dependency]. When compared at human total drug Cmax (vancomycin, 50 mg/L; telavancin, 90 mg/L) towards MSSA, MRSA and VISA, telavancin caused both a faster and more marked decrease of cfu, with the limit of detection (>5 log decrease) reached already at 6 versus 24 h for vancomycin. Intracellularly, the bactericidal activity of telavancin was less intense [-3 log (MSSA) to -1.5 log (VRSA) at Cmax and at 24 h]. A bimodal relationship with respect to concentration (at 24 h) was observed for both MSSA and MRSA. In contrast, vancomycin exhibited only marginal intracellular activity towards intraphagocytic MSSA, MRSA and VISA (max. -0.5 log decrease at 24 h and at Cmax). CONCLUSIONS: Telavancin showed time- and concentration-dependent bactericidal activity against both extracellular and intracellular S. aureus with various resistance phenotypes. The data support the use of telavancin in infections where intracellular and extracellular S. aureus are present. Bimodality of dose responses (MSSA and MRSA) could indicate multiple mechanisms of action for telavancin