Activity of ceftaroline against extracellular (broth) and intracellular (THP-1 monocytes) forms of methicillin-resistant Staphylococcus aureus: comparison with vancomycin, linezolid and daptomycin

Self Cite

bGSK1322322 is a peptide deformylase inhibitor active against Staphylococcus aureus strains resistant to currently marketed antibiotics. Our aim was to assess the activity of GSK1322322 against intracellular S. aureus using an in vitro pharmacodynamic model and, in parallel, to examine its cellular pharmacokinetics and intracellular disposition. For intracellular activity analysis, we used an established model of human THP-1 monocytes and tested one fully susceptible S. aureus strain (ATCC 25923) and 8 clinical strains with resistance to oxacillin, vancomycin, daptomycin, macrolides, clindamycin, linezolid, or moxifloxacin. Uptake, accumulation, release, and subcellular distribution (cell fractionation) of [ 14 C]GSK1322322 were examined in uninfected murine J774 macrophages and uninfected and infected THP-1 monocytes. GSK1322322 demonstrated a uniform activity against the intracellular forms of all S. aureus strains tested, disregarding their resistance phenotypes, with a maximal relative efficacy (E max ) of a 0.5 to 1 log 10 CFU decrease compared to the original inoculum within 24 h and a static concentration (C s ) close to its MIC in broth. Influx and efflux were very fast (<5 min to equilibrium), and accumulation was about 4-fold, with no or a minimal effect of the broad-spectrum eukaryotic efflux transporter inhibitors gemfibrozil and verapamil. GSK1322322 was recovered in the cell-soluble fraction and was dissociated from the main subcellular organelles and from bacteria (in infected cells). The results of this study show that GSK1322322, as a typical novel deformylase inhibitor, may act against intracellular forms of S. aureus. They also suggest that GSK1322322 has the ability to freely diffuse into and out of eukaryotic cells as well as within subcellular compartments.

Section: Susceptibility Of S Aureus Strains To Gsk1322322 and Comparsupporting

confidence: 65%

Section: Discussionmentioning

confidence: 96%

Cellular Pharmacokinetics and Intracellular Activity of the Novel Peptide Deformylase Inhibitor GSK1322322 against Staphylococcus aureus Laboratory and Clinical Strains with Various Resistance Phenotypes: Studies with Human THP-1 Monocytes and J774 Murine Macrophages

Peyrusson

Butler

Tulkens

et al. 2015

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“…Thus, while fluoroquinolones remain globally more active intracellularly against susceptible strains, our data clearly high- light that RX-P873 may offer a clear advantage when dealing with resistant strains. However, as previously described for many other classes of antibiotics, even those accumulating within cells (18,20,24,25), the intracellular bacteriostatic concentration of RX-P873 remains close to its MIC, as measured in broth. While it is premature to ascribe this to insufficient bioavailability (as was suggested for fluoroquinolones [26]), it nevertheless points again to the fact that intracellular potency and accumulation are not necessarily linked.…”

Section: Discussionsupporting

confidence: 78%

RX-P873, a Novel Protein Synthesis Inhibitor, Accumulates in Human THP-1 Monocytes and Is Active against Intracellular Infections by Gram-Positive (Staphylococcus aureus) and Gram-Negative (Pseudomonas aeruginosa) Bacteria

Buyck

Peyrusson

Tulkens

et al. 2015

Self Cite

The pyrrolocytosine RX-P873, a new broad-spectrum antibiotic in preclinical development, inhibits protein synthesis at the translation step. The aims of this work were to study RX-P873's ability to accumulate in eukaryotic cells, together with its activity against extracellular and intracellular forms of infection by Staphylococcus aureus and Pseudomonas aeruginosa, using a pharmacodynamic approach allowing the determination of maximal relative efficacies (E max values) and bacteriostatic concentrations (C s values) on the basis of Hill equations of the concentration-response curves. RX-P873's apparent concentration in human THP-1 monocytes was about 6-fold higher than the extracellular one. In broth, MICs ranged from 0.125 to 0.5 mg/liter (S. aureus) and 2 to 8 mg/liter (P. aeruginosa), with no significant shift in these values against strains resistant to currently used antibiotics being noted. In concentration-dependent experiments, the pharmacodynamic profile of RX-P873 was not influenced by the resistance phenotype of the strains. E max values (expressed as the decrease in the number of CFU from that in the initial inoculum) against S. aureus and P. aeruginosa reached more than 4 log units and 5 log units in broth, respectively, and 0.7 log unit and 2.7 log units in infected THP-1 cells, respectively, after 24 h. C s values remained close to the MIC in all cases, making RX-P873 more potent than antibiotics to which the strains were resistant (moxifloxacin, vancomycin, and daptomycin for S. aureus; ciprofloxacin and ceftazidime for P. aeruginosa). Kill curves in broth showed that RX-P873 was more rapidly bactericidal against P. aeruginosa than against S. aureus. Taken together, these data suggest that RX-P873 may constitute a useful alternative for infections involving intracellular bacteria, especially Gram-negative species.

“…Compared to previous evaluations of the intracellular activity of antimicrobials, the present study was specifically adapted to BJI by the following: (i) the use of a human osteoblast infection model, thereby allowing a better estimation of the situation encountered in BJI, as opposed to using monocyte-macrophage cells, as previously described (22,23), and (ii) the evaluation of the antimicrobial intraosseous concentrations reached in humans when using standard therapeutic doses and not plasmatic (or higher) concentrations, which do not correspond to the therapeutic tissue reality (19). Even if the distribution of antibiotics in the different parts of bones and joints (i.e., cortical and medullar bone tissue, joint fluid, synovial .…”

Section: Discussionmentioning

confidence: 99%

Antimicrobial Activity against Intraosteoblastic Staphylococcus aureus

Valour

Trouillet‐Assant

Riffard

et al. 2015

112

Although Staphylococcus aureus persistence in osteoblasts, partly as small-colony variants (SCVs), can contribute to bone and joint infection (BJI) relapses, the intracellular activity of antimicrobials is not currently considered in the choice of treatment strategies for BJI. Here, antistaphylococcal antimicrobials were evaluated for their intraosteoblastic activity and their impact on the intracellular emergence of SCVs in an ex vivo osteoblast infection model. Osteoblastic MG63 cells were infected for 2 h with HG001 S. aureus. After killing the remaining extracellular bacteria with lysostaphin, infected cells were incubated for 24 h with antimicrobials at the intraosseous concentrations reached with standard therapeutic doses. Intracellular bacteria and SCVs were then quantified by plating cell lysates. A bactericidal effect was observed with fosfomycin, linezolid, tigecycline, oxacillin, rifampin, ofloxacin, and clindamycin, with reductions in the intracellular inocula of ؊2.5, ؊3.1, ؊3.9, ؊4.2, ؊4.9, ؊4.9, and ؊5.2 log 10 CFU/100,000 cells, respectively (P < 10 ؊4 ). Conversely, a bacteriostatic effect was observed with ceftaroline and teicoplanin, whereas vancomycin and daptomycin had no significant impact on intracellular bacterial growth. Ofloxacin, daptomycin, and vancomycin significantly limited intracellular SCV emergence. Overall, ofloxacin was the only molecule to combine an excellent intracellular activity while limiting the emergence of SCVs. These data provide a basis for refining the choice of antibiotics to prioritise in the management of BJI, justifying the combination of a fluoroquinolone for its intracellular activity with an anti-biofilm molecule, such as rifampin.