1. J Antimicrob Chemother. 2012 Sep;67(9):2158-64. Epub 2012 May 21.

Cellular pharmacokinetics and intracellular activity against Listeria
monocytogenes and Staphylococcus aureus of chemically modified and
nanoencapsulated gentamicin.

Imbuluzqueta E, Lemaire S, Gamazo C, Elizondo E, Ventosa N, Veciana J, Van
Bambeke F, Blanco-Prieto MJ.

Department of Pharmacy and Pharmaceutical Technology, University of Navarra,
31008 Pamplona, Spain.

OBJECTIVES: The aim of this study was to investigate different hydrophobic
gentamicin formulations [gentamicin-bis(2-ethylhexyl) sulfosuccinate (GEN-AOT),
microstructured GEN-AOT (PCA GEN-AOT) and GEN-AOT-loaded
poly(lactide-co-glycolide) acid (PLGA) nanoparticles (NPs)] in view of improving 
its therapeutic index against intracellular bacteria. The intracellular
accumulation, subcellular distribution and intracellular activity of GEN-AOT and 
NPs in different monocytic-macrophagic cell lines were studied.
METHODS: Human THP-1 and murine J774 phagocytic cells were incubated with GEN-AOT
formulations at relevant extracellular concentrations [from 1× MIC to 18 mg/L
(human C(max))], and their intracellular accumulation, subcellular distribution
and toxicity were evaluated and compared with those of conventional unmodified
gentamicin. Intracellular activity of the formulations was determined against
bacteria showing different subcellular localizations, namely Staphylococcus
aureus (phagolysosomes) and Listeria monocytogenes (cytosol).
RESULTS: GEN-AOT formulations accumulated 2-fold (GEN-AOT) to 8-fold (GEN-AOT
NPs) more than gentamicin in phagocytic cells, with a predominant subcellular
localization in the soluble fraction (cytosol) and with no significant cellular
toxicity. NP formulations allowed gentamicin to exert its intracellular activity 
after shorter incubation times and/or at lower concentrations. With an
extracellular concentration of 10× MIC, a 1 log(10) decrease in S. aureus
intracellular inoculum was obtained after 12 h instead of 24 h for NPs versus
free gentamicin, and a static effect was observed against L. monocytogenes at 24 
h with NPs, while free gentamicin was ineffective.
CONCLUSIONS: GEN-AOT formulations yielded a high cellular accumulation,
especially in the cytosol, which resulted in improved efficacy against both
intracellular S. aureus and L. monocytogenes.

PMID: 22615297  [PubMed - in process]