1: Antimicrob Agents Chemother. 2008 Sep;52(9):3040-6. Epub 2008 Jun 23.

Cooperation between prokaryotic (Lde) and eukaryotic (MRP) efflux transporters in
J774 macrophages infected with Listeria monocytogenes: studies with ciprofloxacin
and moxifloxacin.

Lismond A, Tulkens PM, Mingeot-Leclercq MP, Courvalin P, Van Bambeke F.

Unité de Pharmacologie Cellulaire et Moléculaire, Université Catholique de
Louvain, Brussels, Belgium.

Antibiotic efflux is observed in both eukaryotic and prokaryotic cells,
modulating accumulation and resistance. The present study examines whether
eukaryotic and prokaryotic fluoroquinolone transporters can cooperate in the
context of an intracellular infection. We have used (i) J774 macrophages
(comparing a ciprofloxacin-resistant cell line overexpressing an MRP-like
transporter with wild-type cells with basal expression), (ii) Listeria
monocytogenes (comparing a clinical isolate [CLIP21369] displaying ciprofloxacin 
resistance associated with overexpression of the Lde efflux system with a
wild-type strain [EGD]), (iii) ciprofloxacin (substrate of both Lde and MRP) and 
moxifloxacin (nonsubstrate), and (iv) probenecid and reserpine (preferential
inhibitors of MRP and Lde, respectively). The ciprofloxacin MICs for EGD were
unaffected by reserpine, while those for CLIP21369 were decreased approximately
fourfold (and made similar to those of EGD). Neither probenecid nor reserpine
affected the moxifloxacin MICs against EGD or CLIP21369. In dose-response studies
(0.01x to 100x MIC) in broth, reserpine fully restored the susceptibility of
CLIP21369 to ciprofloxacin (no effect on EGD) but did not influence the activity 
of moxifloxacin. In studies with intracellular bacteria, reserpine, probenecid,
and their combination increased the activity of ciprofloxacin in wild-type and
ciprofloxacin-resistant macrophages in parallel with an increase in ciprofloxacin
accumulation in macrophages for EGD and an increase in accumulation and decrease 
in MIC (in broth) for CLIP21369. Moxifloxacin accumulation and intracellular
activity were consistently not affected by the inhibitors. A bacterial efflux
pump may thus actively cooperate with a eukaryotic efflux transporter to reduce
the activity of a common substrate (ciprofloxacin) toward an intracellular
bacterial target.

PMID: 18573933 [PubMed - in process]

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