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

Lismond, Ann [UCL] Tulkens, Paul M. [UCL] Mingeot-Leclercq, Marie-Paule [UCL] Courvalin, Patrice Van Bambeke, Françoise [UCL]

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 (non-substrate); (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 4-fold (and made similar to those of EGD). Neither probenecid nor reserpine affected the moxifloxacin MICs against EGD or CLIP21369. In dose-response studies (0.01-100 x MIC) in broth, reserpine fully restored susceptibility of CLIP21369 to ciprofloxacin (no effect on EGD), but did not influence the activity of moxifloxacin. In dose-response studies against intracellular bacteria, reserpine, probenecid, and their combination increased the activity of ciprofloxacin in wild-type and ciprofloxacin-resistant macrophages in parallel to their increase in ciprofloxacin accumulation in macrophages for EGD, and (ii) increase in accumulation and decrease in MIC (in broth) for CLIP21369. Moxifloxacin accumulation and intracellular activity were not consistently 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) towards an intracellular bacterial target.