Chloroquine does not enhance the activity of clarithromycin against multiplication of Mycobacterium avium within human macrophages

Setting: Chloroquine, an alkalinizing lysosomotropic agent, enhances the intracellular activity of antibiotics against Mycobacterium tuberculosis or Coxiella burnetii. Objective: To determine if chloroquine modifies the activity of clarithromycin, less effective at acidic pH, against intracellular Mycobacterium avium. Design: The activity of clarithromycin (4 μg/ml) against the MO-1 strain of M. avium was evaluated within human macrophages in presence of chloroquine (5 μg/ml). The minimal inhibitory concentration of clarithromycin for the strain was 2 μg/ml. Results: While clarithromycin alone did decrease the intracellular infection at day 7 of culture (P < 0.01), chloroquine alone did not impede the intracellular growth of M. avium, and did not enhance the activity of clarithromycin. Conclusion: Chloroquine should not improve clarithromycin treatment against M. avium infection.