A subinhibitory concentration of clarithromycin inhibits Mycobacterium avium biofilm formation

Abstract

Mycobacterium avium causes disseminated infection in immunosuppressed individuals and lung infection in patients with chronic lung diseases. M. avium forms biofilm in the environment and possibly in human airways. Antibiotics with activity against the bacterium could inhibit biofilm formation. Clarithromycin inhibits biofilm formation but has no activity against established biofilm.

FIG. 1.

Scanning electron micrograph of M. avium 101 biofilm. Bacteria were seeded on a PVC plate (10⁸ bacteria) and allowed to establish biofilm for 14 days at room temperature. Then the wells were washed and dried, and the bottom of the PVC plate was cut with a blade. It was fixed and stained as described previously (4).

FIG. 2.

Effect of azithromycin, clarithromycin, and moxifloxacin on the ability of M. avium to form biofilm. Bacteria were seeded onto a PVC plate and incubated with a subinhibitory concentration of azithromycin (8 μg/ml), clarithromycin (1 μg/ml), or moxifloxacin (1 μg/ml) for 14 days. Biofilm establishment was determined as described in the text. *, P < 0.05.

FIG. 3.

Ability of clarithromycin to inhibit biofilm formation when added to M. avium at 0, 4, or 7 days after seeding, at a subinhibitory concentration. Biofilm establishment was determined as described in the text. *, P < 0.05.