Growth in catheter biofilms and antibiotic resistance of Mycobacterium avium

Cells of Mycobacterium avium strain A5 adhered to plasticized polyvinyl chloride catheter tubing and grew at low nutrient concentration, consistent with reports of catheter-associated M. avium infection. Starting with initial cell densities of 1-2x10(6) c.f.u. ml-1, biofilms of approximately 350 c.f.u. cm-2 formed within 24 h at room temperature. Growth rates of cells in biofilms were exponential and equal to 2.45 days doubling time. Rates were exponential for 1-2 weeks incubation and reached cell densities of 6.5x10(4) c.f.u. cm-2 by 4 weeks. Cells grown in catheter biofilms were significantly more resistant to clarithromycin and rifamycin than cells grown in suspension.