Growth in catheter biofilms and antibiotic resistance of Mycobacterium avium

Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA Correspondence Joseph O. Falkinham III jofiii{at}vt.edu Received 7 September 2006 Accepted 25 October 2006 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 1–2 x 10 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 6.5 x 10 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.