Early colonization of the rat upper respiratory tract by temperature modulated Bordetella bronchiseptica

The ability of nonmodulated Bvg(+) phase cultures, temperature modulated Bv g(-) phase cultures, and a Bvg(-) phase-locked mutant of Bordetella bronchi septica to colonize the rat upper respiratory tract was investigated. Initi ally, greater numbers of the temperature modulated Bvg- phase bacteria adhe red to the nasal cavity of the rats. The temperature modulated Bvg(-) phase bacteria appeared to be quickly cleared to levels lower than the Bvg(+) ph ase bacteria by 4 h after inoculation and stayed lower until 48 h after ino culation when colonization levels were equal to the Bvg(+) phase bacteria. The level of colonization with the Bvg(-) phase-locked mutant of B. bronchi septica was lower than both the nonmodulated Bvg(+) phase and temperature m odulated Bvg(-) phase cultures and declined over time during the experiment . These findings suggest that there may be increased adherence from an envi ronmental phase to ensure bacteria survive initial clearance mechanisms unt il the switch to the Bvg(+) phase occurs. (C) 1999 Federation of European M icrobiological Societies. Published by Elsevier Science B.V. All rights res erved.