OUTER-MEMBRANE ANTIGEN EXPRESSION BY MORAXELLA (BRANHAMELLA) CATARRHALIS INFLUENCES PULMONARY CLEARANCE

Moraxella (Branhamella) catarrhalis is a common respiratory tract path ogen in man. The bacterium shows a strong tendency to form aggregates in vitro. A variant strain of M. catarrhalis that showed a reduced ten dency to form aggregates was selected by successive in-vitro passage i n broth culture from which aggregates had settled. The non-clumping va riant strain showed alteration in expression of outer-membrane antigen s, including the HMW-OMP, an outer-membrane protein of c. 200 kDa, out er-membrane protein CD and lipo-oligosaccharide. A mouse model for pul monary challenge with M. catarrhalis revealed significant differences in the rate of clearance of the isogenic variant strains from the lung . The parent strain caused enhanced recruitment of neutrophils to the lung and more rapid clearance of bacteria from the lungs in comparison to the non-clumping variant. It is concluded that alteration of expre ssion of surface molecules by M. catarrhalis has a significant impact in an in-vivo model of pulmonary clearance.