An aerosol challenge mouse model for Moraxella catarrhalis

A simple, reproducible, and non-invasive mouse pulmonary clearance model fo r Moraxella catarrhalis via aerosol challenge was established. All of eight tested strains could be inoculated into mice at more than 10(5) colony-for ming units (CFU)/lung with a challenge concentration of 1 x 10(9)-6 x 10(9) CFU/ml in a nebulizer. The number of bacteria retained at 6 h postchalleng e was more than 10(4) CFU/lung while at 24 h postchallenge, approximate 10( 3) CFU/ml or less remained in the lungs. A maximum of 100 mice could be cha llenged per aerosol exposure. The number of bacteria inoculated in the lung s could be adjusted by the bacterial challenge concentration, the exposure time, and the negative pressure. Lung tissue sections revealed that bacteri a were evenly distributed in the lungs. Passive immunization significantly enhanced pulmonary clearance of the homologous strain in this model. These data indicate that this model will be useful for evaluating M. catarrhalis vaccine candidates and studying roles of immunity against M, catarrhalis. ( C) 1999 Elsevier Science Ltd. All rights reserved.