M. catarrhalis usually resides in respiratory tract, but can gain access to the lower respiratory tract in patients with chronic chest disease or compromised host defenses, thus causing tracheobronchitis and pneumonia. For example, it causes a significant proportion of lower respiratory tract infections in elderly patients with COPD and chronic bronchitis.
M. catarrhalis usually resides in the respiratory system but can enter the lower respiratory tract in patients with chronic chest conditions or weakened immune systems, causing tracheobronchitis and pneumonia. It frequently contributes to significant lower respiratory infections among elderly individuals with COPD and chronic bronchitis.