Head-out spirometry accurately monitors the course of Pseudomonas aeruginosa lung infection in mice.

BACKGROUND Classic infection models in rodents use lethal doses of bacteria as inocula, thus creating models which are rarely comparable to the clinical situation. Moreover, single time-point evaluation requires killing of the animals, necessitating large numbers of animals. Longitudinal parameters such as temperature appear to have a relatively low accuracy. Spirometry might be an accurate method to assess the course of a bacterial lung infection without the necessity to sacrifice the animals. OBJECTIVES We measured lung function in C57BL/6JZtm mice following intratracheal infection with Pseudomonas aeruginosa and compared it to physiological parameters and lung histology. METHODS Head-out spirometry measuring 14 parameters was performed on C57BL6/J mice for eight days following a P. aeruginosa lung infection. Additionally rectal temperature, body weight and condition were assessed together with histological data and bacteriological clearance. RESULTS Several spirometric parameters were significantly altered for more than 72 h after inoculation, which was four times longer than observed alterations in physiological parameters such as temperature. Volume (amount of air inspired) decreased more than seven-fold within 6 h after inoculation and required 72 h to recover, rendering it the most sensitive spirometric parameter investigated. Spirometric and histological data correlated well. CONCLUSIONS Our findings suggest that non-invasive head-out spirometry is a reliable and highly sensitive method to longitudinally assess the course of bacterial lung infections.