Lower levels of bacterial aerobic respiration in sputum from people with cystic fibrosis with chronic lung infection

Bacterial aerobic respiration has recently been related to the outcome of antibiotic treatment in experimental studies, but clinical relevance of the levels of bacterial aerobic respiration remains to be evidenced. Therefore, we hypothesized that bacterial aerobic respiration is lower in sputum from people with cystic fibrosis (pwCF) and chronic lung infection, where clinical cure is difficult and rare, than in sputum from patients with acute lower respiratory tract infections (aLRTI), where clinical cure is frequent. Oxygen (O2) consumption was measured by microrespirometry and microprofiling in newly expectorated sputum from 52 patients with aLRTI and in cultures of common aLRTI pathogens. The bacterial aerobic respiration was further separated from other mechanisms of O2 consumption by treatment with potassium cyanide (KCN). In this study, we measured active O2 consumption and estimated bacterial aerobic respiration in sputum from aLRTI patients and compared the levels of bacterial aerobic respiration to previously published similar examinations in sputum from pwCF with chronic lung infection. By inhibition with KCN, the mean bacterial aerobic respiration in aLRTI sputum was determined to account for 55% of the total O2 consumption (n = 12), which was significantly higher (p = 0.0087) than previously published for pwCF with chronic lung infection. In addition, depletion of O2 was more frequent in aLRTI sputum when bacterial pathogens were detected (p = 0.0048). We demonstrated lower bacterial aerobic respiration in sputum from pwCF with chronic lung infection than in aLRTI patients. These variations in bacterial physiology between pwCF with chronic lung infection and aLRTI patients may, at least in part, contribute to the huge variation in treatment success for the two patient groups. Thus, bacterial aerobic respiration has the potential to function as a physiological determinant of the outcome of antibiotic treatment.