Prevalence of biofilms in acute infections challenges a longstanding paradigm.

The significance of bacterial biofilm formation in chronic bacterial lung infections has long been recognized [1]. Likewise, chronic biofilm formation on medical devices is well accepted as a nidus for recurrent bacteremia [2,3]. Even though the prevailing paradigm relies on the dominance of planktonic bacteria in acute endobronchial infections, our understanding of the bacterial organization during acute infection is, so far, limited - virtually absent. However, by comparing similar clinical samples, we have recently demonstrated massive bacterial biofilm formation during acute lung infections resembling the immense bacterial biofilm formation during chronic lung infections. These findings pose major challenges to the basic paradigm of chronic infections being dominated by biofilm forming bacteria while acute infections are dominated by planktonic bacteria. As opposed to the similar high amount of bacterial biofilm found in chronic and acute lung infections, we found that the fast bacterial growth in acute lung infections differed from the slow bacterial growth in chronic lung infections. By highlighting these new findings, we review modes of improved treatment of biofilm infections and the relevance of bacterial growth rates for other bacterial biofilm infections than human lung infections.