Haemophilus parainfluenzae Strain ATCC 33392 Forms BiofilmsIn Vitroand during Experimental Otitis Media Infections

Haemophilus parainfluenzae is a nutritionally fastidious, Gram-negative bacterium with an oropharyngeal/nasopharyngeal carriage niche that is associated with a range of opportunistic infections, including infectious endocarditis and otitis media (OM). These infections are often chronic/recurrent in nature and typically involve bacterial persistence within biofilm communities that are highly resistant to host clearance. This study addresses the primary hypothesis thatH. parainfluenzae forms biofilm communities that are important determinants of persistencein vivo . The results fromin vitro biofilm studies confirmed thatH. parainfluenzae formed biofilm communities within which the polymeric matrix was mainly composed of extracellular DNA and proteins. Using a chinchilla OM infection model, we demonstrated thatH. parainfluenzae formed surface-associated biofilm communities containing bacterial and host components that included neutrophil extracellular trap (NET) structures and that the bacteria mainly persisted in these biofilm communities. We also used this model to examine the possible interaction betweenH. parainfluenzae and its close relativeHaemophilus influenzae , which is also commonly carried within the same host environments and can cause OM. The results showed that coinfection withH. influenzae promoted clearance ofH. parainfluenzae from biofilm communities during OM infection. The underlying mechanisms for bacterial persistence and biofilm formation byH. parainfluenzae and knowledge about the survival defects ofH. parainfluenzae during coinfection withH. influenzae are topics for future work.