Novel concepts in nontypeable Haemophilus influenzae biofilm formation

Nontypeable Haemophilus influenzae (NTHi) is a Gram-negative microbe that frequently colonizes the human host without obvious signs of inflammation, but is also a frequent cause of otitis media in children and exacerbations in chronic obstructive pulmonary disease patients. Accumulating data suggest that NTHi can reside in biofilms during both colonization and infection. Recent literature proposes roles for phosphorylcholine, sialic acid, bacterial DNA, but also eukaryotic DNA in the development of NTHi biofilms. However, many questions remain. Until now, there are insufficient data to explain how NTHi forms biofilms. Here, we review the recent advances in NTHi biofilm formation with particular focus on the role that neutrophils may play in this process. We propose that recruitment of neutrophils facilitates NTHi biofilm formation on mucosal sites by the initiation of neutrophil extracellular traps.