Nasal delivery of a commensal Pasteurellaceae species inhibits nontypeable Haemophilus influenzae colonisation and delays onset of otitis media in mice

Nasopharyngeal colonization with nontypeable Haemophilus influenzae (NTHi) is a prerequisite for developing NTHi-associated infections, including otitis media. Therapies that block NTHi colonization may prevent disease development. We previously demonstrated that Haemophilus haemolyticus, a closely related human commensal, can inhibit NTHi colonization and infection of human respiratory epithelium in vitro We have now assessed whether Muribacter muris (a rodent commensal from the same family) can prevent NTHi colonization and disease in vivo using a murine NTHi otitis media model. Otitis media was modeled in BALB/c mice using coinfection with 1 x 10(4.5) PFU of influenza A virus MEM H3N2, followed by intranasal challenge with 5 x 10(7) CFU of NTHi R2866 Spec(r) Mice were pretreated or not with an intranasal inoculation of 5 x 10(7) CFU M. muris 24 h before coinfection. NTHi and M. muris viable counts and inflammatory mediators (gamma interferon [IFN-gamma], interleukin-1beta [IL-1beta], IL-6, keratinocyte chemoattractant [KC], and IL-10) were measured in nasal washes and middle ear tissue homogenate. M. muris pretreatment decreased the median colonization density of NTHi from 6 x 10(5) CFU/ml to 9 x 10(3) CFU/ml (P = 0.0004). Only 1/12 M. muris-pretreated mice developed otitis media on day 5 compared to 8/15 mice with no pretreatment (8% versus 53%, P = 0.0192). Inflammation, clinical score, and weight loss were also lower in M. muris-pretreated mice. We have demonstrated that a single dose of a closely related commensal can delay onset of NTHi otitis media in vivo Human challenge studies investigating prevention of NTHi colonization are warranted to reduce the global burden of otitis media and other NTHi diseases.