Oropharyngeal Carriage of hpl-Containing Haemophilus haemolyticus Predicts Lower Prevalence and Density of NTHi Colonisation in Healthy Adults

Nontypeable Haemophilus influenzae (NTHi) is a major respiratory pathogen that initiates infection by colonising the upper airways. Strategies interfere with this interaction may therefore have clinically significant impact on ability of NTHi to cause disease. We previously shown strains commensal bacterium haemolyticus (Hh) produce novel haem-binding protein, haemophilin, can prevent growth and interactions host cells in vitro. hypothesized natural pharyngeal carriage Hh hpl open reading frame (Hh-hpl+) would be associated lower prevalence and/or density colonisation healthy individuals. Oropharyngeal swabs were collected from 257 adults Australia between 2018 2019. Real-time PCR was used quantitatively compare oropharyngeal load populations Hh-hpl+ or Hh-hpl− genotype. The likelihood acquiring/maintaining status over two- six-month period assessed individuals carried either (n = 25) 25). Compared strains, adult (18–65 years) elderly (>65 participants colonised 2.43 2.67 times less likely carry their oropharynx, respectively. Colonisation high densities correlated low 2.63 visits. Together supporting vitro studies, these results encourage further investigation into potential use as probiotic candidate for prevention infection.