Moraxella catarrhalis Promotes Stable Polymicrobial Biofilms With the Major Otopathogens.

Kirsten L Bair,Anthony A Campagnari

doi:10.3389/fmicb.2019.03006

Kirsten L Bair, Anthony A Campagnari

Open Access

https://doi.org/10.3389/fmicb.2019.03006

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Abstract

Otitis media (OM) is a prevalent pediatric infection characterized by painful inflammation of the middle ear. The Gram-negative diplococcus Moraxella catarrhalis is a commensal of the nasopharynx and one of three leading causative agents of OM. The most recent work on this multifaceted disease indicates that biofilms and polymicrobial infections play a pivotal role in recurrent and chronic OM, which are difficult to eradicate using standard antibiotic protocols. Although there have been significant advances in OM research, the actual bacterial and viral interactions leading to pathogenesis remain largely uncharacterized. However, colonization and persistence in the nasopharynx is clearly an essential first step. In this study, we assessed the role M. catarrhalis plays in the co-colonization and persistence of the other major otopathogens, Streptococcus pneumoniae and non-typeable Haemophilus influenzae (NTHi). We characterized both monomicrobial and polymicrobial biofilms using an in vitro nasopharyngeal colonization model. Biofilm assays were designed to mimic the nasopharynx and bacterial persistence was quantified over time. NTHi showed a steady and significant decline in viability over 20–48 h when this organism was in a dual species biofilm with S. pneumoniae. However, when M. catarrhalis was present in the polymicrobial biofilm NTHi survived for 48 h at 107 CFU per mL. In addition, an isogenic M. catarrhalis catalase-deficient mutant was also fully capable of protecting NTHi from the bactericidal activity of S. pneumoniae in a polymicrobial biofilm. Our results show that M. catarrhalis promotes a favorable environment for stable polymicrobial biofilms by enhancing the survival of NTHi in the presence of S. pneumoniae. These data suggest that colonization with M. catarrhalis promotes stable co-colonization with other otopathogens.

Highlights

There are more than 700 million cases of acute otitis media (AOM) diagnosed globally each year, with 50% of affected children under 5 years of age (Monasta et al, 2012)
Our results indicate that M. catarrhalis is able to promote survival of non-typeable Haemophilus influenzae (NTHi) even in the presence of S. pneumoniae in triple species biofilms like those that have been previously shown to colonize the human nasopharynx (Hoa et al, 2009; Casey et al, 2010; Palmu et al, 2019)
Moraxella catarrhalis Promotes the Growth of NTHi in Dual Species Biofilms in vitro Previous studies have shown that colonization with M. catarrhalis occurs very early in life and M. catarrhalis is more likely to be present in polymicrobial AOM than infections resulting from a single bacterial species (Broides et al, 2009)

Summary

Introduction

There are more than 700 million cases of acute otitis media (AOM) diagnosed globally each year, with 50% of affected children under 5 years of age (Monasta et al, 2012). The polymicrobial biofilms associated with AOM are incredibly resistant and difficult to treat using classic antibiotic protocols (Pichichero, 2000b; Leibovitz et al, 2003; Libson et al, 2005; Asher et al, 2008; Leibovitz, 2008; KoronaGlowniak et al, 2018). This is a result of conferred β-lactamase protection, quiescent bacteria within biofilms, poor antibiotic penetration and persister cells. When taken in combination with the continued prevalence of AOM in the post-vaccine era, these challenges demand novel preventative and treatment strategies

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