Abstract
Bacteria form complex and highly elaborate surface adherent communities known as biofilms which are held together by a self-produced extracellular matrix. We have previously shown that by adopting a biofilm mode of existence in vivo, the Gram negative bacterial pathogens Bordetella bronchiseptica and Bordetella pertussis are able to efficiently colonize and persist in the mammalian respiratory tract. In general, the bacterial biofilm matrix includes polysaccharides, proteins and extracellular DNA (eDNA). In this report, we investigated the function of DNA in Bordetella biofilm development. We show that DNA is a significant component of Bordetella biofilm matrix. Addition of DNase I at the initiation of biofilm growth inhibited biofilm formation. Treatment of pre-established mature biofilms formed under both static and flow conditions with DNase I led to a disruption of the biofilm biomass. We next investigated whether eDNA played a role in biofilms formed in the mouse respiratory tract. DNase I treatment of nasal biofilms caused considerable dissolution of the biofilm biomass. In conclusion, these results suggest that eDNA is a crucial structural matrix component of both in vitro and in vivo formed Bordetella biofilms. This is the first evidence for the ability of DNase I to disrupt bacterial biofilms formed on host organs.
Highlights
The genus Bordetella currently consists of nine species of Gram negative bacteria
After 72h of flow, the biofilms were stained with DDAO which binds to extracellular DNA or DNA inside the cells that have compromised membranes [34]
The results showed that biofilms formed by the wild type strain of B. bronchiseptica, RB50 (Fig. 1, top panels) were mainly composed of cells which were not stained by DDAO, and have impermeable membranes
Summary
The genus Bordetella currently consists of nine species of Gram negative bacteria. Some members of this genus are known mammalian and avian pathogens that colonize the respiratory tracts of humans, animals and birds. B. pertussis and some strains of B. parapertussis are the causative agents of whooping cough in humans, while B. bronchiseptica causes multiple respiratory syndromes and diseases in a wide variety of animal species, including dogs, pigs, cats, rabbits and rats. A hallmark of B. bronchiseptica and B. avium infections is longterm to life-long asymptomatic carriage. Vaccination considerably decreases mortality and severity of the respiratory disease, B. bronchiseptica and B. avium continue to circulate and persist in mammalian and avian species. It is becoming clear that the current pertussis vaccines, effective against severe symptoms of the disease, do not prevent prolonged colonization. B. pertussis continues to circulate by residing mainly in the nasopharynx of adolescents and adults, resulting in asymptomatic or milder infections [5,6,7]
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