The Bordetella Bps Polysaccharide Is Critical for Biofilm Development in the Mouse Respiratory Tract

Abstract

Bordetellae are respiratory pathogens that infect both humans and animals. Bordetella bronchiseptica establishes asymptomatic and long-term to life-long infections of animal nasopharynges. While the human pathogen Bordetella pertussis is the etiological agent of the acute disease whooping cough in infants and young children, it is now being increasingly isolated from the nasopharynges of vaccinated adolescents and adults who sometimes show milder symptoms, such as prolonged cough illness. Although it has been shown that Bordetella can form biofilms in vitro, nothing is known about its biofilm mode of existence in mammalian hosts. Using indirect immunofluorescence and scanning electron microscopy, we examined nasal tissues from mice infected with B. bronchiseptica. Our results demonstrate that a wild-type strain formed robust biofilms that were adherent to the nasal epithelium and displayed architectural attributes characteristic of a number of bacterial biofilms formed on inert surfaces. We have previously shown that the Bordetella Bps polysaccharide encoded by the bpsABCD locus is critical for the stability and maintenance of three-dimensional structures of biofilms. We show here that Bps is essential for the formation of efficient nasal biofilms and is required for the colonization of the nose. Our results document a biofilm lifestyle for Bordetella in mammalian respiratory tracts and highlight the essential role of the Bps polysaccharide in this process and in persistence of the nares.Bacteria belonging to the genus Bordetella cause respiratory tract infections in both humans and animals (42). Bordetella pertussis is the etiological agent of pertussis, cases of which are steadily increasing in number, even in vaccinated populations (9). It has been proposed that the resurgence of pertussis is due in part to carriage within adolescent and adult populations because of waning immunity (3,4,9). Bordetella bronchiseptica has a broad host range and naturally infects a wide variety of nonhuman animals. It typically establishes asymptomatic infections but can cause atrophic rhinitis in pigs, kennel cough in dogs, snuffles in rabbits, and bronchopneumonia in guinea pigs (18,42).B. bronchiseptica is capable of establishing a chronic and asymptomatic infection and can be harvested from the nasal cavities of rats and mice for extended periods (1, 37). A convincing and frequently proposed hypothesis to explain long-term carriage is the ability of microorganisms to exist as biofilms. Bacterial biofilms are increasingly recognized as important contributors to chronic or persistent diseases. A biofilm is generally defined as a surface-attached population of one or more types of bacteria encased in a polymeric matrix, which can be composed of a number of different macromolecules, including nucleic acids, proteins, and polysaccharides (5). Numerous studies have documented the ability of biofilm bacteria to be recalcitrant to antibiotic treatments and to the host immune system (31,39,40,53).We and others have recently demonstra...

Proteome approaches combined with Fourier transform infrared spectroscopy revealed a distinctive biofilm physiology in Bordetella pertussis

“…[41,42], nevertheless no capsular or slime polysaccharides have been isolated or characterized for Bordetella yet. Recently, Parise et al [22] reported the expression of a polysaccharide (Bps) biochemically similar to poly-b-1,6-Nacetyl-D-glucosamine polymer during the biofilm lifestyle of some Bordetella species, and Sloan et al [3] showed that Bps is critical for biofilm formation of B. bronchiseptica in the respiratory tract of a mouse model. The results presented here from proteome and FT-IR analysis suggest the expression of an acidic-type polysaccharide by B. pertussis, probably an N-acetyl galactosaminuronic acid-like polymer (see Table 1 and Fig.…”

“…Although historically the occurrence of pertussis was associated with an acute infection, primarily in not-or under-immunized infants, a shift in the incidence of the disease towards adolescents and adults with the appearance of persistent asymptomatic or mild infections is becoming increasingly evident [1]. Recent reports support the hypothesis that B. pertussis could adopt a biofilm lifestyle as a strategy to colonize the host, but the mechanisms leading to persistent B. pertussis infections are largely unknown [2][3][4]. Biofilm is a community-based mode of existence of microbes in which cells are enclosed in a self-producing matrix and adhered to an inert or living surface [5].…”

“…Planktonic cells were washed with PBS or water for FT-IR spectroscopy experiments to remove any remaining components of the broth. Biofilms were grown on flat polypropylene beads (300 g; f = 4.2 mm, h = 1.5 mm, with an average density of 0.901 g/cm 3 , Petroken, Argentina) in glass column reactors (f = 6 cm, h = 45 cm, IVA SA, Argentina). Experiments were carried out essentially as described previously by Bosch et al [21].…”

The Structure- and Metal-dependent Activity of Escherichia coli PgaB Provides Insight into the Partial De-N-acetylation of Poly-β-1,6-N-acetyl-d-glucosamine

“…A wide variety of medically important biofilm-forming bacteria produce partially de-N-acetylated poly-␤-1,6-N-acetyl-D-glucosamine (dPNAG) 5 exopolysaccharides, also referred to as polysaccharide intercellular adhesin. dPNAG was first described in Staphylococcus epidermidis (8) but has now been determined to be a component of the biofilm matrices of Staphylococcus aureus (9), Escherichia coli (10), Acinetobacter baumannii (11), Bordetella bronchiseptica (12), Bordetella pertussis (13), Actinobacillus pleuropneumoniae (14), Yersinia pestis (15), and Burkholderia species (16).…”

Structural Basis for the De-N-acetylation of Poly-β-1,6-N-acetyl-d-glucosamine in Gram-positive Bacteria

“…The conserved exopolysaccharide known as polysaccharide intercellular adhesin was originally identified in the biofilms of S. epidermidis (11) and Staphylococcus aureus (12) and has now been shown to be produced by various Gram-negative bacteria (13)(14)(15)(16)(17)(18)(19) and higher eukaryotes (20). Polysaccharide intercellular adhesin is synthesized as a ␤-1,6-linked poly-N-acetyl-Dglucosamine (PNAG) 5 polymer and subsequently modified by partially de-N-acetylation and/or O-succinylation.…”