Abstract
BackgroundNontypeable Haemophilus influenzae is an important cause of otitis media in children and lower respiratory tract infection in adults with chronic obstructive pulmonary disease (COPD). Several lines of evidence suggest that the bacterium grows as a biofilm in the human respiratory tract.ResultsFifteen clinical isolates from middle ear fluid of children with otitis media and 15 isolates from sputum of adults with COPD were studied in an in vitro assay of biofilm formation. Striking variability among isolates was observed in their ability to form biofilms. Analysis of cell envelopes revealed minimal differences in banding patterns in polyacrylamide gels, alteration of expression of an epitope on lipooligosaccharide, and preservation of expression of selected epitopes on outer membrane proteins P2, P5 and P6 in biofilms compared to planktonically grown cells. A pilus-deficient variant showed a marked impairment in biofilm formation compared to its isogenic parent.ConclusionsNontypeable H. influenzae forms biofilms in vitro. Clinical isolates show substantial variability in their ability to grow as biofilms. Three major outer membrane proteins (P2, P5 and P6) are expressed during growth as a biofilm. Expression of lipooligosaccharide is altered during growth as a biofilm compared to planktonic growth. Pili are important in biofilm formation. As the role of biofilms in human infection becomes better defined, characterization of biofilms may be important in understanding the pathogenesis of infection and immune response to nontypeable H. influenzae in children with otitis media and adults with COPD.
Highlights
Nontypeable Haemophilus influenzae is an important cause of otitis media in children and lower respiratory tract infection in adults with chronic obstructive pulmonary disease (COPD)
Nontypeable H. influenzae has been implicated as a cause of otitis media with effusion, which refers to the presence of fluid in the middle ear in the absence of acute symptoms
Sputum cultures reveal intermittent negative cultures in spite of continuous colonization by the same isolate proven by molecular typing, indicating that the organism is present in spite of negative cultures of sputum [32]. These observations suggest that nontypeable H. influenzae grows as a biofilm in the respiratory tract of adults with COPD, reminiscent of Pseudomonas aeruginosa and its well established propensity to grow as a biofilm while causing infection in patients with cystic fibrosis [27]. In view of these lines of evidence suggesting that nontypeable H influenzae grows as a biofilm during human respiratory tract infection, the goals of the present study are to 1) Develop an assay to study biofilms of nontypeable H. influenzae in vitro; 2) Characterize the extent to which isolates from the middle ear fluid of children with otitis media and from the sputum of adults with COPD form biofilms; 3) Begin to elucidate the characteristics of the outer membrane antigens of nontypeable H. influenzae during growth as a biofilm; and 4) Preliminarily assess the role of pili in biofilm formation
Summary
Nontypeable Haemophilus influenzae is an important cause of otitis media in children and lower respiratory tract infection in adults with chronic obstructive pulmonary disease (COPD). Nontypeable H. influenzae has been implicated as a cause of otitis media with effusion, which refers to the presence of fluid in the middle ear in the absence of acute symptoms. Reverse transcriptase PCR-based assays have shown the presence of bacterial mRNA, indicating that bacteria are present in a viable and metabolically active but non-culturable state [21]. These observations suggest that in otitis media with effusion, bacteria are in a physiological state which differs from that of bacteria growing planktonically in a free floating phase. Some authors have proposed that in otitis media with effusion, nontypeable H. influenzae grow in the form of a biofilm in the middle ear [15,22,23]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
