ROLE OF PNEUMOCOCCAL VIRULENCE GENES INTHE ETIOLOGY OF RESPIRATORY TRACT INFECTION AND BIOFILM FORMATION, ACTA UNIVERSITATIS OULUENSIS D Medica 1098
|ISBN-13:||978-951-42-9428-0 || |
|Kustantaja:||Oulun yliopisto|| |
|Laitos:||Lääketieteellinen tiedekunta|| |
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|Tekijät:||KUROLA PAULA || |
Streptococcus pneumoniae, pneumococcus, is a common cause of respiratory tract infections andalso a common inhabitant of the upper respiratory tract of healthy people. At present, 93 differentpolysaccharide types have been identified and in addition to them, unencapsulated pneumococciare found especially in healthy carriers. Pneumococci are usually identified by using a bacterialculture combined with biochemical or immunochemical tests. Recently, new DNA-basedmethods, such as PCR, have been applied. Many PCR methods that detect pneumococci aretargeted at genes which encode virulence factors such as pneumolysin, autolysin andpneumococcal surface antigen A.
S. pneumoniae is a common causative agent of otitis media. In clinical trials, xylitol has beenshown to decrease the occurrence of otitis media but the mechanism of action is not known.Xylitol has been shown to reduce pneumococcal growth and adherence to nasopharyngeal cellsand its effect on the appearance of the pneumococcal polysaccharide structure has been shown byelectron microscopy. Xylitol has also been demonstrated to inhibit biofilm formation ofStaphylococcus aureus and Pseudomonas aeruginosa. Biofilms have been associated with otitismedia and pneumococci have been shown to form biofilms.
The purpose of this work was to study the role of capsular and other virulence genes inpneumococcal infection and biofilm formation. A new PCR method was developed to detect thepneumococcal capsule and it appeared to have potential when studying the pneumococcal etiologyof pneumonia. Widely used PCR methods were used to study pneumococcal isolates, andconflicting results were obtained when the results were compared with conventionalimmunochemical methods. In addition, xylitol was shown to inhibit capsular gene expression andbiofilm formation of pneumococci. Glucose and fructose appeared to enhance biofilm formation.
The conflicting results between PCR and immunochemical methods suggest that furtheridentification methods are needed in the diagnosis of pneumococcal infection. The observedinhibitory effect of xylitol on pneumococcal capsule gene expression and biofilm formation maypartly explain the efficacy of xylitol in preventing acute otitis media in previous clinical trials.