Presence of capsular locus genes in immunochemically identified encapsulated and unencapsulated Streptococcus pneumoniae sputum isolates obtained from elderly patients with acute lower respiratory tract infection.
The principal virulence factor of Streptococcus pneumoniae is capsular polysaccharide, and encapsulated pneumococci are more common causes of disease than unencapsulated strains. This study analysed the presence of capsular genes in 59 pneumococcal isolates using two PCR methods targeted at the cpsA and cpsB genes of the capsular biosynthesis locus. The PCR method targeted at the cpsB gene, reported to be essential for encapsulation, was developed in this study. Of 59 pneumococcal isolates, 49 (83 %) were obtained from the sputum samples of elderly patients (≥65 years) with community-acquired pneumonia (CAP) and 10 (17 %) were from those with other acute lower respiratory tract infections (ARIs). Forty (82 %) of the CAP isolates and two (20 %) of the ARI isolates were encapsulated, as assessed by conventional immunochemical methods. Forty-one (98 %) of the 42 encapsulated strains had the cpsB gene present, and in 38 strains the cpsA gene was also detected. One of the unencapsulated isolates gave a positive result for the cpsB gene, and neither of the capsular locus genes were present in all the other unencapsulated strains. The distribution of encapsulated and unencapsulated isolates differed significantly between the two patient groups regardless of whether the presence of capsule was determined immunochemically (P<0.001) or by cpsB PCR (P=0.002). The cpsB PCR developed here was found to be a rapid and reliable method to detect the pneumococcal capsule locus and may have potential in sputum diagnostics when investigating the pneumococcal aetiology of CAP.
Kurola
Paula
P
National Institute for Health and Welfare, Oulu, Finland.
Erkkilä
Leena
L
National Institute for Health and Welfare, Oulu, Finland.
Kaijalainen
Tarja
T
National Institute for Health and Welfare, Oulu, Finland.
Palmu
Arto A
AA
National Institute for Health and Welfare, Helsinki, Finland.
Hausdorff
William P
WP
GlaxoSmithKline Biologicals, Rixensart, Belgium.
Poolman
Jan
J
GlaxoSmithKline Biologicals, Rixensart, Belgium.
Jokinen
Jukka
J
National Institute for Health and Welfare, Helsinki, Finland.
Kilpi
Terhi M
TM
National Institute for Health and Welfare, Helsinki, Finland.
Leinonen
Maija
M
National Institute for Health and Welfare, Oulu, Finland.
Saukkoriipi
Annika
A
National Institute for Health and Welfare, Oulu, Finland.
D000368:Aged; D000369:Aged, 80 and over; D001426:Bacterial Proteins / Q000235:genetics*; D001431:Bacteriological Techniques / Q000379:methods; D017714:Community-Acquired Infections / Q000382:microbiology; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D011008:Pneumococcal Infections / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000379:methods; D017027:Protein Tyrosine Phosphatases / Q000235:genetics*; D012141:Respiratory Tract Infections / Q000382:microbiology*; D013183:Sputum / Q000382:microbiology*; D013296:Streptococcus pneumoniae / Q000235:genetics* / Q000302:isolation & purification; D037521:Virulence Factors / Q000235:genetics*
D001426:Bacterial Proteins; C500439:CpsA protein, Streptococcus pneumoniae; D037521:Virulence Factors; C500440:CpsB protein, Streptococcus pneumoniae; D017027:Protein Tyrosine Phosphatases