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A successful, diverse disease-associated lineage of nontypeable pneumococci that has lost the capsular biosynthesis

W P Hanage1, T Kaijalainen, A Saukkoriipi

  • 1Department of Infectious Disease Epidemiology, St. Mary's Hospital, Imperial College London, Norfolk Place, London W2 1PG, United Kingdom. w.hanage@imperial.ac.uk

Journal of Clinical Microbiology
|March 7, 2006
PubMed

Insights

Nontypeable Streptococcus pneumoniae strains lacking a polysaccharide capsule are common. A specific lineage of these bacteria, identified through multilocus analysis, has spread globally and is linked to various infections, including conjunctivitis.

Area of Science:

  • Microbiology
  • Genetics
  • Epidemiology

Background:

  • Nontypeable Streptococcus pneumoniae (NTS) strains lacking polysaccharide capsules are frequently found in both asymptomatic carriage and disease states.
  • Distinguishing true NTS from other nontypeable streptococci is crucial for understanding pneumococcal epidemiology.

Purpose of the Study:

  • To identify and characterize genuine nontypeable pneumococcal strains within a collection of untypeable isolates.
  • To investigate the genetic lineage, geographic distribution, and clinical associations of capsule-deficient pneumococci.

Main Methods:

  • Multilocus sequence typing (MLST) was employed to differentiate pneumococcal strains from other streptococci.
  • Analysis of a dataset of 121 untypeable pneumococcal isolates from Finnish children's nasopharyngeal swabs and middle ear fluid.

Main Results:

  • Seventy of the 121 untypeable isolates belonged to a distinct pneumococcal lineage that had lost its capsular locus.
  • This lineage includes sequence types 344, 448, and 449 and has demonstrated intercontinental spread.
  • The lineage was associated with carriage, mucosal infections, invasive disease, and notably, outbreaks of conjunctivitis.

Conclusions:

  • The capsule-deficient pneumococcal lineage shows significant long-term persistence and global dissemination, challenging assumptions about the capsule's necessity for transmission.
  • Loss of the polysaccharide capsule does not preclude successful pneumococcal evolution and spread.
  • Further research is needed to elucidate the precise role of the capsule in Streptococcus pneumoniae transmission dynamics.

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