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Using the Overlay Assay to Qualitatively Measure Bacterial Production of and Sensitivity to Pneumococcal Bacteriocins
06:05

Using the Overlay Assay to Qualitatively Measure Bacterial Production of and Sensitivity to Pneumococcal Bacteriocins

Published on: September 30, 2014

Clonal success of piliated penicillin nonsusceptible pneumococci

K Sjöström1, C Blomberg, J Fernebro

  • 1Department of Bacteriology, Swedish Institute for Infectious Disease Control, SE-171 82 Solna, Sweden.

Proceedings of the National Academy of Sciences of the United States of America
|July 24, 2007
PubMed

Insights

The Spain(9V)-3 clone (ST156) significantly increased pneumococci nonsusceptible to penicillin (PNSP) in Sweden. A pilus islet (rlrA) present in ST156 strains enhances bacterial carriage success.

Area of Science:

  • Microbiology
  • Genetics
  • Epidemiology

Background:

  • Antibiotic resistance in *Streptococcus pneumoniae* is driven by successful clones.
  • The Spain(9V)-3 clone (ST156) is a highly successful clone associated with reduced penicillin susceptibility (PNSP).

Purpose of the Study:

  • To investigate the clonal composition of PNSP isolates in Sweden.
  • To identify genetic factors contributing to the success of resistant pneumococcal clones.

Main Methods:

  • Molecular characterization of PNSP isolates using sequence typing (ST).
  • Microarray and PCR analysis to detect the rlrA pilus islet.
  • Competitive growth experiments in an animal model of carriage.

Main Results:

  • A dramatic increase in PNSP isolates was observed in Sweden (2000-2003), largely due to the ST156 clone.
  • The ST156 clone expanded significantly within serotype 14 and dominated serotypes 9V and 19F.
  • All ST156 isolates, regardless of capsular type, carried the rlrA pilus islet, also found in the penicillin-sensitive ancestor ST162.
  • Strains with the rlrA pilus islet showed increased success in carriage models.

Conclusions:

  • The rlrA pilus island is a key factor contributing to the success of ST156 and other PNSP clones.
  • This genetic element likely plays a significant role in pneumococcal colonization and spread, independent of antibiotic usage levels.

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