Acute onset pneumonia: Laboratory Identification

Pneumococcal Resistance

  • Most S. pneumoniae strains gain penicillin resistance by altering the penicillin-binding proteins in their cell wall.
  • Penicillin molecules that cannot find a penicillin binding site cannot interfere with cell wall synthesis.
  • Several different types of penicillin binding proteins may be involved, explaining the various levels of intermediate resistance that may be encountered with different strains of S. pneumoniae.
  • Because different penicillin binding proteins may be involved, the level of penicillin resistance cannot be predicted by the oxacillin screening test.
  • Infections caused by isolates of S. pneumoniae showing penicillin resistance in the intermediate range may be successfully treated by administering high doses of antibiotic.
  • For this reason, the level of resistance with an accurate MIC test must be determined for all clinically significant isolates of S. pneumoniae.

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