title: Proinflammatory activation of Toll-like receptor-2 during exposure of penicillin-resistant Streptococcus pneumoniae to beta-lactam antibiotics.
abstract: OBJECTIVE
  Disease caused by penicillin-resistant Streptococcus pneumoniae (PRSP) is associated with more suppurative complications than disease caused by penicillin-susceptible S. pneumoniae (PSSP). Exposure of S. pneumoniae to beta-lactam antibiotics enhances the proinflammatory activation of human cells by pneumococci via Toll-like receptor-2 (TLR2). To test the hypothesis that penicillin resistance influences cellular TLR2 activation by beta-lactam-exposed pneumococci, we compared TLR2 induction by PSSP (MIC 0.06 mg/L) and a high-level PRSP clinical isolate (159; MIC 16 mg/L) following exposure to penicillin and cefotaxime.
  
  
  METHODS
  Both organisms were treated with penicillin or cefotaxime at and around the MIC. TLR2 signalling was measured as relative IL-8 promoter activation in transfected HeLa cells.
  
  
  RESULTS
  On exposure to penicillin, log-phase PSSP and PRSP induced TLR2-proinflammatory activation at levels significantly higher than unexposed bacteria, and maximal in each case at the MIC. Transformants containing low-affinity penicillin-binding proteins (PBP) 2x, 1a and 2b exhibited stepwise resistance to cefotaxime and penicillin. TLR2 activation following penicillin treatment was dependent on an abnormal cell wall (PBP1a and 2x) and autolysis (PBP2b). High affinity PBP2x was required for this effect to be observed in log-phase pneumococci exposed to cefotaxime at the MIC. Cefotaxime-mediated TLR2 activation was not observed in lag-phase transformants exposed to sub-lethal concentrations.
  
  
  CONCLUSIONS
  These data show that PRSP have similar TLR2-proinflammatory effects to PSSP when exposed to beta-lactam antibiotics but the antibiotic concentration relative to the MIC is critical. This has implications for treatment of pneumococcal disease when tissue concentrations of antibiotic are close to the MIC.
authors.affiliation: Division of Genomic Medicine, University of Sheffield Medical School, Beech Hill Road, Sheffield S10 2RX, UK.
authors.forename: Lisa J
authors.initials: LJ
authors.lastname: Moore
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Gilbey
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Dowson
authors.forename: Alison C
authors.initials: AC
authors.lastname: Pridmore
authors.forename: Steven K
authors.initials: SK
authors.lastname: Dower
authors.forename: Robert C
authors.initials: RC
authors.lastname: Read
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002439:Cefotaxime / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D018950:Lipopolysaccharide Receptors / Q000502:physiology; D008826:Microbial Sensitivity Tests; D010403:Penicillin Resistance; D046915:Penicillin-Binding Proteins / Q000378:metabolism; D010406:Penicillins / Q000494:pharmacology; D013296:Streptococcus pneumoniae / Q000187:drug effects*; D051195:Toll-Like Receptor 2 / Q000502:physiology*; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D018950:Lipopolysaccharide Receptors; D046915:Penicillin-Binding Proteins; D010406:Penicillins; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D047090:beta-Lactams; D002439:Cefotaxime