Influence of subinhibitory concentrations of protein-synthesis-inhibiting antibiotics on production and release of the pneumococcal virulence factor pneumolysin in vitro.
OBJECTIVE
Pneumolysin is an important virulence factor of Streptococcus pneumoniae with cytotoxic and proinflammatory activities released during growth and autolysis. At concentrations above the minimal inhibitory concentration, the protein-synthesis-inhibiting antibiotics erythromycin, clindamycin and rifampicin inhibit the production and/or release of virulence factors in various bacterial species. We investigated the influence of subinhibitory concentrations of these antibiotics on production and release of pneumolysin by S. pneumoniae strain D39.


METHODS
The pneumococcal strain D39 was grown in broth and treated with antibiotics at a concentration of 1/32 of the respective minimal inhibitory concentration. Cytoplasmic and extracellular pneumolysin was measured by quantitative immunoblotting with recombinant pneumolysin as standard.


RESULTS
The subinhibitory antibiotic concentrations evaluated did not affect bacterial growth. During logarithmic growth, production of pneumolysin was decreased by clindamycin, erythromycin and rifampicin by approximately 50% compared with untreated controls. The release of pneumolysin was decreased to a similar extent.


CONCLUSIONS
A decrease in pneumolysin production by 50% probably has a moderate biological effect. We do not advocate the use of subinhibitory concentrations of antibiotics to modulate the expression of virulence factors during pneumococcal disease, particularly with regard to the risk of development of antibiotic resistance.
Spreer
Annette
A
Department of Neurology, University of Gottingen, Gottingen, Germany.
von Ruden
Christian
C
Mitchell
Timothy J
TJ
Eiffert
Helmut
H
Nau
Roland
R
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000378:metabolism; D050296:Microbial Viability / Q000187:drug effects; D014176:Protein Biosynthesis / Q000187:drug effects*; D013296:Streptococcus pneumoniae / Q000166:cytology / Q000378:metabolism* / Q000472:pathogenicity*; D013301:Streptolysins / Q000378:metabolism*; D014774:Virulence
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D013301:Streptolysins; C032290:plY protein, Streptococcus pneumoniae