title: Release of SpeA from Streptococcus pyogenes after exposure to penicillin: dependency on dose and inhibition by clindamycin.
abstract: The amount and time course of SpeA release from group A streptococci (GAS) was studied at different starting inoculate after exposure to different doses of penicillin, clindamycin or a combination of the 2. The release was related to the bacterial concentration and killing rate. A clinical GAS strain was exposed to benzylpenicillin, 2 and 1000 x MIC, clindamycin, 2 and 32 x MIC, or combinations of the 2. Samples for viable counts and SpeA analyses were drawn before and after the addition of antibiotics and at 3, 6 and 24 h. The SpeA release was higher at low than at high concentrations of penicillin and the combination (both, p<0.05). The addition of clindamycin to penicillin reduced SpeA production at both concentrations (p<0.01). Most SpeA was released before 3 h, and for penicillin and the combination, the amount correlated to the number of killed bacteria during this period (r=0.50; p<0.05). A positive correlation was found between the inoculum size and the SpeA concentration at time zero (r=0.54; p<0.05). The SpeA concentration was dependent on the initial number of bacteria, the class of antibiotic, the dose of penicillin and the killing rate.
authors.affiliation: Section of Infectious Diseases, Department of medical Sciences, Uppsala University, Sweden. hjerdt.goscinski@akademiska.se
authors.forename: Gunilla
authors.initials: G
authors.lastname: Goscinski
authors.forename: Eva
authors.initials: E
authors.lastname: Tano
authors.forename: Pontus
authors.initials: P
authors.lastname: Thulin
authors.forename: Anna
authors.initials: A
authors.lastname: Norrby-Teglund
authors.forename: Jan
authors.initials: J
authors.lastname: Sjölin
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000187:drug effects* / Q000378:metabolism*; D002981:Clindamycin / Q000494:pharmacology*; D015169:Colony Count, Microbial; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005098:Exotoxins / Q000378:metabolism*; D007700:Kinetics; D008565:Membrane Proteins / Q000187:drug effects* / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D010403:Penicillin Resistance / Q000187:drug effects; D010406:Penicillins / Q000494:pharmacology*; D013297:Streptococcus pyogenes / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D005098:Exotoxins; D008565:Membrane Proteins; D010406:Penicillins; C117980:SpeA protein, Streptococcus pyogenes; D002981:Clindamycin