title: The effect of subminimal inhibitory concentrations of penicillin on growth rate and haemolysin activity of group G Streptococcus.
abstract: The influence of the subminimal inhibitory concentrations (1/3 and 1/4 of the MIC) of penicillin on growth rate and on haemolysin production of a strain of group G Streptococcus was studied. It was shown that 1/3 of the MIC almost completely inhibited the bacterial growth, but it was not able to inhibit haemolysin activity in the culture supernate. The generation time of bacteria grown in 1/4 of the MIC was approximately twice longer than that of the control culture. In all cultures, the haemolysin, after being produced (or liberated), reached a peak and decreased to low levels, which could suggest that group G Streptococcus produces some end products of metabolism that are able to inhibit haemolysin activity.
authors.affiliation: Departamento de Microbiologia Médica, Universidade Federal do Rio de Janeiro, Brasil.
authors.forename: V V
authors.initials: VV
authors.lastname: Vieira
authors.forename: L
authors.initials: L
authors.lastname: Barrucand
authors.forename: A C
authors.initials: AC
authors.lastname: Castro
mesh_terms: D006460:Hemolysin Proteins / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D010406:Penicillins / Q000008:administration & dosage / Q000494:pharmacology*; D013291:Streptococcus / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*
chemical_list: D006460:Hemolysin Proteins; D010406:Penicillins