title: Effects of macrolides on pneumolysin of macrolide-resistant Streptococcus pneumoniae.
abstract: To clarify the discrepancy between increasing resistance and conservative clinical effects of macrolides on macrolide-resistant Streptococcus pneumoniae, the authors evaluated the effects of sub-minimum inhibitory concentrations of macrolides on pneumolysin. In vitro, S. pneumoniae was incubated with 1, 2 and 4 microg.mL(-1) of clarithromycin (CLR) and azithromycin (AZM) for 8 h. Western blot analysis and haemolytic assay were performed to examine the production and activities of pneumolysin. In vivo, mice were infected with S. pneumoniae intra-nasally and treated with CLR (40 or 200 mg.kg(-1) twice daily) or AZM (40 or 200 mg.kg(-1) once daily) orally for 7 days. After 72 h post-infection, western blot analysis was performed to examine pneumolysin production in lungs. Survival rates were observed for 10 days. In vitro, every concentration of macrolide inhibited pneumolysin production more than the control. CLR (2 and 4 microg.mL(-1)) and AZM (4 microg.mL(-1)) reduced the pneumolysin activities more than the control. In vivo, macrolides (200 mg.kg(-1)) reduced pneumolysin in murine lungs more than the control. CLR (40 and 200 mg.kg(-1)) and AZM (200 mg.kg(-1)) improved the survival rates more than the control. The study results show that sub-minimum inhibitory concentrations of macrolides reduced pneumolysin. This might be related to the effectiveness of macrolides against pneumonia caused by high-level macrolide-resistant Streptococcus pneumoniae. Further investigations are necessary to evaluate the effects of macrolides on macrolide-resistant Streptococcus pneumoniae.
authors.affiliation: Second Dept of Internal Medicine, Nagasaki University School of Medical Sciences, Sakamoto, Nagasaki, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Fukuda
authors.forename: K
authors.initials: K
authors.lastname: Yanagihara
authors.forename: Y
authors.initials: Y
authors.lastname: Higashiyama
authors.forename: Y
authors.initials: Y
authors.lastname: Miyazaki
authors.forename: Y
authors.initials: Y
authors.lastname: Hirakata
authors.forename: H
authors.initials: H
authors.lastname: Mukae
authors.forename: K
authors.initials: K
authors.lastname: Tomono
authors.forename: Y
authors.initials: Y
authors.lastname: Mizuta
authors.forename: K
authors.initials: K
authors.lastname: Tsukamoto
authors.forename: S
authors.initials: S
authors.lastname: Kohno
mesh_terms: D001426:Bacterial Proteins / Q000187:drug effects; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D006801:Humans; D018942:Macrolides / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D013296:Streptococcus pneumoniae / Q000187:drug effects*; D013301:Streptolysins
chemical_list: D001426:Bacterial Proteins; D018942:Macrolides; D013301:Streptolysins; C032290:plY protein, Streptococcus pneumoniae