Use of antibacteria drugs to optimise killing of streptococci by immune defences

Abstract

Intermedilysin is a cytolytic toxin produced by Streptococcus intermedius, a pathogen of man. In vitro studies showed that exposure of S. intermedius to sub-minimum inhibitory concentration (MIC) levels (1/2 MIC) of protein-inhibiting antibiotics and nucleic acid-inhibiting antibiotics can inhibit intermedilysin production by S. intermedius. On the other hand, exposure to cell wall-inhibiting antibiotics showed an insignificant reduction on intermedilysin production at sub-MIC concentrations. Investigations in possible mechanisms behind this sub-MIC effect showed that there is selective decrease in biosynthesis and release toxin after exposure to A? MIC clindamycin. However, no significant difference was seen for the mRNA levels of intermedilysin gene. A? MIC clindamycin also increase phagocytosis of S. intermedius by polymorphonuclear leukocytes (PMNs). Finally, post-antibiotic effect (PAE) was observed for protein-inhibiting and nucleic acid-inhibiting antibiotics on toxin release. While cell wall-inhibiting antibiotics in general resulted in increase in toxin release with exception of vancomycin.