Macrolide antibiotics are known to be effective in spite of their low blood levels. This results in an exception to the customary rule of antibiotics evaluation, of judging the in-vivo effect of an antibiotic in terms of blood levels and MICs. Most efforts to improve blood levels of macrolides have been unsuccessful because of hepatic toxicity. Intravenous administration of macrolides has been difficult because of the frequent incidence of severe side effects. In the present paper, the in-vivo distribution characteristics and metabolic features of macrolides are summarized with some mention of those of lincosamides and streptogramins. Results show that macrolides are intrinsically toxic to man as a protein synthesis inhibitor, but that they are easily metabolized and destroyed in the body. In the course of this destruction, minute amount of a macrolide and its active metabolites distribute selectively in some tissues owing to their higher tissue affinity. Thus a delicate balance between tissue affinity and metabolism makes effective and safe oral therapy with minimum side activities.
SUMMARYThree kinds of temperate Staphylococcus aureus phages were differentiated by serological, sedimentation and electron microscopic studies. Phage S 1 had a long hexagonal head and a long tail, a density in Cs2SO 4 of 1.365 g/ml and belonged to serological group A; phage $2 had a short hexagonal head and a short tail, a density of 1.385 to 1.392 g/ml and belonged to serological group B; phage $3 had a shape similar to phage $2 except for some minor differences, but had a density of 1-416 g/ml and belonged to serological group F. S. aureus MS27 was found to be singly lysogenic for $2. However, S. aureus MS3878 was a doubly lysogenic strain carrying S1 and $2 and S. aureus E169 was a triply lysogenic strain carrying S1, $2 and $3. All these temperate phages showed similarity in shape to typing phages belonging to the same serological group. The temperate S. aureus phages revealed the presence of a hexagonal baseplate with spikes. The burst sizes of phages $1, $2 and $3 were about 50, 110 and 120 respectively. The DNA from S1, $2 and $3 ranged from 29-4 to 30 megadaltons in size.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.