title: Electron microscopic study of the effect of gentamicin and oxacillin on Staphylococcus aureus cells: significance of time and sequence of application in combined effect.
abstract: The ultrastructure of Staphylococcus aureus cells was studied after their treatment with gentamicin and oxacillin, each used alone or in a simultaneous or successive combination. Gentamicin (concentrations 1 or 2 micrograms/ml, incubation time 1-24 h) did not produce any ultrastructural changes in staphylococcus cells. Oxacillin in the same concentrations caused derangement of cell division accompanied by an increase in cross-wall and decrease of peripheral cell wall thicknesses. Simultaneous incubation of staphylococcus cells with gentamicin and oxacillin (both 1 microgram/ml) led to morphological changes corresponding to those induced by oxacillin. On the other hand, successive incubation with oxacillin (2-5 h), followed by gentamicin (5-24 h) caused complete destruction of staphylococci. This effect was not observed when cells were first incubated with gentamicin and then oxacillin. The study shows the importance of time and sequence factors in the combined effect of tested antimicrobials.
mesh_terms: D002473:Cell Wall / Q000187:drug effects / Q000648:ultrastructure; D005839:Gentamicins / Q000494:pharmacology*; D008854:Microscopy, Electron; D010068:Oxacillin / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000648:ultrastructure; D013997:Time Factors
chemical_list: D005839:Gentamicins; D010068:Oxacillin