Further studies on post-antibiotic effect and synergism in two strains of Streptococcus faecalis.
The differences in the synergistic potential for either killing effect or increase in duration of post-antibiotic effect (PAE) seen with various beta-lactam-aminoglycoside combinations in two strains of Streptococcus faecalis were further studied to examine this relationship in more detail. It was seen that a strain which produced a synergistic increase in recovery period (PAE greater than or equal to 0.5 h), comparing the beta-lactam antibiotics alone and when combined with streptomycin, showed increased sensitivity (greater than or equal to 1 log10 reduction in viable counts) to a subinhibitory concentration of streptomycin added to a culture recovering from the PAE; this was not demonstrated with a strain showing no increase in PAE when briefly exposed to a combination therapy, although its corresponding killing curve was clearly synergistic. Moreover, it was seen that the differences in the synergistic prolongation of recovery period when combining various aminoglycosides at 1/4 x MIC with ampicillin were consistent with the different duration of PAE with the particular aminoglycoside alone at the MIC.
Fuursted
K
K
Department of Clinical Microbiology, Odense University Hospital, Denmark.
D000667:Ampicillin / Q000008:administration & dosage; D004357:Drug Synergism; D013293:Enterococcus faecalis / Q000187:drug effects*; D005839:Gentamicins / Q000008:administration & dosage; D015378:Imipenem / Q000008:administration & dosage; D008826:Microbial Sensitivity Tests; D009428:Netilmicin / Q000008:administration & dosage; D010878:Piperacillin / Q000008:administration & dosage; D013307:Streptomycin / Q000008:administration & dosage; D013997:Time Factors; D014031:Tobramycin / Q000008:administration & dosage; D014640:Vancomycin / Q000008:administration & dosage
D005839:Gentamicins; D009428:Netilmicin; D014640:Vancomycin; D015378:Imipenem; D000667:Ampicillin; D014031:Tobramycin; D010878:Piperacillin; D013307:Streptomycin