In vitro bactericidal activity of peak serum concentrations of co-amoxiclav, amoxicillin and vancomycin against methicillin-resistant Staphylococcus aureus.
In order to explore the bactericidal activity of concentrations similar to the peak serum concentrations obtained after a single i.v. dose of 2,000/200 mg co-amoxiclav and 500 mg vancomycin, killing curves with co-amoxiclav (69/10 microg/ml), amoxicillin (69 microg/ml), clavulanic acid (10 microg/ml), and vancomycin (15 microg/ml) were performed against two isogenic (ss-lactamase positive and negative) methicillin-resistant Staphylococcus aureus strains in cation-supplemented Mueller-Hinton broth with 2% NaCl incubated at 35 degrees C. Colony counts were performed at 0, 1, 2, 3 and 4 hours in Mueller- Hinton plates supplemented with 4% NaCl and 25 microg/ml oxacillin to measure the resistant population. Similar initial inocula reductions were obtained for amoxicillin-clavulanic acid and vancomycin for both strains, and significant differences were found in comparison to the control. Clavulanic acid decreased the growth rate of the ss-lactamase negative strain when compared to control curves. The penicillin-binding protein 2a affinity of old ss-lactams in conjunction with clavulanic acid overcoming ss-lactamase resistance may explain these results.
Gómez-Lus
M L
ML
Microbiology Dept., School of Medicine, Universidad Complutense, Madrid.
Prieto
J
J
Giménez
M J
MJ
García
M
M
Anta
L
L
Aguilar
L
L
D000658:Amoxicillin / Q000097:blood* / Q000494:pharmacology*; D019980:Amoxicillin-Potassium Clavulanate Combination / Q000097:blood* / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000097:blood* / Q000494:pharmacology*; D004359:Drug Therapy, Combination / Q000097:blood* / Q000494:pharmacology*; D006801:Humans; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D010406:Penicillins / Q000097:blood* / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects*; D014640:Vancomycin / Q000097:blood* / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D010406:Penicillins; D014640:Vancomycin; D019980:Amoxicillin-Potassium Clavulanate Combination; D000658:Amoxicillin