In vitro bactericidal activity of peak serum concentrations of co-amoxiclav, amoxicillin and vancomycin against methicillin-resistant Staphylococcus aureus
Gómez-Lus, M.L.; Prieto, J.; Giménez, M.J.; García, M.; Anta, L.; Aguilar, L.
Revista Espanola de Quimioterapia Publicacion Oficial de la Sociedad Espanola de Quimioterapia 12(2): 136-139
1999
ISSN/ISBN: 0214-3429 PMID: 10562674 Document Number: 499047
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.