In vitro susceptibility of bacteria to a ticarcillin-clavulanic acid combination

In vitro testing of bacterial susceptibility to a combination of ticarcillin and clavulanic acid was done, using 406 aerobic gram-positive and gram-negative isolates (considered to be pathogens) cultured from equine and small animal specimens. A microdilution broth technique of susceptibility testing was performed, using trays with wells containing a range of doubling concentrations of dehydrated ticarcillin (range, 0.50 to 128 micrograms/ml) with fixed concentration of clavulanic acid (4 micrograms/ml). The following isolates of equine origin were (90%) susceptible to concentrations of ticarcillin and clavulanic acid combinations of less than or equal to 16 and 4 micrograms/ml, respectively: Staphylococcus aureus, S intermedius, Klebsiella pneumoniae, Enterobacter aerogenes, Ent agglomerans, Ent cloacae, Escherichia coli, Actinobacillus sp, Corynebacterium pseudotuberculosis, Rhodococcus equi, Proteus vulgaris, and Bordetella bronchiseptica. Isolates of small animal origin (90%) susceptible to less than or equal to 16 and 4 micrograms of ticarcillinclavulanic/ml included S aureus, S intermedius, Ent aerogenes, Ent agglomerans, Pasteurella multocida, B bronchiseptica, Pr mirabilis, and Serratia sp.