Agar disk diffusion susceptibility characteristics of azlocillin, carbenicillin, mezlocillin, piperacillin, and ticarcillin.

The agar disk diffusion susceptibility of Enterobacteriaceae to mezlocillin and piperacillin was correlated with agar minimal inhibitory concentrations and compared with the susceptibility to carbenicillin. The agar disk susceptibility of Pseudomonas aeruginosa to azlocillin, mezlocillin, and piperacillin was correlated with agar minimal inhibitory concentrations and compared with the susceptibility to carbenicillin and ticarcillin. Criteria are offered for the zones of inhibition to provide information about resistant and susceptible isolates that correlate with known serum levels.