FIG. 1.
Antibiotic susceptibilities of E. tarda, E. ictaluri, and E. hoshinae. The number of strains for the corresponding MIC is cited. A number in the lowest concentration of the antibiotic represents the maximal MIC at this concentration (MIC = cmin → MIC ≤ cmin). An MIC higher than the highest concentration tested is cited in the subsequent higher concentration step. MICs in shaded areas indicate the clinically intermediate area according to the American standard (NCCLS) valid for Enterobacteriaceae (NCCLS-E) (18), Pseudomonas aeruginosa and other non-Enterobacteriaceae (NCCLS-P) (19), Neisseria gonorrhoeae (NCCLS-N) (21), and Staphylococcus spp. (NCCLS-S) (20). A black thick line indicates the breakpoint between the clinically sensitive and clinically resistant strains, if the intermediate interpretation does not exist. For antibiotics for which NCCLS clinical assessment criteria do not exist, breakpoints according to German (DIN) (7), French (SFM) (5), or Swedish (SWE) (25) standards were employed. Breakpoints for ribostamycin, apramycin, and lividomycin were used as published recently (34). A superscript 1 indicates susceptibility testing in the presence of sodium chloride (2%). Oxacillin breakpoints: susceptible, ≤2 mg/liter; resistant, ≥4 mg/liter. A superscript 2 indicates the MIC distribution for sulfamethoxazole for higher concentrations: MIC = 128 mg/liter, n = 18; MIC = 256 mg/liter, n = 9; MIC = 512 mg/liter, n = 17; MIC = 1,024 mg/liter, n = 22; breakpoint for sensitivity, ≤256 mg/liter (NCCLS-E).