Natural antibiotic susceptibility of recently established coryneform bacteria.

The natural susceptibility of 20 strains each of Brevibacterium casei (formerly CDC coryneform groups B-1 and B-3), Dermabacter hominis (formerly CDC coryneform groups 3 and 5), and Turicella otitidis (formerly coryneform group ANF-1-like) isolated from clinical specimens to 71 antibiotics was investigated. Susceptibility testing was carried out with a microdilution procedure using H medium. All three species were naturally sensitive to tetracyclines, most aminoglycosides, carbapenems, macrolides, lincosamides, glycopeptides, and rifampin. Susceptibility patterns indicating natural resistance to pipemidic acid, sulfamethoxazole, and cotrimoxazole also were found for all three species. Species-dependent discrepancies in susceptibility leading to completely different categorizations (changing from sensitive to resistant or vice versa) were found for some penicillins (e.g., oxacillin and amoxicillin), a few cephalosporins (e.g., ceftibutene), aztreonam, tobramycin, norfloxacin, fleroxacin, trimethoprim, nitrofurantoin, fosfomycin, and fusidic acid. For the majority of antibiotics, Brevibacterium casei was the least susceptible species and Turicella otitidis the most susceptible taxon. The present study describes a database on the natural susceptibility of Brevibacterium casei, Dermabacter hominis, and Turicella otitidis to a wide range of antibiotics. This database can be applied for the validation of susceptibility testing results of these recently established coryneform bacteria.