Citreamicin alpha (LL-E 19085-alpha) is an antibiotic whose in vitro antimicrobial activity against 429 clinical isolates of Gram-positive cocci has been tested by the agar dilution method. These microorganisms included 313 strains of Staphylococci and 116 strains of Streptococci. The in vitro activity of Citreamicin alpha was compared with that of ampicillin, amoxicillin, ceftriaxone, erythromycin, and vancomycin. For Staphylococci, the MIC values of Citreamicin alpha ranged from 0.12-4.0 μg/ml, and for Streptococcus pyogenes of the genus Streptococcus, it was 0.03-0.12 μg/ml. However, enterococci were relatively resistant, requiring 2.0 μg/ml of the agent to inhibit 64% of the 62 tested strains. The in vitro activity of this antibiotic was much better than that of ampicillin, amoxicillin, ceftriaxone, and erythromycin, but comparable or slightly inferior to that of vancomycin.
