Characteristics of Antibiotic-Producing Strains of the Ocular Bacterial Flora

Abstract

Summary The antibiotics produced by a series of 22 ocular Micrococci have proven to be heterogeneous. Nine different antibiotic agents were produced by the 22 strains. These were apparently active by at least 3 distinct and independent metabolic mechanisms. Fourteen of the 22 antibiotics were rather clearly of polypeptide nature, as evidenced by enzyme destruction and other properties. The remaining 8 agents were resistant to enzyme activity, but a few observations suggest that these too, could be peptide structures. The antibacterial spectra of samples of these strains have been examined in some detail. Only gram positive species were affected significantly. Micrococcus strains were inhibited most frequently, while Corynebacterium, Sarcina, and Bacillus cultures were also commonly and highly susceptible. Streptococci, Clostridia and Mycobacteria were moderately susceptible. In general, the spectra were grossly similar for the three groups of antibiotics which acted by differing metabolic mechanisms. A high degree of variability was often shown in the susceptibility of strains of a given species to a given antibiotic producer.