The bactericidal and bacteriostatical action of antibiotics on marine bacteria: I. Penicillin and Streptomycin

Abstract

       Experiments have been made about the bacteriostatical and bactericidal action of penicillin and streptomycin on single species of sea bacteria (altogether 41 species), as well as on sea bacteria in natural sea water under laboratorial conditions.

      Most of the sea bacterial species are susceptible towards penicillin (70%), towards streptomycin (75%) and towards combined penicillin and streptomycin (97%). - The coccus (gram-positive) are all susceptible to very low concentrations of antibiotics, in all three cases and for the rods gram-positive and gram-negative no regularity could be ascertained in the reaction against these antibiotics. There is a certain parallelism in the reaction of the species against penicillin, streptomycin and their combinations, so 52.5% of the species are suceptible in all the three cases and 10% of the species are resistant in all the three cases. The action of the combined penicillin and streptomycin on the species is about 20 times more effective than the action of either antibiotics indipendently.

     The results of the effects of penicillin and streptomycin on bacteria in sea water, in general agree with those of the action of these antibiotics on the single species of sea bacteria. The same concentration of antibiotics and their combinations have a somewhat more effective destructive action in the natural sea water than in the culture of the single species in broth. The lowest concentration of penicillin, streptomycin and their combinations with a total destructive effect on bacteria in sea water have been established: penicillin 2000 units/ccm, streptomycin 26,0 mgr/ccm, penicillin and streptomycin 100 units/ccm +1,0 mgr/ccm. The sinergetic action of penicillin streptomycin is about 20 times more effective than the action of either antibiotic separately.

      Some phenomena of the sinergetic action of penicillin and streptomycin have been discussed as well as of the stimulating effect of these antibiotics on the development of bacterial population, some regularities in the mutability of the bacterial population in the course of the experiments, and the possibility of using the reaction of the species against penicillin and streptomycin for the purpose of determining the bacterial species.