Laboratory studies of a multiple-antibiotic spray

A spray delivering neomycin, bacitracin and polypmyxin in powder form was tested for its effect upon potentially pathogenic bacteria under laboratory conditions. Cultures of all of the 168 bacterial strains tested were inhibited by the spray. Agar-diffusion methods were employed to demonstrate various interactions between the component antibiotics. The various bacterial groups studied revealed different antibiotic-interaction patterns. Tube tests confirmed that the majority of these were not diffusion artefacts. No evidence was found of antagonism sufficiently pronounced to contraindicate the use of this antibiotic triad. It is possible, though by no means certain, that neomycin alone would be as useful as the triad.(AU)