Effect of borate on the growth of coagulase-positive and coagulase-negative staphylococci.

Of 235 strains of coagulase-positive Staphylococcus aureus studied, 221 or 94% were inhibited by 1.5 x 10(-8)m sodium borate, whereas only 6 of 57 (10.5%) coagulase-negative strains were inhibited by the same borate concentration. Four of the six coagulase-negatives were food poisoning strains and one was a hospital pathogen. Borate sensitivity was found to correlate well with lysozyme and alpha-toxin production by coagulase-positive strains.