Growth Inhibition of Staphylococci by Sodium Thiosulphate

The addition of sodium thiosulphate to a medium as neutralizer of an iodine antiseptic resulted in unexpected growth inhibition of various strains of staphylococci and micrococci. The minimum growth inhibiting concentration varied with different strains. The inhibitory effect of sodium thiosulphate was more pronounced in media with low pH values than in those with high pH values, and was diminished by the addition of Tween 80. The action was also found to depend on the concentration of l ‐cystine in the medium. It is suggested that the use of sodium thiosulphate be avoided in growth media designed to neutralize iodine in disinfection efficiency tests when staphylococci or micrococci are used as test organisms.