Table I shows the logarithmic reduction obtained following aerosolized hydrogen peroxide treatment; it was very efficient (no survivors in samples) on ATCC strains of E. coli and C. krusei but clinical isolates presented a wide range of susceptibility. Susceptibility was very low in some micro-organisms (enterobacter: reduction from 0.87 to 1.3 log10), whereas others were slightly more susceptible (Klebsiella pneumoniae, acinetobacter, proteus, or serratia: reduction from 1.04 to 2.69 log10). Finally, susceptibility was maximum for some Gram-positive micro-organisms, such as MRSA (>4.78), enterococcus or Staphylococcus epidermidis (>4.3) and yeasts (>3.2)..