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A comparison was made of the effectiveness of popular disinfectants (Cavicide, Cidexplus, Clorox, Exspor, Lysol, Renalin, and Wavicide) under conditions prescribed for disinfection in the respective product labels on Pseudomonas aeruginosa either in suspension or deposited onto surfaces of metallic or polymeric plastic devices. The testing also included 7 nonformulated germicidal agents (glutaraldehyde, formaldehyde, peracetic acid, hydrogen peroxide, sodium hypochlorite, phenol, and cupric ascorbate) commonly used in disinfection and decontamination. Results showed that P. aeruginosa is on average 300-fold more resistant when present on contaminated surfaces than in suspension. This increase in resistance agrees with results reported in studies of biofilms, but unexpectedly, it precedes biofilm formation. The surface to which bacteria are attached can influence the effectiveness of disinfectants. Viable bacteria attached to devices may require dislodging through more than a one-step method for detection. The data, obtained with a sensitive and quantitative test, suggest that disinfectants are less effective on contaminated surfaces than generally acknowledged.

This study compares the effects of various concentrations of salt or serum in the killing of Bacillus subtilis spores by either glutaraldehyde, sodium hypochlorite, cupric ascorbate, hydrogen peroxide, peracetic acid, formaldehyde, or phenol. Salt affected only glutaraldehyde, its sporicidal activity increasing with an increase in concentration of sodium bicarbonate or sodium chloride. The sporicidal activity of glutaraldehyde was minimal when the concentrations of aldehyde groups and lysine residues from protein were similar. We present an equation describing the effect of serum on spore survival as a function of glutaraldehyde concentration that fits the data with a regression coefficient of 0.9. Cupric ascorbate and peracetic acid were inhibited by serum, but this effect was linked to a rise in pH. Sodium hypochlorite was the agent most sensitive to protein, with its sporicidal activity nearly disappearing in the presence of 2% serum or an equivalent amount of purified protein.