Disinfection with gaseous formaldehyde. Fifth Part: Influence of albumin, mucin and blood on the bactericidal and sporicidal effectiveness.

The influence of 0.1% peptone, 0.2% albumin, 1% mucin solutions and whole human blood on the inactivation of Staphylococcus aureus ATCC 6538 and spores of Bacillus subtilis var. niger DSM 675 was determined. The bactericidal and sporicidal effectiveness of 0.75, 1.5 and 3.2 mg HCHO l-1 air at temperatures of 35, 40, 45 degrees C and a relative humidity (RH) of 90% decreased in the following order of loading substances: peptone, albumin, mucin and blood. The calculated D-values of the microorganisms suspended and dried in 0.1% petone and in 0.2% albumin after exposure to 3.2 mg HCHO l-1 air at 40 degrees C and a relative humidity of approximately 90% were in both suspensions 1.9 min for S. aureus and 6.1 and 7.3 min respectively for B. subtilis spores. Under the same exposure conditions but with an addition of 1% mucin D-values of 2.5 min and 7.7 min for S. aureus and B. subtilis spores respectively were found. In the presence of blood, D-values of 12.3 and 18.3 min were obtained under the same conditions for S. aureus and B. subtilis spores respectively. Thus the suspension in blood caused a 2-fold increase in D-value compared to the other substances. The nature of the anticoagulant in the whole blood did not cause much difference in the inactivation of B.subtilis spores. Decreasing concentrations of blood caused an increase in sensitivity of B.subtilis spores to gaseous formaldehyde, whereby diluting blood 1:6 reduced the D-value from 23.9 min to only 7.1 min.