The influence of atmospheric drying on the survival of wound flora

Abstract

Suspensions ofStrep. pyogenes, Staph. aureus, Ps. pyocyaneaand micrococci in serum, distilled water, saline and oleic acid solution were allowed to dry on cover-slips. The numbers of bacteria surviving after periods of exposure were estimated from viable counts of extracted cover-slips.All the organisms tested showed after drying a fall in viable count that was absent in aqueous suspensions not allowed to dry.Ps. pyocyaneawas shown to have a lower survival rate on drying than the other organisms.Serum afforded moderate protection to the suspended organisms during the period of drying.0·1 mg./ml. oleic acid caused a rapid destruction ofStrep. pyogenesand a significant destruction ofPs. pyocyaneaas well as ofStaph. aureusand micrococci in drying films of these organisms. The similarity of the fate ofStaph. aureusand micrococci during drying in low concentrations of oleic acid is in contrast to the previously reported greater sensitivity ofStaph. aureusto higher concentrations of oleic acid (1–10 mg./ml.) in the test-tube.The implications of these findings are discussed in relation to skin and wound flora, and to environmental hygiene.