The effect of different environmental conditions on the survival of Enterobacter cloacae, Pseudomonas aeruginosa and Staphylococcus aureus on stainless steel surfaces was determined using direct epifluorescence microscopy (DEM) and plate count method. A strong linear relation (R2 = 0.97; P < 0.01) between DEM and plate counts over the range of 104-107 CFU/cm2 was observed when counts by DEM were performed over viable microorganisms. However, when microorganisms were subjected to adverse conditions, such as slow air-drying, the correlation between both methods diminished considerably (R2 = 0.225). This may be due to microorganisms subjected to adverse conditions can be injured, so some bacteria can not be detected by cultivation, but they still present a danger. Microorganisms on wet surfaces had the ability to produce biofilm after 24 h. However, air-drying on surfaces, reduced considerably the bacterial count. E. cloacae was the most susceptible to slow air-drying on surfaces at room temperature however, S. aureus, remained viable for at least 72 h. The characteristics of an organism and its surrounding environment are among the important factors that may affect the survival of bacterial cells on surfaces. © 2007 Elsevier Ltd. All rights reserved.
- Epifluorescence microscopy