Staphylococcus viable counts

Traditionally methods of viable counting and microscopy have been used to study phagocytosis of bacteria and subsequent survival or destruction." However, such indirect methods give an underestimate of bacterial survival within cells. It has been shown that bioluminescence acts as a convenient real-time method for monitoring survival of Bordetella bronchiseptica in vitro, whilst a dual gfp-luxABCDE operon has been used to monitor real-time replication of Staphylococcus aureus. The use of clinically important bacteria transformed with the lux cassette overcomes the problems with viable but non-culturable bacteria, as the expression of lux genes depends on the functional biochemistry of the bacteria. ""... 

Several types of testing were employed to evaluate the bactericidal efficacies of the coated substrates. Five of the coatings on circular glass cover-slips (12 mm diameter) were challenged with the bacterium Staphylococcus aureus (ATCC 6538). This was accomplished by adding a 50- jlL suspension of 10 CFU S. aureus to the surface of each sample. At predetermined contact times a 25- jlL aliquot was removed from the surface, quenched with sterile 0.02 N sodium thiosulfate, and plated on nutrient agar. The viable bacterial colonies were then counted after 48 h incubation at 37°C. Fabric samples were tested by two methods. In one, small squares (1.0-1.5 cm) were placed on a Tryptic Soy agar plate that was inoculated... 

The ability of this medical micro-plasma system to sterilize surface has been demonstrated by Misynetal. (2000). Staphylococcus culture in liquid media ( 2 10 cfu/ml) have been treated by the air plasma plume of 3 mm diameter, incubated for 24 h, and counted (see Table 12-8). A 6-log reduction in viable bacteria is achieved in 25 s of treatment however the sterilization efficiency drops off with increasing volume of liquid which inhibits UV penetration and diffusion of active species generated in plasma. Nevertheless, the microplasma system should be a good solution for treatment of living human and animal skin as the bacteria are normally at much lower concentrations on skin (< 10 cfu/cm ). 

---