A sensitive fluorescence method for detection of E. Coli using rhodamine 6G dyeing.

Negatively charged bacteria combined with positively charged alkaline dye rhodamine 6G (Rh6G) in NaH2 PO4 -Na2 HPO4 buffer solution pH 7.4, by electrostatic interaction. The dyed bacteria exhibited a strong fluorescence peak at 552 nm and fluorescence intensity was directly linear to Escherichia coli (E. coli), Bacillus subtilis (B. subtilis) and Staphylococcus aureus (S. aureus) concentrations in the range of 7.06 × 10(4) to 3.53 × 10(7) , 4.95 × 10(5) to 2.475 × 10(8) and 32.5 to 16250 colony forming unit/mL (cfu/mL) respectively, with detection limits of 3.2 × 10(4) cfu/mL E. coli, 2.3 × 10(5) cfu/mL B. subtilis and 16 cfu/mL S. aureus, respectively. Samples were cultured for 12 h, after which the linear detection range for E. coli was 2 to 88 cfu/mL. This simple, rapid and sensitive method was used for the analysis of water and drinking samples.