Impact of KCL on flow cytometric viability determination. Comparison of Ringer solution without and with 3 M KCl. Viability was determined by membrane integrity analysis using SYBR Green I (dilution of 5 × 103) and PI (5 μg/mL). Relative frequencies of (A) viable and dead cells of P. aeruginosa, (B) of viable and dead cells of B. cepacia and (C) of viable, damaged and dead cells of S. aureus in exponential and stationary growth phases in pure culture. Relative frequencies were determined based on all SYBR Green I and PI fluorescence positive events. Error bars represent standard deviation of three biological replicates; # indicates a statistically significant difference (p < 0.05, paired Student t-test).