3.1.3 Reproducibility of the method
The comparison of the 13 common peaks from protein spectra obtained from the different spots in which the same isolate was smeared (inter-spot variability) showed 11.0 % and 14.5% of mean of their CVs values for day 1 and day 2, respectively. Besides, the analysis of the variance yielded a maximum of 20.5% CV for the most common peaks detected within the 7000-10000 m/z range, although most peaks between 2000 and 7000 m/z interval showed CV values between 10.0% and 15.0% (Figure S3A). The mean and median inter-day CV values were 9.2% and 5.8%, respectively. CV values varied between 0.02-18.0%, a range considered as acceptable by other authors (R. T. K. Pang et al., 2004) -Figure S3B-. The only exception here was the 5740 m/z peak, whose inter-day CV was almost 30.0%.
The reproducibility of the specific biomarkers that allowed the differentiation of the P. aeruginosa isolates belonging to the outbreak was further analysed. In this case, three peaks were identified as potential biomarkers for differentiation between outbreak strains and those not related with the outbreak (peaks 5169, 6915 and 7236m/z ). The average intra-day CV for these peaks was 13.6% and this value varied between 7.0 and 20.5% (Figure S3C). However, the biomarker peak at 6915 m/z showed 32.5% inter-day CV variability (Figure S3D).