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Table 1 Definition of extended microbiological thresholds according to the risk areas

From: Experimental based experiences with the introduction of a water safety plan for a multi-located university clinic and its efficacy according to WHO recommendations

Risk area Parameter Warning* Threshold Alert* Worst case*
1 and 2 TMC 22°C and 36°C 80 – 100 CFU/ml >100 CFU/ml** >200 – 500 CFU/ml >500 CFU/ml
  Coli-like, E. coli, Enterococci   0 CFU/100 ml** 1–10 CFU/100 ml >10 CFU/100 ml
  P. aeruginosa   0 CFU/100 ml** 1–10 CFU/100 ml >10 CFU/100 ml
  Legionella spp.(shower, tap)   0 CFU/100 ml* 1–100 CFU/100 ml >100 CFU/100 ml
  fungi   0 CFU/100 ml* 10–100 CFU/100 ml >100 CFU/100 ml
3 TMC 22°C and 36°C   >100 CFU/ml** >500 CFU/ml >1000 CFU/ml
  Coli-like, E. coli Enterococci   0 CFU/100 ml** 1–10 CFU/100 ml >10 CFU/100 ml
  P. aeruginosa   0 CFU/100 ml** 1–50 CFU/100 ml >50 CFU/100 ml
  Legionella spp.(shower)   0 CFU/100 ml* >5–50 CFU/100 ml >50 CFU/100 ml
  Legionella spp. (tap)   0 CFU/100 ml* >200 CFU/100 ml >500 CFU/100 ml
  1. *our in-house recommendation ** law(2001) resp. water quideline (2004)