Fig 3. Determination of the lower limit of detection for water samples obtained ultrapure water (A), river (B), pond (C) and sewage (D).

Ultrapure water (A) was tested with and without the addition of 1 × 10⁷ E. coli/mL. All the samples were spiked with 10⁶ Leptospira/mL and 10-fold serially diluted down to 1 Leptospira/mL. Error bars represent the geometric mean ± SD of three independent experiments.