Optimization of the live E. coli assay on well devices. (A)
Equivalent E. coli O157:H7 samples are lysed for various sonication
durations (in seconds) with subsequent colorimetric detection on the
paper device. (B) Enrichment volume study with live E. coli O157:H7.
Aliquots of E. coli cells were diluted in 10, 5, and 1 mL of TSB growth
medium and enriched for 5 h and then tested for β-galactosidase
activity. The bacteria grown in 1 mL of growth medium gave a more
distinct and intense color change, indicating the enzyme was more
concentrated.