Inhibition of urease B enzymatic activity by specific mAb U001. Urease (25 μl) was incubated with 25 μl mAb U001 or U002 (equivalent to 0-25 μg) in 96-well microtitre plates overnight at 4°C, with PBS as a control. On the following day, 50 μl 50 mM phosphate buffer (pH 6.8) that contained 500 mM urea, 0.02% phenol red, and 0.1 mM DTT was added to each well. The colour development was monitored at 550 nm with a microplate reader. The inhibition ratio was determined by the following equation: [(activity without Ab - activity with Ab)/(activity without Ab)] × 100.