The qPCR reaction was carried out in a final volume of 25 mL with the following components:
12.5 mL of Brilliant III Ultra-Fast QPCR Master Mix (Agilent Technologies, Inc., USA),
100 nM primers and 100 nM probe were used for vvhA,
75 nM primers and were used for tlh and ompW,
with 100 nM and 150 nM probe, respectively.