The role of midgut nonspecific esterase in the susceptibility of Galleria mellonella larvae to Bacillus thuringiensis

Some mechanisms of resistance to Bacillus thuringiensis, including esterase activity in the midgut, can appear in laboratory and field insect populations. We found that B. thuringiensis infection significantly reduced the esterase activity in the midgut of greater wax moth Galleria mellonella 48 h post infection. Esterase activity was inhibited 1.5-fold by triphenyl phosphate to test the impact of the enzyme in resistance to the bacteria. Bioassays demonstrated that pre-exposure of the insects to triphenyl phosphate followed by bacterial infection resulted in two-fold elevated susceptibility of the greater wax moth larvae to B. thuringiensis.