Antibacterial activity of Eisenia fetida andrei coelomic fluid: Evidence, induction, and animal protection

Coelomic fluid of the earthworm, Eisenia fetida andrei, naturally inhibits the in vitro growth of the two worm pathogen bacteria, Aeromonas hydrophila (Gram-negative) and Bacillus megaterium (Gram-positive). LD50 values (injected dose causing death of 50% of the worm population) indicated that E. fetida andrei is more susceptible to A. hydrophila (5 × 103 living bacteria) than to B. megaterium (5 × 105). One injection of LD50 resulted in an increased humoral bacteriostatic activity peaking 4 days after injection. Such enhanced activity totally protected the worms against infestation with 200 to 2000 times the LD50 dose and persisted for 4 days with A. hydrophila and 11 days with B. megaterium. Secondary response, different from the first one, was obtained on animals reinjected with the LD50 dose at the time when normal bacteriostatic activity was recovered (respectively 15 and 22 days after the first injection) but not 15 days later.