Silkworms Are Used to Test Antibiotics

An Insect Standing In for a Patient

Before a candidate antibiotic reaches a mouse, it can be tested in a silkworm. Bombyx mori has been validated as a trustworthy in vivo infection model — a living animal you can infect with a real human pathogen and then attempt to cure.

How the Test Works

Larvae are infected with a bacterium of interest, then dosed with the compound being evaluated. What is measured is straightforward: do the treated larvae survive, and does the treatment shut down the infection?

One published example used Staphylococcus epidermidis, a bacterium responsible for hospital-acquired infections, and tested three glycopeptide antibiotics: vancomycin, teicoplanin and dalbavancin. All three cured infected larvae, significantly reducing mortality and blocking activation of the insect's immune response.

Those are real clinical drugs. The silkworm gave the right answer about compounds whose behaviour in humans is already known — which is exactly how a model gets validated.

Why Use an Insect at All

Three reasons, and they compound:

• Scale. Silkworms can be reared in enormous numbers on a known diet, so a screen can run across many compounds and doses at once.
• Speed. The animal's life cycle is short and fixed.
• Ethics and cost. Early screening in an insect means fewer mammals used on compounds that were never going to work.

It Is Not a Substitute for Everything

An insect is not a mammal, and nothing about a silkworm result predicts how a drug behaves in human tissue over months. What it does well is filter — separating candidates worth pursuing from those that fail in a living animal, before anything more expensive begins.

It is one more use for a species that was domesticated for cloth: the same features that made it farmable — docile, dense, predictable, well-understood — are what make it useful in a laboratory.

Related: the silkworm genome · the four silkworm diseases