Pathogenicity of intrathoracically administrated Bacillus thuringiensis spores in Blatta orientalis

Area of Science:

• Microbiology
• Entomology
• Insect Pathology

Background:

• Bacillus thuringiensis (Bt) is a bacterium known for its insecticidal properties.
• Its efficacy varies significantly depending on the insect species and route of administration.
• Understanding Bt's pathogenicity in different insect orders is crucial for developing targeted biocontrol agents.

Purpose of the Study:

• To investigate the potential of Bacillus thuringiensis to cause septicaemia in two cockroach species: Periplaneta americana and Blatta orientalis.
• To compare the susceptibility of these species to Bt spores and crystals via different administration routes.

Main Methods:

• Oral administration of wild-type Bt spores and crystals, and a crystal-deficient mutant, to P. americana and B. orientalis.
• Intrathoracic injection of Bt spore suspensions into P. americana.
• Determination of LD50 (lethal dose for 50% of the population) for B. orientalis after injection.

Main Results:

• Oral administration of high doses of Bt spores and crystals did not result in significant mortality in either cockroach species.
• Intrathoracic injection of Bt spores showed low susceptibility in P. americana.
• Blatta orientalis exhibited high susceptibility to intrathoracically injected Bt spores, with an LD50 of approximately 35,000 spores.

Conclusions:

• Periplaneta americana is not highly susceptible to Bacillus thuringiensis spores.
• Blatta orientalis is highly susceptible to Bacillus thuringiensis, particularly via parenteral injection, similar to Lepidoptera.
• The route of administration is a critical factor in Bacillus thuringiensis pathogenicity against cockroaches.