VIRULENCE AND MUTATION OF THE BACILLUS OF RABBIT SEPTICEMIA

Area of Science:

• Microbiology
• Bacteriology
• Pathogenesis

Background:

• Type D bacillus, a cause of rabbit septicemia, is known for its stable virulence.
• Understanding bacterial virulence and attenuation is crucial for disease control.

Purpose of the Study:

• To investigate the stability of Type D bacillus virulence under various conditions.
• To characterize the properties of Type G forms arising from Type D cultures.
• To elucidate mechanisms of bacterial attenuation and virulence factors.

Main Methods:

• Regular transplantation of Type D cultures on serum agar and in broth.
• Subjecting Type D cultures to unfavorable conditions (e.g., prolonged incubation without transplant).
• Virulence testing of individual organisms and mixed cultures using Barber pipette and animal passage.

Main Results:

• Type D bacillus exhibited remarkable virulence stability, even after prolonged incubation in broth.
• G forms arising from Type D cultures showed a lack of invasibility.
• Mixed cultures of Type D and G showed virulence proportional to the Type D population.
• Animal passage increased Type G virulence and granular growth, broadening its acid agglutination zone.
• Type D's invasiveness is partly attributed to antiphagocytic activity, absent in Type G.

Conclusions:

• Type D bacillus demonstrates high stability in virulence.
• The D to G mutation is a key factor in bacterial attenuation.
• Type D's antiphagocytic properties contribute to its invasiveness, differentiating it from Type G.