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Effects of Fusobacterium necrophorum leukotoxin on rabbit peritoneal macrophages in vitro
Abstract:
A method to demonstrate leukotoxic activity of Fusobacterium necrophorum in vitro is described. Continuous dialysis sac culture system, using reduced liquid medium was used to grow F necrophorum for 7-day periods. The continuous culture dialysis filtrate contained leukotoxic substance(s) which appeared to be less than 10,000 in molecular weight, heat resistant, and stable at 4 C for at least 10 days. Leukotoxic activity was demonstrated in vitro by determining the percentage of macrophages taking up trypan blue dye after these were exposed to a 1:2 solution of continuous culture dialysis filtrate and Eagle's minimal essential medium at 1, 2, 4, and 6 hours. Approximately 90% of these macrophages were destroyed during the 6-hour incubation period.
Insights
Researchers developed a method to show Fusobacterium necrophorum
Area of Science:
- Microbiology
- Immunology
- Bacteriology
Background:
- Fusobacterium necrophorum is an anaerobic bacterium implicated in various animal infections.
- Understanding its virulence factors, such as leukotoxicity, is crucial for disease control.
- Previous methods for assessing leukotoxicity have limitations.
Purpose of the Study:
- To establish a reliable in vitro method for demonstrating the leukotoxic activity of Fusobacterium necrophorum.
- To characterize the properties of the leukotoxic substance produced by F. necrophorum.
Main Methods:
- Utilized a continuous dialysis sac culture system to grow F. necrophorum for 7 days.
- Collected and filtered the culture supernatant to isolate the leukotoxic substance.
- Exposed macrophages to the filtrate and assessed cell viability using trypan blue uptake over 6 hours.
Main Results:
- The continuous culture dialysis filtrate contained a leukotoxic substance.
- This substance has a molecular weight under 10,000 Da, is heat-resistant, and stable at 4°C for at least 10 days.
- Exposure to the filtrate resulted in approximately 90% macrophage destruction within 6 hours.
Conclusions:
- The described method effectively demonstrates the in vitro leukotoxic activity of Fusobacterium necrophorum.
- The leukotoxin is a small, heat-stable molecule.
- This in vitro system provides a valuable tool for studying F. necrophorum virulence.