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Dermonecrotic toxin and tracheal cytotoxin, putative virulence factors of Bordetella avium
C R Gentry-Weeks1, B T Cookson, W E Goldman
1Department of Biology, Washington University, St. Louis, Missouri 63130.
Abstract:
We examined Bordetella avium for virulence factors common to Bordetella pertussis, including pertussis toxin, filamentous hemagglutinin, adenylate cyclase, dermonecrotic toxin, and tracheal cytotoxin. B. avium produced a dermonecrotic toxin and a tracheal cytotoxin. The dermonecrotic toxin of B. avium is a 155,000-molecular-weight, heat-labile protein which was lethal for mice, guinea pigs, young chickens, and turkey poults and produced dermonecrosis when injected intradermally into guinea pigs, chickens, and turkey poults. High-pressure liquid chromatography of B. avium culture supernatant fluid revealed the presence of a tracheal cytotoxin chemically identical to that produced by B. pertussis. B. avium isolates were negative for B. pertussis-like filamentous hemagglutinin and pertussis toxin when assayed with antibody against B. pertussis filamentous hemagglutinin and pertussis toxin. Furthermore, B. avium failed to induce the clustered CHO cell morphology characteristic of pertussis toxin. Adenylate cyclase assays indicated that B. avium does not produce an extracytoplasmic adenylate cyclase, even after passage through embryonated turkey eggs. Since production of virulence proteins by B. pertussis is regulated by growth in media containing nicotinamide or MgSO4 or by growth at reduced temperatures, we determined the effect of these supplements and growth conditions on production of dermonecrotic toxin by B. avium. Production of dermonecrotic toxin in B. avium was not altered by growth in media containing 100 microM FeSO4 or 500 micrograms of nicotinamide per ml or by growth at 25 or 42 degrees C, but production was significantly decreased by growth in media containing 20 mM MgSO4 and slightly reduced by growth in media containing 500 micrograms of nicotinic acid per ml. These studies revealed that B. avium is similar to B. pertussis in that both species produce a dermonecrotic toxin and a tracheal cytotoxin and production of dermonecrotic toxin is regulated by nicotinamide and MgSO4. The presence of dermonecrotic toxin and tracheal cytotoxin in all Bordetella species indicates that these products may be important virulence factors in bordetellosis.
Insights
Bordetella avium produces dermonecrotic and tracheal cytotoxins, similar to Bordetella pertussis. Dermonecrotic toxin production is regulated by nicotinamide and MgSO4, suggesting these toxins are key virulence factors in bordetellosis.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Comparative Genomics
Background:
- Bordetella pertussis is a significant human pathogen responsible for whooping cough.
- Virulence factors of B. pertussis, such as pertussis toxin and filamentous hemagglutinin, are well-characterized.
- Bordetella avium is an avian pathogen whose virulence factors have not been extensively studied in comparison to B. pertussis.
Purpose of the Study:
- To investigate the presence and characteristics of virulence factors in Bordetella avium that are common to Bordetella pertussis.
- To compare the production and regulation of these virulence factors between B. avium and B. pertussis.
Main Methods:
- B. avium isolates were screened for pertussis toxin, filamentous hemagglutinin, adenylate cyclase, dermonecrotic toxin, and tracheal cytotoxin.
- High-pressure liquid chromatography (HPLC) was used to analyze tracheal cytotoxin.
- Animal models (mice, guinea pigs, chickens, turkey poults) were used to assess the lethality and dermonecrotic activity of B. avium toxins.
- Growth conditions (nicotinamide, MgSO4, temperature) were manipulated to study the regulation of dermonecrotic toxin production.
Main Results:
- B. avium produced a heat-labile dermonecrotic toxin (155,000 MW) lethal to multiple animal species and caused dermonecrosis.
- Tracheal cytotoxin produced by B. avium was chemically identical to that of B. pertussis.
- B. avium lacked B. pertussis-like filamentous hemagglutinin and pertussis toxin, and did not induce characteristic CHO cell morphology.
- Dermonecrotic toxin production in B. avium was regulated by MgSO4 and nicotinic acid, but not by FeSO4, nicotinamide, or temperature variations.
- Adenylate cyclase was not detected in B. avium.
Conclusions:
- Bordetella avium shares key virulence factors, dermonecrotic toxin and tracheal cytotoxin, with Bordetella pertussis.
- The regulation of dermonecrotic toxin production by nicotinamide and MgSO4 in B. avium mirrors that of B. pertussis.
- These shared toxins are likely important virulence factors contributing to bordetellosis in avian species.