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Variability in derivative strains of Bordetella pertussis
Abstract:
Bordetella pertussis strain UT25 was isolated on Bordet-Gengou(B-G) agar from a child with whooping cough in 1977. Derivative strains were isolated from UT25 by serial passages on Trypticase Soy Agar (TSA) containing blood,followed by serial passages on plain TSA. At passage 69, UT25 was subcultured in parallel on TSA and B-G. For experiments, strains were grown in defined liquid medium, adjusted to a standard turbidity, and tested in parallel. Tests were performed to detect changes in immunogenicity, production of dermonecrotic toxin, histamine sensitizing ability, serologic properties, infectivity for mice by the intranasl route, production of adenylate cyclase, patterns of outer membrane proteins. Notable changes occurred in the properties of UT25 at passage 16, just when stable growth on blood-fresh medium was established. After 5 additional passages on TSA, however, the strain resembled the original isolate. At about passage 45, biological activity began to decline, and by passage 60 most biological activities were sharply diminished or undetectable. No recovery of biological activity was observed during a further 15 passages on TSA. Strains derived from the sixty-ninth passage of UT25, after passage on B-G for 5 subcultures, showed partial recovery of biological activity. Ten additional subcultures on B-G yielded strains which showed even higher biological activity. Fluorescent antibody staining confirmed that all strains studied were B. pertussis, and maintained reactive surface antigen(s), in spite of loss of agglutinability in specific antiserum.
Insights
Serial passage of Bordetella pertussis strain UT25 on artificial media led to loss of biological activity. Recovery was achieved by readapting the strain to Bordet-Gengou agar.
Area of Science:
- Microbiology
- Immunology
- Bacterial Pathogenesis
Background:
- Bordetella pertussis causes whooping cough and its virulence factors are crucial for pathogenesis.
- Strain UT25, isolated in 1977, was used to study the stability of B. pertussis characteristics during laboratory cultivation.
- Understanding bacterial adaptation and loss of virulence during serial passage is important for vaccine development and strain characterization.
Purpose of the Study:
- To investigate the effects of serial passage on artificial media on the biological properties of Bordetella pertussis strain UT25.
- To determine if virulence factors and immunogenicity could be restored after loss during laboratory cultivation.
Main Methods:
- Serial passage of B. pertussis UT25 on Trypticase Soy Agar (TSA) and Bordet-Gengou (B-G) agar.
- Assessment of various biological activities including immunogenicity, dermonecrotic toxin production, histamine sensitizing ability, and mouse infectivity.
- Analysis of outer membrane protein patterns and adenylate cyclase production.
- Fluorescent antibody staining to confirm strain identity.
Main Results:
- B. pertussis UT25 exhibited significant changes in biological properties, including loss of virulence factors, after extensive serial passage on TSA.
- Stable growth on blood-containing media at passage 16 was associated with initial property changes.
- Biological activity sharply diminished by passage 60, with no recovery on TSA.
- Readaptation to B-G agar at passage 69 led to partial and then increased recovery of biological activity.
Conclusions:
- Serial subculturing of B. pertussis UT25 on standard laboratory media like TSA results in a significant loss of key biological activities and virulence.
- Bordet-Gengou agar, a more traditional medium, can facilitate the recovery of these lost biological properties.
- This study highlights the plasticity of B. pertussis and the importance of appropriate culture conditions for maintaining virulence characteristics.