[Selection of Bvg- variants of Bordetella pertussis].
Bordetella pertussis virulent strains (Bvg+) produce a wide array of virulence factors. The production of these factors is coordinately regulated by the locus bvg in response to environmental signals in a process known as antigenic modulation. Mutations in the bvg locus originate avirulent variants (Bvg-) that are unable to express virulence factors regardless of growth conditions. In this paper we have obtained spontaneous variants Bvg- of B. pertussis Tohama I and 10536, which would be useful for studying virulence markers, using the selective media Stainer-Scholte agar supplemented with 1% Casamino-acids (SSA-CAS) and Jones-Kendrick with 0.20 microgram of erythromycin per ml (JK-Ery). We have also studied the efficiency of plating of B. pertussis Tohama I, 10536 and 40103 cells (Bvg+ strains) and of Bvg- strain 347 (control of the avirulent phenotype) on SSA-CAS and Stainer-Scholte agar (SSA), and we have analyzed the phenotype of the cells recovered from these media. The bacterial phenotype was characterized by using the following virulence markers: hemolysis production, hemagglutinin production, and outer membrane protein (OMP) enriched profiles. The three Bvg+ strains showed different behaviour in these selective media. B. pertussis Tohama I and 10536 could not be recovered on SSA, whereas on SSA-CAS the efficiency of plating was poor, less than 0.001%, but nevertheless allowed the selection of stable Bvg- variants of Tohama I since the OMP profile of this stain did not change after subculture in Cyclodextrin liquid medium. By contrast, strain 10536 grown on SSA-CAS suffered the process of antigenic modulation since this strain recovered the virulent phenotype when it was subcultured in Bordet-Gengou. Stable Bvg- variants from Tohama I and 10536 were obtained on JK-Ery. On the other hand, Bvg+ strain 40103 showed a high efficiency of plating on SSA and SSA-CAS and retained the virulent phenotype in all the selective media. Bvg- strain 347, in spite of being an avirulen variant, showed a poor efficiency of plating in SSA and a scant growth in JK-Ery, in agreement with the findings of other investigators which suggest that not all avirulent strains posses the ability to grow on media that inhibit most of virulent strains.
Passerini de Rossi
B N
BN
Cátedra de Microbiología, Facultad de Farmacia y Bioquímica, U.B.A., Argentina.
Friedman
L E
LE
Darnaud
S
S
de Torres
R A
RA
Franco
M A
MA
D001425:Bacterial Outer Membrane Proteins / Q000096:biosynthesis / Q000235:genetics; D015415:Biomarkers; D001886:Bordetella pertussis / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity; D003470:Culture Media / Q000494:pharmacology; D004917:Erythromycin / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006388:Hemagglutinins / Q000096:biosynthesis / Q000235:genetics; D006460:Hemolysin Proteins / Q000096:biosynthesis / Q000235:genetics; D010641:Phenotype; D018085:Regulon; D014774:Virulence / Q000235:genetics
D001425:Bacterial Outer Membrane Proteins; D015415:Biomarkers; D003470:Culture Media; D006388:Hemagglutinins; D006460:Hemolysin Proteins; D004917:Erythromycin