Affiliation:
1. Life Sciences Division, SRI International, Menlo Park, California 94025
Abstract
In a series of seven experiments, the virulent Nichols strain of
Treponema pallidum
was shown to attach and replicate on the surface of tissue culture cells of cottontail rabbit epithelium (Sf1Ep) growing in conventional monolayer cultures under an atmosphere of 1.5% oxygen. Five days after inoculation of 10
6
T. pallidum
, the number of treponemes had increased to between 8 × 10
6
and 2.59 × 10
7
. The viability of harvested organisms ranged from 86 to 97%. The number of
T. pallidum
continued to increase, generally reaching a plateau between days 9 and 12 of incubation, with increases ranging up to 100-fold and averaging 49-fold. There appeared to be a ceiling of multiplication of about 2 × 10
8
irrespective of the inoculum, which ranged from 10
6
to 10
8
T. pallidum.
Concurrent deoxyribonucleic acid assays were performed on the cultures containing
T. pallidum
to obtain further evidence of replication. Significant increases in treponemal deoxyribonucleic acid were observed when the inocula ranged from 10
6
to 10
7
, with the greatest increases, as might be expected, being in the former group. There was also excellent correlation in the amount of deoxyribonucleic acid per treponeme; the averages for the 10
6
, 2.5 × 10
6
, and 10
7
groups were 3.46 × 10
−14
, 3.28 × 10
−14
, and 2.79 × 10
−14
g per treponeme, respectively (3.14 ± 0.72 × 10
−14
g per treponeme). In each experiment, organisms were harvested from the group inoculated with 10
6
T. pallidum
after 7 days of incubation to test for virulence. In all instances, the organisms were virulent; erythematous, indurated, treponeme-containing lesions were produced from an average of six to seven organisms. Scanning electron microscopy revealed that during the course of replication many microcolonies of treponemes formed on the surface of the cells.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Reference25 articles.
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3. Nutrition needs of mammalian cells in tissue culture;Eagle H.;Science,1955
4. Serological relationship between five cultured strains of supposed T. paUidum (Noguchi, Kroo, Nichols, Reiter, and Kazan) and two strains of mouth treponemata;Eagle H.;J. Immunol.,1948
5. Prolonged survival of virulent Treponema pallidum (Nichols strain) in cell-free and tissue culture systems;Fieldsteel A. H.;Infect. Immun.,1977
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