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S J Norris

Publications and source records attributed to S J Norris.

At least 37 records · Page 2Linked to original sources
PubMed1997

Identification and transcriptional analysis of a Treponema pallidum operon encoding a putative ABC transport system, an iron-activated repressor protein homolog, and a glycolytic pathway enzyme homolog.

We have characterized a 5.2-kilobase (kb) putative transport related operon (tro) locus of Treponema pallidum subsp. pallidum (Nichols strain) (Tp) encoding six proteins: TroA, TroB, TroC, TroD, TroR and Phosphoglycerate mutase (Pgm). Four of these gene products (TroA-TroD) are homologous to members of the ATP-Binding Cassette (ABC) superfamily of bacterial transport proteins. TroA (previously identified as Tromp1) has significant sequence similarity to a family of Gram-negative periplasmic substrate-binding proteins and to a family of streptococcal proteins that may have dual roles as substrate binding proteins and adhesins. TroB is homologous to the ATP-binding protein component, whereas TroC and TroD are related to the hydrophobic membrane protein components of ABC transport systems. TroR is similar to Gram-positive iron-activated repressor proteins (DesR, DtxR, IdeR, and SirR). The last open reading frame (ORF) of the tro operon encodes a protein that is highly homologous to the glycolytic pathway enzyme, Pgm. Primer extension results demonstrated that the tro operon is transcribed from a sigma 70-type promoter element. Northern analysis and reverse transcriptase-polymerase chain reactions provided evidence for the presence of a primary 1-kb troA transcript and a secondary, less abundant, troA-pgm transcript. The tro operon is flanked by a Holliday structure DNA helicase homolog (upstream) and two ORFs representing a purine nucleoside phosphorylase homolog and tpp15, a previously characterized gene encoding a membrane lipoprotein (downstream). The presence of a complex operon containing a putative ABC transport system and a DtxR homolog indicates a possible linkage between transport and gene regulation in Tp.

ATP-Binding Cassette Transporters↗
PubMed1997

Antigenic variation in Lyme disease borreliae by promiscuous recombination of VMP-like sequence cassettes.

We have identified and characterized an elaborate genetic system in the Lyme disease spirochete Borrelia burgdorferi that promotes extensive antigenic variation of a surface-exposed lipoprotein, VlsE. A 28 kb linear plasmid of B. burgdorferi B31 (lp28-1) was found to contain a vmp-like sequence (vls) locus that closely resembles the variable major protein (vmp) system for antigenic variation of relapsing fever organisms. Portions of several of the 15 nonexpressed (silent) vls cassette sequences located upstream of vlsE recombined into the central vlsE cassette region during infection of C3H/HeN mice, resulting in antigenic variation of the expressed lipoprotein. This combinatorial variation could potentially produce millions of antigenic variants in the mammalian host.

Amino Acid Sequence↗
PubMed1997

Relationship of Treponema denticola periplasmic flagella to irregular cell morphology.

Treponema denticola is an anaerobic, motile, oral spirochete associated with periodontal disease. We found that the periplasmic flagella (PFs), which are located between the outer membrane sheath and cell cylinder, influence its morphology in a unique manner. In addition, the protein composition of the PFs was found to be quite complex and similar to those of other spirochetes. Dark-field microscopy revealed that most wild-type cells had an irregular twisted morphology, with both planar and helical regions, and a minority of cells had a regular right-handed helical shape. High-voltage electron microscopy indicated that the PFs, especially in those regions of the cell which were planar, wrapped around the cell body axis in a right-handed sense. In those regions of the cell which were helical or irregular, the PFs tended to lie along the cell axis. The PFs caused the cell to form the irregular shape, as two nonmotile, PF-deficient mutants (JR1 and HL51) were no longer irregular but were right-handed helices. JR1 was isolated as a spontaneously occurring nonmotile mutant, and HL51 was isolated as a site-directed mutant in the flagellar hook gene flgE. Consistent with these results is the finding that wild-type cells with their outer membrane sheath removed were also right-handed helices similar in shape to JR1 and HL51. Purified PFs were analyzed by two-dimensional gel electrophoresis, and several protein species were identified. Western blot analysis using antisera to Treponema pallidum PF proteins along with N-terminal amino acid sequence analysis indicated T. denticola PFs are composed of one class A sheath protein of 38 kDa (FlaA) and three class B proteins of 35 kDa (FlaB1 and FlaB2) and one of 34 kDa (FlaB3). The N-terminal amino acid sequences of the FlaA and FlaB proteins of T. denticola were most similar to those of T. pallidum and Treponema phagedenis. Because these proteins were present in markedly reduced amounts or were absent in HL51, PF synthesis is likely to be regulated in a hierarchy similar to that found for flagellar. synthesis in other bacteria.

Amino Acid Sequence↗
PubMed1996

Characterization of the cytoplasmic filament protein gene (cfpA) of Treponema pallidum subsp. pallidum.

Treponema pallidum and other members of the genera Treponema, Spirochaeta, and Leptonema contain multiple cytoplasmic filaments that run the length of the organism just underneath the cytoplasmic membrane. These cytoplasmic filaments have a ribbon-like profile and consist of a major cytoplasmic filament protein subunit (CfpA, formerly called TpN83) with a relative molecular weight of approximately 80,000. Degenerate DNA primers based on N-terminal and CNBr cleavage fragment amino acid sequences of T. pallidum subsp. pallidum (Nichols) CfpA were utilized to amplify a fragment of the encoding gene (cfpA). A 6.8-kb EcoRI fragment containing all but the 5' end of cfpA was identified by hybridization with the resulting PCR product and cloned into Lambda ZAP II. The 5' region was obtained by inverse PCR, and the complete gene sequence was determined. The cfpA sequence contained a 2,034-nucleotide coding region, a putative promoter with consensus sequences (5'-TTTACA-3' for -35 and 5'-TACAAT-3' for -10) similar to the sigma70 recognition sequence of Escherichia coli and other organisms, and a putative ribosome-binding site (5'-AGGAG-3'). The deduced amino acid sequence of CfpA indicated a protein of 678 residues with a calculated molecular mass of 78.5 kDa and an estimated pI of 6.15. No significant homology to known proteins or structural motifs was found among known prokaryotic or eukaryotic sequences. Expression of a LacZ-CfpA fusion protein in E. coli was detrimental to survival and growth of the host strain and resulted in the formation of short, irregular filaments suggestive of partial self-assembly of CfpA. The cytoplasmic filaments of T. pallidum and other spirochetes appear to represent a unique form of prokaryotic intracytoplasmic inclusions.

Amino Acid Sequence↗
PubMed1996

Conversion of a linear to a circular plasmid in the relapsing fever agent Borrelia hermsii.

Spirochetes of the genus Borrelia have genomes composed of both linear and circular replicons. We characterized the genomic organization of B. burgdorferi, B. hermsii, B. turicatae, and B. anserina with pulsed-field gel electrophoresis. All four species contained a linear chromosome approximately 1 Mb in size and multiple linear plasmids in the 16- to 200-kb size range. Plasmids 180 and 170 kb in size, present in the relapsing fever agents B. hermsii and B. turicatae but not in the other two species, behaved as linear duplex DNA molecules under different electrophoretic conditions. A variant of strain HSI of B. hermsii had a 180-kb circular instead of linear plasmid. There were no detectable differences in the growth rates or in the expression of cellular proteins between cells bearing linear forms and those bearing circular forms of the plasmid. The conversion to a circular conformation of monomeric length was demonstrated by the introduction of strand breaks with irradiation, restriction endonuclease analysis, and direct observation of the DNA molecules by fluorescent microscopy. Consideration of different models for the replication of linear DNA suggests that circular intermediates may be involved in the replication of linear replicons in Borrelia spp.

Borrelia↗
PubMed1995

Modulation of immunity to Borrelia burgdorferi by ultraviolet irradiation: differential effect on Th1 and Th2 immune responses.

Ultraviolet B (UVB) radiation suppresses the delayed-type hypersensitivity (DTH) response to alloantigen by a mechanism involving interleukin (IL)-10. It has been hypothesized, based on this result, that UV irradiation shifts the immune response from a Th1 to a Th2 response. We tested this hypothesis using Borrelia burgdorferi (Bb) as an antigen under conditions where both DTH and antibody responses could be assessed. Mice were irradiated with a single dose of UV and then immunized with Bb in complete Freund's adjuvant (CFA). DTH was assessed by footpad challenge. At various time points thereafter, mice were bled, and the serum antibodies to Bb were quantitated. Only IgG1, IgG2a, and IgG2b were produced in response to Bb. The IgG2a and IgG2b antibody responses, as well as the DTH response to Bb, showed UV dose-dependent reductions after UV irradiation. The primary IgG1 response to Bb was very low and was unaffected by UV irradiation; however, the IgG1 secondary response was elevated in UV-irradiated mice. Injection of anti-IL-10 antibody into UV-irradiated mice within 24 h after UV exposure restored the DTH response, as well as the IgG2a and IgG2b antibody responses. In addition, injecting recombinant murine IL-10 mimicked some of the effects of UV radiation. Our results support the hypothesis that in vivo, UV irradiation down-regulates Th1 immune responses, while leaving Th2 responses intact, and suggest that IL-10 is an important mediator of this effect.

Animals↗
PubMed1995

High- and low-infectivity phenotypes of clonal populations of in vitro-cultured Borrelia burgdorferi.

Borrelias that cause Lyme disease lose the ability to infect and cause disease in laboratory animals following 10 to 16 passages of in vitro culture. In this study, clonal populations of the Sh-2-82 (Sh2) and B31 strains of Borrelia burgdorferi were isolated by subsurface plating on BSK-II agar plates and examined for infectivity in the C3H/HeN mouse model. Mice were injected intradermally with 10(5) B. burgdorferi organisms, and the tibiotarsal joint, heart, and bladder were cultured 2 to 4 weeks postinfection to determine whether viable organisms were present. Clones exhibited either a high-infectivity phenotype, in which cultures were consistently positive at all organ sites, or a low-infectivity phenotype, in which a low proportion of cultures were positive (5 of 40 in a representative experiment). In an Sh2 population that had undergone five in vitro passages, 7 of 10 clones were of the high-infectivity phenotype, and the remaining clones were of the low-infectivity phenotype. The proportion of high-infectivity clones decreased with continued in vitro passage, with only 1 of 10 clones exhibiting the high-infectivity phenotype after 10 passages and 0 of 10 clones yielding positive cultures after 20 passages. Representative high- and low-infectivity clones from passage 5 Sh2 cultures had 50% infectious doses of 1.8 x 10(2) and 1 x 10(5), respectively. Subclones consistently reflected the same infectivity phenotypes as those of the parent clones. The protein profiles and plasmid contents of the high- and low-infectivity clones were compared and exhibited few discernible differences. On the basis of these results, the loss of infectivity during in vitro culture results from the outgrowth of low-infectivity clones and begins to occur within the first five in vitro passages. Further examination of clonal populations may lead to the identification of genetic and protein factors important in the virulence and pathogenicity of Lyme disease borrelias.

Animals↗
PubMed1995

Adherence of Borrelia burgdorferi to the proteoglycan decorin.

Lyme disease is a tick-borne infection that can develop into a chronic, multisystemic disorder. The causative agent, Borrelia burgdorferi, is initially deposited by the tick into the host dermis, where it associates with collagen fibers, replicates, and eventually disseminates to other tissues. We have examined the adherence of the spirochete to different components of the collagen fiber and demonstrated that decorin, a proteoglycan which decorates collagen fibers, can support the attachment of B. burgdorferi. No significant direct attachment to isolated type I or III collagens could be detected. Attachment of the spirochetes to decorin was highly specific, and the process could be inhibited by soluble decorin but not by various unlabeled, unrelated components. B. burgdorferi also bound soluble 125I-labeled decorin in a time- and concentration-dependent manner. Spirochete binding of soluble 125I-labeled decorin required intact proteoglycan and could not be inhibited by either isolated core protein or glycosaminoglycan chain. B. burgdorferi expresses two decorin-binding proteins with apparent molecular masses of 19 and 20 kDa as revealed in a Western blot (immunoblot)-type assay. Our results indicate that decorin may mediate the adherence of B. burgdorferi to collagen fibers in skin and other tissues.

Animals↗
PubMed1995

Physical map of the genome of Treponema pallidum subsp. pallidum (Nichols).

A physical map of the chromosome of Treponema pallidum subsp. pallidum (Nichols), the causative agent of syphilis, was constructed from restriction fragments produced by NotI, SfiI, and SrfI. These rare-cutting restriction endonucleases cleaved the T. pallidum genome into 16, 8, and 15 fragments, respectively. Summation of the physical lengths of the fragments indicates that the chromosome of T. pallidum subsp. pallidum is approximately 1,030 to 1,080 kbp in size. The physical map was constructed by hybridizing a variety of probes to Southern blots of single and double digests of T. pallidum genomic DNA separated by contour-clamped homogeneous electric field electrophoresis. Probes included cosmid clones constructed from T. pallidum subsp. pallidum genomic DNA, restriction fragments excised from gels, and selected genes. Physical mapping confirmed that the chromosome of T. pallidum subsp. pallidum is circular, as the SfiI and SrfI maps formed complete circles. A total of 13 genes, including those encoding five membrane lipoproteins (tpn47, tpn41, tpn29-35, tpn17, and tpn15), a putative outer membrane porin (tpn50), the flagellar sheath and hook proteins (flaA and flgE), the cytoplasmic filament protein (cfpA), 16S rRNA (rrnA), a major sigma factor (rpoD), and a homolog of cysteinyl-tRNA synthetase (cysS), have been localized in the physical map as a first step toward studying the genetic organization of this noncultivable pathogen.

Chromosome Mapping↗
PubMed1995

OptiSol corneal storage medium and transmission of Treponema pallidum.

This study was conducted to provide experimental information on the probability of syphilis transmission resulting from corneal transplantation. To determine the effects of commonly employed corneal storage conditions on the survival and infectivity of Treponema pallidum, T. pallidum subsp. pallidum (Nichols) was inoculated into OptiSol storage medium or a T. pallidum survival medium at a concentration of 10(6)/ml and incubated in cornea viewing chambers for 24 h at 4 degrees C. When inoculated intradermally into rabbits (0.1 ml per site), none of the 10 sites developed lesions from suspensions incubated in OptiSol in the presence or absence of 100 microgram/ml gentamicin; T. pallidum incubated in the survival medium yielded lesions at one of 10 sites, whereas freshly extracted organisms produced lesions at all 10 sites. In another set of experiments, the infectivity of corneal tissue from rabbits inoculated intratesticularly with 2 x 10(7) T. pallidum 10 days earlier was determined. Corneas from five T. pallidum-infected rabbits were excised, extracted, and tested for infectivity either immediately after removal or after 24-h storage in OptiSol. Recipient rabbits developed lesions at five of 50 intradermal sites when the corneas were neither stored in OptiSol nor rinsed before extraction. Corneas from 10 donor rabbits that were rinsed with phosphate-buffered saline to remove blood and aqueous humor before extraction did not yield lesions at any of 200 sites in the recipient animals. The results of this study indicate that retention of T. pallidum infectivity is poor under typical corneal storage conditions and that rabbit corneal tissue contains few, if any, infectious T. pallidum organisms under the experimental conditions employed.

Animals↗
PubMed1994

A family of surface-exposed proteins of 20 kilodaltons in the genus Borrelia.

Relapsing fever and Lyme disease spirochetes of the genus Borrelia display at their surfaces abundant lipoproteins: Vmp proteins in Borrelia hermsii and Osp proteins in Borrelia burgdorferi. Vmp and Osp proteins largely determine serotype specificity, and neutralizing antibodies of infected or immunized animals are directed at them. For the present study, we examined B. hermsii serotype 33, which is unique among strain HS1 serotypes in the low frequency of switches to other serotypes during infections and in vitro cultivation. Failing to clone the complete vmp33 gene, we accomplished its further characterization by (i) determining three partial amino acid sequences, (ii) designing oligonucleotide primers based on these amino acid sequences, (iii) cloning and sequencing the central portion of vmp33, and (iv) using outwardly directed primers and the inverse PCR to clone the 5' and 3' ends of the gene and flanking regions. The transcriptional start site was identified by primer extension analysis. Vmp33 was a polypeptide of 211 amino acids; the three partial amino acid sequences were identified in the open reading frame. Vmp33 was found to be more similar to other 20-kDa Vmp proteins of B. hermsii and to OspC proteins of B. burgdorferi than it was to 35- to 39-kDa Vmp proteins of the same strain. Moreover, OspC proteins were more similar to Vmp33 than they were to OspA, -B, or -D proteins of B. burgdorferi. These sequence similarities were consistent with Western blot (immunoblot) findings of cross-reactions between Vmp33 and OspC with anti-Vmp33 and anti-OspC sera. The promoter for the expressed vmp33 gene was found to be different from the expression site for other active vmp genes characterized to date. These results indicate that Vmp33 and other small Vmp's belong with OspC to a genus-wide family of 20-kDa proteins and that expression of these proteins may be coordinated with expression of other Vmp and Osp proteins in Borrelia spp.

Amino Acid Sequence↗
PubMed1993

Polypeptides of Treponema pallidum: progress toward understanding their structural, functional, and immunologic roles. Treponema Pallidum Polypeptide Research Group.

Treponema pallidum subsp. pallidum, the spirochete that causes syphilis, is unusual in a number of respects, including its small genome size, inability to grow under standard in vitro culture conditions, microaerophilism, apparent paucity of outer membrane proteins, structurally complex periplasmic flagella, and ability to evade the host immune responses and cause disease over a period of years to decades. Many of these attributes are related ultimately to its protein content. Our knowledge of the activities, structure, and immunogenicity of its proteins has been expanded by the application of recombinant DNA, hybridoma, and structural fractionation techniques. The purpose of this monograph is to summarize and correlate this new information by using two-dimensional gel electrophoresis, monoclonal antibody reactivity, sequence data, and other properties as the bases of polypeptide identification. The protein profiles of the T. pallidum subspecies causing syphilis, yaws, and endemic syphilis are virtually indistinguishable but differ considerably from those of other treponemal species. Among the most abundant polypeptides are a group of lipoproteins of unknown function that appear to be important in the immune response during syphilitic infection. The periplasmic flagella of T. pallidum and other spirochetes are unique with regard to their protein content and ultrastructure, as well as their periplasmic location. They are composed of three core proteins (homologous to the other members of the eubacterial flagellin family) and a single, unrelated sheath protein; the functional significance of this arrangement is not understood at present. Although the bacterium contains the chaperonins GroEL and DnaK, these proteins are not under the control of the heat shock regulon as they are in most organisms. Studies of the immunogenicity of T. pallidum proteins indicate that many may be useful for immunodiagnosis and immunoprotection. Future goals in T. pallidum polypeptide research include continued elucidation of their structural locations and functional activities, identification and characterization of the low-abundance outer membrane proteins, further study of the immunoprotective and immunodiagnostic potential of T. pallidum proteins, and clarification of the roles of treponemal proteins in pathogenesis.

Amino Acid Sequence↗
PubMed1992

Low-passage-associated proteins of Borrelia burgdorferi B31: characterization and molecular cloning of OspD, a surface-exposed, plasmid-encoded lipoprotein.

Borrelia burgdorferi, the causative agent of Lyme disease, loses its ability to infect and cause disease in mammalian hosts after repeated in vitro passage. To identify proteins preferentially expressed by the low-passage strain and thus representing potential virulence factors, the polypeptide profiles of virulent, low-passage and nonvirulent, high-passage forms of B. burgdorferi B31 were compared by nonequilibrium pH gradient two-dimensional gel electrophoresis. Four low-passage-associated proteins with relative molecular masses (M(r)s) of 35,000, 28,000, 24,000, and 20,000 were identified. Of these, the 28- and 35-kDa polypeptides were not expressed in detectable quantities in the high-passage B31 strain, whereas the 24- and 20-kDa proteins were present in reduced quantities. All four of these proteins were lipoproteins, as determined by labelling with [3H]palmitate. The abundant 28-kDa component, called outer surface protein D (OspD), is surface exposed on the basis of its proteolysis during treatment of intact organisms with proteinase K. The ospD gene is located on a 38-kb linear plasmid present in seven of nine low-passage strains of B. burgdorferi examined but absent in most high-passage, nonvirulent strains tested. Molecular cloning and sequence analysis of the ospD gene locus revealed an open reading frame encoding a 28,436-Da polypeptide with a putative signal peptidase II leader sequence. An unusual feature of the region upstream of the gene was the presence of seven contiguous, direct repeats of a 17-bp sequence that includes consensus -35 and -10 transcription initiation signals; however, only one transcription initiation site was active as determined by primer extension analysis. Further study of these and other polypeptides associated with low-passage strains may lead to identification of B. burgdorferi gene products required for infection and pathogenesis in mammalian hosts.

Amino Acid Sequence↗
PubMed1991

Treponema pallidum subsp. pallidum has a single, circular chromosome with a size of approximately 900 kilobase pairs.

The genome size and chromosome conformation of Treponema pallidum subsp. pallidum, Nichols strain, were determined by contour-clamped homogeneous electric field electrophoresis, a pulsed-field gel electrophoresis technique. Digestion of T. pallidum subsp. pallidum DNA with the restriction endonucleases NotI and SpeI produced 12 and 26 fragments, respectively. Summation of the physical lengths of the fragments produced by NotI and SpeI cleavage yielded average sizes of 900 and 913 kbp, respectively, for the genome of T. pallidum subsp. pallidum. Contour-clamped homogeneous electric field electrophoresis of T. pallidum subsp. pallidum DNA exposed to 4 krads of gamma irradiation resolved a single band of 800 to 1,000 kbp; treatment of the DNA with 16 krads of gamma irradiation resulted in the production of smaller fragments, whereas untreated DNA did not migrate into the gels. The gamma irradiation results indicate that T. pallidum subsp. pallidum has a single, circular chromosome that was linearized at a dosage of 4 krads of gamma irradiation. The size estimate provided by restriction endonuclease digestion with NotI and SpeI shows that the genome of T. pallidum subsp. pallidum, at approximately 900 kbp, is considerably smaller than the 13,700-kbp genome size calculated from renaturation kinetics.

Chromosomes, Bacterial↗
PubMed1990

Isolation and characterization of a Treponema pallidum major 60-kilodalton protein resembling the groEL protein of Escherichia coli.

A native structure containing the major 60-kilodalton common antigen polypeptide (designated TpN60) was isolated from Treponema pallidum subsp. pallidum (Nichols strain) through a combination of differential centrifugation and sucrose density gradient sedimentation. Gel filtration chromatography indicated that this structure is a high-molecular-weight homo-oligomer of TpN60. Antisera to TpN60 reacted with the groEL polypeptide of Escherichia coli, as determined by immunoperoxidase staining of two-dimensional electroblots. Electron microscopy of the isolated complex revealed a ringlike structure with a diameter of approximately 16 nm which was very similar in appearance to the groEL protein. Comparison of the N-terminal amino acid sequence of TpN60 with the deduced sequences of the E. coli groEL protein, related chaperonin proteins from mycobacteria and Coxiella burnetti, the hsp60 protein of Saccharomyces cerevisiae, the wheat ribulose bisphosphate carboxylase-oxygenase-subunit-binding protein (alpha subunit), and the human P1 mitochondrial protein indicated sequence identity at 8 of 22 to 10 of 22 residues (36 to 45% identity). We conclude that the oligomer of TpN60 is homologous to the groEL protein and related chaperonins found in a wide variety of procaryotes and eucaryotes and thus may represent a heat shock protein involved in protein folding and assembly.

Amino Acid Sequence↗
PubMed1988

In vitro culture system to determine MICs and MBCs of antimicrobial agents against Treponema pallidum subsp. pallidum (Nichols strain).

A new procedure for determining the susceptibility of Treponema pallidum subsp. pallidum to antimicrobial agents was developed, utilizing a tissue culture system which promotes the in vitro multiplication of this organism. In the absence of antibiotics, T. pallidum (Nichols virulent strain) multiplied an average of 10-fold when incubated for 7 days in the presence of Sf1Ep cottontail rabbit epithelial cell cultures. Varied concentrations of penicillin G, tetracycline, erythromycin, and spectinomycin were added to triplicate cultures to determine their effects on treponemal multiplication, motility, and virulence. The MIC of each antibiotic was defined as the lowest concentration which prevented treponemal multiplication, whereas the MBC was defined as the lowest concentration which abrogated the ability of the cultured treponemes to multiply and cause lesions in rabbits. The in vitro culture technique provided highly reproducible MICs and (in parentheses) MBCs of each of the antibiotics tested: aqueous penicillin G, 0.0005 (0.0025) microgram/ml; tetracycline, 0.2 (0.5) microgram/ml; erythromycin, 0.005 (0.005) microgram/ml; and spectinomycin, 0.5 (0.5) microgram/ml. The significance of these results in light of the in vivo activities and the previous in vitro evaluations of these antibiotics is discussed. The T. pallidum in vitro cultivation system shows promise as a method for studying the interaction between T. pallidum and antimicrobial agents and for screening new antibiotics for syphilis therapy.

Animals↗