[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$f6lgzzMpUIkOe11SUlN2-PsjT70W9I7-1SIKv73C8jkE":32,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":115},[4,8,12,16,20,24,28],{"title":5,"slug":6,"path":7},"About Microbeonline.com","about-microbeonline-com","\u002Fabout-microbeonline-com\u002F",{"title":9,"slug":10,"path":11},"About Me","about-me","\u002Fabout-microbeonline-com\u002Fabout-me\u002F",{"title":13,"slug":14,"path":15},"Advertise with Us","advertise-us","\u002Fadvertise-us\u002F",{"title":17,"slug":18,"path":19},"Privacy Policy","privacy-policy","\u002Fprivacy-policy\u002F",{"title":21,"slug":22,"path":23},"Abbreviations","abbreviations","\u002Fabbreviations\u002F",{"title":25,"slug":26,"path":27},"Microbes","microbes","\u002Fmicrobes\u002F",{"title":29,"slug":30,"path":31},"Books","recommended-books","\u002Frecommended-books\u002F",{"type":33,"data":34},"blog",{"slug":35,"title":36,"description":36,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":39,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"body":43,"faq":44,"tags":45,"related":47},"treponema-pallidum-properties-pathogenesis-and-disease","Treponema pallidum: Properties, Pathogenesis, and Disease",null,"Acharya Tankeshwar","2022-02-22","2026-07-05",false,"bacteriology","*Treponema* (trepos meaning turn and nema meaning thread) *pallidum* is a member of the [spirochete family](\u002Fspirochetes-morphology-classification-disease\u002F) having a characterized distinct helical shape. It is the causative agent of syphilis, an infectious venereal disease in humans.\n\n> Treponema pallidum was first discovered in 1905 by Fritz Schaudinn and Erich Hoffmann in chancres and inguinal lymph nodes of the patients.\n\n## Properties\n\n- **Morphology**: Treponemes are extremely thin and delicate with tapering ends. Treponemes cannot be visualized by light microscope but can be seen under dark ground or phase contrast microscope.\n- **Staining:** Treponemes do not take ordinary stain but can be stained by fluorescence staining and silver impregnation methods.\n- **Size**: 6-14μm \\* 0.2 μm\n- **Spirals**: They are flexible, spirally coiled around the long axis; possess 6-14 spirals spaced at intervals of 1 μm with amplitude of 1-1.5 μm\n- **Motility**: actively motile exhibiting flexion extension, translatory, and corkscrew motility. They have a typical tendency to bend at right angle at the midpoint.\n- **Endoflagella**\n\nAbout 3-4 flagella are present in periplasmic space. Flagella provide motility to bacteria thus helping in tissue invasion and dissemination. Highly antigenic, thus stimulating a strong early antibody response.\n\n- Anaerobic\u002Fmicroaerophilic (i.e. requires a very low concentration of oxygen)\n- Extremely delicate organisms (heat, drying, disinfectants)\n- Pathogenic treponemes are obligate intra-cellular parasites (i.e. they cannot be grown in artificial culture media but are maintained by subcultures in susceptible animals such as rabbit testes).\n- Humans are the only source of treponemal infection; there are no known nonhuman reservoirs.\n\n## Classification\n\nClassification of the pathogenic treponemes is based primarily upon the clinical manifestations of the respective diseases they cause. Four members are human pathogens\n\n1. *Treponema pallidum* subsp *pallidum* that causes venereal syphilis;\n2. *T. pallidum* subsp *pertenue* that causes yaws;\n3. *T. pallidum* subsp *endemicum* that causes endemic syphilis; and\n4. *T. carateum* that causes pinta.\n\nBesides, there are few commensal treponemes found in the mouth and GI tract of humans and few animal treponemes found in rabbits.\n\n## Pathogenesis\n\n### Transmission\n\nInfection begins when *T. pallidum* penetrates the host, usually through intact or abraded mucous membranes. Venereal syphilis is transmitted by sexual contact; other diseases are transmitted by close non-venereal contact.\n\n#### Acquired Syphilis\n\n1. *Treponema pallidum* enters **via body fluids**\n\nCuts\u002Fbreaks in skin or mucous membranes (external genitalia) Mouth\n\n1. Sexual contact: **abrasions** during sexual contact\u002Fdirect contact with a syphilis **chancre** increases risk of transmission.\n2. Contaminated needles or blood transfusion (rare)\n3. Direct contact with a skin lesion\n\n#### Congenital Syphilis\n\n*T. pallidum* infects the fetus in the uterus \\*\\*(transplacental)\\*\\*or when **exiting through birth canal** of an infected mother.\n\n### Pathogenesis Mechanism\n\n- Within few hours of entry via skin or mucosa, the organism enters the lymphatics and blood to produce systemic infection and metastatic foci.\n- **Incubation period is variable (9-90 days; median 21 days)** and is inversely proportional to the number of organisms (average inoculum size is 500-1000) inoculated. During the incubation period, the bacteria not only invade the lymphatics but also disseminate to the bloodstream where it adheres to the surface proteins of endothelial cells. After an incubation of 2-4 weeks, the clinical sign and symptoms appear.\n- Approximately, 30% of persons who have sexual exposure with an infected partner develop syphilis.\n- Clinically, patients suffering from syphilis pass through four stages if left \\*\\*untreated, primary, secondary, latent and tertiary (or late)\\*\\*stages.\n\n### Virulence factors\n\nPotential virulence factors which account for *T. pallidum*‘s ability to cause disease include\n\n1. **Endoflagella:** They provide motility to the bacteria, thus helping in tissue invasion and dissemination. They are also highly antigenic, stimulating a strong early antibody response.\n2. **Outer membrane proteins** promote adherence to host cells.\n3. **Hyaluronidase** (an enzyme produced by virulent treponemes) facilitate perivascular infiltration\n4. Coating with host cell fibronectin protects against phagocytosis\n\nTissue destruction primarily results from host’s immune response to infection.\n\n### Antigens\n\n*T. Pallidum* is antigenically complex and poorly understood. Based on the type of antibody response, three antigens are identified;\n\n1. **Group-specific antigen**: Protein antigen present in all treponemes (pathogenic and nonpathogenic). Antibodies to this antigen can be detected in sera of syphilitic patients by using antigens of Reiter treponemes.\n2. **Species-specific antigen**: It appears to be polysaccharide in nature. Treponemal antibodies induced by this antigen in a syphilitic patient can be detected by using specific *T. pallidum* antigens.\n3. **Non-specific antigen**: It is a [heterophile antigen](\u002Fheterophile-antigen\u002F). Antibody against this antigen is detected by using beef heart antigen by various non-treponemal tests.\n\n## Clinical Manifestations\n\nClinically, syphilis can be of two types acquired syphilis (in adults by sexual contact excluding neurosyphilis) and congenital syphilis (acquired from mother to child). Acquired syphilis: On the basis of disease progression, acquired syphilis has been further divided into stages.\n\n![ - Stages of Syphilis](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FStages-of-Syphilis.png)Figure: Stages of Syphilis\n\n### Primary syphilis\n\n- Primary syphilis is the stage of infection that occurs in 2-4 weeks after infection and usually begins as a single painless papule that rapidly becomes ulcerated, hard, and indurated (popularly called **hard chancre**). It is covered by thick exudate, every rick in spirochetes.\n- Chancre appears on external genital corona of the penis, labia, vaginal wall cervix, perianal area, mouth, anal canal. Serological tests are positive in 80% individuals at this stage.\n- Regional lymphadenopathy appears within 1 week of onset of skin lesions. **Lymph nodes are painless firm, non-suppurative, and often bilateral**.\n- The chancre generally heals within 4-6 weeks (range 2-12 weeks), but lymphadenopathy may persist for months.\n- If acquired by non-veneral mode, then the primary syphilis is presented as follows:\n\nIf transmitted by **direct contact**: The primary chancre is extra genital, usually on the **fingers**. If transmitted by \\*\\*blood transfusion-\\*\\*the **primary chancre does not occur.**\n\nIn some individuals, the appearance of primary chancres does not fit the classic description. Nonindurated lesions with irregular borders, multiple and\u002For painful lesions, especially in the anal area are seen in HIV-infected individuals. The untreated lesion or lesions usually heal spontaneously in 2 to 8 weeks.\n\n### Secondary syphilis\n\nSecondary syphilis usually develops 4-8 weeks after the healing of primary lesions. In secondary syphilis, skin and mucous membranes are primarily affected. During this stage, widespread dissemination of the infection to various parts of the body occurs.\n\nIn most cases, the widely disseminated maculopapular rash appears at palms and soles. Symptoms such as fever, malaise, anorexia, weight loss, pharyngitis, laryngitis, and\u002For arthralgias are also common. Other clinical manifestations include lesions in the mouth and oral cavity, lymphadenopathy, condyloma latum, glomerulonephritis, nephritic syndrome, hepatitis, arthritis, osteitis, and periosteitis. Temporary **alopecia** may occur. Nails become brittle and pitted.\n\n**Condylomata lata** represent one of the manifestations of secondary syphilis in which beningn and painless mucocutaneous papules are formed in warm moist intertriginous areas which later coalesce to form large pink to grey lesions\n\nThe manifestations of secondary syphilis are transient because most patients at this stage develop immune responses and the disease gets cured. In 13-15% of cases, the disease progress to the latent stage and finally to the tertiary stage.\n\n### Latent syphilis\n\nThe period between secondary and tertiary syphilis, termed latency, can last for many years. After several weeks, secondary lesions disappear and disease becomes latent. Latent syphilis is divided into two stages, based upon an approximation of the time of infection.\n\n1. Early latent syphilis: occurs within 1st year of infection\n2. Late latent syphilis: occurs after one year of infection\n\nDisease is not infectious at this stage, except for transmission from mother to fetus (congenital syphilis). Positive serological tests for syphilis and normal CSF findings.\n\nPossible fates of latent syphilis:\n\n- Persistent lifelong infection (common)\n- Development of late syphilis (rare)\n- Spontaneous cure\n\n### Tertiary or Late Syphilis\n\nDevelops after many years (decades) in persons with untreated secondary syphilis.\n\nTertiary syphilis develops in up to 35% of untreated secondary syphilis patients after 10-25 years of initial infection. Late syphilis can be categorized into neurosyphilis, cardiovascular syphilis, and granulomatous syphilis.\n\n1. Appearance of degenerative granulomatous lesions called **GUMMAS** in skin, bone and nervous system.\n2. Approx 20% patients may develop neurosyphilis or cardiovascular syphilis.\n\nCardiovascular syphils and granulomatus syphilis are uncommon in the antibiotic era due to the frequent exposure to antibiotics while neurosyphilis is the most common manifestation of tertiary\u002Flate syphilis because of the generally poor penetration of antibiotics into the CNS.\n\n1. **Neurosyphilis** may manifest as meningitis, meningovascular syphilis, general paresis of insane (paralytic dementia) and tabes dorsalis.\n2. **Cardiovascular syphilis** is characterized by aneurysm of ascending aorta and aortic regurgitation\n\n### Congenital syphilis\n\n*T. pallidum* can be transmitted from the bloodstream of the infected woman to the developing fetus at any time during pregnancy, although the risk is much higher during early maternal syphilis than during later stages. Neonates may also be infected during passage through the infected birth canal at delivery.  Affected infants typically have low weight at birth, pulmonary hemorrhage, secondary bacterial infection, and severe hepatitis.\n\nCongenital syphilis is divided into stages: early manifestations appearing in the first two years of life, late manifestations appearing after two years, and residual stigmata.\n\n1. Early manifestations are infectious and resemble severe symptoms of adult secondary syphilis; they usually become apparent 2 to 10 weeks after delivery. Symptoms include persistent rhinitis with a whitish discharge that is sometimes tinged with blood, accompanied by desquamation of the skin of palms and soles.\n2. Late manifestations of congenital syphilis occur between the 5-25 years of ages interstitial keratitis may cause damage to the cornea and iris, and eighth-nerve deafness may be apparent. Hutchinson’s teeth, peg-shaped notched upper incisors, is another characteristic late stigma of congenital syphilis.\n\n**References and Further Readings**\n\n1. [Medical Microbiology](https:\u002F\u002Fwww.ncbi.nlm.nih.gov\u002Fbooks\u002FNBK7716\u002F), 4th edition. Editor: Samuel Baron\n2. Fantry L E., Tramont E C “[Treponema Pallidum (Syphilis)](http:\u002F\u002Fwww.antimicrobe.org\u002Fb242.asp)”\n3. Blenden D. C. “The Application of A Silver Impregnation Stain for Treponema Pallidum” The Journal of Investigative Dermatology,1965, Vol. 45, No. 1",[],[46],"spirochetes",[48,54,61,84,90],{"slug":49,"title":50,"description":50,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":51,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"faq":52,"tags":53},"relapsing-fever-etiology-diagnosis","Borrelia species: Properties, Pathogenesis, Lab Diagnosis","2022-04-10",[],[46],{"slug":55,"title":56,"description":57,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":58,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"faq":59,"tags":60},"borrrelia-burgdorferi-lyme-disease","Borrelia burgdorferi (Lyme disease): Clinical Features, Diagnosis","Lyme disease is caused by Borrelia burgdorferi and transmitted by Ixodes ticks. Learn the three stages, the bull's-eye rash, laboratory diagnosis, and treatment — with clinical pearls for medical students.","2021-05-21",[],[46],{"slug":62,"title":63,"description":64,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":65,"lastUpdatedDate":66,"draft":41,"category":42,"image":37,"faq":67,"tags":83},"demonstration-of-treponema-pallidum-using-dark-field-microscopy","Demonstration of Treponema pallidum Using Dark-Field Microscopy","The full dark-field procedure for detecting Treponema pallidum in a chancre, the 20-minute window that makes or breaks it, and why oral or rectal samples can give a false positive.","2021-05-07","2026-07-06",[68,71,74,77,80],{"question":69,"answer":70},"Can dark-field microscopy be used on an oral or rectal lesion to diagnose syphilis?","No. Both the mouth and rectal mucosa normally carry commensal spirochetes, such as Treponema denticola in the oral cavity, that are morphologically and behaviorally indistinguishable from Treponema pallidum under dark-field examination. A positive result from these sites risks a false-positive diagnosis; specimens from oral or rectal lesions should instead be tested by a pathogen-specific method or serology.",{"question":72,"answer":73},"Why must the dark-field specimen be examined within 20 minutes of collection?","Motility is often essential to correctly identifying Treponema pallidum, and the organism loses motility quickly once outside the host. A delayed examination can produce a false-negative result even if the organism was present in the original specimen.",{"question":75,"answer":76},"What does \"Treponemas resembling T. pallidum observed\" mean, exactly?","This reporting language reflects that the identification is based on characteristic morphology (a tightly wound, corkscrew shape) and motility (rotation, flexion, and snapping movements), not a pathogen-specific molecular or antigen-based marker. This is also why the technique isn't reliable on specimen sites with look-alike commensal organisms.",{"question":78,"answer":79},"How sensitive is dark-field microscopy for diagnosing syphilis?","Approximately 80% in primary syphilis, but sensitivity declines as the infection progresses into later stages and can be further reduced if the patient has already applied topical antibiotics to the lesion.",{"question":81,"answer":82},"What size is Treponema pallidum, and how does that compare to a red blood cell?","It measures roughly 6 to 14 μm in length, slightly longer than the diameter of a typical erythrocyte, which serves as a useful visual size reference during dark-field examination.",[46],{"slug":85,"title":86,"description":86,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":87,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"faq":88,"tags":89},"leptospira-interrogans-characteristics-pathogenesis-and-lab-diagnosis","Leptospira interrogans: Characteristics, Pathogenesis, Lab Diagnosis","2020-10-02",[],[46],{"slug":91,"title":92,"description":93,"seoTitle":37,"seoDescription":37,"author":94,"createdDate":95,"lastUpdatedDate":96,"draft":41,"category":42,"image":37,"faq":97,"tags":113},"dark-field-microscopy","Dark-field Microscopy: Principle and Uses","How dark-field microscopy makes spirochetes like Treponema pallidum visible without staining, by detecting scattered light rather than resolving fine detail.","Nisha Rijal","2020-04-21","2026-07-21",[98,101,104,107,110],{"question":99,"answer":100},"Why is dark-field microscopy used to diagnose primary syphilis instead of a routine stain?","Treponema pallidum does not stain well with routine methods and is difficult to see by bright-field microscopy. Dark-field microscopy shows the organism as a bright, motile, corkscrew-shaped structure against a completely dark background, using its live motility as the identifying feature.",{"question":102,"answer":103},"Does dark-field microscopy improve resolution compared to bright-field microscopy?","No. The fundamental resolving power of the microscope, roughly 0.2 μm, stays the same. Dark-field microscopy instead improves contrast and the ability to detect structures at or below that resolving limit by showing only the light they scatter, rather than trying to resolve their fine detail directly.",{"question":105,"answer":106},"Why can spirochetes like Treponema pallidum be seen with dark-field microscopy but not bright-field?","Spirochetes are roughly 0.1 to 0.18 μm wide, thinner than the light microscope's ~0.2 μm resolving limit, so bright-field microscopy cannot resolve them. Dark-field microscopy detects the light they scatter instead, making them visible as bright, moving threads against a dark background even though their fine structure still can't be resolved.",{"question":108,"answer":109},"What are the main limitations of dark-field microscopy?","The specimen must be living, unstained, and examined very quickly since motility is often essential for identification. Strong illumination can damage the sample, dust particles can be mistaken for organisms, and thick preparations reduce contrast and accuracy.",{"question":111,"answer":112},"Is dark-field microscopy used routinely in diagnostic laboratories?","Not routinely. It requires a special condenser setup, a fresh, living specimen examined immediately, and a trained microscopist, which limits its use to specific point-of-care situations like suspected primary syphilis rather than general diagnostic panels.",[114,46],"microscopy",[116,122,129,134,138,142,147,152,156,160],{"slug":117,"name":38,"description":118,"image":119,"body":120,"postCount":121},"acharya-tankeshwar","Editor-in-chief","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Ftankeshwar-acharya-author-microbeonline.jpg","***Tankeshwar Acharya, MSc (Medical Microbiology)***\n\n*Tankeshwar Acharya is an Assistant Professor in the Department of Microbiology at Patan Academy of Health Sciences (PAHS), Nepal, where he has been teaching and practicing clinical microbiology for over 14 years. He is the founder of Microbe Online, one of the leading free microbiology education resources on the web, covering bacteriology, mycology, parasitology, immunology, and clinical laboratory diagnostics written from direct experience in both the classroom and the diagnostic laboratory.*",433,{"slug":123,"name":124,"description":125,"image":126,"body":127,"postCount":128},"ashma-shrestha","Ashma Shrestha","SEO Copywriter and Science Communicator\nKathmandu, Nepal","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fashma-shrestha.png","Ashma Shrestha holds a Master of Science in Medical Microbiology from the Institute of Science and Technology (IOST), Tribhuvan University, Nepal, where she developed a strong foundation in virology, molecular biology, and diagnostic microbiology.\n\nShe now works as an SEO Copywriter at Resolution Digital, where she combines her scientific training with research-driven content strategy. She is certified in Google Analytics and Google Business Profile (GBP), and brings a data-informed approach to science communication writing content that is not only accurate but structured to reach and serve the students who need it most.\n\nAt microbeonline, Ashma contributes articles primarily in virology and molecular biology, areas she finds most compelling for their mechanistic depth and their growing clinical relevance. Her writing reflects the same standard the site is built on: factual rigor, clear explanation of the *why* behind microbiology concepts, and content that helps students move from memorization to genuine understanding.\n\nShe is passionate about making complex microbiological concepts accessible without sacrificing accuracy; a skill that sits at the intersection of her scientific training and her professional work in content and SEO.",81,{"slug":130,"name":131,"description":132,"image":37,"body":37,"postCount":133},"sushmita-baniya","Sushmita Baniya","Author \u002F Contributor",32,{"slug":135,"name":136,"description":132,"image":37,"body":37,"postCount":137},"samikshya-acharya","Samikshya Acharya",20,{"slug":139,"name":140,"description":132,"image":37,"body":37,"postCount":141},"alisha-tripathi","Alisha Tripathi",6,{"slug":143,"name":144,"description":145,"image":37,"body":37,"postCount":146},"aastha-shrestha","Aastha Shrestha"," Author \u002F Contributor",10,{"slug":148,"name":149,"description":150,"image":37,"body":37,"postCount":151},"guest-author","Guest Author","Guest Author \u002F Contributor",2,{"slug":153,"name":154,"description":132,"image":37,"body":37,"postCount":155},"srijana-khanal","Srijana Khanal",18,{"slug":157,"name":158,"description":150,"image":37,"body":37,"postCount":159},"dr-poonam-acharya","Dr. Poonam Acharya",1,{"slug":161,"name":94,"description":132,"image":37,"body":162,"postCount":163},"nisha-rijal","**Nisha Rijal** is a microbiologist and quality assurance specialist. She served for nearly 12 years as a microbiologist at the National Public Health Laboratory (NPHL), Nepal's national reference laboratory, and continues to work as a consultant microbiologist in international public health organization. ",51]