[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$fD0tDzuSsiIwN5KbbDHrBTi7t-ICmPFHKi7LLNtcyXuY":32,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":101},[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":48},"clostridium-tetani-properties-pathogenesis-diagnosis","Clostridium tetani: Properties, Pathogenesis, Lab Diagnosis",null,"Acharya Tankeshwar","2020-05-02","2026-07-05",false,"bacteriology","*Clostridium tetani* is an obligate anaerobic, gram-positive bacillus with terminal round spore (**drumstick appearance**). It is the causative agent of **tetanus,** a vaccine-preventable disease that classically follows a puncture wound by a rusty nail (or any object contaminated with spores of *C. tetani*). Tetanus is manifested by skeletal muscle spasms and autonomic nervous system disturbance. Tetanus **only affects skeletal muscle**, smooth muscle, and cardiac muscle function normally.\n\n![](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FClostridium-tetani-cover-image.jpg)Tetanus has been known since ancient times; however, its causative organism was isolated by Kitasato in 1889.\n\n## Pathogenesis\n\n### Mode of transmission\n\n*C. tetani* are primarily saprophytic (live in the dead or decaying matter) and **only incidentally infect humans**. There is **no person-to-person** spread of *C. tetani*.\n\nHuman acquires tetanus when *Clostridium tetani* endospores are inoculated into sterile body tissues through traumas (for example, lacerations, deep puncture, or crush injuries) or fecal contamination of the umbilical cord (neonatal tetanus). The organism would grow and produce tetanus toxin in the anoxic zones created by local tissue death.\n\n### Virulence Factors\n\n*C. tetani* produces two **exotoxins**–**tetanolysin and tetanospasmin**.\n\n1. **Tetanolysin** is a heat-labile, oxygen-labile hemolysin antigenically related to the oxygen-labile hemolysins produced by *C. perfringens*, *S. pyogenes,* and *S. pneumoniae*. Tetanolysin damages otherwise viable tissue surrounding the infection and optimizes the conditions for bacterial multiplication.\n2. **Tetanospasmin (or tetanus toxin)** is a heat-labile, oxygen-stable, plasmid-coded neurotoxin responsible for disease manifestations. Tetanus neurotoxin is released upon cell lysis after bacterial growth under anaerobic conditions (e.g., in deep puncture wounds). It is antigenic and is specifically neutralized by its antitoxin. Its toxoid form is used for vaccine preparation.\n\n### Mechanism of Tetanus Toxin\n\nTetanus toxin binds to **polysialogangliosides receptors** present on motor nerve terminals which results in toxin internalization. Following internalization, tetanus toxin gets transported in a **retrograde way** from the peripheral nervous system to the central nervous system by retrograde axonal transport. When tetanus toxin reaches **inhibitory neuron terminals**, it **prevents the presynaptic release of inhibitory neurotransmitters glycine and gamma-aminobutyric acid (GABA).**\n\n![Tetanus toxin mechanism - Route of tetanus toxin, from entry into an α-motor neuron to its site of action in an inhibitory neuron in the central nervous system (CNS).(Image source: sciencedirect.com)](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FMechanism-of-action-of-Tetanus-toxin-1.jpg)Figure: Route of tetanus toxin, from entry into an α-motor neuron to its site of action in an inhibitory neuron in the central nervous system (CNS).(Image source: sciencedirect.com)\n\n> In normal condition, Glycine and GABA released from inhibitory interneurons induce muscle relaxation by acting on the motor neurons and blocking excitation and release of acetylcholine at the motor endplate.\n\nLack of inhibitory signals to the motor neurons and constant release of acetylcholine to the muscle fibers leads to irreversible contraction of the muscles and **spastic paralysis.**\n\n![Mechanism of action of tetanus toxin - Mechanism of action of tetanus toxin](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FMechanism-of-action-of-tetanus-toxin.jpg)Figure: Mechanism of action of tetanus toxin\n\n> Flaccid paralysis vs. Spastic paralysis\n>\n> Flaccid paralysis occurs when the muscle cannot contract at all. The muscle stays weak and floppy. Spastic paralysis occurs when the muscle stays in contraction. The muscle is too rigid and the patient can not move the muscle properly.  It causes muscles to twitch uncontrollably or spasm.\n\n### Clinical manifestations of Tetanus\n\nIncubation period of tetanus is about 6-10 days. Shorter the incubation period, graver is the prognosis. Muscles of the face and jaw are often affected first (due to shorter distances for the toxin to reach the presynaptic terminals).\n\n![Clinical Manifestations and Complications of Tetanus - Clinical Manifestations and Complications of Tetanus(Image source: osmosis.org)](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002Ftetanic-triad.png)Figure: Clinical Manifestations and Complications of Tetanus (Image source: osmosis.org)\n\nPatients have prolonged muscle spasms of both **flexor** and **extensor muscles**. Patients with tetanus have spastic muscle contractions, difficulty opening the jaw (called lockjaw, “**trismus**”), a characteristic smile called “**risus sardonicus**” and contractions of back muscles resulting in backward arching (**Opisthotonos position)**. Patients are extremely irritable, and tetanic seizures develop, brought about by violent, painful muscle contractions following some minor stimulus, such as noise.\n\n## Laboratory Diagnosis\n\nThe diagnosis of tetanus is clinical and does not require a demonstration of *C. tetani*. Treatment should be started immediately based on clinical diagnosis. Laboratory diagnosis provides supportive evidence for confirmation.\n\n#### Specimen\n\nExcised tissue bits from the necrotic depths of wounds are more reliable than wound swabs.\n\n#### Gram staining\n\n![Spores of Clostridium tetani](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FSpores-of-Clostridium-tetani.png)Figure: Spores of *Clostridium tetani*\n\nGram staining reveals gram-positive bacilli with terminal and round spores **(drum stick appearance or tennis racket appearance**). However, microscopy alone is unreliable as it cannot distinguish *C. tetani* from morphologically similar non-pathogenic clostridia like *C. tetanomorphum* and *C. sphenoides.*\n\n#### Culture\n\nCulture is more reliable than microscopy.\n\n1. [Robertson cooked meat(RCM) broth](\u002Frobertsons-cooked-meat-medium-principle-composition-procedure-and-uses\u002F) – *C. tetani* being proteolytic turns the meat particles black and produces a foul odor.\n2. Blood agar with polymyxin B: *C. tetani* produce **characteristic swarming growth** when incubated at 37°C for 24-48 hours under anaerobic conditions.\n\n#### Toxigenicity Test\n\nAs pathogenesis of tetanus is toxin mediated, the association of the isolated organism can only be established when its toxin production is demonstrated. Toxigenicity can be detected by both in vitro and in vivo methods.\n\n1. *In vitro* **hemolysis inhibition test:** *C. tetani* produces hemolysis on blood agar which is inhibited by adding antitoxin. This test indicates the production of **tetanolysin** only but **not tetanospasmin.**\n2. *In vivo* **mouse inoculation test:** RCM broth with black turbid growth is injected into the root of the tail of a test mouse. The test animal develops stiffness which begins with the tail and progresses to involve the hind limbs on the inoculated side- the other limb-trunk-forelimbs. Death occurs within two days. This test indicates the production of **tetanospasmin.**\n\n#### References and further readings\n\n- Tille, P. (2017). *Bailey & Scott’s Diagnostic Microbiology* (14 edition). Mosby.\n- Procop, G. W., & Koneman, E. W. (2016). [Koneman’s Color Atlas and Textbook of Diagnostic Microbiology](https:\u002F\u002Famzn.to\u002F2vRkUvk)(Seventh, International edition). Lippincott Williams and Wilkins.",[],[46,47],"anaerobic-bacteriology","gram-positive-rods",[49,55,61,71,77,83,89,95],{"slug":50,"title":51,"description":51,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":52,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"faq":53,"tags":54},"clostridium-perfringens-properties-diseases-and-diagnosis","Clostridium perfringens: Properties, Diseases, Diagnosis","2020-05-03",[],[47,46],{"slug":56,"title":57,"description":57,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":58,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"faq":59,"tags":60},"toxins-clostridium-perfringens-roles","Toxins of Clostridium perfringens and their roles","2020-04-06",[],[46,47],{"slug":62,"title":63,"description":64,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":65,"lastUpdatedDate":66,"draft":41,"category":67,"image":37,"faq":68,"tags":69},"robertsons-cooked-meat-medium-principle-composition-procedure-and-uses","Robertson's Cooked Meat (RCM) Medium: Principle, Composition, Uses, and Interpretation","Robertson's cooked meat medium cultivates and enriches anaerobes — especially Clostridium species — using meat particles as natural reducing agents. Learn the principle, preparation, how to interpret saccharolytic vs proteolytic reactions, and how it compares to thioglycollate broth.","2016-11-29","2026-07-06","culture-media",[],[46,47,70],"anaerobic-culture-techniques",{"slug":72,"title":73,"description":73,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":74,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"faq":75,"tags":76},"clostridium-difficile-characteristics-disease-laboratory-diagnosis","Clostridioides difficile: Characteristics, Disease, Lab Diagnosis","2015-11-30",[],[47,46],{"slug":78,"title":79,"description":79,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":80,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"faq":81,"tags":82},"bacillus-cereus","Bacillus cereus: Morphology, Disease, Biochemical Tests","2021-05-31",[],[47],{"slug":84,"title":85,"description":85,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":86,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"faq":87,"tags":88},"clostridium-botulinum-properties-pathogenesis-diagnosis","Clostridium botulinum: Properties, Pathogenesis, Lab Diagnosis","2020-05-01",[],[47],{"slug":90,"title":91,"description":91,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":92,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"faq":93,"tags":94},"bacillus-anthracis-properties-pathogenesis-diagnosis","Bacillus anthracis: Properties, Pathogenesis, Lab Diagnosis","2020-04-21",[],[47],{"slug":96,"title":97,"description":97,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":98,"lastUpdatedDate":66,"draft":41,"category":42,"image":37,"faq":99,"tags":100},"gaspak-anaerobic-system","GasPak Anaerobic System: Principle, Application","2020-03-28",[],[46,70],[102,108,115,120,124,128,133,138,142,146],{"slug":103,"name":38,"description":104,"image":105,"body":106,"postCount":107},"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":109,"name":110,"description":111,"image":112,"body":113,"postCount":114},"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":116,"name":117,"description":118,"image":37,"body":37,"postCount":119},"sushmita-baniya","Sushmita Baniya","Author \u002F Contributor",32,{"slug":121,"name":122,"description":118,"image":37,"body":37,"postCount":123},"samikshya-acharya","Samikshya Acharya",20,{"slug":125,"name":126,"description":118,"image":37,"body":37,"postCount":127},"alisha-tripathi","Alisha Tripathi",6,{"slug":129,"name":130,"description":131,"image":37,"body":37,"postCount":132},"aastha-shrestha","Aastha Shrestha"," Author \u002F Contributor",10,{"slug":134,"name":135,"description":136,"image":37,"body":37,"postCount":137},"guest-author","Guest Author","Guest Author \u002F Contributor",2,{"slug":139,"name":140,"description":118,"image":37,"body":37,"postCount":141},"srijana-khanal","Srijana Khanal",18,{"slug":143,"name":144,"description":136,"image":37,"body":37,"postCount":145},"dr-poonam-acharya","Dr. Poonam Acharya",1,{"slug":147,"name":148,"description":118,"image":37,"body":149,"postCount":150},"nisha-rijal","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]