[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$fxEJ9XyOO71afVDGR5aKP5x-upTwqL0KiiAJ2DdVAmSs":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":47},"gram-positive-bacilli-rods-and-diseases","Gram-Positive Bacilli (Rods) and Diseases",null,"Acharya Tankeshwar","2020-01-31","2026-07-05",false,"bacteriology","Gram-positive bacteria retain the primary stain (crystal violet) color in the Gram staining procedure and appear purple under a light microscope. These bacteria have a cell wall containing a thick layer of [peptidoglycan](\u002Fpeptidoglycan-mureinmucopeptide-structure-and-medical-significance\u002F). Based on cell morphology, Gram-positive bacteria are divided mainly into “Gram-positive cocci” and “Gram-positive bacilli.”\n\n## Classification of Gram-positive rods\n\nGram-positive bacilli are a diverse group of bacteria that can further be classified into various subgroups based on their characteristics. There are five medically important genera of gram-positive bacilli: *Bacillus, Clostridium, Corynebacterium,* *Listeria*, and *Gardnerella.*\n\n1. **Endospore-forming ability**: *Bacillus* and Clostridia are spore-forming rods, while *Listeria, Gardnerella,* and *Corynebacterium* are not.\n2. **Gaseous (oxygen requirements):**  *Bacillus* species are obligate aerobes, whereas *Clostridium* species are obligate anaerobes.\n\nSome Gram-positive rods have a unique shape based on spores’ position, branches’ presence, etc. *Actinomyces* appear as irregular, branching gram-positive rods, Corynebacteria appear as club-shaped, *Clostridium tetani* appear as drum-stick appearances, and *Nocardia* appears as branching filaments.\n\n## Pathogenic Gram-Positive Bacilli\n\nGram-positive bacilli are responsible for “classical” diseases such as anthrax, diphtheria, listeriosis, and newer syndromes, particularly in immunocompromised individuals.\n\n### Bacillus cereus\n\nThere are two medically important *Bacillus* species; *Bacillus anthracis* and *Bacillus cereus. Bacillus cereus* is an aerobic, spore-forming, Gram-positive bacillus.  Domestic animals, soil, and rice grains are the main reservoirs of this organism.  *Bacillus cereus* spores can survive boiling during rice preparation and may germinate when rice is held at room temperature.\n\n![Bacillus cereus](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FBacillus-cereus-signs-and-symptoms.jpg)Figure: Bacillus cereus\n\n*Bacillus cereus* causes [food poisoning](\u002Ffoodborne-illness-food-poisoning-and-causative-agents-of-foodborne-illness\u002F) and is acquired by eating “reheated rice.” The spores germinate when rice is kept warm for many hours. The organism produces two toxins, one is like [cholera toxin](\u002Fvibrio-cholerae-laboratory-diagnosis-confirmation\u002F), and the another is like staphylococcal enterotoxin. The main symptoms of *Bacillus cereus* food poisoning are nausea, vomiting, and non-bloody diarrhea.\n\n### Bacillus anthracis\n\n*Bacillus anthracis* is a large gram-positive bacillus with square ends (bok-car-like) frequently found in chains. It is a non-motile, spore-forming, and [capsule-forming organism](\u002Fbacterial-capsule-structure-and-importance-and-examples-of-capsulated-bacteria\u002F). The capsule of *Bacillus anthracis* is composed of D-glutamate (most capsules are polysaccharides).\n\n![Bacillus anthracis important properties - Major characteristics ofBacillus anthracis](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FBacillus-anthracis.jpg)Figure: Major characteristics of *Bacillus anthracis*\n\nTraumatic inoculation and inhalation of spores are two major routes of acquiring infection. Anthrax is a rare human disease caused by *B. anthracis*. It typically manifests as one of three forms; cutaneous, pulmonary, or gastrointestinal anthrax.\n\n### Clostridium perfringens\n\n*Clostridium perfringens* is one of four medically important species of *Clostridium*. Others are; *Clostridium tetani,* *Clostridium botulinum* and  *Clostridioides difficile*. All clostridia are anaerobic, spore-forming, gram-positive rods.\n\n*Clostridium perfringens* is a large gram-positive rod. Soil, animals, and humans are the main reservoirs. It is a normal flora of the colon and female genital tract.\n\n![Common properties of Clostridium perfringens - Major characteristics ofClostridium perfringens](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FClostridium-perfringens.jpg)Figure: Major characteristics of *Clostridium perfringens*\n\nIt causes two distinct diseases, gas gangrene and food poisoning, depending on the route of infection. Food poisoning is transmitted by eating partially cooked meat, stew, and gravy. Gas gangrene (myonecrosis, necrotizing fasciitis) is associated with road-traffic accidents and septic abortions.\n\n### Clostridium tetani\n\n*Clostridium tetani* is an anaerobic, gram-positive, spore-forming rod. *C. tetani* looks like a **tennis racket** because of a terminal spore. It is found ubiquitously in soil, and the mode of infection is traumatic inoculation of bacterial spores.\n\n![Clostridium tetani cover image - Major characteristics ofClostridiumtetani](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FClostridium-tetani-cover-image.jpg)Figure: Major characteristics of *Clostridium tetani*\n\n*Clostridium tetani* causes tetanus, a typical spastic paralysis with characteristic manifestations like “lock-jaw” and “risus sardonicus.” Tetanus toxin (tetanospasmin) is the major virulence factor of this organism. Tetanus toxoid and hyperimmune globulin are used to prevent the occurrence of tetanus.\n\n### Clostridium botulinum\n\nAn anaerobic, gram-positive, spore-forming rod found commonly in the soil, *Clostridium botulinum* is the causative agent of botulism.\n\n![Clostridium botulinum cover image - Major characteristics ofClostridium botulinum](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FClostridium-botulinum-cover-image.jpg)Figure: Major characteristics of *Clostridium botulinum*\n\nInfection with *Clostridium botulinum* is acquired by ingesting preformed **botulinum toxin** found in improperly **canned foods** and smoked fish. **Botox** is a commercial preparation of tetanus toxin used to **remove facial wrinkles**. Botulinum toxin is also used **to treat certain spasmodic muscle disorders** such as torticollis, “writer’s cramp,” and blepharospasm.\n\n### Clostridioides difficile\n\n*Clostridioides difficile* is an anaerobic, gram-positive, spore-forming rod.  It is transmitted by the fecal-oral route and colonizes the large intestine of approximately 3% of the general population, increasing up to 30% in hospitalized patients.\n\n![Fecal Transplant](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002Ffecal-transplant.jpg)Figure: Fecal Transplant\n\n*Clostridioides difficile* is a common cause of hospital-acquired diarrhea and can cause antibiotic-associated pseudomembranous colitis. [Fecal transplantation](\u002Ffecal-transplant-principle-procedure-uses-risks\u002F) is a newer therapeutic approach for the treatment of this disease.\n\n### Corynebacterium diphtheriae\n\n*Corynebacterium* is a club-shaped (i.e., they are thinner on one end than the other) gram-positive rod. In Gram stain, these bacteria appear as V-in Y-shaped arrangements or in clumps that resemble Chinese letters. The rods have a beaded appearance, and the bead consists of highly polymerized polyphosphate granules. These granules stain metachromatically in [Albert staining](\u002Falbert-stain-principle-procedure-results-uses\u002F).\n\n![Pseudomembrane in Corynebacterium diphtheriae - Pseudomembrane seen in a diphtheria case](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FPseudomembrane-seen-in-Corynebacterium-diphtheriae.jpg)Figure: Pseudomembrane seen in a diphtheria case\n\nToxigenic strains of *C. diphtheriae* are responsible for diphtheria and are transmitted by airborne droplets. Diphtheria is characterized by the presence of thick, gray, adherent pseudomembrane over the tonsils and throat.\n\n### Listeria monocytogenes\n\n*Listeria monocytogenes* is a small gram-positive rod arranged in V or L-shaped forms similar to corynebacteria. Domestic animals (cows) are the main reservoir of this organism. It exhibits tumbling movement, gives a narrow zone of beta-hemolysis, and grows well at cold temperatures.\n\n![Listeria monocytogenes in Gram and Culture - Major characteristics ofListeria monocytogenes](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002Flisteria-monocytogenes-gram-and-culture.jpg)Figure: Major characteristics of *Listeria monocytogenes*\n\n*Listeria monocytogenes* causes neonatal sepsis, diarrhea, and meningitis (in immunocompromised individuals). People acquire listeria infection by ingesting unpasteurized milk products or contaminated refrigerated food products. Listeriolysin is the major virulence factor of this organism.\n\n### Actinomyces israelii\n\nActinomyces israelii is one of the medically important *Actinomycetes*, the other being *Nocardia asteroides. Actinomycetes are gram-positive* bacteria with filaments that resemble the hyphae of fungi.\n\n![Actinomyces in culture and gram-stain - Actinomycesin Gram-stain and culture](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002Factinomyces-culture-and-gram-stain.png)Figure: Actinomyces in Gram-stain and culture\n\n[Actinomyces israelii](\u002Factinomyces-properties-disease-laboratory-diagnosis\u002F) is a normal flora of the oral cavity. These anaerobic gram-positive branching rods cause the disease actinomycosis.\n\n### Nocardia asteroides\n\n\\*Nocardia asteroides is an aerobe found in the soil.\\*This weakly acid-fast bacteria appear as thin, gram-positive branching filaments on Gram stain.\n\n| Etiological agents | Disease (s) |\n| --- | --- |\n| Actinomyces israelii | Actinomycosis |\n| Corynebacterium diphtheriae | Diphtheria |\n| Listeria monocytogenes | Listeriosis, neonatal meningitis, sepsis, etc. |\n| Clostridium perfringens | Gas gangrene (clostridial myonecrosis) |\n| Clostridioides difficile | Diarrhea and colitis |\n| Clostridium tetani | Tetanus |\n| Clostridium botulinum | Botulism |\n| Bacillus cereus | Foodborne diseases |\n| Bacillus anthracis | Anthrax |\n| Erysipelothrix rhusiopathiae | Erysipeloid |\n| Nocardia asteroides | Nocardiosis |\n| Cutibacterium (formerly Propionibacterium) acnes | Acne |\n| Mycobacterium tuberculosis | Tuberculosis |\n| Mycobacterium leprae | Leprosy |\n\n![FIlamentous Nocardia - Nocardiain Gram-stain](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FFilamentous-Nocardia.jpg)Figure: Nocardia in Gram-stain\n\n*Nocardia asteroides* can cause pneumonia, lung abscess with cavity formation, lung nodules, or empyema in immunocompromised individuals.\n\nSome of the diseases caused by gram-positive bacilli are as follows:\n\n## Non-pathogenic Gram-positive rods\n\n### Lactobacillus\n\nLactobacilli are gram-positive, non-sporing rods. They are an essential microbiota of the mouth, colon, and female genital tract. In the female genital tract, they are the main source of lactic acid that helps to prevent the growth of many potential pathogens.\n\nLactobacilli are beneficial bacteria mainly used to manufacture fermented dairy, sourdough, meat, and vegetable foods and as [probiotics.](\u002Fprobiotics-prebiotics\u002F)\n\n### Streptomyces\n\n*Streptomyces* is a Gram-positive bacteria whose shape resembles filamentous fungi. *Streptomyces* produces bioactive secondary metabolites such as antifungals, antivirals, and antibiotics. Today, nearly 80% of the antibiotics are sourced from the genus *Streptomyces* such as penicillin, streptomycin, gentamicin, linezolid, tetracycline, etc.\n\n**References and further readings**\n\n1. [Bailey & Scott’s Diagnostic Microbiology](https:\u002F\u002Famzn.to\u002F2WZxPHL), Forbes, 11th edition\n2. [Review of Medical Microbiology and Immunology](https:\u002F\u002Fwww.amazon.com\u002FReview-Medical-Microbiology-Immunology-Lange\u002Fdp\u002F0071818111), Lange Medical Books, 13th edition\n3. [Koneman’s Color Atlas and Textbook of Diagnostic Microbiology (Color Atlas & Textbook of Diagnostic Microbiology)](https:\u002F\u002Fwww.amazon.com\u002FKonemans-Color-Textbook-Diagnostic-Microbiology\u002Fdp\u002F1451116594), 7th edition",[],[46],"gram-positive-rods",[48,54,61,67,73,79,85,95],{"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},"bacillus-cereus","Bacillus cereus: Morphology, Disease, Biochemical Tests","2021-05-31",[],[46],{"slug":55,"title":56,"description":56,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":57,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"faq":58,"tags":59},"clostridium-perfringens-properties-diseases-and-diagnosis","Clostridium perfringens: Properties, Diseases, Diagnosis","2020-05-03",[],[46,60],"anaerobic-bacteriology",{"slug":62,"title":63,"description":63,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":64,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"faq":65,"tags":66},"clostridium-tetani-properties-pathogenesis-diagnosis","Clostridium tetani: Properties, Pathogenesis, Lab Diagnosis","2020-05-02",[],[46,60],{"slug":68,"title":69,"description":69,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":70,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"faq":71,"tags":72},"clostridium-botulinum-properties-pathogenesis-diagnosis","Clostridium botulinum: Properties, Pathogenesis, Lab Diagnosis","2020-05-01",[],[46],{"slug":74,"title":75,"description":75,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":76,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"faq":77,"tags":78},"bacillus-anthracis-properties-pathogenesis-diagnosis","Bacillus anthracis: Properties, Pathogenesis, Lab Diagnosis","2020-04-21",[],[46],{"slug":80,"title":81,"description":81,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":82,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"faq":83,"tags":84},"toxins-clostridium-perfringens-roles","Toxins of Clostridium perfringens and their roles","2020-04-06",[],[60,46],{"slug":86,"title":87,"description":88,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":89,"lastUpdatedDate":90,"draft":41,"category":91,"image":37,"faq":92,"tags":93},"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",[],[60,46,94],"anaerobic-culture-techniques",{"slug":96,"title":97,"description":97,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":98,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"faq":99,"tags":100},"clostridium-difficile-characteristics-disease-laboratory-diagnosis","Clostridioides difficile: Characteristics, Disease, Lab Diagnosis","2015-11-30",[],[46,60],[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]