[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$fJAxQTQY51jd88isdX_8lVwaNqJtouu6f6zx2-vGOy3Y":32,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":126},[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},"short-notes-atypical-mycobacterial-infections","Atypical Mycobacterial Infections",null,"Acharya Tankeshwar","2014-11-07","2026-07-04",false,"bacteriology","Atypical mycobacterial infections caused by a species of mycobacterium other than *M*. *tuberculosis* complex,  the causative bacteria of pulmonary TB and extrapulmonary TB including cutaneous TB; and *Mycobacterium leprae*, the cause of leprosy. Atypical mycobacteria include species such as *M. avium, M. intracellularae*, *M. kansasii, M. xenopi,* and *M. fortuitum.*\n\nIn the acquired immunodeficiency syndrome (AIDS),  *Mycobacterium avium-intracellulare*, *Mycobacterium kansasii,* and *Mycobacterium xenopi* have caused widely disseminated infection.\n\n**Other names used to designate Non-tuberculous mycobacteria**\n\n- MOTT (mycobacteria other than tubercle bacilli)\n- Anonymous\n- Atypical\n- Tuberculoid\n- Environmental\n- Opportunistic\n\n## Differences with *Mycobacterium tuberculosis*\n\n1. MOTTs infections are not spread from person to person. With the exception of organisms causing skin lesions (*M. kansasii*, and possibly *M. simiae*), there is very little evidence of person-to-person spread of these organisms.\n2. Isolation of MOTTs is not equated with a disease whereas if *M. tuberculosis*is always considered a pathogen when isolated.\n\n> NTM lung infections occur more frequently in older adults and people with other lung diseases, like bronchiectasis and chronic obstructive pulmonary disease (COPD).\n\n## Some characteristics of Atypical Mycobacteria\n\n- Significant geographical variability both in prevalence and species responsible for the disease.\n- Location:\n\nUbiquitous in the environment Colonize skin, respiratory and GI tract\n\n- Little is known about how the infection is acquired.\n\nNot usually transmitted from person to person\n\n- Transmission via:\n\nTrauma Inhalation of aerosols or ingestion Nosocomially or iatrogenically\n\n- Interpretation of positive NTM culture is complicated\n\nWidespread distribution in nature Colonization without causing disease\n\n- With some exceptions, little is known about the pathogenesis of infections caused by NTM\n- Atypical Mycobacteria\n- Incidence: MOTT is being detected more frequently:\n\nbetter identification techniques becoming more prevalent\n\n- Clinical disease: Presentation is variable.\n\nSimilar to tuberculosis Predominantly localized skin infection.\n\n## Runyon Classification of NTM\n\n- A typical mycobacteria were first classified by Runyon into four groups\n- Basis\n\nGrowth rate Colonial pigmentation\n\n**Runyon proposed the following scheme:**\n\n- **Group I**: Photochromogens (**photo** means light; and **chromogen** means color, i.e producing color in light)\n- **Group II**: Scotochromogens (*scoto*-, darkness, Greek σκότος (skotos); chromogen means color i.e. produce the pigments **chiefly** in dark)\n- **Group III**: Non-chromogens (non: no; chromogen: color) These NTMs produce little or no yellow-orange pigment, irrespective of presence or absence of light\n- **Group I-III are slow growers**: Group IV- Fast growers (3-5 day)\n\n*Note:Chromogen (a substance that can be readily converted into a dye or other colored compound.)*\n\n### Group I: Photochromogens\n\nAmong the NTM classified as photochromogens, *M. kansasii, M. marinum* are the major potential pathogens. *M. asiaticum, M. intermedium* are found to be associated with pulmonary disease.\n\n1. ***Mycobacterium Kansasii*** Causes chronic pulmonary disease as well as infections of the skin and subcutaneous lymph nodes. The disease tends to progress slowly and is susceptible to usual mycobacterial drugs. ***M.kansasii*** causes lungs disease (resembling tuberculosis). Antigenically similar to *M*.*tuberculsois* ([tuberculin test positive](\u002Ftuberculin-skin-test-mauntoux-testprinciple-procedure-results-limitations\u002F)) Susceptible to standard anti-tuberculosis drugs Environmental habitat: Tap water Geographical habitat: USA (Texas)\n2. **Mycobacterium marinum** It grows at much lower temperatures than other mycobacteria (i.e. around 30°C) and is present in both fresh and saltwater.  It causes nodular ulcerative lesions of the skin at the site of trauma. The infection may spread to the liver through lymphatic circulation. \\\n   \\\n   **Source:** fresh and saltwater \\\n   **Disease**: Infects fish. Causes superficial granulomatous nodular skin disease of man at the site of trauma called fishtank granuloma also known as “aquarium granuloma” and “swimming pool granuloma,“ \\\n   **Treatment**: Susceptible to tetracyclines, trimethoprim-sulfamethoxazole, and to the usual antituberculous drugs.\n\n![ Swimming pool granuloma caused by Mycobacterium marinum - Swimming pool granuloma caused byMycobacterium marinum](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FSwimming-pool-granumola-300x225.png)Figure: Swimming pool granuloma caused by *Mycobacterium marinum*\n\n### Group II (Scotochromogens)\n\n*M. scrofulaceum* is an NTM classified as scotochromogens and is found in raw milk, soil, water, and dairy products. It is the most common cause of granulomatous cervical lymphadenitis in children. The disease is characterized by enlarged lymph nodes, which may ulcerate or form draining sinus tracts.\n\n- Natural habitat: environmental water source; human respiratory tract.\n- *M. scrofulaceum* causes scrofula- granulomatous cervical adenitis in children.\n- Enters through oropharynx and infects the draining lymph nodes\n- Treatment: surgical excision of affected lymph nodes.\n\n### Group III (Non-chromogens)\n\n- Includes *M. avium* and *M. Intracellularae* also referred to as *M. avium-intracellularae* (MAC\u002FMAI) Complex\n- The important pathogen in immunocompromised individuals.\n- Source: ubiquitous in the environment: water, soil, dust, animals, and poultry\n- Infection acquired by ingestion or inhalation.\n- Pathogenesis not clearly understood.\n\n#### Mycobacterium avium-intracellulare Complex (MAC)\n\nThese Non-Tuberculous Mycobacteria (NTM) are classified as Nonphotochromogens in Runyon classification. *M. avium* complex was first recognized as human pathogens in the 1990s.  They are an important pathogen in immunocompromised and immunocompetent populations.\n\nThey are ubiquitous in environmental sources including natural waters; soil etc.  Taxonomically, the *M. avium-intracellularae* complex comprises *M. avium, M. intracellularae, M. paratuberculosis, M. lepraemurium,* and the “wood pigeon” bacillus.\n\nThese organisms cause opportunistic infections in immunocompromised patients such as individuals infected with HIV. The lungs are primarily affected, but infection can spread to other organs as well. Disseminated disease is seen in the case of AIDS patients.\n\n- **Disease:**\n\nMAC\u002FMAI causes opportunistic infections in immunocompromised patients g. those with AIDS who have CD4 cell count less than 200\u002Fμl Pulmonary disease caused by MAC is clinically indistinguishable from pulmonary tuberculosis.\n\n- **Highly resistant to antituberculous drugs**\n\nAs many as six drugs in combination are frequently required for adequate treatment. The current drug of choice-clarithromycin plus one or more of the following: ethambutol, rifabutin, or ciprofloxacin.\n\n#### Mycobacterium ulcerans\n\n- *Mycobacterium ulcerans* causes Buruli ulcer: a necrotising disease (causing tissue death) of the skin and underlying tissue.\n\nBuruli ulcer presents in two different forms\n\n- Non-ulcerative forms are nodules, plaques and oedema.\n- The ulcerative form may be small or large with the typical undermined edges\n\n### Group IV: Rapid growers\n\nColonies appear on solid media in 7 days or less.\n\n#### Mycobacterium fortuitum complex (Rapid growers)\n\nIt is a group of free-living; rapid-growing NTM. The colonies of these organisms appear on solid media in 7 days or less. They constitute the second major group of NTM.\n\nThey have been found in soils, marshes, rivers etc. People acquire the infection when organisms gain entry into the host by inoculation into skin and subcutaneous trauma, injections, or surgery or through animal contact.\n\nInjection site abscesses among drug users are the most common form of this disease but pulmonary infection occurs occasionally. Infection can also be associated with implanted devices.  Little is known about the pathogenesis of these organisms.\n\nOf the potentially pathogenic, rapidly growing NTM, *M. fortuitum, M. chelonae*, and *M. abscessus* constitute approximately 97% of disease.\n\n- Group of free living, rapid growing mycobacteria.\n- Rarely cause human disease\n- Common disease: injection-site abscesses among drug abusers.\n- Infections has also been associated with implanted devices such as heart valves, surgery and breast abscesses.\n\n## Laboratory diagnosis of Atypical Mycobacterial diseases\n\nSpecimen: Sputum, pus, or exudate\n\n**Microscopy:**[Ziehl-Neelsen staining (AFB staining)](\u002Fziehl-neelsen-technique-principle-procedure-reporting\u002F) of smear shows acid-fast bacilli.\n\n**Culture**: Atypical mycobacteria grow well in LJ, Middlebrook, and Dubo’s media.\n\nDifferentiation from *M. tuberculosis* requires\n\n- biochemical tests (Niacin, Nitrate Reduction Test, catalase test,Tween 80 hydrolysis, etc).\n- molecular methods (e.g., DNA probes or 16S rRNA gene sequencing\n\n**References**\n\n1. Bhambri, S., Bhambri, A., & Del Rosso, J. Q. (2009). Atypical mycobacterial cutaneous infections. *Dermatologic clinics*, *27*(1), 63–73. \u003Chttps:\u002F\u002Fdoi.org\u002F10.1016\u002Fj.det.2008.07.009>\n2. Greinert U. (1992). Clinical atypical mycobacterial infections. *Immunitat und Infektion*, *20*(2), 32–35.",[],[46],"mycobacteria",[48,56,65,71,88,105,112,118],{"slug":49,"title":50,"description":50,"seoTitle":37,"seoDescription":37,"author":51,"createdDate":52,"lastUpdatedDate":53,"draft":41,"category":42,"image":37,"faq":54,"tags":55},"mycobacterium-tuberculosis-lab-diagnosis","Laboratory Diagnosis of Mycobacterium tuberculosis Infection","Nisha Rijal","2020-05-26","2026-07-19",[],[46],{"slug":57,"title":58,"description":59,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":60,"lastUpdatedDate":61,"draft":41,"category":62,"image":37,"faq":63,"tags":64},"preparation-uses-lowenstein-jensen-lj-medium","Löwenstein-Jensen (LJ) Medium: Principle, Preparation, Uses, and Colony Characteristics","Löwenstein-Jensen (LJ) medium is the standard solid culture medium for Mycobacterium tuberculosis. Learn its principle, preparation by inspissation, colony characteristics of M. tuberculosis and NTM, and how LJ compares to MGIT liquid culture.","2016-04-29","2026-07-05","culture-media",[],[46],{"slug":66,"title":67,"description":67,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":68,"lastUpdatedDate":61,"draft":41,"category":42,"image":37,"faq":69,"tags":70},"genexpert-mtbrif-assay-principle-procedure-results-interpretations","GeneXpert MTB\u002FRIF Assay","2016-01-04",[],[46],{"slug":72,"title":73,"description":74,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":75,"lastUpdatedDate":53,"draft":41,"category":76,"image":37,"faq":77,"tags":87},"auramine-rhodamine-fluorochrome-staining-principle-procedure-results-limitations","Auramine-Rhodamine Fluorochrome Staining: Principle, Procedure, and Results","Auramine-rhodamine is a WHO-recommended fluorochrome stain for detecting acid-fast bacilli — more sensitive than Ziehl-Neelsen and faster to screen. Learn the Truant method procedure, results grading, and when to confirm with ZN staining.","2015-04-03","staining-techniques",[78,81,84],{"question":79,"answer":80},"Why is auramine-rhodamine staining more sensitive than Ziehl-Neelsen for detecting acid-fast bacilli?","Auramine-rhodamine allows smear screening at 250x or 400x magnification — compared to 1,000x oil immersion required for ZN staining. At lower magnification, a much larger area of the slide can be examined per unit time (3-5 minutes vs 15-20 minutes per slide). This means more of the smear is examined, increasing the chance of detecting paucibacillary specimens. Studies consistently show auramine-rhodamine detects approximately 10% more positive cases than ZN in direct smear microscopy, which is why WHO recommends it as the preferred method where fluorescence microscopy is available.",{"question":82,"answer":83},"What is the two-step workflow for auramine-rhodamine results?","Positive auramine-rhodamine results should be confirmed by ZN staining of the same slide, as fluorescence artefacts (dust, fibres, non-AFB structures) can occasionally give false-positive fluorescence. Negative auramine-rhodamine results require examination of the minimum required number of fields before reporting — at 200-250x this is typically 30-100 fields. In high-suspicion patients, a negative fluorochrome result should prompt ZN confirmation and repeat specimen collection, as the minimum detection threshold for smear microscopy (approximately 5,000-10,000 AFB\u002FmL) means culture is more sensitive than any smear method.",{"question":85,"answer":86},"Can auramine-rhodamine staining detect organisms other than mycobacteria?","Yes. A modified fluorochrome method using a weaker decolouriser (0.5% sulphuric acid instead of 3% acid-alcohol) detects partially acid-fast organisms including Cryptosporidium parvum, Cyclospora cayetanensis, and Isospora belli oocysts in stool specimens, and Nocardia species in respiratory or wound specimens. These organisms share a partial acid-fast property with mycobacteria. The oocysts appear as bright yellow-orange fluorescent structures against a dark background. This application requires the modified decolouriser — the standard 3% acid-alcohol used for TB smears will over-decolourise these weakly acid-fast organisms.",[46],{"slug":89,"title":90,"description":91,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":92,"lastUpdatedDate":93,"draft":41,"category":76,"image":37,"faq":94,"tags":104},"ziehl-neelsen-technique-principle-procedure-reporting","Ziehl-Neelsen Staining: Principle, Procedure, Grading, and Interpretation","Ziehl-Neelsen (ZN) staining detects acid-fast bacilli in sputum and other specimens. Learn the hot and cold methods, AFB grading scale, smear reporting, troubleshooting, and when to use fluorochrome staining instead.","2013-12-06","2026-07-07",[95,98,101],{"question":96,"answer":97},"Why does Ziehl-Neelsen staining require heat while other staining techniques do not?","Mycobacteria have a cell wall rich in mycolic acids — long-chain fatty acids that make the wall waxy, hydrophobic, and impermeable to most dyes at room temperature. Heat acts as a mordant by disrupting this waxy barrier and allowing carbol fuchsin to penetrate the cell wall. Once inside, the stain is held so tightly by the mycolic acids that even acid-alcohol — one of the strongest decolorisers used in microbiology — cannot remove it. This is why the stain is called 'acid-fast' — the organisms hold fast to the dye even after acid treatment.",{"question":99,"answer":100},"How is an AFB smear graded and what does the grade mean clinically?","AFB smears are graded using the WHO\u002FIUATLD scale: No AFB seen (after examining 300 fields); Scanty — 1-9 AFB per 100 fields (report exact count and request repeat); 1+ — 10-99 AFB per 100 fields; 2+ — 1-10 AFB per field in at least 50 fields; 3+ — more than 10 AFB per field in at least 20 fields. Higher grades indicate greater organism burden and greater infectiousness. Grade is recorded at treatment initiation and at months 2, 5, and 6 to monitor bacteriological response. Conversion from positive to negative smear during treatment indicates therapeutic response.",{"question":102,"answer":103},"What is the difference between Ziehl-Neelsen and Kinyoun (cold) acid-fast staining?","Both methods use carbolfuchsin as the primary stain and acid-alcohol for decolourisation, but they differ in how the dye penetrates the mycobacterial cell wall. Ziehl-Neelsen uses heat (the hot technique) — the slide is steamed to drive the dye through the waxy cell wall. Kinyoun's cold technique achieves penetration without heat by increasing the concentration of both carbolfuchsin and phenol and incorporating a wetting agent (Triton X-100 or similar). The results are equivalent. Kinyoun is preferred where open flames are unsafe or inconvenient, and for partial acid-fast organisms (Nocardia, Cryptosporidium) where lower decoloriser concentrations are needed.",[46],{"slug":106,"title":107,"description":107,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":108,"lastUpdatedDate":40,"draft":41,"category":109,"image":37,"faq":110,"tags":111},"key-biochemical-methods-used-to-distinguish-mycobacterial-group","Biochemical Tests to identify Mycobacteria, NTM","2013-07-22","biochemical-tests",[],[46],{"slug":113,"title":114,"description":114,"seoTitle":37,"seoDescription":37,"author":38,"createdDate":115,"lastUpdatedDate":40,"draft":41,"category":42,"image":37,"faq":116,"tags":117},"introduction-transmission-pathogenesis-and-lab-diagnosis-of-leprosy-hansens-disease","Leprosy: Etiology, Pathogenesis, Lab Diagnosis","2012-05-15",[],[46],{"slug":119,"title":120,"description":121,"seoTitle":37,"seoDescription":37,"author":51,"createdDate":122,"lastUpdatedDate":53,"draft":41,"category":42,"image":123,"faq":124,"tags":125},"tuberculin-skin-test-mantoux-test-principle-procedure-results","Tuberculin Skin Test (Mantoux test): Principle, Procedure, Results","Details about Tuberculin Skin Test.","2023-02-02","https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FMantoux_tuberculin_skin_test-1.jpg",[],[46],[127,133,140,145,149,153,158,163,167,171],{"slug":128,"name":38,"description":129,"image":130,"body":131,"postCount":132},"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":134,"name":135,"description":136,"image":137,"body":138,"postCount":139},"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":141,"name":142,"description":143,"image":37,"body":37,"postCount":144},"sushmita-baniya","Sushmita Baniya","Author \u002F Contributor",32,{"slug":146,"name":147,"description":143,"image":37,"body":37,"postCount":148},"samikshya-acharya","Samikshya Acharya",20,{"slug":150,"name":151,"description":143,"image":37,"body":37,"postCount":152},"alisha-tripathi","Alisha Tripathi",6,{"slug":154,"name":155,"description":156,"image":37,"body":37,"postCount":157},"aastha-shrestha","Aastha Shrestha"," Author \u002F Contributor",10,{"slug":159,"name":160,"description":161,"image":37,"body":37,"postCount":162},"guest-author","Guest Author","Guest Author \u002F Contributor",2,{"slug":164,"name":165,"description":143,"image":37,"body":37,"postCount":166},"srijana-khanal","Srijana Khanal",18,{"slug":168,"name":169,"description":161,"image":37,"body":37,"postCount":170},"dr-poonam-acharya","Dr. Poonam Acharya",1,{"slug":172,"name":51,"description":143,"image":37,"body":173,"postCount":174},"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]