[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$fWOj_Lh8lXwMY85q5k1pdlV3Uot0UxjIHQp8Lh4IEQIo":32,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":165},[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":37,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":40,"lastUpdatedDate":41,"draft":42,"category":43,"image":38,"body":44,"faq":45,"tags":55,"related":57},"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.",null,"Acharya Tankeshwar","2015-04-03","2026-07-19",false,"staining-techniques","Tuberculosis kills approximately 1.5 million people annually — more than any other single infectious pathogen. In high-burden countries, the first microbiological evidence of TB comes from a sputum smear. The faster and more sensitive that smear, the sooner treatment begins.\n\nAuramine-rhodamine fluorochrome staining was developed specifically to address a fundamental limitation of Ziehl-Neelsen staining: ZN requires examination under oil immersion at 1,000x magnification, meaning a single slide takes 15–20 minutes to screen. Auramine-rhodamine allows screening at 250x or 400x — the entire slide area in 3–5 minutes — while detecting approximately 10% more positive cases. This speed advantage is most important in high-volume laboratories processing hundreds of sputum specimens per day.\n\nAuramine-rhodamine fluorochrome staining, also known as “Truant method of staining,” is used to visualize acid-fast bacilli (AFB). Ziehl-Neelsen (hot) and Kinyoun (cold) are still widely used in developing countries. CDC recommends fluorochrome staining for detecting AFB in primary patient specimens.\n\n![Comparison of ZN Staining an Flurochrome Staining - Comparison of ZN Staining and Flurochrome staining](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002Fzn-staining-vs-flurochrome-staining-300x200.jpg)Figure: Comparison of ZN Staining and Flurochrome staining\n\nThe acid fastness of Mycobacteria is due to their thick cell wall composed of waxes and lipids with a high content of mycolic acid.\n\nFluorescent dyes like auramine-rhodamine bind to the mycolic acid present in them and impart bright **yellow or orange fluorescence against a greenish background** when viewed using a fluorescent microscope. It is also used to stain all acid-fast organisms including the sporozoan parasites.\n\nThe modified fluorochrome method (using a weaker decolorizer; 0.5% sulphuric acid rather than 3% acid-alcohol) also detects partially acid-fast organisms including *Cryptosporidium parvum*, *Cyclospora cayetanensis*, and *Isospora belli* oocysts in stool specimens. These coccidian parasites share the partial acid-fast property with *Nocardia* species and are detected by both auramine-rhodamine and the cold modified ZN method. The oocysts appear as bright yellow-orange fluorescent circles against a dark background — much easier to find at low magnification than on a standard modified ZN smear.\n\n## Principle\n\nThe fluorochrome dye, auramine-rhodamine, forms a complex with mycolic acids found in the acid-fast cell wall of organisms which resist decolorization by acid-alcohol. The counterstain, **potassium permanganate,** renders tissue and its debris nonfluorescent, thus reducing the possibility of artifacts. The cells visualized under ultraviolet light appear bright yellow or reddish-orange.\n\n## Materials\n\n**Reagents:**\n\n- **Primary stain**: auramine rhodamine solution (**caution**: possible carcinogen)\n- **Decolorizer**: 0.5% acid alcohol  (5 ml HCl in 995 ml 70% alcohol). (**Caution**: flammable, corrosive)\n- Counterstain: 0.5% potassium permanganate (0.25 gm in 50 ml). (**caution**: corrosive)\n\n**Others:**\n\n1. **Slide:** use only new, unscratched, and clean slides; using old, scratched, or dirty slides can lead to erroneous results.\n2. **Identifier**: Properly label each slide using graphite pencils or use a diamond or tungsten carbide stylus.\n3. Slide racks\n4. [Bunsen burner](\u002Fbunsen-burner-parts-principle-and-applications\u002F)\n\n## Procedure\n\n**1.Preparation of Smear:**\n\n1. **For Sputum**: Using a piece of stick, transfer a purulent part of the sputum (containing any yellow caseous material), to a slide and make a thin smear. An area of approximately **½ by 1 inch (or 2-cm square)** is recommended. Spread the smear using circular movements. Allow to air dry.\n\n![Fig: Smear Thickness - Fig 1: Smear Thickness](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FSmear-quality-300x195.jpg)Figure: Smear Thickness\n\n**Note:** Be sure to prepare smears of suitable thickness. Smears that are too thick may flake during staining and may be difficult to decolorize. Acid-fast organisms that might be present may be obscured. Smears that are too thin may not contain enough sample.\n\nEither condition–too thick or too thin–can lead to erroneous results, particularly false negatives. Here (image 1) the smear in the center is of the proper thickness. Hold a smear about 3 to 4 inches over news-print, if you are just able to read the print, the smear is of proper thickness.\n\n1. **For urine**: Make a smear of the deposit from **three** centrifuged **early morning urine** sediments.\n\nAllow to air dry and heat fix the specimen. The use of an electric slide warmer is usually the preferred method for heat-fixing smears.  An alternate method of heat-fixing is to pass the dried slide, smear facing upward, 2 to 3 times through the blue cone of a burner flame.\n\n![Fig. Heat Fixation of smear (Upper: using electric heater, lower: using burner) - Fig. Heat Fixation of smear (Upper: using electric heater, lower: using burner)](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FHeat-fixation-of-smear-240x300.jpg)Figure: Fig. Heat Fixation of smear (Upper: using electric heater, lower: using burner)\n\n1. **Staining Method**\n\n- Place the fixed smear on a staining rack and flood slide with **rhodamine-auramine for 15 minutes**. Do not let the surface dry. (*Note: Fluorochrome dyes used for acid-fast staining include Auramine O, and Auramine O in combination with another fluorochrome, Rhodamine B).*\n- Wash off the stain with distilled water.\n- Flood slide with fluorescent **decolorizer (i.e acid-alcohol)for2-3 minutes**.\n- **Rinse** thoroughly with distilled water.\n- Flood slide with **potassium permanganate for 3-4 minutes**. Do not allow slides to dry.\n- **Rinse** thoroughly with **distilled water** and air dry.\n- Examine microscopically under the same light source as used for fluorescent microscopy (i.e. a K530 excitation filter and a BG 12 barrier or G-365 excitation filter and an LP 420 barrier filter). Slides can be screened on high power (400X) and verified under oil immersion.\n\n## Result and Interpretation\n\n- **Positive Test** – Acid-fast organisms fluoresce reddish-orange against a dark background.\n- **Negative Test** – Non-acid-fast organisms will not fluoresce or may appear a pale yellow, quite distinct from the bright acid-fast organisms.\n\n![Patterns for Examining the slide - Patterns for Examining the slide](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FPatterns-for-Examining-the-slide-300x188.jpg)Figure: Patterns for Examining the slide\n\n**Number of Fields to Examine:**\n\nThe minimum number of fields to examine before reporting a smear as negative for acid-fast organisms.\n\nFinal magnification (the objective lens magnification multiplied by the eyepiece magnification) Vs. Number of slides\n\n1. *200x: 30*\n2. *250x: 30*\n3. *400x: 55*\n4. *450x: 70*\n\n**Reporting of smears**\n\n- If Fluorescent AFB are seen, report the smear as AFB positive, and give an indication of the number of bacilli present in plus signs (+ to +++)\n- If no fluorescent rods are seen, report the smear as **NO AFB seen.**\n\n![Examining and Reporting Acid Fastness - Examining and Reporting Acid fastness](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FExamining-and-reporting-Acid-fastness.jpg)Figure: Examining and Reporting Acid fastness\n\n**Fluorochrome AFB Grading Scale (WHO\u002FIUATLD):**\n\n| Grade | Number of AFB Seen | Magnification | Report As |\n| --- | --- | --- | --- |\n| No AFB | 0 in minimum fields examined | 200–450x | Negative — No AFB seen |\n| Scanty | 1–9 per 100 fields | 200–250x | Report exact count; request repeat specimen |\n| 1+ | 10–99 per 100 fields | 200–250x | Positive 1+ |\n| 2+ | 1–10 per field (50 fields) | 200–250x | Positive 2+ |\n| 3+ | >10 per field (20 fields) | 200–250x | Positive 3+ |\n\n**Note:** The fluorochrome grading scale uses the same WHO\u002FIUATLD criteria as Ziehl-Neelsen  but fields are examined at lower magnification (200–250x for fluorochrome vs 1,000x oil immersion for ZN), which is why fluorochrome screening is significantly faster. For the full ZN grading discussion including clinical implications of each grade, see: [Ziehl-Neelsen Staining: Principle, Procedure, Grading, and Interpretation](\u002Fziehl-neelsen-technique-principle-procedure-reporting\u002F)\n\n## Advantages\n\n1. **Faster screening** of smears than with ZN- Smear can be examined rapidly using a **40x objective** or **25x objective**. This increases the chances of detecting AFB especially when they are few.\n2. \\~10% more sensitive than ZN.\n3. Does not require the use of oil immersion.\n4. No heat is required for staining.\n\n![Fig:Fluorochrome stained smear showing numerous green acid fast bacilli - Fig: Fluorochrome stained smear showing numerous green acid-fast bacilli](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FFluorochrome-stained-smear-showing-numerous-green-acid-fast-bacilli-300x198.jpg)Figure: Fig: Fluorochrome stained smear showing numerous green acid-fast bacilli\n\n## Limitations of Fluorochrome Staining\n\n1. A fluorescent microscope is required, which may be readily unavailable and also costly **(limitation for developing countries)**\n\n2. A positive staining reaction provides presumptive evidence of the presence of mycobacteria. A negative staining reaction does not indicate that the specimen will be culturally negative. Therefore, **cultural methods must be employed.**\n\n3. Reagents like auramine-rhodamine are **possible carcinogens**, acid –alcohol and potassium permanganate is also a **strong irritant** to skin, eyes, and respiratory system. Caution is required while handling and staining using such reagents.\n\n4. Most strains of rapid growers may not appear fluorescent.\n\n5. It is recommended that all negative fluorescent smears **be confirmed with Ziehl-Neelsen stain**; at least 100 fields should be examined before being reported as negative.\\\n   \\\n   **Key practical rule — the two-step workflow:**\n\n   - **Positive auramine-rhodamine result** → confirm with ZN staining of the same slide (fluorochrome artefacts can occasionally give false-positive results)\n   - **Negative auramine-rhodamine result** → examine minimum required fields before reporting; high clinical suspicion warrants ZN confirmation and repeat specimen\n\n   The fluorochrome result is a screen; ZN confirmation is the standard. Both together give maximum sensitivity and specificity.\n\n6. **Excessive exposure** to the counterstain may result in a **loss of brilliance** of the fluorescing organism.\n\n7. Stained smears should be observed within 24 hours of staining because of the possibility of fluorescence fading.\n\n## Key Exam Facts in One Table\n\n| Feature | Detail |\n| --- | --- |\n| Also known as | Truant method of staining |\n| Primary stain | Auramine O + Rhodamine B (fluorochrome dyes) |\n| Decolouriser | 0.5% acid-alcohol |\n| Counterstain | 0.5% potassium permanganate (renders background non-fluorescent) |\n| AFB appearance | Bright yellow-orange rods against dark background |\n| Screening magnification | 250x or 400x (vs 1,000x oil immersion for ZN) |\n| Sensitivity vs ZN | \\~10% more sensitive |\n| WHO recommendation | Preferred method where fluorescence microscope available |\n| Positive confirmation | Confirm with ZN staining of same slide |\n| Negative confirmation | Examine minimum required fields; high suspicion → ZN + repeat specimen |\n| Grading scale | Same WHO\u002FIUATLD criteria as ZN (Scanty, 1+, 2+, 3+) |\n| Modified method | 0.5% H₂SO₄ decolouriser detects *Cryptosporidium*, *Cyclospora*, *Nocardia* |\n| Key limitation | Fluorescence microscope required; artefacts possible; results fade within 24 hours |\n| Safety | Auramine-rhodamine — possible carcinogen; handle in BSC with gloves |\n\n**References**\n\n1. Hooja, S., Pal, N., Malhotra, B., Goyal, S., Kumar, V., & Vyas, L. (2011). Comparison of Ziehl Neelsen & Auramine O staining methods on direct and concentrated smears in clinical specimens. *The Indian journal of tuberculosis*, *58*(2), 72–76.\n2. Tarhan, G., Ordulu, L., Gümüşlü, F., Ceyhan, I., & Cesur, S. (2003). Tüberküloz tanisinda auramine-rhodamine ve Erlich-Ziehl-Neelsen boyama yöntemlerinin karşilaştirilmasi \\[Comparison of auramine-rhodamine and Erlich-Ziehl-Neelsen staining methods for the diagnosis of tuberculosis\\]. *Mikrobiyoloji bulteni*, *37*(2-3), 131–136.\n3. Bayot ML, Mirza TM, Sharma S. Acid Fast Bacteria. \\[Updated 2023 Aug 7\\]. In: StatPearls \\[Internet\\]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: \u003Chttps:\u002F\u002Fwww.ncbi.nlm.nih.gov\u002Fbooks\u002FNBK537121\u002F>",[46,49,52],{"question":47,"answer":48},"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":50,"answer":51},"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":53,"answer":54},"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.",[56],"mycobacteria",[58,66,75,120,127,144,151,157],{"slug":59,"title":60,"description":60,"seoTitle":38,"seoDescription":38,"author":61,"createdDate":62,"lastUpdatedDate":41,"draft":42,"category":63,"image":38,"faq":64,"tags":65},"mycobacterium-tuberculosis-lab-diagnosis","Laboratory Diagnosis of Mycobacterium tuberculosis Infection","Nisha Rijal","2020-05-26","bacteriology",[],[56],{"slug":67,"title":68,"description":69,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":70,"lastUpdatedDate":71,"draft":42,"category":72,"image":38,"faq":73,"tags":74},"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",[],[56],{"slug":76,"title":77,"description":78,"seoTitle":79,"seoDescription":38,"author":39,"createdDate":80,"lastUpdatedDate":81,"draft":42,"category":63,"image":38,"faq":82,"tags":119},"genexpert-mtbrif-assay-principle-procedure-results-interpretations","GeneXpert MTB\u002FRIF: How to Read the Result and What to Do Next","Semi-quantitative grades, probe-level RIF calls, error codes, and the traps: why a \"RIF resistance detected\" result still needs confirmation and why \"not detected\" never rules out TB.","GeneXpert MTB\u002FRIF Assay: Principle, Procedure, Results, and Interpretation","2016-01-04","2026-07-25",[83,86,89,92,95,98,101,104,107,110,113,116],{"question":84,"answer":85},"Does GeneXpert detect isoniazid resistance?","No. The assay reads only the rpoB gene and reports rifampicin resistance. Isoniazid resistance requires a line probe assay, targeted sequencing, or phenotypic DST. Because rifampicin resistance usually co-exists with isoniazid resistance, a positive RIF result is used as a marker for probable MDR-TB, but it is an inference, not a measurement.",{"question":87,"answer":88},"Can GeneXpert replace sputum smear microscopy and culture?","It replaces smear microscopy as the initial diagnostic test under current WHO guidance. It does not replace culture. Culture is still needed for phenotypic drug susceptibility testing, genotyping, detection of non-tuberculous mycobacteria, and confirmation of cure.",{"question":90,"answer":91},"What does \"MTB detected, trace\" mean?","It means the multicopy IS6110 or IS1081 targets were detected but rpoB was essentially unread, so bacillary load is at the very bottom of the assay's range and rifampicin resistance cannot be reported. In children, people living with HIV, and extrapulmonary specimens, trace counts as bacteriological confirmation of TB. In previously treated adults it should be repeated on a fresh specimen, because it may represent residual DNA from cured disease.",{"question":93,"answer":94},"Why does the report say \"very low\" or \"high\"?","That is the semi-quantitative grade, derived from the cycle threshold of the first rpoB probe to bind. It estimates bacillary load, which relates to infectiousness, to how reliable the rifampicin call is, and to the likelihood that a weak positive represents old rather than active disease.",{"question":96,"answer":97},"What is the difference between Invalid and Error?","Invalid means the Sample Processing Control failed: something about the specimen, usually inhibitors or inadequate processing, prevented a trustworthy result. Repeat with a new specimen. Error means the run aborted on an instrument or cartridge fault, most often a failed probe check or a pressure problem. Repeat with a new cartridge.",{"question":99,"answer":100},"Can a GeneXpert result be falsely positive for rifampicin resistance?","Yes. The assay infers resistance from a probe failing to bind, not from reading the mutation, so silent mutations and non-resistance-conferring polymorphisms in the RRDR are reported as resistance. False positives are most common on paucibacillary specimens. This is why a positive result should be confirmed by a line probe assay, targeted sequencing, or phenotypic DST, while treatment is started in parallel.",{"question":102,"answer":103},"Can GeneXpert miss rifampicin resistance?","Yes. Approximately 5% of rifampicin-resistant strains carry mutations outside the 81-bp RRDR. These leave all probes binding normally and are reported as susceptible.",{"question":105,"answer":106},"How long does the GeneXpert MTB\u002FRIF test take?","Under two hours from loading. The standard Xpert MTB\u002FRIF run is about 112 minutes; Xpert Ultra is faster at roughly 65 to 87 minutes. Specimen preparation adds about 15 to 20 minutes before loading.",{"question":108,"answer":109},"Can GeneXpert be used on non-sputum specimens?","Yes. WHO endorses its use on CSF, lymph node aspirate and tissue, gastric aspirate, nasopharyngeal aspirate, and stool, with sensitivity varying by specimen type. It is strongly recommended as the initial test in suspected TB meningitis. Sensitivity is lowest in pleural fluid.",{"question":111,"answer":112},"Can GeneXpert be used to monitor response to treatment?","No. It detects DNA from both living and dead bacilli, so it can remain positive for months in patients who are responding well. Smear microscopy and culture are used for treatment monitoring.",{"question":114,"answer":115},"Does a positive GeneXpert distinguish M. tuberculosis from M. bovis?","No. It detects the M. tuberculosis complex as a group and cannot separate M. tuberculosis, M. bovis, M. africanum, or BCG. Species-level identification requires culture-based methods.",{"question":117,"answer":118},"Is a biological safety cabinet required to run GeneXpert?","Specimen manipulation before the 15-minute inactivation step should be done in a Class II BSC where available. After that step the cartridge is closed and the risk is minimal. WHO permits Xpert testing at the same biosafety level as direct sputum smear microscopy in settings without a BSC.",[56],{"slug":121,"title":122,"description":122,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":123,"lastUpdatedDate":124,"draft":42,"category":63,"image":38,"faq":125,"tags":126},"short-notes-atypical-mycobacterial-infections","Atypical Mycobacterial Infections","2014-11-07","2026-07-04",[],[56],{"slug":128,"title":129,"description":130,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":131,"lastUpdatedDate":132,"draft":42,"category":43,"image":38,"faq":133,"tags":143},"ziehl-neelsen-technique-principle-procedure-reporting","Ziehl-Neelsen Staining: Principle, Procedure, Grading, and Interpretation","The hot ZN acid-fast staining method step by step, why mycolic acid holds carbol fuchsin against acid-alcohol, WHO smear grading from scanty to 3+, and what a negative smear does and does not rule out in TB.","2013-12-06","2026-07-22",[134,137,140],{"question":135,"answer":136},"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":138,"answer":139},"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":141,"answer":142},"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.",[56],{"slug":145,"title":146,"description":146,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":147,"lastUpdatedDate":124,"draft":42,"category":148,"image":38,"faq":149,"tags":150},"key-biochemical-methods-used-to-distinguish-mycobacterial-group","Biochemical Tests to identify Mycobacteria, NTM","2013-07-22","biochemical-tests",[],[56],{"slug":152,"title":153,"description":153,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":154,"lastUpdatedDate":124,"draft":42,"category":63,"image":38,"faq":155,"tags":156},"introduction-transmission-pathogenesis-and-lab-diagnosis-of-leprosy-hansens-disease","Leprosy: Etiology, Pathogenesis, Lab Diagnosis","2012-05-15",[],[56],{"slug":158,"title":159,"description":160,"seoTitle":38,"seoDescription":38,"author":61,"createdDate":161,"lastUpdatedDate":41,"draft":42,"category":63,"image":162,"faq":163,"tags":164},"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",[],[56],[166,172,179,184,188,192,197,202,206,210],{"slug":167,"name":39,"description":168,"image":169,"body":170,"postCount":171},"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":173,"name":174,"description":175,"image":176,"body":177,"postCount":178},"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":180,"name":181,"description":182,"image":38,"body":38,"postCount":183},"sushmita-baniya","Sushmita Baniya","Author \u002F Contributor",32,{"slug":185,"name":186,"description":182,"image":38,"body":38,"postCount":187},"samikshya-acharya","Samikshya Acharya",20,{"slug":189,"name":190,"description":182,"image":38,"body":38,"postCount":191},"alisha-tripathi","Alisha Tripathi",6,{"slug":193,"name":194,"description":195,"image":38,"body":38,"postCount":196},"aastha-shrestha","Aastha Shrestha"," Author \u002F Contributor",9,{"slug":198,"name":199,"description":200,"image":38,"body":38,"postCount":201},"guest-author","Guest Author","Guest Author \u002F Contributor",2,{"slug":203,"name":204,"description":182,"image":38,"body":38,"postCount":205},"srijana-khanal","Srijana Khanal",18,{"slug":207,"name":208,"description":200,"image":38,"body":38,"postCount":209},"dr-poonam-acharya","Dr. Poonam Acharya",1,{"slug":211,"name":61,"description":182,"image":38,"body":212,"postCount":213},"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]