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my cobacterium
| Question | Answer |
|---|---|
| What are the general characteristic of Mycobacteria? | -obligate anaerobes 5-10% CO2 -slow growing 2-6 weeks -non spore-forming, non motile -slender, slightly curved or straight rods *high lipid content on cell wall so they are acid fast |
| How are Mycobacteria identified? | based on growth rate, colony morphology, incubation temperature, and biochemical reaction |
| How should expectorated sputum be collected and handled? | Spontaneous expectorated sputum • 5-10 ml of specimen with little oral flora • Best done 3-5 consecutive days • Early morning specimen |
| How should aerosol induced sputum be collected and handled? | Aerosol induced sputum • NaCl mist-nebulizer. This is done by respiratory therapy • Early morning specimen is best • Advantages: 1. Fewer contaminates 2. Faster growing |
| How should gastric lavage be collected and handled? | 1. Done 1/2 hr. after aerosol-induced sputum - collected to obtain swallowed sputum 2. Overnight fast 3. gastric + induced sputum combo yield more positive cultures than alone 4. Disadvantage: frequently contaminated with commensal Mycobacteria |
| How should urine be collected and handled? | Urine 1. Early morning clean catch 2. 3-5 specimens 3. 24 hour collection is not recommended |
| How should stool be collected? | Stool 1. Naturally passed 2. 3-5 consecutive days |
| How should Blood be collected? | 1. Sterile technique for draw 2. Special blood culture bottles (BACTEC or BACT/Alert) – continuous monitoring 3. Isolator lysis-centrifugation system 4. Sodium heparin tubes collected and sent to Mayo within 48 hours |
| How should tissue specimen be collected and handled? | Tissue Specimen 1. Grind 2. Incubate cutaneous tissue cultures at 35oC and 30oC |
| How should sterile body fluid be collected and handled? | 1. Sterile container or capped syringe, preferred 2. Anticoagulant could be added to fluids that may clot (citrate or heparin) 3. Swab is Discouraged, unless E-swab |
| What is Digestion of non-sterile specimens? | Digestion: • breaks up mucous and cells in specimen to liberate A.F.B. |
| What is the purpose of timed decontamination process of non-sterile specimens? | • Kills normal flora and contaminating bacteria without harming A.F.B. • Use strong acidic or alkaline solutions - the lipid content of A.F.B. cell walls protects them from extremes of pH • Decontamination increases the chances of recovering A.F.B. |
| What is the procedure of the traditional method of Digesting and decontaminating specimen? | NaOH 4% is the "traditional“ method to digest and decontaminate • Time carefully; needs to stand for 15 minutes • Neutralize sediments (phenol red indicator • 5% Oxalic acid - useful to decontaminate specimen contaminated with Pseudomonas (CF patients) |
| What is the procedure of the gold standard method of Digesting and decontaminating specimen? | NALC-NaOH 2% "gold standard“ • N-acetyl-L-cysteine is the mucolytic agent • NaOH 2% is the decontaminant • Neutralize with phosphate buffer • If after using the NALC method a specimen is still viscous a small amount of crystalline NACL can be added |
| What are properties of A.F.B (acid fast bacteria)? | • Cell walls have high lipid content enabling A.F.B. to retain stain when decolorized with acid alcohol • Stain morphology - slender, curved, pointed and beaded |
| What is the procedure to stain AFB using carbolfuchsin | 1. Carbolfuchsin - Fuchsin with phenol a) Primary stain: Carbolfuchsin b) Decolorizer: acid alcohol c) Counter stain: methylene blue d) Two techniques: 1. Ziehl-Nielsen "hot stain“ 2. Kinyoun "cold stain“ e) A.F.B. stain red; other bacteria stain blue |
| What is the procedure to stain AFB using fluorochrome dye? | Fluorochrome dye a) Primary stains: 1. Auramine 2. Rhodamine b) Decolorizer: acid alcohol c) Counter stain: potassium permanganate d) Screen slides using fluorescent scope on 25 or 40 objective e) A.F.B. will stain yellow against black background |
| What are the advantages of using fluorochrome dye? | 1. More fields scanned in less time 2. Yield higher number of positive stains 3. Questionable smears can be overlaid using Carbolfuchsin method |
| What is the disadvantage of using fluorochrome dye? | Dead mycobacteria will stain with fluorochrome method |
| Why are Stain results important? | 1. Early detection means early treatment 2. Monitor response to drug therapy 3. Must be paired with culture • 10,000 AFB/ml = positive smear • Sensitivity of 22-80% |
| What are Non-selective mycobacteria media? | 1. Egg based media 2.Agar based media |
| What are broth media used for mycobacteria? | 1.Middlebrook 7H9 2.Blood culture systems to detect A.F. • BACTEC systems • BacT/Alert system • Septi-Chek bottles • Isolator Lysis-Centrifugation system 3. MGIT 960 system: Modified 7H9, non-radiometric microbial detection system |
| What is used to interpret cultures? | 1. Testing of bottles -Culture held six weeks - Bottles are continuously monitored and automatically flagged as positive when growth is detected 2. Primary L-J slants- checked weekly |
| Preliminary identification made based on what? | Colony morphology: smooth or rough ▪ Rate of growth: rapid grower (colonies in <5 days) ▪ Optimal temperature of growth ▪ Pigment production: buff vs. yellow ▪ Photoreactivity |
| Name some mycobacteria and their optimal growth temperatures | - most grow at 35° - 42°-M. xenopi, - 30-32°-M. marinum, M. ulcerans, M. haemophilum |
| What are the different type of photo reactivity? | ▪ Photochromogens: produce pigment when exposed to light ▪ Scotochromogens: produce pigment in light or dark ▪ Non-chromogens: No pigment formation |
| How is Niacin accumulation tested? (media used & interpretation) | ■ an LJ slant with >50 colonies that are 3 weeks old need to be tested for niacin. ■ If niacin is present a yellow color will develop. |
| What is the Nitrate reduction test? | Test if bacteria conduct nitrate reduction, if they have the gene for the nitrate reductase enzyme. Red is positive for nitrite. 1: nitrate reduction to nitrite 2: nitrate reduction to ammonia 3: no reduction of nitrate |
Created by:
lemon8
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