tb_sunday Flashcards
partially acid fast organisms that might give a false+ auramine stain
rhodococcus, nocardia, legionella, crypto cysts, isosproa, cyclospora, microsporidia
number of fields that must be read on ZN smear
300
Mycobacti organisms that show cording?
M. tb & M. kansasii
Name organism that is a scotochromogen at 37C but photochromogen at 25C?
M. szulgai
Describe handling of gastric specimens?
process in 4h, or add 100mg sodium carbonate to neutralize acidity
List unsat specimens
pooled sputum or urine, nonsterile containers, waxy containers or dry swabs
Reagents used for digestion of normal flora?
NALC, NaOH
Mucolytic agent
N-acetyl-L-cysteine, digests sputum and allows NaOH to be used a lower concentration
Decontaminating agent
4% NaOH
Purpose of sodium citrate
binds heavy metals present in specimens to inactivate acetylcysteine.
Decontaminating agent for Pseudomonas
%5 oxalic acid
Holding time for LJ slants?
37^C, 6-8w
Mycobacteria characteristics
not readily gram-stained, nonmotile rods, high lipid content, hydrophobic surface
Differentiate M. tb from M. bovis
M.bovis: susceptible to T2H & niacin -, pza-, nitrate-
NTMS?
photo, scoto, nonphoto, rapid growers
Genera containing mycolic acid
Corynebacterium, Gordona, Mycobacterium, Nocardia, Rhodococcus, Tsukamurella
acid-fastness describes which characteristic?
waxy envelope and presence of mycolic acid (lipid)
Culture used for M. leprae
none. Alright, armadillos and can be injected into footpads of mice.
Saprophytic mycobacterium
M. gordonae, M. pheli, smegmatis
Media growth for semi-quantitative catalase test?
LJ
mycobacti distinguised by salt tolerance?
rapid growers, fortuitum, chelonae, flavescens++, trivale
media growth for niacin and nitrate test and age requirement of culture.
LJ nitrate : 3-5 wLj niacin: 18-28 day growth
MTB organisms
tb, bovis, africanum, microti, canetti
HPLC IDs mycobacti based on which characteristic?
mycolic acids in cell wall
Differentiate M. simiae from MTB complex?
M. simiae: SQ cat+, pigment+, catalae+ at 68^C, nitrate-, accuprobe and NAAT
Rate of air flow in BSC?
70% recirculated air, inward face velocity of 75ft/min
BacTec 960 MGIT detects growth by which method?
reduced oxygen produces fluorescence due to organism growth.
Incubation temperature for skin-specific mycobacti
30C (marinum, ulcerans, haemophilum)
RFLP enzyme?
restriction endonuclease
procedure used to reduce tb exposure?
open safety cups under BSC
sensitivity of PCR using smear+ organism
> 95%
genera that contain mycolic acid
mycobacteria, rhodococcus, nocardia
Partially acid fast organisms
rhodococcus, nocardia, gordona
organisms with thin braching filaments
nocardia
Cell component used to identify mycobacti using HPLC?
mycolic acid
length of time required to hold negative organisms
6-8w,+4 if smear+
Biochems for M. tb
niacin, nitrate, citrate
TB positive for growth on MAC without crystal violet?
group 4 rapid growers
biochems used to differentiate 2 chelonae subspp. & M. kansasii from M. fortuitum?
5% NaCl
niacin test summary
4 w old LJ culture+cyanogen bromide &amine=yellow (+)
SQ catalase test summary
2w LJ (NOT BAP) culture+Tw80&30H2O2, measure height of bubbles (>45mm ,45mm)
> 45mm SQ catalase organisms
M. kansasii, simiae, scotochromogens, nonphotochromogenic saprophytes
growth on MAC without crystal violet
m. fortuitum and m. phlei
QC+ for heat-stable catalase test
M. kansasii+
iron uptake organisms
m. fortuitum+, chelonae-
tellurite reduction test
MAC+, black precipitate
nitrate reduction organisms+
mtb, ks, sz, sm, fo
mycobacteria tuberculosis characteristics:
slow growth, nonphoto, nude color dry crumbly morphology, nitrate+, niacin+, catalase 68-
M. xenopi characteristics in culture
hot water, G at 42^C, 10x magnifaction show birds nest-like growth
mycobacti responsible for AIDS patients
MAC
3 mycobacti that grow at 30^C
haemophilum, ulcerans, marinum HUM
ABCs for mycobacti
streptomycin, isoniazid, rifampin, ethambutol, pyrazinamide
Optimal growth temperature for rapid growers?
28^C
GenProbe Accuprobe: type of reading and organisms tested?
chemiluminisecence/ M. tb, MAC, M. gord, M. kan, cocci
BacTec MGIT PANTA
polymyxin B, amphotericin b, nalidixic acid, trimethoprim, azolcillin
pigment in mycobacti?
carotenoids
MGIT growth supplement
albumin-protective agent to bind free fatty acid, dextrose is energy source, catalsase destroys toxic peroxides in media, oleic acid involved in metabolism
MGIT growth explanation
oxygen sensitive fluorescent compound suppressed by high oxygen concentration dissolved in 7H9 broth. As bacteria grow and consume oxygen, suppression released and fluorescence detected.
NaCl 5% growth
flavescens and triviale
describe accuprobe (genprobe) assay
tubes labeled with chemiluminiscent ssDNA probe complementary to rRNA of target organism forming DNA_RNA hybrid.
Name acceptable tb specimens
Sputum: 3 separate samples, from am collections. 5 ml/each.Urine: 2 ml, am samples, transport to lab in 30 minBlood: 10ml use DuPont isolator tube at RTGastric: 5-10 Ml from fasting patient, transport in 4h or add sodium carbonateStool: sterile container, only AIDS patients
Tb SOC
Early am sputum or aerosol collection
Why unsat pooled specimens?
- Contamination increased
2. Positive sample may be diluted by negative sample
Compounds used to neutralize gastric lavage specimens
Sodium carbonate
10% tri sodium phosphate
Crystalline di sodium phosphate
3 Anticoagulants that don’t inhibit acid fast bacilli
CitrateHeparinAmmonium oxalate
+- for 68 catalase test
+M. fortuitum, -M tuberculosis
3 staining procedures for acid fast bacilli
ZnKinyounRhodamone-aura mine
Hazards of cyanogen bromide (niacin test)
Volatile and toxic
Gives off cyanide gas
Impure CB decomposes and explodes
Suitable disinfectants for tb?
70% ethyl alcohol
Phenolic soap
Sodium hypochlorite
Formaldehyde 3-8%
Preferred media for isoniazid resistant m tb?
Middle brook 7h11 because it contains casein hydrolysate to improve strain reccoery
Unsuitable disinfectant for tb?
Quaternary ammonium compounds
Requirements to identify mtb
Cellular and colonial characteristics, rate of growth, niacin, nitrate, 68 catalase-
3 Sputum methods reagents acceptable for recovery of m tb
NalcNaoh
Zephiran
tri sodium phosphate
Describe xenopi culture characteristics
Slow growth
Circular colonies
Filamentous extensions on cornmeal agar
Mycobacterium cutaneous lesions secondary to post surgical wound infections, trauma or needle injections caused by:
M fortuitum chelonae complex
Recovery of m marinum and m ulcer ans enhanced by
Incubation at 30c
Tellurite reduction test positive for
Rapid growers and Mac
Factors affecting photochromogenicity
Oxygen
Age of culture
Exposure to light1 hr
Crowding in culture
3 d arylsulfatase positive organisms
Xenopi (@42C) and Fortuitum
BACTEC 460TB media used in machine
12B vials use 7H12 broth. 7h12 broth has ABCs and c14 labeled palmitic acid
M bovis biochemical tests
Niacin weak/negative
Nitrate reduction
Catalase inactivated at 68
T2H sensitivity
Bactec MGIT 960 and BACTEC 460TB advantages over conventional media
Reduced time from 19 d to 8d. Bactec used for susceptibility testingAutomated monitorLarge inoculum and liquid media increase sensitivity
BACTEC 460TB GI positive reads?
10
BACTEC 460TB disadvantages?
Radioactive material
Expensive inst reqd
Not possible to examine colonial morphology
Possible cross contamination if needle heater fails
Tween hydrolysis test helpful for identification of:
Scotochromogenic and nonphotochromigenic