Lab Diagnosis

Question 1

direct specimen

Answer 1

no normal flora present; collected from normally sterile tissue and body fluids (lung, liver, blood, CSF)

Question 2

indirect specimen

Answer 2

no normal flora present at site BUT specimen passes through a site with normal flora during collection, becoming contaminated (vomit, urine, sputum)

Question 3

specimen from site with normal flora

Answer 3

pathogen and normal flora are mixed at infection site (throat swab, stool, etc.); selective media for culture of pathogen or discounting normal flora

Question 4

specimen transport

Answer 4

buffered liquid or semi-solid media with minimal nutrients, prevent drying, maintain neutral pH, minimize contaminant growth

Question 5

anaerobic cultures

Answer 5

specimens with normally sterile sites (wound, CSF, joint fluid; NO sputum, urine, stool)

Question 6

anaerobic culture transport

Answer 6

tissue in dry container with no oxygen, liquid in container with special medium

Question 7

light microscopy used for _

Answer 7

gram stain, acid-fast stain, decolorize, counterstain

Question 8

fluorescence microscopy used for _

Answer 8

auramine-rhodamine stain, mycobacteria in sputum (TB)

Question 9

gram stain

Answer 9

differentiate gram positive and negative

Question 10

acid fast stain

Answer 10

used when gram stain doesn’t work due to mycolic acid; confirms auramine-rhodamine test for mycobacteria

Question 11

pink/red acid-fast

Answer 11

acid-fast positive (mycobacteria)

Question 12

blue acid-fast

Answer 12

acid-fast negative (not mycobacteria)

Question 13

nucleic acid amplification tests (NAAT)

Answer 13

PCR, transcription-mediated amplification

Question 14

when are NAATs done?

Answer 14

before culture, directly on specimen

Question 15

PCR used for _

Answer 15

c. diff, mycobacterium tuberculosis, bordetella pertussis, chlamydophila pneumoniae, mycoplasma pneumoniae

Question 16

c. diff PCR

Answer 16

specimen is diarrhea sample

Question 17

m. tuberculosis PCR

Answer 17

specimen is sputum sample

Question 18

pertussis, atypical pneumonia PCRs

Answer 18

specimen is nasal swab

Question 19

transcription mediated amplification (TMA)

Answer 19

based on repeated amplification of ribosomal RNA of microorganism

Question 20

TMA used for _

Answer 20

neisseria gonorrheae or chlamydia trachomatis (genital swab or urine)

Question 21

When is TMA done?

Answer 21

directly on specimen, before culture

Question 22

immunological methods

Answer 22

antigen detection and detection of Ab against pathogen (serology)

Question 23

antigen detection mechanisms

Answer 23

enzyme immunoassay, latex agglutination

Question 24

enzyme immunoassays used for _

Answer 24

group A strep (throat swab), E.coli (stool), legionella pneumophila (urine)

Question 25

latex agglutination

Answer 25

antibody on beads

Question 26

latex agglutination used for _

Answer 26

staph. aureus AFTER culturing from specimen

Question 27

serology done at LSUHS

Answer 27

t. pallidum (syphilis)

Question 28

bacterial cultures

Answer 28

agar plates, blood culture bottles, MGIT tubes

Question 29

EMB agar

Answer 29

only gram-negative will grow

Question 30

blood agar

Answer 30

many things grow

Question 31

chocolate agar

Answer 31

many things grow, including haemophilus (flu)

Question 32

hektoen enteric agar

Answer 32

salmonella and shigella (e. coli)

Question 33

example of bacteria on EMB agar

Answer 33

k. pneumoniae

Question 34

example of bacteria on chocolate agar

Answer 34

streptococcus pneumoniae, s. aureus, k. pneumoniae, h. influenzae

Question 35

example of bacteria on blood agar

Answer 35

streptococcus pneumoniae, s. aureus, k. pneumoniae

Question 36

hemolysis

Answer 36

some bacteria secrete toxins that can lyse RBCs which can be detected on a blood agar plate

Question 37

complete hemolysis

Answer 37

beta

Question 38

partial hemolysis

Answer 38

alpha

Question 39

no hemolysis

Answer 39

gamma

Question 40

hektoen enteric agar for stool

Answer 40

salmonella or shigella

Question 41

MacConkey/sorbitol agar for stool

Answer 41

distinguishes e. coli's

Question 42

campy agar for stool

Answer 42

campylobacter

Question 43

MacConkey agar mechanism

Answer 43

based on ability to ferment lactose --> bacteria that can will turn agar pink, such as e. coli

Question 44

usual contaminant in blood cultures

Answer 44

staph. epidermidis (USE ANTISEPTIC WIPES!!)

Question 45

which will almost always represent a true infection when found in blood culture?

Answer 45

s. aureus, e. coli, streptococcus pneumoniae, pseudomonas aeruginosa

Question 46

mycobacteria growth indicator tube (MGIT)

Answer 46

several specimen types (sputum, pleural fluid), treated with chemicals to inactivate normal flora; growth detected by UV light

Question 47

tests for identification of organisms after culture

Answer 47

manual (spot) tests or automated systems

Question 48

spot tests

Answer 48

catalase, coagulase, oxidase

Question 49

catalase spot tests

Answer 49

all staphylococci will be positive and all streptococci will be negative

Question 50

coagulase spot tests

Answer 50

s. aureus is positive and s. epidermidis is negative

Question 51

oxidase spot tests

Answer 51

neisseria and pseudomonas are positive

Question 52

automated systems at LSUHS

Answer 52

mass spec, microscan

Question 53

mass spectrometry

Answer 53

ID takes two minutes; ID by analysis of ribosomal proteins-high abundance

Question 54

does mass spec give any info on antibiotic susceptibility?

Answer 54

no

Question 55

microscan system

Answer 55

multiwell plates each having a different ingredient (carbohydrate, protein, or nitrogen compound) and will test which ones the bacterium can metabolize

Question 56

Which plates will test for antibiotic sensitivity in the microscan system?

Answer 56

gram(-) and gram(+); NOT yeast