BB Ch 12; microbiological quality control

Question 1

define gnotobiotic

Answer 1

have a completely defined microflora

Question 2

define SPF

Answer 2

free from infection with a defined list of infectious agents

Question 3

what are the characteristics used to distinguish pathogenic bacteria and fungi from commensal and autochthonous (indigenous)

Answer 3

their ability to cross anatomic and biochemical barriers to establish themselves in niches devoid of other microorganisms

Question 4

ls it some common bacterial pathogens found in rodent species

Answer 4

Salmonella, mycoplasma pulmonis, helicobacter hepaticus, clostridium piliforme

Question 5

list some opportunistic bacterial pathogens found in rodent species

Answer 5

Pseudomonas aeruginosa, B hemolytic streptococci, Staphylococcus aureus, and Pneumocystis

Question 6

what does SOPF stand for? why is it significant?

Answer 6

specific opportunistic pathogen free. free of opportunistic as well as primary pathogens

Question 7

what is the most effective “gold standard” for rederivation of mice?

Answer 7

embryo transfer, the zona pellucida that surrounds embryos and oocytes excludes pathogens

Question 8

food is typically heated to what temp during pelleting?

Answer 8

75-80 C

Question 9

gamma radiation of food is performed using what source?

Answer 9

cobalt 60 source

Question 10

UV radiation of supplies is done at what wavelength?

Answer 10

210-328 nm, peak DNA absorption is 260nm

Question 11

limitations of UV radiation

Answer 11

UV light source loses intensity or becomes dirty and by the presence of particles and dissolved organics in water. does not pass through solid objects

Question 12

limitations of radiosensitivity?

Answer 12

correlates with genome volume and the ability of the organism to repair DNA damage. small viruses such as parvoviruses are highly resistant to UV and gamma irradiation, as are bacterial spores, protozoan cysts, and vegetative bacteria with highly efficient DNA repair.

Question 13

give some examples of denaturant disinfectants?

Answer 13

quaternary ammonium compounds
phenolics
alcohols

Question 14

give some examples of reactant disinfectants?

Answer 14

aldehydes

ethylene oxide

Question 15

give some examples of oxidant disinfectants?

Answer 15

halogens (chlorine bleach, chlorine dioxide)

peroxygens (vapor phase H2O2, virkon S)

Question 16

mechanism of action for phenolics and quaternary ammonium compounds

Answer 16

disrupt lipid membranes, potent against lipophilic (paramyxo, corona, arena) viruses than hydrophilic

Question 17

mechanism of action of oxidants?

Answer 17

attack all organic compounds, inactivate hydrophilic (picorna, parvo) as well as lipophilic viruses

Question 18

what tests are traditionally used to screen rodent biologicals for rodent viruses? and how is this test performed?

Answer 18

mouse or rat antibody production tests
SPF rodents are inoculated with the test article orally and parenterally, held in isolation for a month, and tested by serology for antibodies to rodent viruses.

Question 19

define direct health monitoring

Answer 19

testing is performed on specimens from the principle/resident colony

Question 20

define indirect health monitoring

Answer 20

testing is performed on dedicated animals that have been exposed to the principle/resident colony or their bedding or environment

Question 21

what is considered the gold standard for detecting helminth infections?

Answer 21

low power dissecting microscopy of macerated GI tract, ie direct microscopic examination

Question 22

what is the sensitivity of gross and microscopic examination of lesions?

Answer 22

low, lesions must be present at high concentrations to be observed

Question 23

efficacy of transimission of mite infections via soiled bedding?

Answer 23

mites are NOT transmitted well between animals via soiled bedding

Question 24

MacConkey’s agar contains what additive, and this additive has what effect?

Answer 24

crystal violet and bile salts, inhibit growth of gram + bacteria while allowing most gram - bacteria to grow

Question 25

what enrichment broth is used to recover salmonella from feces or the intestinal tract?

Answer 25

selenite broth

Question 26

what are the conditions that most cultures are incubated at?

Answer 26

aerobically at 35-37C

Question 27

what are some fastidious lab animal pathogens for which other identification methods are most ideal?

Answer 27

Mycoplasma pulmonis, Helicobacter, Clostridium pilliforme, CAR bacillus, Pneumocystis.
PCR and/or serology are more often used

Question 28

what are two ways to identify a bacterial colony from culture?

Answer 28

create a biochemical profile

PCR

Question 29

what does MALDI-TOF MS stand for

Answer 29

matrix assisted laser desorption ionization time of flight mass spectrometry

Question 30

what does MFIA stand for, how does the test work?

Answer 30

multiplexed fluorometric immunoassay, antigen is covalently coupled to beads of a specific color, antigen-antibody complexes form during serum incubation, incubated with biotinylated anti-species immunoglobulin. Lastly, the complex is incubated with there is a phycoerythrin streptavidin conjugate for color development

Question 31

define sensitivity

Answer 31

the number of known positive samples that are classified correctly

Question 32

define specificity

Answer 32

the number of known negative samples that are classified correctly

Question 33

if you increase the cutoff values what changes about specificty or sensitivity

Answer 33

you increase the specificity (decreases number of false positives, however increase the number of false negatives)

Question 34

if you decrease the cutoff values, what changes about the specificity or sensitivity?

Answer 34

you increase the sensitivity (increase number of false positives)

Question 35

a high specificity test is used to detect pathogens with a high/low prevalence?

Answer 35

low/rare pathogens (avoid false positives)

Question 36

a high sensitivity test is used to detect pathogens with a high/low prevalence?

Answer 36

high/common pathogens (avoid false negatives)

Question 37

define analytical specificity

Answer 37

the ability of an assay to distinguish target from nontarget analytes

Question 38

define a selective assay

Answer 38

one with the capacity to resist matrix-mediated effects, such as sample mediated inhibition of PCR, nonspecific binding of serum antibodies

Question 39

define an inclusive assay

Answer 39

detect related organisms of interest

Question 40

define an exclusive assay

Answer 40

describes a test able to differentiate an infectious agent from others that are closely related

Question 41

what is the component of the assay for a serologic test that determines the analytical specifity of that assay?

Answer 41

the antigen bound to the immunoassay solid phase

Question 42

what is the component of the assay for PCR that determines the analytical specificity of that assay?

Answer 42

the genomic sequence to which the primers anneal

Question 43

formula for positive predictive value

Answer 43

TP/(TP+FP)

Question 44

how do you calculate the KP (number of known positives)

Answer 44

number tested * prevalence

Question 45

how do you calculate the KN (number of known negatives)

Answer 45

tested- KP or (# tested * (1-prevalence))

Question 46

how do you calculate the number of tested positives

Answer 46

KP*sensitivity

Question 47

how do you calculate the number of false positives

Answer 47

KN* (1-specificity) or KP-true positives

Question 48

how do you calculate the number of tested negatives

Answer 48

KN*specificity