BB Ch 12; microbiological quality control Flashcards
define gnotobiotic
have a completely defined microflora
define SPF
free from infection with a defined list of infectious agents
what are the characteristics used to distinguish pathogenic bacteria and fungi from commensal and autochthonous (indigenous)
their ability to cross anatomic and biochemical barriers to establish themselves in niches devoid of other microorganisms
ls it some common bacterial pathogens found in rodent species
Salmonella, mycoplasma pulmonis, helicobacter hepaticus, clostridium piliforme
list some opportunistic bacterial pathogens found in rodent species
Pseudomonas aeruginosa, B hemolytic streptococci, Staphylococcus aureus, and Pneumocystis
what does SOPF stand for? why is it significant?
specific opportunistic pathogen free. free of opportunistic as well as primary pathogens
what is the most effective “gold standard” for rederivation of mice?
embryo transfer, the zona pellucida that surrounds embryos and oocytes excludes pathogens
food is typically heated to what temp during pelleting?
75-80 C
gamma radiation of food is performed using what source?
cobalt 60 source
UV radiation of supplies is done at what wavelength?
210-328 nm, peak DNA absorption is 260nm
limitations of UV radiation
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
limitations of radiosensitivity?
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.
give some examples of denaturant disinfectants?
quaternary ammonium compounds
phenolics
alcohols
give some examples of reactant disinfectants?
aldehydes
ethylene oxide
give some examples of oxidant disinfectants?
halogens (chlorine bleach, chlorine dioxide)
peroxygens (vapor phase H2O2, virkon S)
mechanism of action for phenolics and quaternary ammonium compounds
disrupt lipid membranes, potent against lipophilic (paramyxo, corona, arena) viruses than hydrophilic
mechanism of action of oxidants?
attack all organic compounds, inactivate hydrophilic (picorna, parvo) as well as lipophilic viruses
what tests are traditionally used to screen rodent biologicals for rodent viruses? and how is this test performed?
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.
define direct health monitoring
testing is performed on specimens from the principle/resident colony
define indirect health monitoring
testing is performed on dedicated animals that have been exposed to the principle/resident colony or their bedding or environment
what is considered the gold standard for detecting helminth infections?
low power dissecting microscopy of macerated GI tract, ie direct microscopic examination
what is the sensitivity of gross and microscopic examination of lesions?
low, lesions must be present at high concentrations to be observed
efficacy of transimission of mite infections via soiled bedding?
mites are NOT transmitted well between animals via soiled bedding
MacConkey’s agar contains what additive, and this additive has what effect?
crystal violet and bile salts, inhibit growth of gram + bacteria while allowing most gram - bacteria to grow
what enrichment broth is used to recover salmonella from feces or the intestinal tract?
selenite broth
what are the conditions that most cultures are incubated at?
aerobically at 35-37C
what are some fastidious lab animal pathogens for which other identification methods are most ideal?
Mycoplasma pulmonis, Helicobacter, Clostridium pilliforme, CAR bacillus, Pneumocystis.
PCR and/or serology are more often used
what are two ways to identify a bacterial colony from culture?
create a biochemical profile
PCR
what does MALDI-TOF MS stand for
matrix assisted laser desorption ionization time of flight mass spectrometry
what does MFIA stand for, how does the test work?
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
define sensitivity
the number of known positive samples that are classified correctly
define specificity
the number of known negative samples that are classified correctly
if you increase the cutoff values what changes about specificty or sensitivity
you increase the specificity (decreases number of false positives, however increase the number of false negatives)
if you decrease the cutoff values, what changes about the specificity or sensitivity?
you increase the sensitivity (increase number of false positives)
a high specificity test is used to detect pathogens with a high/low prevalence?
low/rare pathogens (avoid false positives)
a high sensitivity test is used to detect pathogens with a high/low prevalence?
high/common pathogens (avoid false negatives)
define analytical specificity
the ability of an assay to distinguish target from nontarget analytes
define a selective assay
one with the capacity to resist matrix-mediated effects, such as sample mediated inhibition of PCR, nonspecific binding of serum antibodies
define an inclusive assay
detect related organisms of interest
define an exclusive assay
describes a test able to differentiate an infectious agent from others that are closely related
what is the component of the assay for a serologic test that determines the analytical specifity of that assay?
the antigen bound to the immunoassay solid phase
what is the component of the assay for PCR that determines the analytical specificity of that assay?
the genomic sequence to which the primers anneal
formula for positive predictive value
TP/(TP+FP)
how do you calculate the KP (number of known positives)
number tested * prevalence
how do you calculate the KN (number of known negatives)
tested- KP or (# tested * (1-prevalence))
how do you calculate the number of tested positives
KP*sensitivity
how do you calculate the number of false positives
KN* (1-specificity) or KP-true positives
how do you calculate the number of tested negatives
KN*specificity
