Biosecurity Flashcards
What is the most dependable approach for eliminating infections with unrecognized and known pathogens?
Rederivation
What has fostering Cesarian-section derived pups onto gnoto or SPF dams largely been replaced by?
Embryo transfer into pseudopregnant females.
How does embryo transfer protect against vertical transmission?
Zona pellucida surrounding embryo and oocytes excludes pathogens. Risk of infecting recipient females minimized by washing of embryos.
Vertical transmission has been demonstrated for viruses and bacteria capable of colonizing the uterus.
How does neonatal transfer of pups work?
Within several days of parturition. Pups transferred to SPF dams after being immersed in a disinfectant. Does not require euthanasia of dam.
Can fostering be cross-species?
Yes. Gerbils onto rats and mice, with gerbil pup survival higher for those weaned onto mice.
How are pinworm and mite infestations typically treated?
Chemotherapy - Avermectins and benzimidazoles. Risk of toxicity from crossing BBB in young, genetic background, or GEM.
For which agents has antibiotic treatment been efficacious?
P. pneumotropica and H. hepaticus. They do not survive long ex vivo and are unlikely to infect host after treatment is stopped.
Burnout is historically applied to what type of agents? Is burnout recommended?
Nonpersistent infections of immunocompetent hosts with enveloped viruses. Sendai, SDAV
Not recommended due to increasing number of genetically modified rodents and unknown immune competence and atypical response to infection.
Why is MNV not susceptible to burnout?
Shed indefinitely
What is the principal reservoirs of adventitious infection for SPF animals?
Infected animals of the same or related species.
Which agent is notable exception to most pathogens being efficiently transmitted via direct contact?
Lactate dehydrogenase-elevating virus (LDV)
Generally, what type of pathogens do not transmit well in soiled bedding?
Host-adapted bacteria, enveloped viruses, and organisms that are unstable ex vivo.
Diet has been linked to outbreaks of what pathogens? (2) How can this be reduced?
MPV and mouse rotavirus
Gamma irradiation of diets
What the erythrocyte parasites of mice and rats?
M: Eperythrozoon coccoides
R: Mycoplasma haemofelis
What agents are generally resistant to inactivation?
Bacterial spores, free-living stages of parasites (pinworm eggs and protozoan cysts), and hydrophilic nonenveloped viruses.
What are two physical processes for disinfection?
Autoclaving and electromagnetic irradiation
What temps are foods heated to during pelleting? What does this result in?
Heated to 75-80C. Substantially reduces bacterial count but not sufficient to inactivate thermostable pathogens.
Why is gamma irradiation of diets preferred to autoclave?
Autoclaving causes a greater reduction in nutritional content of feed. Also difficult to achieve uniform steam penetration and temperature throughout a load.
How is gamma radiation typically emitted? What does this create at the microscopic level?
From a cobalt-60 source. Creates breakages in the nuclei acid of microorganisms.
What wavelengths is UV? Where on the spectrum is the peak of UV bactericidal activity? How does UV function in inactivation?
UV = 210-328 nm. Bactericidal activity is maximal near peak of DNA absorption at 260 nm.
UV does not have sufficient energy to cause ionization. Damages DNA but does not cause DNA breaks. Instead, produces thiamine and other pyrimidine dimers.
How does UV and gamma radiation interact with solid objects?
Gamma radiation passes through solid objects, UV does not. UV only for disinfection of surfaces and drinking water.
What factors reduce the efficacy of UV sterilization of water?
Intensity of UV source, cleanliness of source, and particles or dissolved organics in water.
Why is UV irradiation an attractive option for water disinfection?
Viricidal. In contrast to chlorination, does not convert organic precursors into potentially carcinogenic trihalomethanes.
Generally, what is the radiosensitivity of organisms related to? What are examples of resistant agents?
Correlates with genome volume and ability of an organism to repair DNA damage. Small viruses, such as parvoviruses, bacterial spores, protozoan cysts, and vegetative bacteria with highly efficient DNA repair capabilities are resistant.
Describe depth versus membrane filters.
Depth filters entrap and adsorb, membrane filters exclude particles according to pore site. Depth filters have no meaningful pore size, and thus are given nominal ratings to indicate the efficiency with which they retain particles of a particular size.
What are the three classifications of filtration size? What can each catch?
Microfiltration = 0.1-10 um
Ultrafiltration = 1k - 1000k molecular weight
Reverse osmosis = low molecular weight molecules, including salts.
Microfiltration retains bacteria, fungi, and their spores, but only ultrafiltration or RO can remove viruses.
What are the characteristics of waterborne viruses?
Small to medium sizes, nonenveloped, and shed in feces.
How do denaturants, reactants, and oxidants act?
Denaturants - Disrupt protein or lipid structures
Reactants - Form or break covalent bonds
Oxidants.
What class of chemical disinfectants are most commonly used? Why? What are examples?
Oxidants, as they are generally considered more effective than reactants and denaturants for inactivating resistant pathogens such as spore-forming bacteria, nonenveloped viruses, and free-living forms of parasites.
Can disinfectants be layered?
Yes, especially when disinfection requirements are especially strict.
What agents are phenolics and quarternary ammonium compounds effective against?
Lipophilic, enveloped viruses
What agents are oxidants effective against?
All organic compounds, inactivating hydrophilic and lipophilic viruses
How does pH and temperature affect chlorine’s function?
Increasing the pH or temp of the water reduces chlorine concentration of hypochlorous acid in favor of hypochlorite ion, which is less biocidal
Where do the majority of mycoplasma found in cell culture originate from?
Human, porcine, and bovine origin.
