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Principles of infectious disease > Final > Flashcards

Final Flashcards

1
Q

What is a reservoir?

A

the reservoir of an infectious agent is the habitat in which the agent lives, grows, and multiplies

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2
Q

How do you neutralize a reservoir?

A
  • remove infected individuals (testing + slaughtering those who found to be infected)
  • Mass therapy (treatment of possibly infected herd without testing to see if infected or not)
  • Environmental manipulation (break chain of transmission between portal of exit of infected host and susceptible host by reducing survival of agent in vector or vehicles)
  • Reduce contact potential
  • Protection against portals of entry
  • Increasing host resistance
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3
Q

What are some methods of vector control?

A
  • Source reduction
  • Biological control (use natural enemies)
  • Chemical controls (insecticides)
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4
Q

What are some methods of reducing contact potential?

A
  • isolation (of animals known to be contagious)
  • Quarantine (of those who have been exposed)
  • Population reduction (culling)
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5
Q

What is chemoprophylaxis?

A

use of antimicrobial drugs. Attempts to prevent infection or reduce the severity of the disease

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6
Q

What does an immunization do?

A
  • protect susceptible individuals from infection or disease

- prevent transmission of infectious agents by creating an immune population

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7
Q

What are the features of a good vaccine?

A
  • safe to use
  • effective against diverse strains of same pathogen
  • Few side effects
  • Give long lasting, appropriate protection
  • low in cost
  • stable with long shelf life
  • easy to administer
  • inexpensive
  • benefit outweighs risk
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8
Q

What is herd immunity?

A

a form of immunity that occurs when the vaccination of a significant portion of a population provides a measure of protection for individuals who have not developed immunity.

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9
Q

What are the OIE guidelines for establishing an animal disease control program?

A
  1. Rationale for establishing a disease control program
  2. Strategic goal and objectives
  3. Program planning
  4. Implementation
  5. Monitoring, evaluation and review (go to 2 and repeat.)
    - - diagnostic capability
    - - vaccination and control measures
    - - Tracability
    - - Regional cooperation
    - - Social participation
    - - Role of research in support of disease control programme
    - - Training and capacity building
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10
Q

What info must be provided for Rationale for establishing a disease control program?

A
  • disease situation
  • impact of the disease
  • identify level of interest and involvement of stakeholders
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11
Q

What is the distribution of TGE?

A

reported in USA, the americas, europe, and many parts of asia primarily in the northern hemisphere

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12
Q

What does DIVA stand for?

A

differentiating infected from Vaccinated Animals

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13
Q

What are the typical steps of outbreak investigation?

A
  • preparation for field work
  • coordination with public health competent authorities in case of zoonosis
  • confirmation of the report triggering the investigation
  • confirmation of diagnosis
  • epidemiological follow up and tracing
  • collection an analysis of data including the animals involved and the spatial and temporal distribution
  • implementation of control and preventative measures
  • documentation and reporting
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14
Q

What is an infected premises?

A

premises where a presumptive positive case or confirmed case exists based on laboratory results, compatible clinical signs, case definition, and international standards

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15
Q

What is a contact premises?

A

premises with susceptible animals that may have been exposed to the FAD agent, either directly or indirectly, including but not limited to exposure to animals, animal products, fomites, or people from infected premises.

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16
Q

What is an infected zone?

A

zone immediately surrounding infected premises

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17
Q

What is a buffer zone?

A

zone that immediately surrounds and infected zone or a contact premises

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18
Q

What is a control area?

A

consists of an infected zone and a buffer zone

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19
Q

What is a surveilance zone?

A

zone outside and along the border of the control area

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20
Q

What is a free area?

A

area not included in any control area

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21
Q

What is a vaccination zone?

A

emergency vaccination zone classified as either a containment vaccination zone (typically inside a control area) or a protection vaccination zone (typically outside a control area). This may be a secondary zone designation

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22
Q

What causes a localized emergence of a zoonosis?

A
  • encroachment into wildlife habitat
  • increased contact with wildlife
  • wildlife hunting and trade
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23
Q

What causes pre-emergence “spill over”?

A
  • introduction of livestock
  • increased human pop.
  • deforestation and land use change
  • biodiversity of wildlife hosts and their pathogens
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24
Q

Who is involved in the collaboration of global early warning system for major animal diseases including zoonoses?

A
  • FAO (food and agriculture organization of the united nations) - animal disease info system
  • OIE (world organization for animal health) - world animal health info database
  • WHO (world health organization) - global health atlas
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25
Q

What are the objectives of control of infectious diseases in wildlife?

A
  • primarily to protect human health against zoonoses in wildlife
  • prevent diseases in the wildlife from being transmitted
  • Protect wildlife from certain destructive diseases
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26
Q

How do you prevent transmission of infectious diseases from wildlife to livestock?

A
  • separate livestock from wildlife
  • vector control
  • vaccination of livestock
  • surveillance and risk assessment
  • antemortem diagnostic tests
  • Necropsy
  • Wildlife population control
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27
Q

How do you perform disease control in wildlife?

A
  • burning and burying of carcasses
  • disinfection of water holes
  • remote vaccination by darts, bio-bullets, baits
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28
Q

How do bacteria increase in numbers?

A

Binary fission - a simple asexual process

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29
Q

What is generation time?

A

the length of time required for a single bacterial cell to yield two daughter cells

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30
Q

What is generation time influenced by?

A

both genetic and environmental factors

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31
Q

What is required for bacterial growth?

A

appropriate conditions of moisture, pH, temp, osmotic pressure, atmosphere and nutrients are required

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32
Q

What is the range of generation times for bacterial pathogens?

A

less than 30mins to 30 hours

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33
Q

What common bacteria has the shortest generation time under optimal conditions?

A

escherichia coli

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34
Q

What are the phases of the growth curve?

A
  • lag phase
  • log phase
  • stationary phase
  • decline phase
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35
Q

What is lag phase?

A

active metabolism of the cells as they acquire various essential constituents prior to division

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36
Q

what is log phase?

A

binary fission of the young cells results in an exponential increase in numbers

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37
Q

What is Stationary phase

A

exponential growth in a broth culture is limited and eventually ceases as nutrients are depleted and toxic metabolites accumulate in the medium. No net increase in bacterial number

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38
Q

What is Decline phase?

A

old cells die rapidly followed eventually by the younger cells. The resulting rate of cell death is exponential. Abnormally shaped cells, known as involution forms can be seen during the decline phase

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39
Q

What are methods for measurement of cell mass?

A
  • direct physical measurement of dry weight, wet weight, or volume of cells after centrifugation
  • Direct chemical measurement of some chemical component of the cells such as total protein or total DNA
  • Indirect measurement of chemical activity such as rate of O2 production or consumption, CO2 production or consumption, etc.
  • Turbidity measurements employ a variety of instruments to determine the amount of light scattered by a suspension of cells.
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40
Q

How are turbidity measurements performed?

A

employ a variety of instruments to determine the amount of light scattered by a suspension of cells.Particulate objects such as bacteria scatter light in proportion to their numbers. Turbidity or optical density of a suspension of cells is directly related to cell mass or cell number, after construction and calibration of a standard curve. Method is simple and nondestructive but sensitivity limited to about 10 to the 7th cells/mL for most bacteria.

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41
Q

What are the methods of bacterial cell counting?

A
  • direct smear (breed’s method)

- Counting chamber

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42
Q

What is the breed’s method (direct smear) technique?

A

counts carried out on a fixed and stained smear prepared from a defined volume of fluid; 50 microscope fields counted

  • slow and unreliable - can’t differentiate viable from non-viable bacteria
  • traditional method for counting bacteria in milk
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43
Q

What is the counting chamber technique?

A

counts carried out on a fixed volume of bacterial suspension using a calibrated slide
- does not differentiate viable from non-viable bacteria

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44
Q

What is the spread plate technique?

A

following serial ten-fold dilution of bacterial suspension, a fixed volume of each dilution is spread on the surface of agar plates and incubated for 24 - 48hrs.
- colony counts carried out on plates with 30 - 300 colonies after incubation. # of viable organisms in the suspension if calculated and expressed as colony-forming units (CFU)/mL of suspension

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45
Q

What is the pour plate technique?

A

following serial ten-fold dilution of bacterial suspension, 0.1 mL of each dilution is placed in petri dishes and approx. 20mL of molten agar at 45-48 Celsius is added and thoroughly mixed.
- colony counts carried out on plates with 30 - 300 colonies after incubation. # of viable organisms in the suspension if calculated and expressed as colony-forming units (CFU)/mL of suspension

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46
Q

What is the miles-misra technique?

A

Following serial ten fold dilution, 0.002 mL of each dilution is placed on a sector of an agar plate, five dilutions per plate.
- colony counts carried out on plates with 30 - 300 colonies after incubation. average colony count from the 5 drops is used for calculating the number of viable bacterial cells expressed as CFU/mL of fluid

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47
Q

What is the membrane filtration technique?

A

following filtration of a known volume of fluid through a filter of 0.22micrometer pore size, the filter, placed on the surface of an agar plate, is incubated for 24-48hrs
- the number of viable bacteria is expressed as CFU/mL of fluid

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48
Q

What is the opacity tubes technique?

A

the bacterial suspension is matched visually with mcFarland’s standard tubes
- tables indicating the total bacterial cell number/mL equivalent to matching opacities are supplied with the standard tubes

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49
Q

What is the electronic counting technique?

A

electronic counting instruments, such as the coulter counter, when carefully calibrated, give accurate rapid results
- reliability of results is dependant on rigorous quality control. provides total cell count only

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50
Q

What is the real-time PCR technique?

A

the number of bacterial cells in a sample can be qualified based on detection of DNA concentration. For detection of total viable cells, real-time PCR can be used.
- very fast

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51
Q

What are chemoheterotrophes?

A

bacteria that use only organic chemicals as sources of energy and carbon

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52
Q

What are autotrophs?

A
  • self-feeders - making own food by reducing CO2

- inorganic CO2 = carbon source

53
Q

What are photoautotrophs?

A

Autotrophic bacteria that use light as an energy source

eg: green sulfur, purple sulfur, cyanobacteria, algae

54
Q

What are chemoautotrophs?

A

Autotrophic bacteria that use inorganic compounds as an energy source
- eg: archaeobacteria

55
Q

What are heterotrophs?

A

bacteria that use organic compounds as a carbon source. (other-feeders)
- using ready-made organic molecules for food.

56
Q

What are photoheterotrophs?

A

heterotrophic bacteria that use light as an energy source

- eg: purple nonsulfur bacteria, green nonsulfur bacteria

57
Q

What is catabolism and anabolism during chemoheterotrophy?

A

cell oxidizes organic molecules in order to produce energy (catabolism) and then uses the energy to synthesize cellular material from these organic molecules (anabolism)

58
Q

What is heterotrophic metabolism mainly driven by?

A

fermentation and respiration

59
Q

What are the main source of nitrogen in culture? what are they?

A

peptones - mixtures of peptides and amino acids obtained by digestion of meat and other sources of protein, frequently supply other essential nutrients such as phosphate, sulfate, potassium….

60
Q

What are phosphates essential for the production of?

A

nucleic acids and molecules containing energy-rich bonds

61
Q

What are sulfates required for?

A

synthesis f sulfur-containing amino acids, and magnesium, potassium, calcium, and iron are important co-factors for certain enzymes.

62
Q

What is essential for bacterial growth?

A
  • carbon
  • nitrogen (peptones)
  • phosphates
  • sulfates
    trace elements
  • vitamins and other growth factors
63
Q

What are growth factors?

A

small amounts of certain organic compounds that are essential substances that the organism is unable to synthesize from available nutrients
- fulfill specific roles in biosynthesis

64
Q

What are the 3 categories of growth factors? What are they needed for?

A
  • purines and pyrimidines - required for synthesis of nucleic acids
  • Amino acids - required for synthesis of proteins
  • Vitamins - needed as coenzymes and functional groups of enzymes
65
Q

What are some common microbiological media?

A
  • trypticase soy agar (TSA)
  • Blood agar
  • MacConkey agar
66
Q

What is TSA? trypticase soy agar (TSA)

A

a general purpose medium, providing enough nutrients to allow for a wide variety of microorganisms to grow.
made of tryptone, soytone, sodium chloride, and agar

67
Q

What is trypticase soy agar (TSA) used for?

A

a wide range of applications including; culture storage, enumeration (counting), isolation of pure cultures or simply general culture

68
Q

What is blood agar?

A

a general purpose enriched medium often used to:

  • grow fastidious organisms
  • differentiate bacteria based on their hemolytic properties
  • staphylococcus aureus, steptococcus equi, and many more
69
Q

What is MacConkey agar?

A

designed to grow gram-negative bacteria and differentiate lactose fermenters from non-fermenters
- contains blue bile salts (to inhibit most gram-positive bacteria), crystal violet dye (which also inhibits certain gram positive bacteria), neutral red dye (which stains microbes fermenting lactose), lactose and peptone.

70
Q

What color are lactose fermentors in MacConkey agar? What do they do?

A

produce acid and lowers pH of medium –> RED/PINK colored colonies
eg: e. coli (lac +ve)

71
Q

What color are non-lactose fermentors in MacConkey agar and what do they do?

A

utilize peptones instead , which raises pH of the agar, and leads to formation of WHITE/COLORLESS colonies.
eg: salmonella (Lac -ve)

72
Q

After fixation, crystal violet dye, iodine treatment, decolorization and counter staining with safranin, What colors are gram positive and gram negative bacteria?

A

Gram positive: purple (the color of the first dye used)

Gram negative: pink (the color or the second dye used. –> color washes out of gram negative so can be redyed.

73
Q

What are the four basic steps of a gram stain?

A
  1. applying a primary stain (crystal violet) to heat-fixed smear of a bacterial culture
  2. Addition of a mordant (gram’s iodine)
  3. Rapid decolorization with alcohol or acetone
  4. Counterstaining with safranin or basic fuchsin
74
Q

What is the growth of bacteria by culture influenced by?

A
  • temperature
  • hydrogen ion concentration
  • availability of moisture
  • atmospheric composition
  • osmotic pressure
75
Q

What are mesophiles?

A

organisms with an optimum growth temperature near 37 Celsius (body temp)

76
Q

What are thermophiles?

A

organisms with an optimum growth temp between 45 and 70 celsius

77
Q

What are extreme thermophiles or hyperthermophiles?

A

some archaea with an optimum growth temperature of 80 or higher and a maximum temp as high as 115

78
Q

What are psychrophiles?

A

cold-loving organisms defined by their ability to grow at 0 celsius
- usually has an optimum temp of 10 - 15 celsius

79
Q

What is a psychrotroph?

A

a variant of a psychrophile that grows at 0 celsius but displays an optimum temp in the mesophile range, nearer to room temp(37).

80
Q

What scourge food storage in refrigerators and why?

A

psychrotrophes since they are invariably brought in from their mesophilic habitats and continue to grow in a refrigerated environment where they spoil food.
– grow slower at colder temps!

81
Q

At what pH do most bacteria usually grow?

A

7

82
Q

What are acidophiles?

A

microorganisms that grow at an optimum pH well below neutrality (7)

83
Q

What are neutrophiles?

A

microorganisms that grow best at a neutral pH

84
Q

What are alkaliphiles?

A

microorganisms that grow best under alkaline conditions

85
Q

Why are buffers important to include when growing bacteria?

A

to maintain optimum pH of the medium in the changes milieu of bacterial waste products that accumulate during growth.

86
Q

What is the ability to tolerate desiccation (lack water) determined by?

A

cell wall composition and surrounding microenvironment

87
Q

What results in protoplast formation?

A

changes in cell wall composition, induced by action of lysozyme or of antibiotics such as penicillin

88
Q

What are protoplasts?

A

spherical structures that lack rigidity and are susceptible to osmotic change.

89
Q

True or false? pathogenic bacteria without cell walls (L forms) can replicate, causing chronic or persistent infections

A

True

90
Q

True or false? IN the environment, bacterial cells are usually present in hypotonic solutions and, provided the cell wll is intact, remain in a state of turgor and do not lyse.

A

True

91
Q

In what solution do bacterial cells undergo shrinkage?

A

hypertonic solutions

92
Q

What are obligate aerobes?

A

require O2 for growth; they use O2 as a final electron acceptor in aerobic respiration

93
Q

What are obligate anaerobes?

A

do not need or use O2 as a nutrient. O2 is a toxic substance which either kills or inhibits their growth.
- live by fermentation, anaerobic respiration, bacterial photosynthesis, or methanogenesis

94
Q

What are Facultative anaerobes/aerobes?

A

organisms that can switch between aerobic and anaerobic types of metabolism.

  • no O2 = fermentation or anaerobic respiration
  • presence O2 = aerobic respiration
95
Q

What are aerotolerant anaerobes?

A

bacteria with an exclusively anaerobic (fermentative) type of metabolism but they are insensitive to presence of O2

96
Q

What are Capnophiles?

A

bacteria that grow best in carbon dioxide environments

97
Q

What is the energy generating component of metabolism? energy consuming?

A 
Generating = catabolism
Consuming = anabolism
98
Q

What do catabolic pathways produce?

A

energy as ATP

99
Q

In what two ways can cells produce ATP?

A
  • substrate level phosphorylation

- electron transport phosphorylation

100
Q

What is the process of substrate level phosphorylation? (SLP)/ fermentation

A

simplest/oldest and least evolved way of making ATP.
- ATP made during conversion of an organic molecule from one form to another. Energy released during the conversion is partially conserved during synthesis of the high energy bond of ATP. Occurs during fermentations and respiration (TCA)

101
Q

What is the electron transport phosphorylation (ETP)?

A

takes place during respiration. ETP requires that electrons removed from the substrates be dumped into an electron transport system (ETS) contained within a membrane. Electrons are transferred through the ETS to some final electron acceptor in membranes (like O2 in aerobic respiration)

  • outcome is synthesis of ATP
  • requires less energy than fermentors
102
Q

What are the tests for antibiotic susceptibility?

A
  • kirby bauer plate
  • E test
  • Sensititre
103
Q

The baermann method is used to identify what stage? What is it used for?

A

Larvae - used to isolate nematode larvae from feces or other sample, based on inability of larvae to swim against gravity

104
Q

What does sedimentation allow you to identify?

A

cestodes and trematodes

105
Q

What does fecal flotation allow you to identify?

A

Qualitative: Nematodes, cestodes, trematodes, protazoa
Quantitative: Nematodes, cestodes, protazoa

106
Q

What can be identified using adhesive tape?

A

Nematodes, cestodes

107
Q

What can the Baerman method identify?

A

nematodes

108
Q

What does a direct fecal smear/stain identify?

A

Nematodes, cestodes, protazoa

109
Q

What does a blood smear identify?

A

Nematodes and protazoa (really good for protazoa)

- says later that your ONLY looking for protazoa and microfilaria…

110
Q

True or false? Elisa can identify Nematodes, cestodes, trematodes, and protazoa

A

False. It does not work for trematodes.

111
Q

What do you use quantitative fecal flotation as?

A

a decision tool on whether to treat. –> evaluate control program

112
Q

What does culture to L3 help identify?

A

L3 larvae of nematodes

113
Q

What are the major advantages of PCR?

A

high sensitivity and specificity

114
Q

What is bronchoalveolar lavage? (BAL)

A

washing airways and looking at fluid

115
Q

What is Xenodiagnosis?

A

vector acquisition of parasites

116
Q

What is a cryptopathic effect?

A

refers to damage or morphological changes to host cells during virus invasion

117
Q

What are two methods of detecting viruses by cultivation/isolation?

A
  • cultivation/isolation of viruses in cells/tissue of cells

- inoculation in eggs

118
Q

What is a silent mutation?

A

mutations without apparent effect

- base change in DNA, no change in amino acid or change in amino acid does not change function of protein

119
Q

What is a missense mutation?

A

change in codon –> change in amino acid –> change in protein function

120
Q

What is a nonsense mutation?

A

change in a coding codon to a termination codon, resulting in premature termination

121
Q

What is a frameshift mutation?

A

inserting or deleting number of base pairs other than a multiple of three

122
Q

What is a transformation?

A

acquisition of new genetic markers by incorporation of added DNA

123
Q

What is conjunction?

A

“mating” between two bacteria involving transfer of genetic material

124
Q

What is transduction?

A

transfer of bacterial gene from one to another by a phage

125
Q

What is transposition?

A

movement of a transposon to a new site in the genome

126
Q

What are the methods used to detect and identify microorganisms?

A
  • electrophoresis
  • restriction fragment length polymorphism
  • hybridization and probe
  • nuclear acid amplification - single target
  • protein detection - western blot; proteomics
127
Q

What is electrophoresis?

A

separated in an electrophoretic field

  • negatively charged molecules –> positive end
  • smaller = faster
  • structure: supercoiled > linear > nicked
128
Q

What is restriction fragment length polymorphisms?

A

restriction enzymes: cut DNA at or near specific recognition nucleotide sequences
- sequence specific

129
Q

What is hybridization and probe?

A

denatured, single stranded DNA

  • probe binds to complementary single stranded sequences - Dot, in situ, southern, northern, microarray.
  • Probe = fragment of nucleic acids. labeled, isotope, enzyme, or chemiluminescence. detecting complementary sequences in the samples. high degree of specificity

Principles of infectious disease (1 decks)

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