L2. Medical Microbiology and infectious diseases Flashcards
1
Q
Define taxonomy
A
science of classifying organisms
2
Q
two reasons why taxonomy is required?
A
- to identify organisms
- to have a universal name for organism
3
Q
what kingdom do bacteria fall under?
A
there is no kingdom assigned; domain is bacteria
4
Q
species (euk definition)
A
group of closely related organisms that breed among themselves
5
Q
species (prok definition)
A
population of cells with similar characterisitcs
6
Q
define clone
A
population of cells derived from a single cell
7
Q
define strain
A
genetically different cells within a clone!
8
Q
what are the characteristics that are used to identify bacteria? (9)
A
- cell morphology
- growth requirements
- nutritional requirements
- colony morphology
- biochemical tests
- serological tests
- phage typing
- genomics
- MALDI - TOF MS
9
Q
define bacteria growth requirements
A
classification based on interaction w/ oxygen (ex anaerobic etc)
10
Q
define bacteria nutritional requirements
A
could be fastidious in nature (growth only on SPECIAL nutrients only!)
11
Q
define biochemical tests used to identify bacteria
A
presence of particular enzymes (ex Uricase!)
12
Q
define serological tests used to identify bacteria
A
classification based on antigen - antibody interactions of a given bacteria
13
Q
define phage typing
A
classification of bacteria based on sensitivity to bacteriophages!
14
Q
define MALDI - TOF MS
A
a special type of mass spectrometry used to identify bacteria!
15
Q
what is the size of a coccus?
A
1 micrometer
16
Q
what is the formula for compound microscope magnification?
A
total magnification = objective lens x ocular lens
17
Q
Why are immersion oils used to examine bacterial smears?
A
to prevent the bending of light that may lead to missing the small high magnification lens used in a microscope (i.e. not being able to see the bacteria)
18
Q
what is brightfield microscopy used for?
A
to be better able to observe dark objects
19
Q
what is darkfield microscopy used for?
A
to be better able to observe light objects
20
Q
what is phase contrast microscopy used for?
A
to be better able to observe unstained objects (ex flagella on slide 19)
21
Q
what is fluorescence microscopy used for?
A
to be better able to observe the shape of the organism
22
Q
what is electron microscope used for?
A
smaller electron particles allow for greater resolution when viewing microbes under the microscope
23
Q
What is the difference b/w transmission and scanning electron microscope?
A
transmission - to observe components inside the cell
scanning - to observe components on the surface of the cell
24
Q
reasons for heat fixing microbes to the slide (3)
A
- to attach the to slide
- to kill them
- to allow the stain to penetrate better
25
what is the charge of basic vs acidic dyes?
basic - cation
| acidic - anion
26
what is negative staining?
staining the background instead of cell
27
what is india ink used for?
a type of negative staining used to identify whether an organisms has a gelatinous capsule or not (can identify cryptococus spp which can cause cryptococcus meningitis)
28
what is a mordant used for?
to hold/fix the stain or coat the specimen to enlarge it
29
what stain is gram positive vs negative?
positive - purple
| negative - pink
30
which type of bacteria based on gram stain is more resistant to antibiotics?
gram negative
31
what is an acid fast stain?
it is used to identify cells that can retain a basic stain in the presence of acid alcohol - mycobacterium (addition of carbol fuchsin - appear red!)
non acid - fast cells appear blue (addition of methylene blue - appear blue!)
32
what diseases can mycobacterium cause? (2)
TB and leprosy
33
what is negative staining useful for?
for visualizing capsules
34
how do you stain endospores?
though the application of heat to help the stain penetrate
35
how do you stain flagella?
through the addition of a mordant which expands it till it is wide enough to see
36
what is the fluorescent stain - acridine orange used to stain? (2)
bacteria and fungi
37
what is the fluorescent stain - calcofluor used to stain?
the chitin in fungi cell walls
38
what is the difference b/w obligate vs aerotolerant anaerobes?
obligate - can't survive in oxygen rich environments
aerotolerant - can survive in oxygen rich environments
both - can only use non oxygen based methods of using/producing energy
39
what are microaerophiles?
organisms that require lower levels of oxygen than atmospheric levels
40
what is the growth requirement for pseudomonas aeruginosa?
its a strict aerobe (require oxygen for growth)
41
which enzymes are used by bacteria to destroy naturally occurring reactive oxygen species? (2)
superoxide dismutase
catalase
42
what makes strict anaerobes intolerant to oxygen?
lack of superoxide dismutase/ catalase
43
how do facultative/ aerotolerant anaerobes tolerate oxygen/ dispose of peroxide?
using enzyme peroxidase
44
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what is a capnophile?
give examples (3)
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require carbon dioxide rich environments ex strep pneumoniae, hemophilus influenzae, neisseria gonorrhoeae
45
example of a microaerophilic bacteria?
campylobacters
46
define chemotrophs
organisms that use chemical compounds as their energy source
47
define phototrophs
organisms that use light as their energy source
48
define chemolithotrophs
organisms that use inorganic chemicals as their energy source
49
define chemoorganotrophs
organisms that use organic chemicals as their energy source
50
define photoautotrophs
carbon source is carbon dioxide
51
define photoheterotrophs
carbon source is organic compounds ?
52
which important bacteria has not yet been cultured in artificial media?
treponema pallidum
53
what does fastidious mean?
when bacteria have many growth requirements they are called fastidious
54
what most artificial media based on?
soluble extracts of animal tissue treated w/ proteases
55
name an example of protease used to form artificial media
peptone!!!!
56
what is an important nutrient requirement in order to grow of the fastidious legionella?
media supplemented w/ IRON and L-cyteine!
57
what class of bacteria does legionella fall under?
respiratory pathogens
58
what are the different type of organic growth factors used for bacteria? (4)
vitamins
amino acids
purines
pyrimidines
59
define sterile
no living microbes
60
define inoculum
introduction of microbes into medium
61
define culture
microbes that are growing in the culture medium
62
define contaminants
key word here is "unwanted" microbes
63
why do we use aseptic techniques? (2)
- to prevent contamination of culture
| - to prevent infection to the lab worker
64
what is the primary method to sterilize loops and straight wires?
- held into a bunsen burner until they glow red hot
| - held vertically in the outer blue part of the flame
65
what is a bacti incinerator
next gen heat based sterilization instrument that doesn't have a flame
66
how do you inoculate a swab of a bacterial specimen?
- rub the entire surface of the swab onto a small area of the agar plate
- spread the sample over the surface of the agar to form isolated colonies
67
what is "plating out"? why is it necessary?
definition: technique used to spread the sample over the surface to form isolated colonies
- importance: to isolate and identify the bacteria causing pathology from the normal bacteria
68
why is it necessary to centrifuge fluid specimens of bacteria?
this allows bacterial specimens to be concentrated for appropriate identification through plating out!
69
what are the advantages of using agar (a polysacc compound) for growing microbes? (3)
- provides a structure for growth of microbes
- NOT metabolized by bacteria!
- solidifies at 40 deg and liquefies at 100 deg
70
what are main types of culture media?
1. Basic: simple media that don't require special nutrients (nutrient agar)
2. Enriched: additional nutrients such as blood, vitamins are added for "fastidious" organisms (blood agar, chocolate agar)
3. Selective: contain substances that only promote the growth of specific microorganisms (in med: pathogens) and suppress the rest (MacConkey agar)
4. differential: aka indicator media - different types of bacteria produce different colored colonies - helps in identification
5. enrichment: encourages growth of desired media (selenite broth)
6. Transport: media that keeps bacteria alive but stops their multiplication (Stuart's medium)
71
what does chocolate agar contain?
definitely not chocolate
-> contains lysed red blood cells!
(on a diff note vampires may consider this chocolate)
72
what is blood agar used for?
frequently used for throat cultures - useful to differentiate different species of streptococci
73
what is MacConkey agar used for?
selective AND differential media used to isolate enteric bacteria and differentiate them based on lactose fermentation ability
lactose fermenters - pink
non lactose fermenters - orange
74
What is TCBS (Thiosulfate-citrate-bile salts-sucrose) agar used for?
to isolate vibrio cholerae species!
75
Lecture objective
Relate the importance of aseptic technique to specimen collection
Describe the methods used to identify bacteria from a clinical isolate in the clinical laboratory.
Assess the effectiveness and limitations of staining procedures and use of microscopy in the identification of bacteria in the microbiology laboratory
Differentiate between nonselective, selective, and differential growth media and their uses in culturing bacteria.
Evaluate the sensitivity of molecular techniques in the identification of microbial pathogens.
76
what are checkerboard matrix systems used for in microbiology?
(self definition) A very extensive system of identification of bacteria wherein each bacteria is identified based on their ability to react to a set of substances only
-> this is represented numerically
77
what are common serological tests used to identify bacterial species? (3)
- slide agglutination
- western blot
- phage typing
78
What is slide agglutination?
used to detect if certain antigens (that belong to the bacteria being tested for) exist in a sample or not
the swab can be used to collect the sample (saliva from the back of a patients throat)
if the antigen is present in the saliva sample, then agglutination will occur
-> in a strep test this is usually indicated by the occurrence of 2 lines on the strep test "strip" (one line = negative for strep)
79
What is a commonly used molecular technique to identify the presence of a bacteria of interest in a sample?
DNA chip - contains complementary dna to bacteria of interest -> if bacteria of interest's dna is present in sample, it will bind to chip and emit florescence!
80
why is MALDI - TOF useful for identifying bacteria?
generates a unique "fingerprint" spectra for each microorganisms that can be quickly used to identify different bacteria!
81
what are advantages of using molecular methods? (3)
high sensitivity (can detect the presence of even a single organism!)
high specificty (specific genotypes and drug resistances can be determined; virulence can be predicted)
quick (vs traditional methods)
82
what are the disadvantages of using molecular methods? (5)
technically demanding (need specialized technicians?)
high specificity: must have good clinical data to support infection before testing is initiated
new organisms NOT detected!
mixed cultures can create problems
high sensitivity: the results aren't necessarily clinically relevant
