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Medical Microbiology Flashcards

(109 cards)

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1
Q

What are psychrophiles

A

Microorganisms that can grow in extremely cold temperatures (-20)

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2
Q

How many chromosomes do prokaryotes have?

A

1

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3
Q

What type of ribosomes do prokaryotes have?

A

70s

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4
Q

What type of ribosomes do eukaryotes have?

A

80s

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5
Q

How big are prokaryote cells?

A

1 - 10 um

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6
Q

How big are eukaryote cells?

A

10 - 100 um

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7
Q

What are the 6 shapes of bacteria?

A 
Coccus
Bacillus
Spirochete
Spirilium
Coccobacillus
Vibrio
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8
Q

Give an example of a coccus bacteria?

A

Streptococcus

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9
Q

Give an example of a vibrio bacteria

A

Vibrio cholerae

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10
Q

Give an example of a bacillus bacteria?

A

P aeruginosa

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11
Q

Give an example of a coccobacillus?

A

Chlamydia

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12
Q

What are the three growth types for cocci?

A

Chain
Packet
Cluster

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13
Q

What are the 4 components used in the gram stain?

A

Crystal violet primary stain
Iodine mordant
Alcohol decolouriser
Safarin counterstain

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14
Q

What is the primary stain in gram staining and what does it do?

A

Crystal violet dye - stains all cells purple

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15
Q

What is the mordant used in gram staining and what does it do?

A

Iodine. It forms insoluble complexes with the crystal violet dye

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16
Q

What is the decolouriser used in gram staining and what does it do?

A

Removes crystal violet iodine complexes from gram negative but not gram positive

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17
Q

What is the counterstain used in gram staining and what does it do?

A

Safarin. It stains both cell types pink

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18
Q

What does the peptidoglycan layer contain in gram positive cells?

A

Teichoic acids and lipteichoic acids

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19
Q

What is the role of the s layer in bacterial cells?

A

To hide from the immune system

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20
Q

What does the outer membrane of gram negative bacteria contain?

A

Porins and endotoxin. Endotoxin activates the innate immune system.

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21
Q

Where is the s layer found on gram postive and gram negative bacterial cells?

A

Peptidoglycan layer of gram positives. Outer membrane of gram negatives.

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22
Q

What is peptidoglycan made up of?

A

Repeating structure of 2 alternating sugars (nam and nag) crosslinked by peptides

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23
Q

Which enzymes are involved in peptidoglycan synthesis?

A

Transglycosylases which connect sugars and transpeptidases which form peptide crosslinks

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24
Q

How do beta lactams inhibit cell wall synthesis?

A

Inhibit transpeptidase reaction

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25
How does vancomycin inhibit cell wall synthesis?
Binds to d-ala-d-ala to stop cross linking
26
What is the glycocalyx? Give examples
Generic name for extracellular polymers. Capsule and slime layer
27
What is the capsule used for?
Biofilm production
28
What is the slime layer used for?
Movement
29
What are 3 types of pili?
Fimbriae Type 4 pili Sex pili
30
What are fimbriae?
Short pili which are used to attach bacteria to surfaces. They are made up of helically arranged proteins tipped with adhesive proteins.
31
What are type 4 pili used for?
Movement
32
How do cells move?
Runs and tumbles
33
When a cell is near an attractant, how do its runs and tumbles change?
Tumbles are less frequent. Runs are longer.
34
Which type of bacteria form endospores and in what situation?
Gram positive bacteria form endospores when nutrients run out
35
What are the 4 arrangements of flagella?
Monotichous Lophotrichous Amphitrichous Petritrichous
36
What are the 6 shapes of bacterial cells, give examples of each
``` Coccus (streptococci) Bacillus (p aeruginosa) Coccobacillus (chlamydia) Vibrio (vibrio cholerae) Spirilium Spirochete ```
37
What are the 3 growth types for cocci?
Chain Packet Cluster
38
Halophile
Requires salt to grow
39
Halotolerant
Can grow in mild salt concentrations but grow best without salt
40
Osmophiles
Can survive in high sugar environments
41
Xerophiles
Can survive in dry environments (usually fungi)
42
Neutrophile
Grows best between pH 5.4 and 8.5
43
Psychotrophs
Optimum is around room temperature but can grow in the fridge
44
Mesophiles
Optimum between 20 and 40 degrees (all animal pathogens)
45
Thermophiles
Optimum 50 to 80 degrees
46
Obligate aerobe
Has SOD and catalase | Requires oxygen
47
Facultative anaerobe
Has SOD and catalase Does not require oxygen but grows best when oxygen is available S aureus Fermentation when oxygen is unavailable
48
Aerotolerant anaerobe
Has SOD but not catalase Grows equally well with or without oxygen Streptococcus pyogenes
49
Strict anaerobe
Has neither SOD nor catalase | Some tolerate oxygen, some killed by it
50
Microaerophile
Has SOD and some have catalase | Grows best in low oxygen conditions
51
Aerobe
An organism which uses oxygen as the terminal electron acceptor in a respiratory chain
52
Can aerobes carry out fermentation?
No
53
What charge does a biofilm matrix have?
Negative
54
What are persister cells?
They are found in biofilms. They neither grow nor die in the presence of antimicrobials. They are multi drug tolerant (MDT)
55
Why is natural flora important?
Prevents growth of pathogenic flora by competition and amensalism (secretion of inhibitory substances)
56
Factors determining microbiome
``` Host physiology Host pathobiology Immune system Lifestyle Genotype Environment ```
57
How is flora on the skin limited?
Dessication Lack of nutrients Disinfectant secretions (lysozyme which cleaves peptidoglycan and cathelicidin which forms pores)
58
What is the microbiome of the oropharynx?
HACEK organisms | Like elevated CO2 and are slow growing
59
How are microbes removed from the respiratory tract?
Lysozyme Macrophages Mucus Ciliated cells
60
What does the the colon microbiome secrete?
Vitamin k and B
61
What are antimicrobial secretions?
Lysozymes Lactoferrin Cathelicidin Defensins
62
What is found in granules of NK cells?
Perforin and granzyme
63
ID50
Infectious dose 50. Number of cells that results in disease for 50% of population
64
How do pathogens attach to host cells?
Fimbriae | Capsule
65
How do microbes cross the mucosa?
The use M cells
66
Name the 4 classes of s aureus virulence factors
Adhesins Invasins Siderophores Haemolysins
67
Name the 2 invasins in s aureus
Staphylokinase | Hyaluronidase
68
What does staphylokinase do?
Cleaves plasminogen to plasmin which degrades fibrin clots. Cleaves IgG. Cleaves C3b which inhibits phagocytosis
69
What does hyaluronidase do?
Lyses hyaluronic acid found in connective tissue which causes tissue breakdown
70
What 3 substances does s aureus use to evade the immune system?
Coagulase Staphyloxanthin S aureus protein A
71
What does coagulase do?
Reacts with thrombin forming staphylothrombin which cleaves fibrinogen to fibrin. S aureus coated with fibrin can evade the immune system
72
What does staphyloxanthin do?
Antioxidant that protects against ROS
73
What does s aureus protein do?
Binds to Fc portion of IgG and prevents phagocytosis by preventing opsonisation
74
What is PVL?
S aureus toxin which is cytotoxic to WBC
75
Name 3 s aureus toxins
Pyrogenic Exfoliating Membrane damaging
76
What does pyrogenic toxin cause?
Toxic shock syndrome
77
How does superantigen cause toxic shock syndrome?
More T cells activated so more cytokines activated
78
What does exfoliating toxin do?
Cleaves cadherin which forms junctions between skin cells. Leads to skin peeling
79
Infectivity
Propensity for transmission. Measured by secondary attack rate in a household
80
Secondary attack rate
Rates of infection among individuals exposed to a first case
81
Pathogenicity
Measure of disease causing propensity (ID50)
82
Virulence
Propensity to cause severe disease. Measured by fatality ratio or LD50
83
Incubation period
Time between exposure and onset of symptoms
84
What are the 5 Is?
``` Inoculation Isolation Incubation Inspection Identification ```
85
Chocolate agar
Blood heated to release nutrients
86
Name the 5 selective media
``` Phenylethyl alcohol Blood Macconkeys EMB Baird parker ```
87
Phenylethyl alcohol agar
Selects out gram negatives by reversibly inhibiting their dna synthesis
88
Baird parker agar
Selects staphylococci | Contains egg yolk
89
EMB media
Lactose fermenting - metal sheen | Non lactose fermenting - colourless
90
MacConkeys
Selects gram negatives (bile salts inhibit growth of gram positives) Lactose fermenting - produces acid so indicator turns red Non lactose fermenting - colourless
91
Capnophile
Likes elevated CO2 conc
92
Alpha haemolysis
Lots of haemolysis
93
Beta haemolysis
Some haemolysis | Green halo
94
What are 6 biochemical tests?
``` Catalase Oxidase Indole Urease Coagulase Carbohydrate fermenting ```
95
Oxidase test
Cytochrome c oxidase (purple when positive)
96
Indole test
Tests for tryptophanase which turns tryptophan into pyruvate, indole and urea. DMAB turns red when indole present
97
Urease test
Urease hydrolyses urea to ammonia which increases pH. Indicator turns pink
98
Coagulase test
Mix with plasma, look for clot
99
Carbohydrate fermentation
Positive - acid or gas production Acid turns indicator yellow Gas in collected in upturned durham tube
100
What are the cons of traditional methods?
Organism must be able to be cultured in vitro (obligate intracellular cannot) Slow growing Poor discrimination between similar microbes
101
What immunological methods are used?
Agglutination Immunofluorescence ELISA Immunodiffusion assays
102
Direct immunofluorescence
Antigen from patient | Fluorescent antigen from lab
103
Indirect immunofluorescence
Antigen from lab mixed with patient serum. Antibody against patient antibody fluoresces
104
What are the molecular methods used?
PCR and real time PCR Nucleic acid probes RFLP Plasmid fingerprinting
105
What are the 4 different types of CD4 T cells?
Th1 Th2 Th17 TFH
106
What is the role of Th1 cells?
They recognise mycobacteria derived antigens on macrophages and secrete cytokines which help overcome lysosome binding
107
What is the role of Th2 response?
Deals with infections at mucosal surfaces, parasite infections and allergies
108
Th17 response
Deals with extracellular bacteria and fungi
109
TFH response
Helps B cells produce antibody

Biomedical Sciences (6 decks)

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