Medical Microbiology Data Question

Front 1

What are the names for different arrangements and numbers of flagella?

Back 1

Monotrichous - single flagellum

Lophotrichous - multiple, at same spot

Amphitrichous- single flagellum on opposite ends

Peritrichous - project in all directions, E.Coli

Front 2

What is VBNC?

Back 2

Viable but non-culturable

Some die, releasing nutrients

Front 3

What is specific growth rate?

Back 3

meangrowth rate

the number ofgenerations per unit time

u = 1/g

Front 4

What is the doubling time?

Back 4

Mean generation time
Time for all cells to double
g = 1/u

Front 5

What is a mesophile?

Back 5

Optimum growth between 20-45oC

Front 6

What are osmophiles?

Back 6

Able to live in high osmotic pressures - high sugar

Front 7

What are halophiles?

Back 7

Thrive in high salt

Front 8

What are psychrophiles?

Back 8

Optimum 15-20. OK at 0

Front 9

What are psychrotrophs?

Back 9

Optimum room temp.

OK at 5

Front 10

What are thermophiles?

Back 10

Grow 50-80
Survive in higher temps.

Front 11

How are ROS generated?

Back 11

O2 + e− → O2·−
O2·− + e− + 2H+ → H2O2
H2O2 + e− + H+ → H2O + ·OH

Front 12

How are ROS removed?

Back 12

Superoxide Dismutase (SOD)2O2·− + 2H+→ H2O2+ O2

Catalase 2H2O2 → 2H2O + O2

Front 13

How can species be separated based on oxygen-tolerance?

Back 13

Presence of SOD and Catalase - anaerobes have neither

Where does it grow in anaerobic tube? At top, aerobic, etc.

Front 14

What are microaerophiles?

Back 14

Grow best in low 2-10% O2

Helicobacter pylori

Front 15

What is convalescence?

Back 15

Time spent recovering from an illness

Front 16

What are microbes that cause disease in healthy hosts called?

Back 16

Pathogens

Front 17

What are microbes that cause disease in immuno-compromised hosts called?

Back 17

Opportunistic pathogens

e.g. S. aureus

Front 18

What is ID50?

Back 18

Numberof cells administered that result in disease for 50 % of the population

Measure of pathogenicity

Front 19

What is the name for bacteria circulating in blood?

Back 19

Bacteremia

Front 20

What is the name for toxins circulating in blood?

Back 20

Toxemia

Front 21

What is septicemia?

Back 21

Whenthe concentration of the bloodborneagent increases to a life-threatening level

Front 22

What is type III secretion system?

Back 22

Appendage found in several Gram-negative bacteria.

Used as a sensory probe to detect present of host and secrete proteins to help infect them.

Front 23

What are M cells?

Back 23

Gut epithelial cells

Transport antigens from gut lumen by trancytosis to basolateral side - APCs

Subverted by Salmonella.

Front 24

What are invasins?

Example

Back 24

enzymesthat break down host tissues

Staphylokinase - activates plasminogen to form plasmin - digests fibrin clots. Cleaves IgG and C3b - inhibits phagocytosis

Front 25

What are Siderophores

Back 25

small, high-affinity iron chelating compounds

Main classes: hydroxamatesand catechols

Front 26

How can lysozyme action be overcome?

Back 26

S.aureus protein OatA - acetylates NAM

Front 27

How does coagulase aid evasion?

Back 27

Reacts with prothrombin in blood - causes clotting by fibrinogen to fibrin

Front 28

What factors affect transmission?

Back 28

Stability in environment
Environmental conditions
ID50
Sanitation
Host factors - normal flora

Front 29

What is vertical transmission?

Back 29

From parents to offspring
Through sperm, ovum, placenta, milk and blood

Front 30

What is antigenic shift?

Back 30

Exchange of homologous genes between different strains of a virus
Pathogen not recognised by host

Front 31

What is antigenic drift?

Back 31

natural mutation over time of known strains of influenza

Reduced response by immune system

Front 32

What is epidemiology the study of?

Back 32

patterns, causes, and effects of health and disease conditions in defined populations.

Front 33

What is an endemic?

Back 33

The habitual presence of a disease withina given geographic area

Front 34

What is an epidermic?

Back 34

•The occurrence in a community or regionof a group of illnesses of similar nature, clearly in excess of normalexpectancy, and derived from a common or from a propagated source

Front 35

What is a pandemic?

Back 35

•A worldwide epidemic

Front 36

What is infectivity?

Back 36

thepropensityfor transmission

Front 37

What is pathogenicity?

Back 37

• the propensityfor an agent to cause disease or clinical symptoms.

Canbe measured byID50

Front 38

What is virulence?

Back 38

•Thepropensity for an agent to cause severe disease.

Measured by the case fatality ratio,can also be examined in the lab as Lethal Dose 50 (LD50) –the number of cells administered that result in deathfor 50 % of the population

Front 39

What is an incubation period?

Back 39

•Theperiod between exposure to the agent and onset of infection (with symptoms orsigns of infection)

Front 40

What is a A noncommunicable disease?

Back 40

non-infectious and non-transmissible among people

Front 41

iron uptake

Back 41

siderophores are excreted intothe medium and then the iron-siderophorecomplexis takenupby specificreceptors

onceinside the cell they arecleaved torelease the iron molecule

Front 42

iron acquisition - other methods

Back 42

somebacteria can also import siderophores made by other bacteria

some bacteria produce toxins only when iron concentrations are low - killhuman cells,releasing stored iron for uptake

Front 43

iron abstinence

Back 43

replacedits small number of iron-sulphur clusterenzymes with those that use manganese instead

Front 44

What are biofilms?

Name a gram-negative pathogen with a propensity to form biofilms

Back 44

theyexist within an extracellular polysaccharide slime thathelps glue them together and bind them to different surfaces

Pseudomonas aeruginosa

Front 45

Advantage of biofilms

Back 45

biofilmsoffer protection from phagocytes, disinfectants and antibiotics

motile bacteria recognize asurface and aggregate together more readily than non-motilebacteria

Front 46

Mechanism for switching surface proteins

Back 46

1. genetic recombination - RecA-mediatedstrand exchange

2. DNA inversion - occurs between two inverted repeatsites which the recombinase binds

3. strand slippage

Front 47

Natural transformation advantages

Back 47

DNA for:

Genetic diversity, repair and as food

Front 48

What is the source of DNA for transformation

Back 48

free DNA is abundant in theenvironment as it is released by dead organisms

some bacteria secrete DNA or lysetheir cells

Front 49

mechanismof DNA uptake

Back 49

setof competence (com) genes are involved in transformationCompetenceis a specialised physiological state where bacteria become able to take up DNA

Front 50

Which enzyme improves accuracy of DNA replication?

Back 50

proof-reading (3’-5’exonuclease) activity

Front 51

Polymerase involved

Back 51

DNAPIII - alpha subunit with Pol, e - proofreading

DNAPI - both

Front 52

What can defects in MMR encourage?

Back 52

horizontal gene transfer

blocks interspecies recombinationbecause mismatches in heteroduplex DNA are recognised and the exchange aborted by MutHLS

Front 53

Are RNA viruses stable?

Back 53

No - RNA copying enzymes lack proof-reading capacity

Front 54

Retroviruses replication

Back 54

e.g. HIV. Convert RNA genome into DNA for integration.

Front 55

Can + or - function as mRNA?

Back 55

+strand (mRNA) functions as mRNA

–strand (complementary to mRNA) must be copied to make mRNA

Front 56

HIV genetic information conversions

Back 56

RNAgenome into dsDNA

RdDp

DNA strand synthesised first and then RNA degraded by RNaseH before second DNA strandmade for transport to the nucleus

Front 57

What is HIVreverse transcriptase extremely tolerant of?

Back 57

non-standard base pairs

Front 58

What is the source of individual variation in retroviruses?

Back 58

env gene

Front 59

Example of a HIV drug

Back 59

AZT - nucleoside drug inhibitor

Resembles thymidine but blocks DNA synthesis

N3 rather than 3' OH

Front 60

Resistance to AZT

Back 60

block binding of the AZT nucleoside in the polymerase active site

Front 61

Different oxygen enzymes in organisms

Back 61

SOD Catalase

Obligate aerobe Yes Yes

Facultative anaerobe Yes Yes

Aerotolerant anaerobe Yes No

Strict anaerobe No No

Microaerophile Yes Maybe

Front 62

Biofilm steps

Back 62

Cell deposition

cell absorption

Desorption

Cell-to-cell signalling and onset of exopolymer production

Convective and diffusive transport of O2 and nutrients

Replication and growth

Secretion of polysaccharide matrix

Detachment, erosion and sloughing

Front 63

What do biofilms contain?

Back 63

micro-environments

Oxygen-nutrient gradient

Cell-cell signals

positively charger antimicrobial binds to negatively charged slime

Front 64

Three phases response to infection

Back 64

Innate -

Early-induced innate - recruit of effector cells, recognition of PAMPs

Adaptive - Ag to lymphoid tissue, T/B cell recognition - clonal expansion and differentiation

Front 65

innate immunity

Back 65

. Lysozymes. Cleavesβ1-4 glycosidic

Lactoferrin - sequesters free Fe, binds LPS and produces peroxides - disrupts membrane permeability and causes lysis

Cathelicidins -•Destroysbacterial membranes in phagosomes,following fusion with lysosomes of macrophage.•Insertinto bacterial membrane

Defensins -•Inmucus, produced by epithelial cells and phagocytic cell.

•Amphipathicproteins that cause pores to form in bacterial membranes. Ion leaves and waterfollows down the osmotic gradient

Front 66

Complement activation

Back 66

•ClassicalPathway - Antigen:antibody complexes detected on pathogen surface

•MB-LectionPathway - Mannose-bindingprotein (a lectin) is upregulated in acute phase(inflammation). Binds bacterial cell walls, viral envelopes, antigen-antibodycomplexes

•AlternativePathway - Complement proteins(like C3b) bind directly to repetitive pathogen surface structures such as LPS

MAC, opsonisation, phagocyte recruitment

Front 67

How is infection detected?

Back 67

PRR (e.g. TLR) recognise PAMPs


•TLR3 –binds dsRNA
•TLR4– binds LPS
TLR5 - flagellin

Front 68

Role of phagocytic cells in innate immunity

Back 68

Respiratory burst

Or oxygen independent; charged proteinsthat damage the membrane, lysozyme, lactoferrin, proteases and hydrolytic enzymes

Extracellular ; nitric oxideis released and kills nearby microbes

Front 69

NK cells

Back 69

•NKcells contains granules in the cytoplasm, which contain

–Perforin;makes pore in cells

–Proteases, aka granzyme

cells marked by MHCI

•Cancerousand virus-infected cells lose MHCI, and are killed by NK cells

•If acell is coated with antibodies, NK cells recognise this cell and kill it by antibody-dependentcell-mediatedcytoxicity (ADCC)

Front 70

Induced innate response

Back 70

TLR activation triggers cytokine and chemokine production

Front 71

Explain the Inflammatory Response

Back 71

bacteria trigger macrophages to release cytokines and chemokines

Vasodilation and increased vascular permeabiltiy

Inflammatory cell migrate into tissue - release inflammatory mediators

Front 72

What does the innate immune system result in that activates adaptive immunity?

Back 72

–Lymphcontaining antigen and antigen-presenting cells

–Complementfragments on microbial surfaces

–Releaseof cytokines and chemokines thatactivate T lymphocytes

Front 73

Adaptive immunity - T cell-mediated

Back 73

–Recognizeantigen on surface of dendritic cells–ActivatedT cells travel to the thymus to mature

Differentiation

Front 74

Adaptive immunity - B cell antibody response

Back 74

•Whenantigen is detected

–Bcell can act as an APC to activate T cells

–Ifa corresponding Th cell is available, B cell matures in BM anddifferentiates

•Plasmacells–Makeantibodies against antigens

•MemoryB cells–Readyto initiate rapid response

Front 75

Consequences of antibody binding

Back 75

Neutralisation

complement fixation

Agglutination

Opsonisation

Ppt

Front 76

Overview of adaptive

Back 76

(>96 h)

Infection

Transport of antigen to lymphoidtissue

Recognition by B and T cells

Clonal expansion and differentiation

Removal of infectious agent

Front 77

Example of microbes entering through skin q

Back 77

S. aureus

Gram pos

C. tetani - gram-pos.

Front 78

Which organism has type III secretion system?

Back 78

Gram-negative bacteria.

sensory probe to detect the presence of eukaryotic organisms and secrete proteins that help the bacteria infect them.

Front 79

Where aretype III secretion systems encoded?

Back 79

Pathogenicityislands

Front 80

Mucosa entry site - which cells are involved?

How is this function subverted?

Back 80

–Gutepithelia contains microfold (M)cells

roleof M cells is to transport antigens from the gut lumen by transcytosis

–antigenfrom one side of the cell to the other, where it is provided toAPCs on the basolateral side

•Salmonellainduce ruffling in M cells

Front 81

respiratorytract entry

Back 81

- Adhesins

- Inhibitingciliaryactivity

Front 82

Staphylokinase

Back 82

–Activatesplasminogen to form the protease plasmin, which digests fibrin clots and allowsmovement of bacterial cells

–CleavesIgG andcomplement component C3b, inhibiting phagocytosis

Front 83

Hyaluronidase

Back 83

–Hyaluronicacid is a non-sulfated glycosaminoglycan distributed widely throughoutconnective, epithelial and neural tissues

spreadingfactor

Front 84

How is CathelicidinLL-37 cleaved?

Back 84

metalloproteinase secreted from S.aureus

Front 85

Coagulase

Back 85

Coagulasereacts with prothrombin in the blood

cause sblood to clot by converting fibrinogen to fibrin

Front 86

What does superantigen do?

Back 86

–Bridge the MHC class II protein onantigen presenting cells with the T cell receptor on the surface of T cells

Front 87

What is α-haemolysin?

Back 87

cytolytic toxin

Front 88

β-haemolysin

Back 88

sphingomyelinase

targetsmembranes rich in this lipid

Front 89

How can O2 be removed in growing chamber

Back 89

2H2 + O2 ---> 2H2O

Palladium pellets catalyse reaction

Front 90

Indole test;

Back 90

•tryptophanase

Front 91

Kirby-Bauer Method

Back 91

•Canbe used to determine whether the bacterium is “susceptible”, “intermediate”, or“resistant” to the tested antibacterial

Front 92

Methods for MIC

Back 92

Etest strips

Front 93

Endospores

Back 93

Ccore is dehydrated - enables heat resistance, long-term dormancy

Small acid-soluble spore proteins - protect DNA from UV radiation + carbon source

Producing spores enables bacteria to endure extreme stress and spread easily

Front 94

Is TB gram-positive or neg

Back 94

Positive