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Phase 2A > microbiology > Flashcards

microbiology Flashcards

1
Q

whats the resolving power of the naked eye

A

100μm (micrometer)

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2
Q

Resolving power of light microscope

A

0.2um (micrometer)

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3
Q

how are bacteria named

A

first name = genus, second name = species
(genus/general is above species in the rank of biological classification, and species is the lowest level of the rank)
FOR EXAMPLE:
homo (genus) sapiens (species)

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4
Q

define pathogen

A

Organisms that cause/ capable of causing disease within a host

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5
Q

define commensal

A

organism which colonises a host but causes no disease under normal circumstances

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6
Q

define opportunist pathogen

A

microbes that inly cause disease in host defences that are compromised (e.g.: immunosuppression)

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7
Q

define virulence/pathogenicity

A

the degree to which a given organism is pathogenic

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8
Q

define asymptomatic carriage

A

when a pathogen is carried harmlessly at a tissue site where it causes no disease

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9
Q

true all false: bacteria can colonies in any organ of the body without harm

A

false, bacteria can colonise on skin surfaces and surfaces of the digestive system. however the lungs an

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10
Q

name 2 categories of bacteria (based on shape)

A

cocci and rods/Bacillus

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11
Q

how do you determine whether bacteria is gram + or gram -

A

gram positive bacteria stains purple

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12
Q

name 3 ways in which +1 cocci travel/exist

A

diplococcus (2 cocci)
chains of cocci
clusters of cocci

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13
Q

name 1 way in which +1 rods travel exist

A

chains of rods

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14
Q

what other shapes may rod bacteria exist in, other that straight

A 
Curved = VIBRIO
Spiral = SPIROCHAETE
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15
Q

What is the difference between gram negative and gram positive bacteria

A

gram + = single cell membrane (no outer membrane)
gram - = double cell membrane which outer leaflet is made of lipopolysaccharide
note- other leaflet and inner membrane are phospholipids
gram positive bacteria also generally has a thicker layer of peptidoglycan

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16
Q

why do some bacteria have a polysaccharide capsule

A

to protect from complement cascade during an immune response

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17
Q

define endotoxin

A

component of the OUTER MEMBRANE (so within the bacterial cell of GRAM NEGATIVE ONLY)
e.g; lipopolysaccharide in gram -

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18
Q

define exotoxin

A

proteins produced and secreted by the gram + and gram - bacteria that affect and damage the host

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19
Q

can you name 6 difference between exotoxins and endotoxins?

A 
Composition
Action
Effect of heat
Antigenicity
Type of bacteria that produces it
ability to convert to a toxoid
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20
Q

name 3 ways a bacteria may spread genetic information (resulting in genetic variation)

A

Transformation (e.g. via plasmid)
Transduction (e.g. vis Phage)
Conjugation (e.g. via sex pilus)
(mutation can also lead to resistance, a genetic variation)

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21
Q

what are mollicutes

A

a class of bacteria without a cell wall

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22
Q

what is the medical term for a parasitic form

A

helminths

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23
Q

name 3 types of worms

A

Cestodes - tape worms
trematodes - flatworms, flukes
nematodes - roundworms

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24
Q

what is the Prepatent period (IMPORTANT)

A

interval between infection and appearance in eggs In the stool

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25
Q

true of false - hookworms are the most commonest cause of iron-deficiency anaemia in the world

A

true

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26
Q

what makes bacteria prone to infection

A

this is due to the fast growth rate - therefore there is more opportunity for mutation to occur

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27
Q

name 3 ways bacteria can spread genetic material and increase variation

A

Transformation (e.g., via plasmid) - ability to take DNA from the environment and incorporate It for benefit

Transduction (e.g. vid phage - bacterias form of viruses) - movement between bacteria, picking up info and infecting other bacteria with it

Conjugation (e.g. via sex pilus) - like a bacterias way of reproducing

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28
Q

what does it mean for bacteria to be coagulase +Ve

A

Enzymes are produced by bacteria that clot surrounding blood plasma. fibrin clot formation around the blood

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29
Q

name 2 genus of gram positive bacteria

A

staphylococcus

streptococcus

30
Q

what is the only type of coag +ve staphylococcus

A

Staph. aureus

31
Q

how is staph.aureus spread

A

spread through aerosol (sneezing and coughing) and touch

you can be a carrier and a shedder

32
Q

name a strain of s.aureus and the antibiotics they are resistant to

A

MRSA

resistant to b-lactams, gentamicin, erythromycin, Tetracyline

33
Q

what are the virulence factors of s.aureus
THERES 4
TSST in PPPT

A

Pore-forming toxins - causes cell to burst and die

Proteases - causes infection (exfoliating - enzymes that attack desmosomes and cause skin to peel off)

Toxic shock syndrome toxin TSST- huge host response is what causes main damage (not toxin)

Protein A - surface protein - causing immunoglonin to bind backwards

34
Q

what is the most important coat -ve staphylococcus

A

s.epidermis

35
Q

name some factors of s.epidermis

A

lives on the skin

very opportunistic
affects more vulnerable e.g.: debilitated, prostheses, catheters (more vulnerable to infection)

main virulence factor = ability to form persistent biofilms (3D communities of bacteria)

36
Q

what are the main classifications for streptococcus

A

goes through haemolysis
Lancefield typing
biochemical properties

37
Q

what is lance field typing

A

method of grouping catalase-negative, coagulase-negative bacteria based on the carbohydrate composition of bacterial antigens found on their cell walls
(only streptococcus are catalase- negative)

38
Q

what are the 3 results of haemolysis of streptococcus

A

A - haemolysis = partial
greening - as H2O2 reacts with Hb on blood agar - goes green (iron reaction?) - e.g.: S.intermedius

B haemolysis = complete lysis - white line as it completely disappears - S.pyogenes

Gamma = no lysis e.g.: some Mutants

39
Q

what are the virulence factors of streptococcus

A

SURFACE FACTORS

  • capsule - protection
  • M protein - encourages complement degradation to allow to enter host cell
  • inflammatory wall constituent
  • cytotoxins

EXPORTED FACTOR

  • enzymes
  • toxins
40
Q

what is the collective name for oral streptococci

A

Viridans streptococci
- note: viridans means greening - must be a haemolytic (partial)
often causes accesses in cavity
can also cause deep organ abscesses

41
Q

what is the difference between Staphylococcus and streptococcus

A 
Arrangement
Division
Catalase Test
Enriched Media
Habitat
Hemolysis
Species Number
Pathogenesis
Common Diseases
Pathogenic Species
Species Differentiation
42
Q

name some genus of gram neg bacteria

A

E-coli
shigella
salmonella
(more examples)

43
Q

why are some strains of e-coli pathogenic

A

pathogenic valet contains additional genes from other bacteria (due to virulence factor)
- these additional genes may contain virulence determinence

44
Q

how many varieties of coli exist

A

6

45
Q

what are servers/serotypes

A

A distinct variation within a species of bacteria or virus

46
Q

what does ETEC coli cause

A

Travellers diarrhoea

- taken up by intestinal epithelial cell

47
Q

name the other type of gram -ve bacteria that is closely related to ecoli

A

Shigella

48
Q

what are symptoms of shigella

A

Very closely related to E coli (might as well be)
sever blood diarrhoa
frequent passage of stools
small volume, pus and
releasing toxin that leads to cell death
sometimes complication can occur, leading to kidney failure

49
Q

what are 2 species of Salmonella

A 
salmonella bongori (rare)
salmonella enterica (what you would find in humans)
50
Q

what are the 3 main types of infections that can be caused by various forms of salmonella

A

Gastroenteritis/enterocolitis - (serovars enteritidis and typhimurium) - salmonella food poisoning

Enteric fever - typhoid ( serovar typhi and paratyphi)

Bacteraemia (servers cholerasuis and Dublin)

51
Q

why is high infective doses needed to cause infection

A

salmonella is acid sensitive, which certain food can protect the bacteria against acid, causing lower dose so doesn’t have too much effect

52
Q

what makes mycobacteria different to normal bacterial?

A

Different cell wall structure to other bacteria, making their biological reaction different

53
Q 
name the conditions associated with the following medically important bacteria:
M. tuberculosis
M. avid complex (MAC)
M. kansasii
M. marinum
M. ulcerans
M. fortuitum complex
M. leprae
A

tuberculosis
HIV/AIDs (anything that affects immune, also causing lung infection)
Chronic lung infection
fish tank granuloma - infection of the skin
Buruli ulcer (if left untreated, can lead to bone deformation)
skin and soft tissue infection
leprosy

54
Q

name some key factors of Mycobacterium

A

aerobic
non-motile bacillus
thick waxy wall with high molecular weight lipids
acid fast
can survive extreme environments, including inside a macrophage, even in low pH

55
Q

name 4 things mycobacteria is slow at doing

TRCH - Time Really Can Hurt

A

slow Reproduction
slow growth in Humans - gradual onset of disease
slow growth in Culture - takes much longer
slow response to Treatment (6 months minimum) - as it is difficult for antibiotics to target the division phase

56
Q

what is an acid fast mycobacteria

A

think fast as in to fasten

acid fast bacteria is a type of bacteria that resists decolonizing by acid after staining

57
Q

why doesn’t mycobacteria decolourise after staining

A

this is due to the thickness of the cell walls, which contains myolic acid. this retains the carbon fuchsin primary stain

58
Q

what are the agents used in staining acid fast (ziehl-neelsen) staining and what are their purpose

A

carbon fuchsin - primary stain
acid alcohol - decolorisation
methylene blue - secondary/counter stain
(heat for mordant)

59
Q

what are the agents used in gram stain and what are their purpose

A

crystal violet - primary stain
iodine - mordant
alcohol - decolorization
safronin - counter stain

60
Q

how can nucleic acid detection be used to detect pathogenic mycobacterium

A

NA amplification is doe using PCR (polymerase chain reaction)
produce results in a hour for tuberculosis
highly sensitive and specific
recommended for TB diagnosis and being used more for other conditions

61
Q

explain the immunological reaction that occurs with mycobacteria

A

mycobacteria is phagocytosed by macrophages
and exists in a phagolysosome within the macrophage
adapted to intracellular environments and aims to withstand phagolysomal killing by escaping to cytosol (waxy cell wall helps this protection)
macrophage then turns to cell mediated mechanism to kill cell, involving T cels

62
Q

name a type of T cell and 2 cytokines involved in cell mediated response against mycobacteria

A

CD4 T cells (helper t-cells)
Interferon gamma (cytokine)
IL - 12 (cytokine)

63
Q

what is a granuloma, why may it occur and how does it occur

A

Granulomas are lesions that arise in a response that tries to contain mycobacteria
- highly stimulated macrophages becoming EPITHELIOD CELLS (activated macrophages that resemble epithelial cells)
- some macrophage fuse with each other to form giant multinucleate cells ‘LANGHANS GIANT CELLS’
T cells infiltrate the mycobacterial lesion
the central may necrosis and form a caveating granuloma, in the lung this can result in the formation of cavity

64
Q

how is the tuberculin skin test used to identify the presence of M. tuberculosis

A

mycobacterium is slow reaction (6-9weeks for immune response), so if the body has already been exposed to the infection, it would react almost immediately to the antigens injected into the skin, causing a red rash.

65
Q

describe 5 characteristics of a virus

A

grow only inside living cells.
Possess only one type of nucleic acid, RNA or DNA.
No cell wall structure but have an outer protein coat. Some viruses also have a lipid envelope.
Essentially inert outside the host cell, but carry enzymes that function inside the cell.
Protein receptors on virus surface allow attachment to susceptible host cells.

66
Q

what are the stages of viral replication

Hint: Ah, Can I Remember Actual Replication?

A 
attachment
cell entry
interaction with host cell
replication
assembly
release
67
Q

what characteristics do viruses share with a living organisms

A
  • Have Nucleic Acid- RNA or DNA (as core)
  • Have an outer protein coat (capsid)
  • Can replicate (inside living cell) and pass on genetic code-borrow cellular enzymes and organelles
68
Q

what characteristics do viruses share with non living organisms

A
  • Non- cellular- no cell wall
  • Cannot reproduce by themselves
  • Do not have cell organelles
  • Have only one type of nucleic acid – DNA or RNA
69
Q

how do viruses cause disease

hint: in the G-MODE

A

Destruction of host cell
modification of host cells structure/function
over-reactivity of cell
cell growth and cell immortalisation
evasion of extracellular and intracellular

70
Q

what is the steady state in HBV

A

this is where a carrier of HBV reaches a balance between virus replication in host cells and host defence response

Phase 2A (12 decks)

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