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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
true of false - hookworms are the most commonest cause of iron-deficiency anaemia in the world
true
26
what makes bacteria prone to infection
this is due to the fast growth rate - therefore there is more opportunity for mutation to occur
27
name 3 ways bacteria can spread genetic material and increase variation
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
28
what does it mean for bacteria to be coagulase +Ve
Enzymes are produced by bacteria that clot surrounding blood plasma. fibrin clot formation around the blood
29
name 2 genus of gram positive bacteria
staphylococcus | streptococcus
30
what is the only type of coag +ve staphylococcus
Staph. aureus
31
how is staph.aureus spread
spread through aerosol (sneezing and coughing) and touch | you can be a carrier and a shedder
32
name a strain of s.aureus and the antibiotics they are resistant to
MRSA | resistant to b-lactams, gentamicin, erythromycin, Tetracyline
33
what are the virulence factors of s.aureus THERES 4 TSST in PPPT
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
what is the most important coat -ve staphylococcus
s.epidermis
35
name some factors of s.epidermis
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
what are the main classifications for streptococcus
goes through haemolysis Lancefield typing biochemical properties
37
what is lance field typing
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
what are the 3 results of haemolysis of streptococcus
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
what are the virulence factors of streptococcus
SURFACE FACTORS - capsule - protection - M protein - encourages complement degradation to allow to enter host cell - inflammatory wall constituent - cytotoxins EXPORTED FACTOR - enzymes - toxins
40
what is the collective name for oral streptococci
Viridans streptococci - note: viridans means greening - must be a haemolytic (partial) often causes accesses in cavity can also cause deep organ abscesses
41
what is the difference between Staphylococcus and streptococcus
``` Arrangement Division Catalase Test Enriched Media Habitat Hemolysis Species Number Pathogenesis Common Diseases Pathogenic Species Species Differentiation ```
42
name some genus of gram neg bacteria
E-coli shigella salmonella (more examples)
43
why are some strains of e-coli pathogenic
pathogenic valet contains additional genes from other bacteria (due to virulence factor) - these additional genes may contain virulence determinence
44
how many varieties of coli exist
6
45
what are servers/serotypes
A distinct variation within a species of bacteria or virus
46
what does ETEC coli cause
Travellers diarrhoea | - taken up by intestinal epithelial cell
47
name the other type of gram -ve bacteria that is closely related to ecoli
Shigella
48
what are symptoms of shigella
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
what are 2 species of Salmonella
``` salmonella bongori (rare) salmonella enterica (what you would find in humans) ```
50
what are the 3 main types of infections that can be caused by various forms of salmonella
Gastroenteritis/enterocolitis - (serovars enteritidis and typhimurium) - salmonella food poisoning Enteric fever - typhoid ( serovar typhi and paratyphi) Bacteraemia (servers cholerasuis and Dublin)
51
why is high infective doses needed to cause infection
salmonella is acid sensitive, which certain food can protect the bacteria against acid, causing lower dose so doesn't have too much effect
52
what makes mycobacteria different to normal bacterial?
Different cell wall structure to other bacteria, making their biological reaction different
53
``` 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 ```
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
name some key factors of Mycobacterium
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
name 4 things mycobacteria is slow at doing | TRCH - Time Really Can Hurt
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
what is an acid fast mycobacteria
think fast as in to fasten | acid fast bacteria is a type of bacteria that resists decolonizing by acid after staining
57
why doesn't mycobacteria decolourise after staining
this is due to the thickness of the cell walls, which contains myolic acid. this retains the carbon fuchsin primary stain
58
what are the agents used in staining acid fast (ziehl-neelsen) staining and what are their purpose
carbon fuchsin - primary stain acid alcohol - decolorisation methylene blue - secondary/counter stain (heat for mordant)
59
what are the agents used in gram stain and what are their purpose
crystal violet - primary stain iodine - mordant alcohol - decolorization safronin - counter stain
60
how can nucleic acid detection be used to detect pathogenic mycobacterium
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
explain the immunological reaction that occurs with mycobacteria
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
name a type of T cell and 2 cytokines involved in cell mediated response against mycobacteria
CD4 T cells (helper t-cells) Interferon gamma (cytokine) IL - 12 (cytokine)
63
what is a granuloma, why may it occur and how does it occur
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
how is the tuberculin skin test used to identify the presence of M. tuberculosis
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
describe 5 characteristics of a virus
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
what are the stages of viral replication Hint: Ah, Can I Remember Actual Replication?
``` attachment cell entry interaction with host cell replication assembly release ```
67
what characteristics do viruses share with a living organisms
- 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
what characteristics do viruses share with non living organisms
- 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
how do viruses cause disease hint: in the G-MODE
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
what is the steady state in HBV
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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