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BSMS 102 > Theme 4 - Introduction to medical microbiology > Flashcards

Theme 4 - Introduction to medical microbiology Flashcards

(77 cards)

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1
Q

what are the main bacterial infections seen in primary care?

A

UTI, chest infection, sore throat

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2
Q

what are the main bacterial infections seen in secondary care?

A

community acquired and hospital acquired infections

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3
Q

give one example of community and one example of hospital acquired infection

A

community - cellulitis or pneumonia, hospital - vascular line infection

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4
Q

how is a hospital acquired infection defined?

A

infection is acquired 48 hours after admission to hospital

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5
Q

at any given time what % of hospital patients are on antibiotics?

A

25%

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6
Q

what % of antibiotic use is in primary care?

A

80%

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7
Q

how are taxonomic names written

A

genus + species

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8
Q

what is staphylococcus aureus

A

a staphylococcal infection found on the skin

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9
Q

what is streptococcal pyogenes?

A

strep throat

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10
Q

what are the three components of the tree of life?

A

eukaryotes, archaea and bacteria

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11
Q

is bacteria eukaryotic or prokaryotic?

A

prokaryotic

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12
Q

name three eukaryotes that can cause human disease

A

fungi - candida, protazoa - malaria, helminths - tapeworm

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13
Q

list four key features of prokaryotes

A

no nucleus/membrane bound organelles, haploid, 70s ribosomes, peptidoglycan cell wall

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14
Q

list four key features of eukaryotes

A

membrane bound nucleus, diploid, 80s ribosome, no cell wall (unless plant or fungi)

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15
Q

what % of bacteria are medically important?

A

<0.01%

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16
Q

what are round bacteria called?

A

coccus/cocci (streptococcus)

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17
Q

what are long bacteria called?

A

bacillus/bacilli (enterobacter)

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18
Q

what are oval shaped bacteria called?

A

coccobacillus

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19
Q

what are long and curved bacteria called?

A

vibrio (cholera)

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20
Q

how do different coccus arrange?

A

staphylococcus - clusters, streptococcus - chains and diplococci - pairs

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21
Q

what does gram staining depend on?

A

amount of peptidoglycan in the cell wall

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22
Q

describe the gram staining process

A

dry sample on a glass plate, stain with crystal violet and set with iodine, decolourise with alcohol or acetone, counterstain with safranin

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23
Q

what type of bacteria retains the staining when washed with alcohol?

A

gram positive

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24
Q

what colour is safranin?

A

pink

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25
If a bacteria stains purple, what is it?
gram positive
26
if a bacteria stains pink, what is it?
gram negative
27
what aspects of bacteria can be exploited to diagnose infection?
patterns of growth down the microscope (chains or clusters), patterns of growth on culture medium (colonies formed and enzymes excreted), requirements for growth (atmospheric and nutrients)
28
what are two key features of bacterial aerobes?
use oxygen in final stage of metabolism and grow efficiently in oxygen rich conditions
29
what are three key features of obligate anaerobes?
only grow in oxygen absent environments, metabolise glucose to lactic acid, oxygen is usually toxic
30
what is a facultative anaerobe?
prefers anaerobic conditions but can grow in aerobic - carbon dioxide is not toxic to them
31
what substances do bacteria bring in, as they cant be made?
purine, pyrimidines, amino acids and vitamins
32
what nutritional requirements does e coli need to grow?
glucose and inorganic salts (easy to grow in lab)
33
what type of bacteria is hard to grow in the lab as it needs specialised medium?
treponema pallidum (syphillis)
34
what are the three main things used for growth/selection of bacteria in the lab?
temperature, pH and salt content
35
give three examples of medically important gram positive cocci
streptococci, staphylococci and peptococcus (strict anerobes)
36
give three examples of medically important gram negative cocci
neisseria (meningitidis and gonnorhea)
37
give three examples of medically important gram positive rods
bacillus (B. anthracis), clostridium dificle, corynebacterium, propiobacterium
38
give three examples of medically important gram negative rods
haemophilus influezae, eserischa coli, campylobacter/helicobacter, psueudomonas, salmonella, bacterocides (strict anaerobes)
39
which bacteria lack a cell wall?
mycoplasma (pneumoniae) and chlamidiya (trachomatis)
40
which bacteria do have a cell wall but it doesn't stain well?
mycobacteria (pneumoniae)
41
name two key features of a gram positive bacterial envelope
thick peptidoglycan cell wall and lipoteichoic/teichoic acid
42
what type of bacteria have a thick peptidoglycan cell wall?
gram positive
43
name three key features of a gram negative bacterial envelope
thin peptidoglycan cell wall, additional outer membrane, lipopolysaccharide
44
what three things are determined by the bacterial envelope?
gram staining, susceptibility to antibiotics and pathogenicity
45
what type of bacteria are endotoxin found in?
LPS - only in gram negative bacteria
46
what type of bacteria are exotoxins found in?
gram positive and gram negative
47
name two infections that secrete exotoxins
streptococcus pyogenes - toxic shock syndrome, clostridium botulinum - botulism (botox)
48
name three key features of peptidoglycans
3D polymer made of N-acetylated sugars (NAG and NAM), 3-5 amino acid peptides that cross link to the sugars via transpeptidase enzyme, amino acid and NAG/NAM make strong rigid cell wall to protect against degradation
49
what enzyme links NAG/NAM to the amino acids peptides in a peptidoglycan cell wall?
transpeptidase enzymes
50
what are the three key features of synthesising a bacterial peptidoglycan cell wall?
polymerisation of sugars (to make backbone), elongation of side chains (to add to the peptide) and transpeptidase ( for cross linking)
51
which steps of peptidoglycan synthesis are target by antibiotics?
all of them - interact with enzymes, ribosomes or polymerisation of sugars to affect integrity of bacterial cells wall
52
name two features of a mycobacterium cell wall
gram positive with thick lipid membrane anchored to a peptidoglycan layer, doesn't gram stain
53
name three causes of TB
m.tuberculosis, m.bovis, m.africanum
54
name two atypical mycobacteria
m.ulcerans, m.kansassi
55
what is a bacterial capsule made from
polysaccharide
56
name three key features of a bacterial capsule
hides the cell wall (immune system cant detect the endotoxin on the cell wall), can be toxic or pathogenic, is a metabolic burden on the bacteria
57
name four key features of bacterial ribosomes
70s (50s and 30s subunits), contain RNA and proteins, engines of protein synthesis
58
name two things bacterial RNA can be used for
antibiotic target and diagnostic testing
59
name two mobile genetic elements
plasmids and transposons
60
name four key features of plasmids
loops of extra chromosomal DNA, replicate independently, code for lots of genes (can behave like viruses), can be swapped between bacteria
61
name three key features of transposons
small, skip around the genome, encode tranposase, disrupt DNA causing different proteins to be produced, move within genomic DNA or between plasmids
62
what is the main feature of mobile genetic elements
code for toxins and antibiotic resistance genes
63
is bacterial DNA enclosed in a membrane bound nucleus?
no - easy for DNA processes to occur alongside cellular processes and for DNA transfer
64
name two spore forming bacteria
clostridium and bacillus
65
what are three key features of bacteria in a spore?
dormant, dont replicate, are alive
66
what conditions are spore forming bacteria resistant to?
drying, high/low temperature, disinfection and enzyme digestion
67
how do you get rid of spore forming bacteria?
prolonged exposure to very high temperatures and sterilisation
68
how long can bacteria stay in spores?
thousands or millions of years
69
what happens in the lag phase of bacterial growth?
genes are switched on and prepare to grow in a response to sugar or oxygen (no increase in cell number yet)
70
what happens in the exponential phase of bacterial growth?
cell doubling and growth
71
at what phase of bacterial growth is infection seen?
exponential phase - slope of the curve represents the growth rate of the organism in that environment
72
what happens at the stationary phase of bacterial growth?
divison stops, nutrients become depleted and there is a build up of metabolites such as lactic acid
73
what happens in the death phase of bacterial growth?
nutrients are exhausted, environment becomes toxic and cells die
74
how do bacteria sense and adjust to their environment? (gene regulation)
change rate of growth and regulate metabolic pathways
75
what does control of bacterial gene regulation allow?
regulation of virulence factors - adhesion molecules, production of enzymes to degrade host proteins, degrade immune mediators or lyse host cells
76
what is observed in the exponential phase of bacterial growth?
superficial infection eg bacteria detected in blood
77
what is observed in the stationary phase of bacterial growth?
abcess - lots of bacteria in a small space that becomes toxic

BSMS 102 (14 decks)

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