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

Theme 4 - Introduction to medical microbiology Flashcards

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
Q

If a bacteria stains purple, what is it?

A

gram positive

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26
Q

if a bacteria stains pink, what is it?

A

gram negative

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27
Q

what aspects of bacteria can be exploited to diagnose infection?

A

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)

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28
Q

what are two key features of bacterial aerobes?

A

use oxygen in final stage of metabolism and grow efficiently in oxygen rich conditions

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29
Q

what are three key features of obligate anaerobes?

A

only grow in oxygen absent environments, metabolise glucose to lactic acid, oxygen is usually toxic

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30
Q

what is a facultative anaerobe?

A

prefers anaerobic conditions but can grow in aerobic - carbon dioxide is not toxic to them

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31
Q

what substances do bacteria bring in, as they cant be made?

A

purine, pyrimidines, amino acids and vitamins

32
Q

what nutritional requirements does e coli need to grow?

A

glucose and inorganic salts (easy to grow in lab)

33
Q

what type of bacteria is hard to grow in the lab as it needs specialised medium?

A

treponema pallidum (syphillis)

34
Q

what are the three main things used for growth/selection of bacteria in the lab?

A

temperature, pH and salt content

35
Q

give three examples of medically important gram positive cocci

A

streptococci, staphylococci and peptococcus (strict anerobes)

36
Q

give three examples of medically important gram negative cocci

A

neisseria (meningitidis and gonnorhea)

37
Q

give three examples of medically important gram positive rods

A

bacillus (B. anthracis), clostridium dificle, corynebacterium, propiobacterium

38
Q

give three examples of medically important gram negative rods

A

haemophilus influezae, eserischa coli, campylobacter/helicobacter, psueudomonas, salmonella, bacterocides (strict anaerobes)

39
Q

which bacteria lack a cell wall?

A

mycoplasma (pneumoniae) and chlamidiya (trachomatis)

40
Q

which bacteria do have a cell wall but it doesn’t stain well?

A

mycobacteria (pneumoniae)

41
Q

name two key features of a gram positive bacterial envelope

A

thick peptidoglycan cell wall and lipoteichoic/teichoic acid

42
Q

what type of bacteria have a thick peptidoglycan cell wall?

A

gram positive

43
Q

name three key features of a gram negative bacterial envelope

A

thin peptidoglycan cell wall, additional outer membrane, lipopolysaccharide

44
Q

what three things are determined by the bacterial envelope?

A

gram staining, susceptibility to antibiotics and pathogenicity

45
Q

what type of bacteria are endotoxin found in?

A

LPS - only in gram negative bacteria

46
Q

what type of bacteria are exotoxins found in?

A

gram positive and gram negative

47
Q

name two infections that secrete exotoxins

A

streptococcus pyogenes - toxic shock syndrome, clostridium botulinum - botulism (botox)

48
Q

name three key features of peptidoglycans

A

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
Q

what enzyme links NAG/NAM to the amino acids peptides in a peptidoglycan cell wall?

A

transpeptidase enzymes

50
Q

what are the three key features of synthesising a bacterial peptidoglycan cell wall?

A

polymerisation of sugars (to make backbone), elongation of side chains (to add to the peptide) and transpeptidase ( for cross linking)

51
Q

which steps of peptidoglycan synthesis are target by antibiotics?

A

all of them - interact with enzymes, ribosomes or polymerisation of sugars to affect integrity of bacterial cells wall

52
Q

name two features of a mycobacterium cell wall

A

gram positive with thick lipid membrane anchored to a peptidoglycan layer, doesn’t gram stain

53
Q

name three causes of TB

A

m.tuberculosis, m.bovis, m.africanum

54
Q

name two atypical mycobacteria

A

m.ulcerans, m.kansassi

55
Q

what is a bacterial capsule made from

A

polysaccharide

56
Q

name three key features of a bacterial capsule

A

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
Q

name four key features of bacterial ribosomes

A

70s (50s and 30s subunits), contain RNA and proteins, engines of protein synthesis

58
Q

name two things bacterial RNA can be used for

A

antibiotic target and diagnostic testing

59
Q

name two mobile genetic elements

A

plasmids and transposons

60
Q

name four key features of plasmids

A

loops of extra chromosomal DNA, replicate independently, code for lots of genes (can behave like viruses), can be swapped between bacteria

61
Q

name three key features of transposons

A

small, skip around the genome, encode tranposase, disrupt DNA causing different proteins to be produced, move within genomic DNA or between plasmids

62
Q

what is the main feature of mobile genetic elements

A

code for toxins and antibiotic resistance genes

63
Q

is bacterial DNA enclosed in a membrane bound nucleus?

A

no - easy for DNA processes to occur alongside cellular processes and for DNA transfer

64
Q

name two spore forming bacteria

A

clostridium and bacillus

65
Q

what are three key features of bacteria in a spore?

A

dormant, dont replicate, are alive

66
Q

what conditions are spore forming bacteria resistant to?

A

drying, high/low temperature, disinfection and enzyme digestion

67
Q

how do you get rid of spore forming bacteria?

A

prolonged exposure to very high temperatures and sterilisation

68
Q

how long can bacteria stay in spores?

A

thousands or millions of years

69
Q

what happens in the lag phase of bacterial growth?

A

genes are switched on and prepare to grow in a response to sugar or oxygen (no increase in cell number yet)

70
Q

what happens in the exponential phase of bacterial growth?

A

cell doubling and growth

71
Q

at what phase of bacterial growth is infection seen?

A

exponential phase - slope of the curve represents the growth rate of the organism in that environment

72
Q

what happens at the stationary phase of bacterial growth?

A

divison stops, nutrients become depleted and there is a build up of metabolites such as lactic acid

73
Q

what happens in the death phase of bacterial growth?

A

nutrients are exhausted, environment becomes toxic and cells die

74
Q

how do bacteria sense and adjust to their environment? (gene regulation)

A

change rate of growth and regulate metabolic pathways

75
Q

what does control of bacterial gene regulation allow?

A

regulation of virulence factors - adhesion molecules, production of enzymes to degrade host proteins, degrade immune mediators or lyse host cells

76
Q

what is observed in the exponential phase of bacterial growth?

A

superficial infection eg bacteria detected in blood

77
Q

what is observed in the stationary phase of bacterial growth?

A

abcess - lots of bacteria in a small space that becomes toxic

BSMS 102 (14 decks)

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