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Mpharm 1 COPY > PH1123 bacteria > Flashcards

PH1123 bacteria Flashcards

1
Q

what is virulence ?

A

the degree or intensity of pathogenicity of an organism

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2
Q

what does the upper respiratory tract include ?

A

the sinuses, nasal passages, pharynx, and larynx.

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3
Q

where does the lower respiratory tract include ?

A

in the lungs or below the voice box.

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4
Q

what is a virulence factor ?

A

a microbial (bacteria, fungi, protozoa…) product that contributes to virulence

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5
Q

What is a common component in bacterial cell walls ?

A

peptidoglycan (murrain or glycopeptide)

= glycan + peptide bridges

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6
Q

What is glycan ?

A

glycan =N- acetyl muramic acid (NAM) and N - acetyl glucosamine (NAG).

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7
Q

what does the NAM of glycan attach to ?

A
  • To each NAM is attached a tetrapeptide consisting of the amino acids l - alanine, d - alanine, d - glutamic acid and either lysine or diaminopimelic acid (DAP).
  • This glycan tetrapeptide repeat unit is cross - linked to adjacent glycan chains, either through a direct peptide linkage or a peptide interbridge
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8
Q

what are the two main groups of bacteria and how do we differentiate between them ?

A

Gram - positive and Gram - negative, on the basis of a differential staining technique called the Gram stain. Essentially, the Gram stain consists of treating a film of bacteria dried on a microscope slide with a solution of crystal violet, followed by a solution of iodine; these are then washed with an alcohol solution. In Gram - negative organisms the cells lose the crystal violet – iodine complex and are rendered colourless, whereas Gram - positive cells retain the dye.

Gram negative – rendered colourless but when counter stained red
Gram positive – retain colour and when counter stained purple

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9
Q

Why does gram positive bacteria retain the stain better than gram negative

A

The cell wall is thicker

Gram negative bacteria is much thinner and can be inhibited by a capsule

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10
Q

Why does gram positive bacteria retain the stain better than gram negative

A

In Gram-positive, the low lipid concentration is important for the retention of the complex
iodine-crystal violet: the cells remain blue.
The cell wall is thicker
Gram negative bacteria is much thinner and can be inhibited by a capsule

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11
Q

what does the cell envelope usually consist of? (3)

A
  • outer cell wall or peptidoglycan (gram +ve and -ve)
  • cytoplasmic or plasma membrane (gram +ve and -ve)
  • outer membrane (gram -ve only)
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12
Q

what is the chemical property of peptidoglycan? (2)

A
  • chemically inert

- composed of sub-units found nowhere else in nature

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13
Q

what can the cell envelope of gram -ve bacteria produce?

A
  • they can produce symptoms of disease (endotoxins)
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14
Q

where is the site of action of the most effective chemotheraputic antibiotics?

A
  • cell wall peptidoglycan
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15
Q

what does the cell wall prevent?

A
  • prevents osmotic rupture of the protoplast in dilute solutions
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16
Q

what is the protoplast?

A
  • when no cell wall remains
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17
Q

what is the structure of peptidoglycan? (3)

A
  • N-acetyl-muramic acid and N-acetyl glucosamine that alternate to form a high molecular weight polymer
  • a chain of several amino acids is attached to each of the N-acetyl-muramic acid molecules
  • multilayered network around the organism
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18
Q

what are the matrix materials found within the open meshwork? (3)

A
  • chiefly polysaccharides
  • immunology active substances which determine the antigenic specificity of certain organisms
  • techoic acids which are highly acidic substances present only in the cell wall of gram +ve bacteria
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19
Q

what is the peptidoglycan cell wall a target for? (5)

A
  • beta-lactams
  • glycopeptides
  • bacitracin
  • D-cycloserine
  • fosfomycin
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20
Q

what do the drugs that target the peptidoglycan cell wall do to it?

A
  • they inhibit cell wall synthesis
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21
Q

what do beta-lactams and glycopeptides do to the cell wall? (2)

A
  • the different beta- lactams target different enzymes (penicilin-binding enzymes)
  • beta-lactams and glycopeptides interfere with the late stage of cell wall maturation (cross-linking)
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22
Q

what are examples of extended spectrum penicillins? (4)

A
  • amoxicillin
  • ampicillin
  • carbenicillin
  • piperacillin
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23
Q

what bacteria do extended spectrum penicillins target?

A
  • gram negative bacteria
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24
Q

what is the purpose of the plasma membrane?

A

effective permeability barrier of the cell regulating the inflow and outflow of metabolites to and from the protoplast

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25
Q

what can pass through the plasma membrane? (2)

A
  • it is semi permeable

- low molecular weight materials can penetrate to the inside of the cell

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26
Q

what are efflux proteins? (2)

A
  • present in the cytoplasmic membrane (aka vomit pumps)

- gets rid of things the cells doesnt like (removal from cytoplasm

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27
Q

what does the outer membrane of gram -ve bacteria contain?

A

lipopolysaccharides

- one layer of phospholipids

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28
Q

how are bacterial ribosomes characterised?

A
  • by their sedimentation properties when centrifuged at very high speeds in untracentrifuge
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29
Q

what size are bacteria ribosomes?

A

70S

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30
Q

what are the components of bacterial ribosomes? (2)

A
  • ribosomal protein

- ribosomal RNA (rRNA)

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31
Q

what do plasmids play a role in in bacteria?

A
  • transfer of genetic material between bacteria
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32
Q

what happens in binary fission?

A
  • cell elongates and dna is replicated
  • cell wall and plasma membrane begin to divide
  • cross-wall forms completely around divided dna
  • cell separates
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33
Q

what are the phases in bacterial growth? (4)

A
  • lag phase
  • log (exponential) phase
  • stationary phase
  • death phase
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34
Q

what is the lag phase? (4)

A
  • population remains temporarily unchanged
  • bacterial cell may be growing in volume or mass
  • synthesizing enzymes, protein, rna etc.
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35
Q

what happens to the metabolic activity in the lag phase?

A
  • increasing in metabolic activity
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36
Q

what is the stationary phase? (4)

A
  • population growth is limited
  • exhaustion of available nutrients
  • accumulation of inhibitory metabolites or end products
  • exhaustion of space
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37
Q

what is a chemostat? (2)

A
  • bioreactor to which fresh medium is continuously added

- culture liquid is continuously removed to keep the culture volume constant

38
Q

what do the chemostat do?

A
  • control growth rate

- optimise population

39
Q

at which phase are bacteria in whilst in a chemostat and why?

A
  • always in the log (exponential) phase

- optimise growth of microorganisms

40
Q

what are the chemical requirements for growth? (6)

A
  • oxygen, sulphur and phosphorous
  • energy source
  • source of electrons
  • nitrogen source
  • carbon source
  • ions
41
Q

what are the optimum temperatures for the storage of pharmaceutical products? (3)

A
  • deep freeze (-20); total parenteral nutrition and raw materials
  • 8 to 12; reconstituted syrups and multi-dose eye drops
  • 80; for WFI (regrowth of gram -ve and release of toxins)
42
Q

what is the optimum pH for growth?

A
  • 6.5 to 7.5
43
Q

what is the viable count?

A
  • referred as to the number of colony-forming units (cfu) rather than as number of bacteria
44
Q

what might alter bacterial growth and the formation of colonies? (2)

A
  • type of medium used

- conditions of incubation

45
Q

when is the MPN (most probable number) method used?

A
  • reserved for the enumeration of bacteria in situations where no other method is available
46
Q

how do you do the MPN method of enumeration? (4)

A
  • prepare a series of at least 3 subsequent tenfold dilutions of product
  • from each level of dilution three aliquots of 1g or 1ml are used to inoculate
  • three tubes with 9ml to 10ml of a suitable liquid medium
  • incubate all tubes for five days at 30 to 35 degrees and record each level of dilution the number of tubes showing microbial growth
47
Q

what are the different functions of pili? (6)

A
  • adherence; to one another and foreign cells
  • antigenic differences
  • gene transfer; by conjugation
  • attachment sites; for bacteriophages
  • chemotaxis; may keep bacteria near the surface of liquids or where oxygen is most available
  • virulence; enhances the ability of bacteria to cause disease
48
Q

what is the role of the bacterial capsule? (3)

A
  • virulence; prevents phagocytosis from macrophages
  • protection ; contains water which protects bacteria against desiccation
  • protection; exclude bacterial viruses and most hydrophobic toxic materials such as detergents
49
Q

what are endospores?

A
  • unique structure formed within the vegetative cell
50
Q

what is the process of spore formulation? (2)

A
  • sporulation

- it is not a reproductive process

51
Q

what is the main role of spores?

A
  • enable the survival of the bacterium (genetic material) during harsh conditions (lack of food, water, chemical and physical stress)
52
Q

when are spores released?

A
  • following the death of the bacteria
53
Q

what is sterilization?

A
  • a process that kill all micro-organisms including spores
54
Q

what are the structure of bacterial endospores? (5)

A
  • exosporium (hydrophobic) which sticks to surfaces
  • spore coat
  • cortex
  • spore wall and membrane
  • spore core (DNA and ribosomes)
55
Q

what is germination?

A
  • process by which a spore reverts into a (vegetative) bacterium
56
Q

when can germination occur?

A
  • when environmental conditions for bacterial growth is supported (food, water etc.)
  • forced to occur using germinants
57
Q

what happens during germination?

A
  • outgrowing cell becomes susceptible to chemical and physical processes
58
Q

what is stage one of germination? (4)

A
  • cation is released
  • Ca2+ - DPA release
  • partial core hydration
  • some loss of resistance
59
Q

what is stage two of germination? (5)

A
  • cortex hydrolysis
  • further core hydration
  • core expansion
  • more loss of resistance
  • loss of dormancy
60
Q

what is the outgrowth stage of germination? (4)

A
  • metabolism
  • SASP degradation
  • macromolecules synthesis
  • escape from spore coats
61
Q

Describe the process of bacterial germination?

A

Spore is activated.
Stage 1- partial core hydration and loss of resistance due to cation release.
Stage 2- cortex hydrolysis, further core hydration, loss of resistance and dormancy.
Stage 3- outgrowth, metabolism and escape from spore coat.

62
Q

what is the result for a gram negative bacteria in gram staining and why? (3)

A
  • the high lipid concentration found in the outer layer of the cell wall is dissolved
  • this facilitates the release of the iodine-crystal violet complex
  • the cell is left colourless
63
Q

what antibiotics is the plasma membrane a target for? (4)

A
  • polymyxins, colistin and daptomycin
  • polymyxin B and colistin affects membrane permeability
  • daptomycin affects membrane function
  • antimicrobial peptides
64
Q

what antibiotic inhibit the synthesis of nucleic acids? (4)

A
  • quinolones (DNA gyrase which inhibits DNA replication and transcription)
  • rifampicin (RNA polymerasewhich affects transcription)
  • sulphonamides and trimethoprim (folic acid synthesis)
  • nitrofurantoin and mitrodinazole (DNA interactions)
65
Q

what is pili? (2)

A
  • very fine, hair-lie surface filaments

- smaller than flagella (0.5μm)

66
Q

what species of bacteria would you find (endo)spores? (2)

A
  • Bacillus spp

- Clostridium spp

67
Q

what is sterility assurance?

A
  • ensure a process has killed all vegetative bacteria and spores
68
Q

what is rickettsia? (4)

A
  • intracellular parasites
  • aerobic. small gram -ve bacteria
  • non-motile, non-spore forming bacter
  • highly pleomorphic bacteria
69
Q

what is the rickettsia species carried by? (3)

A
  • ticks
  • lice
  • fleas
70
Q

what is the microbial structure of rickettsia? (4)

A
  • peptidoglycan
  • lipopolysaccharide
  • no flagella or attachment proteins (ie no motility)
  • surrounded by a loosely adherent slime layer
71
Q

how does rickettsia enter the host cells? (3)

A
  • attaches to the surface
  • promotes their own entry by phagocytosis
  • escape the phagosomes to the host cell cytoplasm
72
Q

what are the prevention methods for rickettsia? (3)

A
  • vaccination (limited due to a possible change with DNA vaccines)
  • reduce exposure to tick-borne diseases
  • appropriate sanitary hygiene
73
Q

what type of bacteria is chlamydia?

A
  • obligate intracellular bacteria
74
Q

what does chlamydia lack?

A
  • they lack the metabolic pathway to produce their own high-energy phosphate compounds
75
Q

what is the microbial structure of chlamydia? (4)

A
  • internal and external membrane similar to gram -ve bacteria
  • no peptidoglycan layer
  • lipopolysaccharide
  • no flagella and non piliated
76
Q

what are prevention methods of chlamydia? (3)

A
  • safe sex
  • not sharing sex toys
  • appropriate sanitary hygiene
77
Q

what is the structure of mycobacteria? (4)

A
  • polypeptides and free lipids
  • mycolate layer and arabinogalactan
  • peptidoglycan
  • cytoplasmic membrane
78
Q

what is the cell wall of mycobacteria?

A
  • highly hydrophobic

- basic layer; peptidoglycan linked to arabinogalactan wall esterified to mycolic acid structure

79
Q

who are the people most at risk of developing tuberculosis? (5)

A
  • close contact to infectious case
  • those who have lived in places where TB is still common
  • people who experience chronic poor health through lifestyle factors e.g. homelessness, alcoholism and drug abuse
  • those who have weakened immune system by HIV etc.
  • young children and very elderly people more susceptible
80
Q

how long does a course of anti-TB drugs last and why? (2)

A
  • at least 6 months

- the medicine is most effective against bacilli that are ‘awake’ and growing.

81
Q

why are anti-TB drugs always prescribed in combination?

A
  • to reduce risk of TB bacilli becoming resistant to one or more of them
82
Q

how can drug resistance be developed to anti-TB medication? (2)

A
  • if the medication isnt taken correctly

- eg wrong dose, intermittently, too short of a time etc.

83
Q

what are the first line drug for TB? (4)

A
  • isoniazid
  • rifampicin
  • pyrazinamide
  • ethambutol
84
Q

what is the classification of eukaryotic cells?

A
  • a group of closely related organisms, which reproduce sexually to produce a fertile offspring
85
Q

what is classification of bacteria based on? (3)

A
  • based on the nucleotide sequence of rRNA
  • present in all living cells as ribosomes are required to build protein
  • rRNA sequence forms the basis for phylogeny (study of evolution of organisms)
86
Q

what are the simple traditional methods of bacteria identification? (4)

A
  • cultivation; growth requirement
  • cultivation; selective agar
  • biochemical profiling
  • serological testing
87
Q

what are the complex newer methods of bacteria identification? (2)

A
  • nucleic acid techniques

- MALDI_TOFF

88
Q

what is cultivation?

A
  • bacteria grown in lab
  • allows morphological characterisation
  • spore production and flagella
  • staining characteristics (eg gram staining)
  • colony morphology
89
Q

can just the cultivation method identify a bacteria and why?

A
  • no as morphology alone can’t distinguish bacteria

- ne rod looks much like another

90
Q

what does vogel johnson agar indicate?

A
  • indicates S aureus

Mpharm 1 COPY (59 decks)

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