Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Medicine Principles > Microbiology > Flashcards

Microbiology Flashcards

1
Q

Where are the following pathogens found and are they eukaryotes or prokaryotes?:

  • Protozoa
  • Fungi
  • Bacteria
  • Viruses
A
  • Protozoa = found in single celled animals, eukaryotes
  • Fungi = found in higher plant-like organisms, eukaryotes
  • Bacteria = they are generally small and single celled, prokaryotes
  • Viruses = very small, obligate parasites, non-living
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Eukaryote vs Prokaryote:

- Size

A

Eukaryote - 5-50mms (larger)

Prokaryote - 0.5-10mms (smaller)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Eukaryote vs Prokaryote:

- Structure

A

Eukaryote - frequently multicellular complex which is compartmental
Prokaryote - usually single celled and relatively simple

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Eukaryote vs Prokaryote:

- Type of chromosome and DNA

A

Eukaryote - linear chromosomes, histones, introns and exons

Prokaryote - single circular chromosome with gene structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Eukaryote vs Prokaryote:

- Ribosomes

A

Eukaryote - 80S ribosomes

Prokaryote - 70S ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Eukaryote vs Prokaryote:

- Cellular structure and cell cycle

A

Eukaryote - no wall or flexible cell wall. Cell cycle is mitosis/meiosis
Prokaryote - rigid cell wall. Cell cycle is rapid cell cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Nucleoid:

  • What does it contain?
  • How is DNA replicated?
  • How are chromosomes organised?
A
  • DNA and proteins, no nuclear membrane and chromosomes are single circular molecules. Also contains DNA segregation machinery
  • Via DNA dependent RNA polymerase
  • By gyrases and extra chromosomal replicons often exist
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the cell wall made up of?

A

Peptidoglycan and has a repeated polysaccharide structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Cell wall in gram negative vs gram positive organisms

A

Gram negative - single layer. Outer membrane, periplasm then thin peptidoglycan layer
Gram positive - many layers of peptidoglycan ‘roped’ together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Role of lipopolysaccharide

A

Has a structural role and antigen and bacterial toxin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Things required for prokaryotic growth

A

Food, temperature, hydrogen ion concentration, osmotic protection, oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

4 things that can be used to classify microorganisms

A

Appearance/structural features, growth requirements, enzyme/metabolic tests, molecular tests

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Appearance/structural features in classifying microorganisms

A

Shape, size, arrangement, Cell wall (gram +ve/-ve)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Growth requirements in classifying microorganisms

A

Aerobic/anaerobic, requirement for blood products, sensitivity to inhibitory agents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Enzyme/metabolic tests in classifying microorganisms

A

Coagulase test, catalase test, haemolysis (streptococci ONLY), biochemical profiling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Molecular tests in classifying microorganisms

A

Immunological test, DNA sequencing, protein profiling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What can microscopy tell about a microorganism?

A

If its a pure culture or polymorph, its shape, sizing and grouping, structures, staining

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Shapes of bacteria

A

Cocci, bacilli, spiral-shaped

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Divisions of cocci

A

1 plane - diplococcus or chains

3 planes - clumps/clusters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Vibrio

A

Slightly curved rod. Gram negative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Spiral shaped microorganisms - rigid and flexible

A

Rigid - spirillum

Flexible - spirochaete

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Spores

A

Inert structures that are resistant to physical and chemical challenge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Gram stain

A

Process which shows retention of crystal violet/iodine complex by gram positive bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Gram stain procedure

A
  1. Prepare a heat fixed film of bacteria on a glass slide
  2. Stain with crystal violet for 1 minute then rinse with water
  3. Treat with Gram’s iodine for 1 minute then rinse with water
  4. Briefly decolourize with acetone or ethanol
  5. Counter stain with basic fuchsin or safranin for 1 minute then rinse with water
  6. Blot dry and view under oil immersion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What colour to gram positive and gram negative microorganisms stain?

A

Positive = purple, negative = pink

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Examples of microorganisms which don’t stain with the gram stain procedure

A 
Mycobacterium tuberculosis (causes TB) has a waxy cell wall which doesn't take up the stain
Treponema pallidum (causes syphilis)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Aerobic

A

Grow in oxygen/air

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Obligate aerobes

A

Require oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Obligate anaerobes

A

Killed by oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Facultative anaerobes

A

Tolerate oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Capnophillic

A

Prefer high CO2 levels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Selective media

A

A media that selects for the growth of specific prokaryotes. Presence of specific substances permits the growth of one organism over another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Examples of selective media

A

Mannitol salt agar, salmonella-shigella

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Differential media

A

Incorporation of chemicals produces visible changes in colonies that facilitate identification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Alpha hemolysis

A

Greening of colonies, partial hemolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Beta hemolysis

A

Yellowing of colonies, partial hemolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Gamma hemolysis

A

No haemolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What does matrix assisted laser desorption ionisation time of flight do?

A
  • Generates a series of ions from a sample dependent on its constituents
  • Separates the ions according to their mass and charge
  • Detects the spectrum of proteins released from a sample resulting in a characteristic signature
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

How do pathogens cause damage to the host cell?

A
  • Adhere, colonise and invade
  • Evade host defences
  • Multiply and complete life cycle
  • Exit the host
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Virulence

A

The capacity of a microbe to cause damage to the host

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Pathogen

A

A harmful organism which produces a pathology

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Endogenous and exogenous

A

Endogenous - microorganisms which from within a system

Exogenous - not part of the normal flora

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Opportunistic pathogen

A

An organism which causes infection when an opportunity/change in natural immunity arises

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Contaminant

A

An organism that is growing in a culture by accident

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Examples of fungal infections

A

Candida spp. (yeast (budding), from skin infection to Candidaemia)
Aspergillu spp. (moulds, causes infection in immunocompromised)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Examples of protozoal infections

A

Leishmaniasis, malaria, toxoplasma, GI infections

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

2 pathogenic, anaerobic gram negative cocci

A

Neisseria meningitis - commonest cause of bacterial meningitis
Neisseria gonorrhoea - causes gonorrhoea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Coliforms:

  • Do they grow in aerobic or anaerobic conditions?
  • Are they normal/abnormal?
  • How are they differentiated from each other?
A
  • Grow best aerobically but can also grow anaerobically
  • Many of them are part of the normal gut flora
  • They are differentiated by biochemical reactions, serotyping and O antigens and H antigens
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

What are coliforms?

A

Coliform is a term used to describe species of gram negative bacteria that look like E.coli on gram film and when cultured on blood agar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

How do coliforms cause infection? Give examples of infections that can cause

A

Any coliform that gets into a normally sterile site can cause a serious infection e.g. urinary tract infections, peritonitis and biliary tract infections

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

What is the first line antibiotic for the treatment of infections caused by coliforms?

A

Gentamicin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

Why do patients with coliform sepsis become very unwell very quickly?

A

Because of the endotoxin that is released from the gram negative wall when the bacteria die

53
Q

Steps in sepsis

A
  1. Small vessels become ‘leaky’ and lose fluid into the tissues
  2. Lower volume requires heart to work harder to maintain oxygenation of tissues (↑HR)
  3. Poor tissue oxygen perfusion means blood supply to less essential organs is shut down to maintain supply to the brain
  4. Blood clotting system is activated causing blood clot in tiny vessels, using up all clotting factors and increased risk of haemorrhage
54
Q

What is the most significant pathogenic streptococci?

A

Group A streptococci

55
Q

Most important group in non-haemolytic streptococci

A

Enterococci (commonest cause of UTI)

56
Q

Which groups of patients are most likely to get MRSA?

A

Elderly, immunocompromised, those in ICU, burns patients, dialysis patients, surgical patients and patients on dialysis

57
Q

Microorganism that is the most common cause of skin, soft tissue and wound infection

A

Staph aureus

58
Q

Clostridioides:

  • What are they?
  • Where are they found?
  • What concerning things do they produce?
A
  • Gram positive anaerobic bacilli
  • They are found as part of the normal gut flora of man in animals and are found in faeces and soil
  • They produce spores that can survive outside the body for many months and exotoxins that can cause severe tissue damage
59
Q

What does C. difficile cause?

A

Antibiotic associated diarrhoea. It proliferates in absence of normal flora

60
Q

Structure in icosahedral symmetry

A

Made up of repeated subunits, 3 building blocks required apex, edge and centre of face

61
Q

How do viruses enter a cell?

A
  • Viruses interact with specific receptors on the cell membrane and attach via lock and key mechanism
  • They enter by the fusion of viral and cell membranes or endocytosis
  • Uncoating - viral nucleic acid released from the capsid
  • This produces new viral proteins
  • Nucleic acid and proteins are packed together
  • The virus is released from the target cell
62
Q

Ways viruses can be released from target cells

A
  • Via the reverse of entry, a piece of host membrane ends up around the capsid
  • By budding - mature progeny virus is released with envelope derived from host cell membrane
  • Lysis
63
Q

Cell structures targeted by antibiotics

A

Cell wall, bacterial ribosomes, other bacterial structures/enzymes

64
Q

Possible targets for antivirals

A
  • Enzymes involved in viral nucleic acid replication or protein synthesis
  • Uncoating
  • Attachment/entry process
  • Release stage
65
Q

Rational drug design

A

The use of detailed molecular analysis of viral targets to design a molecule that might inhibit its function

66
Q

What happens in immunity against virus infections?

A

Cytotoxic T lymphocytes can recognise proteins on the surface as being foreign and will signal the infected cell to undergo apoptosis to prevent formation of further mature virus

67
Q

Viral persistence

A

Viral may become quiescent (no active replication)
Viruses may reactivate
Viruses may remain continually active for years - chronic infection

68
Q

How is virus infection confirmed in the laboratory?

A

By detecting the antibody response against the virus or by detecting the presence of the virus itself

69
Q

How can recent infection be differentiated from past infection?

A

Detection of virus specific IgM antibodies
Detection of rising titre of IgG antibodies
Detection of very high titre of IgG antibodies

70
Q

Virus detection methods that are currently in use

A

PCR, antigen detection

71
Q

Bacteriostatic vs bactericidal

A

Bacteriostatic - inhibit growth of bacteria

Bactericidal - kill bacteria

72
Q

Ideal antibiotic in relation to the following:

  • Toxicity
  • Inhibition or killing of bacteria
  • Half life
  • Tissue distribution
  • Side effects
  • How it is administered
A
  • Minimal toxicity
  • Bactericidal
  • Long half-life
  • Appropriate tissue distribution
  • No adverse drug interactions/side effects
  • Oral or parenteral preparations
73
Q

How can absorbable antibiotics be secreted from the body?

A

In the urine or via the liver, biliary tract and into the faeces

74
Q

How can drugs be administered?

A

Orally, intravenously or (rarely) intramuscularly

75
Q

When will an antibiotic reach peak serum levels if given orally vs intravenously?

A

Orally - 1 hour

IV - 15 mins

76
Q

Commonly prescribed cell wall antimicrobials

A

Penicillin, cephalosporins, glycopeptides

77
Q

Target of beta lactams

A

Penicillin binding proteins

78
Q

Penicillins:

  • End in what?
  • Side effects
  • Narrow or broad spectrum?
  • Excretion?
  • Safe in pregnancy?
A
  • End in -cillin
  • Very few side effects
  • Range from narrow to broad spectrum
  • Excreted rapidly in the kidneys
  • Safe in pregnancy
79
Q

Limitations of penicillin

A

Patients can be hypersensitive (allergic), they are excreted rapidly via kidneys (results in frequent dosing), increasing resistance

80
Q

Gram positive penicillins

A

Flucloxacillin

81
Q

Gram positive and gram negative penicillins

A

Amoxicillin and co-amoxiclav

82
Q

Gram negative penicillins

A

Temocillin

83
Q

3 principle compounds of penicillin and their administration

A

Benzylpenicillin - IV
Phenoxymethyl penicillin - oral
Benzathine penicillin - IM

84
Q

What is amoxicillin challenged by?

A

Spread of beta lactamases (enzymes that destroy beta lactam ring)

85
Q

Benefit the combination of antimicrobials

A

Extends the range of bacteria that can be treated

86
Q

Flucloxacillin prescribed to treat which type of infections?

A

It is very narrow spectrum and is useful for streptococci and staphylococci only

87
Q

What does the polar side chain on piperacillin do?

A

Enhances penetration into gram negative bacteria

88
Q

What is temocillin?

A

Beta-lactamase resistant form of penicillin that is largely restricted to coliforms and is active against ESBL-producing organisms

89
Q

Cephalosporins:

  • What do they inhibit?
  • Long or short half-life?
  • How are they excreted?
  • Side effects?
  • Safe in pregnancy?
A
  • Inhibit cell wall synthesis and are bacteriocidal
  • They have a longer half-life in plasma
  • Excreted via the kidneys and urine
  • Very few side effects
  • Safe in pregnancy
90
Q

Are cephalosporins narrow or broad spectrum?

A

Broad-spectrum

91
Q

Why are cephalosporins avoided in many hospitals?

A

They kill off the normal gut bacteria and allows the overgrowth of Clostridium difficile, which causes nasty gastroenteritis

92
Q

Examples of glycopeptides

A

Vancomycin, teicoplanin (both given IV)

93
Q

How do glycopeptides work?

A
  • Bind to peptide side chains and prevent incorporation into the cell wall
  • Blocks access to substrate PBP
  • Inhibits peptoglycan synthesis
  • Reduces cross-linking and activity of lytic enzymes weaken bacterial wall
    THEY ARE BACTERICIDAL
94
Q

Glycopeptides:

  • How are they excreted?
  • Narrow or broad spectrum?
A
  • Via the kidneys and in the urine

- Narrow spectrum - gram +ve only

95
Q

Why are vancomycin avoided in patients with kidney failure?

A

Toxic levels can build up in the blood and cause further kidney damage

96
Q

How do antibiotics that inhibit protein synthesis work?

A

They attach to bacterial ribosomes

97
Q

Are antibiotics that inhibit protein synthesis bactericidal or bacteriostatic?

A

Bacteriostatic - usually protein synthesis of the bacteria can resume when the antibiotic is removed with the exception of aminoglycosides

98
Q

Examples of antibiotics that target protein synthesis

A

Aminoglycosides (gentamicin), tetracyclines (doxycycline) and macrolides (erythromycin)

99
Q

Gentamicin:

  • How is it given?
  • How does it work?
  • Gram positive or gram negative infections?
  • How is it excreted?
A
  • Given IV (occasionally IM) as not absorbed by the gut
  • Binds to ribosomes (30s) inhibiting protein synthesis. Bactericidal
  • Works against gram negative infections
  • Excreted in urine
100
Q

Toxicity and side effects of gentamicin

A

Toxic - causes damage to the kidneys and CN VIII, causes dizziness and deafness so level in the blood must be monitored regularly

101
Q

Tetracyclines:

  • Mode of action
  • Spectrum of activity
  • Adverse effects
  • When is use restricted?
A
  • Actively transported into the cell, binds to 30s subunit and prevents attachment of tRNA to receptor sited
  • Broad spectrum
  • Destruction of normal intestinal flora resulting in increased secondary infections, staining and impairment of structure of bones and teeth
  • Use is restricted in children and pregnancy
102
Q

Examples of macrolides

A

Erythromycin, clarythromycin, azithromycin

103
Q

How are macrolides excreted?

A

Through the liver, biliary tree and gut

104
Q

Antibiotics that affect nucleic acids

A

Metronidazole, trimethoprim, fluoroquinolones

105
Q

Common side effects of antibiotics

A

Nausea, vomiting and diarrhoea, renal and CN VIII damage (gentamicin), tendonitis (ciprofloxacin), interactions with alcohol (metronidazole)

106
Q

Why are antibiotics often given in combination?

A

To cover a broad range of possible infecting organisms, to prevent the development of resistance, for the synergistic effect of combination

107
Q

4 antibiotics are that are generally avoided as they are associated with an increased risk of C.difficile

A

Cephalosporins
Co-amoxiclav
Ciprofloxacin
Clindamycin

108
Q

Natural antimicrobial resistance

A

Target not present, target not accessible, metabolism, developmental structure/state

109
Q

Biofilms

A

Organisms resistant to antimicrobial agents and host defences

110
Q

Persistor cells

A

Dormant cells that form spontaneously within a biofilm and are resistant to antimicrobials

111
Q

Resistance

A

Drug is no longer active against an entire population of cells

112
Q

How does resistance come about?

A

Genetic variation, selective pressure, evolution resistance, gene transfer

113
Q

Ways gene transfer can occur horizontally between bacteria

A

Natural competence, bacteriophage, sex pili

114
Q

Cross resistance and multiple resistance

A

Cross resistance - single mechanism. Affects closely related antibiotics
Multiple resistance - mechanisms. Affects unrelated antibiotics

115
Q

Mechanisms of antimicrobial drug resistance

A

Altered permeability, inactivation, altered target site, replacement if a sensitive pathway

116
Q

What are the following resistant to?:

  • Penicillinase
  • Beta-lactmase
  • Carbapenemase
A
  • Early penicillins i.e. amoxicillin
  • All the penicillins
  • All the penicillins, all cephalosporins and all carbapenems
117
Q

Chain of infection

A

Infectious microbe → reservoir (where microbe lives and replicates) → portal of exit (where microbe leaves reservoir) → modes of transmission → portal of entry → susceptible host → infectious microbe

118
Q

Ways to interrupt transmission

A

Sterilisation/disinfection
Isolation/PPE
Decontamination
Vaccination

119
Q

5 ways any infection can spread (5 Is)

A

Inhalation, ingestion, inoculation (direct and indirect), mother to infant, intercourse

120
Q

Standard control of infection precautions

A

Hand hygiene, sharps management, clinical waste, PPE, respiratory etiquette, body fluid spillages, environmental cleanliness, laundry, clean equipment, patient placement

121
Q

6 steps of hand hygiene

A
  1. Palm to palm
  2. Palms over dorsum
  3. Fingers interlaced
  4. Backs of fingers to palms while fingers interlaced
  5. Rotational rubbing of thumbs in opposite palms
  6. Rotational rubbing of clasped fingers in palms
122
Q

5 moments for hand hygiene

A

Before patient contact, before aseptic task, after body fluid exposure risk, after patient contact, after contact with patient surroundings

123
Q

Droplet precautions

A

Single room, ensuite shower/toilet, gloves, apron or fluid resistant gown, mask, eye protection, vaccination (where possible, incl. staff)

124
Q

Disinfection

A

Process by which the number of organisms are reduced to a level that is considered safe

125
Q

Methods of disinfection

A

Hot water and detergent, hypochlorite, chlorohexadine, povidone iodine, ethanol

126
Q

Sterilisation

A

Process by which all microorganisms are killed or removed to render the object incapable of causing infection

127
Q

Methods of sterilisation

A

Heat (autoclave), chemical, radiation, filtration

128
Q

How does an autoclave kill microorganisms?

A

By coagulating and denaturing enzymes and structural proteins

129
Q

Multiple factors influencing disease transmission

A

Agent (infectivity, resistance, virulence etc), Environment (weather, housing, geography, food, air quality etc), Host (age, sex, genetics, behaviour, nutritional status, health status)

Medicine Principles (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions