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Pathology > Introduction to microbiology: Bacteria > Flashcards

Introduction to microbiology: Bacteria Flashcards

0
Q

List the subjects of microbiology

A
  • bacteria
  • viruses
  • fungi
  • Protozoa
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1
Q

Define microbiology

A

The study of organisms and agents too small to be seen by the unaided eye ie microorganisms

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2
Q

List some applications of microbiology

A
  • food industry
  • agriculture
  • medicine
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3
Q

What type of microbiology are light microscopes able to see

A

Bacteria

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4
Q

What type of microscopes are able to see viruses

A

Electron microscopes

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5
Q

What scale of microorganisms are harmful

A

Small amount

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6
Q

How large are viruses

A

10-1000 nanometers (smallest)

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7
Q

What size are bacteria

A

0.1-5 micrometers

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8
Q

What size are Protozoa

A

5-200 micrometers (largest 1/4 of a mm)

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9
Q

What is the name of the virus which causes flu

A

Influenza A

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10
Q

What is the name of the bacteria which is a normal skin resident found throughout the body

A

Staph aureus

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11
Q

Which microorganism can cause MRSA

A

Staphylococcus aureus

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12
Q

What does MRSA stand for

A

Methicillin resistant staphylococcus aureus

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13
Q

What is the name of the antibiotic that MRSA is resistant to

A

Methicillin

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14
Q

Which bacteria is the most common cause of bacterial conjunctivitis

A

Staphylococcus aureus

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15
Q

What type of organism is acanthamoeba

A

Water Bourne organism

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16
Q

What is acanthamoeba found in

A

Domestic water supplies in the UK

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17
Q

What can acanthamoeba cause

A

Corneal infection of contact lens wearers who wash their contact lenses in tap water

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18
Q

What two things do infectious diseases cause

A
  • morbidity

- mortality

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19
Q

What does morbidity cause

A

Harm & disease

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20
Q

What are infectious diseases caused by

A

Pathogenic microorganisms such as bacteria, viruses, parasites or fungi

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21
Q

Which two ways can the diseases be spread by from person to person

A

Directly or indirectly

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22
Q

Which infectious disease is the biggest killer

A

Acute respiratory infection

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23
Q

How much amount of deaths do infectious diseases cause worldwide and are leading cause of death

A

One-third

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24
Q

Why are one third of all deaths caused by infections

A

Because of disease in developing countries

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25
Q

How much percent of deaths are from infectious diseases caused by a handful of diseases

A

90%

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26
Q

Name a viral ocular infection

A

Herpes simplex keratitis

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27
Q

Name a bacterial ocular infection

A

Bacterial keratitis

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28
Q

Name a chlamydial ocular infection

A

Trachoma

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29
Q

Name a protazoal ocular infection

A

Acanthamoeba keratitis

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30
Q

Name a fungal ocular infection

A

Fungal keratitis

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31
Q

Which is the same virus which causes cold sores

A

Herpes simplex

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32
Q

What is the meaning of keratitis

A

Inflammation of the cornea caused by a virus

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33
Q

What type of ulcer does herpes simplex keratitis cause on the cornea

A

Dendritic (multiple branching pattern)

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34
Q

Which type of patients is bacterial keratitis more common in

A

Contact lens wearers (90% who got the infection wear cl’s)

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35
Q

Which part of the eye does the chlamydial infection trachoma affect

A

Conjunctiva

It is a conjunctival infection

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36
Q

What can trachoma be treated with

A

Antibiotics

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37
Q

What does a chlamydial infection do to the eye to cause corneal scarring

A

Turns eyelashes towards the eye

And produces a poor ocular surface

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38
Q

What is the treatment following the protazoal infection, acanthamoeba keratitis

A

Corneal graft due to the scarring

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39
Q

What infection causes a corneal inflammation by a fungus

A

Fungal keratitis

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40
Q

What are the two ways of fighting infection

A
  • vaccination

- antibiotics

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41
Q

What do the majority of present day vaccination programmes use and why

A

Active vaccines containing pathogen-specific antigens to elicit a protective immune response in the recipient

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42
Q

What effect does repeated vaccination have

A

Enhances the effectiveness of the antibody response and for some vaccines
It also elicits cell mediated responses

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43
Q

Which infections were a major killer before there was vaccination

A

Measles
Mumps
Reubella

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44
Q

What vaccine was a combined vaccine for measles, mumps and reubella

A

MMR vaccine

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45
Q

During which period did antibiotics come about

A

1940’s

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46
Q

What microorganism is antibiotics useful for and hopeless against

A

Useful for bacteria

& hopeless against viruses

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47
Q

How do antibiotics cure diseases

A

By killing or interfering with the growth of bacteria

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48
Q

How are antibiotics non toxic compounds

A

They have selective toxicity because bacteria synthesise their DNA differently to body cells

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49
Q

What are narrow spectrum antibiotics

A

Antibiotics which selectively act on a few specific bacteria

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50
Q

What are broad spectrum antibiotics

A

Antibiotics which target a wider range of bacteria

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51
Q

What do bacteria synthesis differently to normal human (eukaryotic) cells

A

DNA & protein

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52
Q

What does a bacteria cell have in addition to a cell wall

A

A cell membrane

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53
Q

How does antibiotic resistance arise

A

By the drug killing the defenceless bacteria and selecting those that can resist it

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54
Q

When was resistance to penicillin identified and how long was that after the mass production

A

1943

4 years after mass production

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55
Q

What is the term superbug often used to refer to

A

Healthcare associated infections eg
- methicillin resistant staphylococcus aureus (MRSA)
&
- clostridium difficile (c.difficile)
Are resistant to commonly used antibiotics

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56
Q

What is clostridium difficile

A

A gut organism

Is usually a small amount but can cause death

57
Q

What is an epidemic most commonly used to describe

A

An outbreak of an illness or disease in which the number of individual cases exceeds the usual or expected number of cases in any given population

58
Q

What is a pandemic describe

A

An epidemic which occurs in more than one country or population simultaneously

59
Q

Give an example of a disease which has reached pandemic proportions

A

AIDS/HIV virus

60
Q

when did AIDS begin

A

early 1980’s

61
Q

when was AIDS identified around

A

1984

62
Q

when was an anti body for AIDS found to test for the disease

A

1986

63
Q

where in the world is AIDS most common

A

africa 5% so 1 in 20 people in Africa had AIDS

64
Q

what is a pathogen

A

a disease causing organism

65
Q

with what cells are there more of bacteria compared to

A

human cells

66
Q

how many types of species of bacteria are there on the body

A

800

67
Q

what are commensals

A

microorganisms that derive benefit from the host and in turn protect the body from the disease (limit the growth of harmful disease)

68
Q

how many % of organisms are commensals in the body

A

90%

69
Q

state the order of which microorganisms are pathogenic and non pathogenic

A
  • very few microbes are always pathogenic (e.g. bacteria which causes TB)
  • many microbes are potentially pathogenic (in particular circumstances)
  • most microbes are never pathogenic (won’t cause disease)
70
Q

what are bacteria usually classified according to

A
  • morphological appearance (size and shape)
  • staining characteristics
  • growth requirements
    recent developments have established a
  • genotype classification (genetic makeup)
71
Q

list the three types of shapes of bacteria

A
  • cocci, diplococci
  • bacilli, coccobacilli
  • spirochetes
72
Q

which shape of bacteria are round

A

cocci & diplococci

73
Q

what is the difference between cocci and diplococci bacteria

A

cocci are individual round shapes and diplococci are pairs of round shape bacteria cells

74
Q

which shape of bacteria are rod-shaped

A

bacilli

75
Q

what is the difference between bacilli and coccobacilli

A

bacilli are rod shaped and coccobacilli are more oval shaped (in-between rod and round)

76
Q

which shape of bacteria are spiral

A

spirochetes

77
Q

what do bacteria cells lack

A

a membrane bound nucleus
&
sub-cellualar organelles

78
Q

what are prokaryotes

A

a cell with a nucleus what doesn’t have a nuclear membrane but does have DNA loose within the cytoplasm
eg bacteria

79
Q

how is the DNA organised in a bacteria cell

A

as a fibrous mass in the cytoplasm

80
Q

what type of ribosome does a bacteria prokaryotic cell have

A

70s

consisting of 30s and 50s sub-units

81
Q

what type of ribosomes does a eukaryotic cell have

A

80s

82
Q

which ribosomes protein synthesis does the antibiotic inhibit

A

70s

83
Q

what does a bacteria cell envelope consist of

A

a plasma membrane and a cell wall

84
Q

what does the bacteria plasma membrane and cell wall contain

A

a special polymer called peptidogylcan

85
Q

what is a peptidoglycan

A

a repeating disaccaride unit which produces the cell wass

86
Q

what do some bacteria which have inclusion bodies act as

A

an energy store

87
Q

what are two sub-divisions of bacteria distinguished according to

A

their ability to retain a crystal violet iodine dye complex

88
Q

describe the method of using a gram stain on bacteria

A
  • place bacteria on a slide
  • air dry it at room temperature
  • stain the slide with crystal violet
  • treat the slide with iodine
  • decolourise with ethanol
89
Q

what do the different staining characteristics of bacteria by crystal violet iodine dye complex relate to

A

differences in the cell wall

90
Q

what is a bacteria which has retained the dye after ethanol has been placed on it called

A

gram positive

91
Q

what is a bacteria which has decolourised after ethanol has been placed on it

A

gram negative

92
Q

how to gram positive bacteria retain the gram stain

A

as it becomes incorporated in the thick peptidoglycan layer that surrounds the organism

93
Q

what type of peptidoglycan layer do gram negative organisms have

A

a reduced/thin peptidoglycan layer

94
Q

what do peptidoglycan consist of a backbone of

A

alternating units of:
- N-acetyl glucosamine (NAG)
&
- N-acetyl muramic acid (NAM)

95
Q

what type of compounds are N-acetyl glucosamine (NAG & N-acetyl muramic acid (NAM)

A

disaccharides assembled together which form two repeating sugar proteins

96
Q

what are gram positive bacteria further characterised by with the presence of

A

teichoic & teichuronic acids bonded to the peptidoglycan layer

97
Q

what is a major component of the outer membrane of gram negative bacteria

A

lipopolysaccharide (incorporating lipid A endotoxin)

98
Q

what do certain gram positive and gram negative bacteria have and what is it for

A

a capsule external to the cell wall
this protects the bacterium and may confer resistance to intracellular killing by phagocytosis (protective capsule is resistance to phagocytosis)

99
Q

what is present on a bacterial cell which allows for locomotion (move around in fluid)

A

flagella

100
Q

what may gram negative organisms be covered in and why

A

fine hairs called fimbriae

which mediates attachment to the host

101
Q

what component of a bacterium cell can attach bacterial cells and for what reason

A

pili
to attach bacterial cells together or/and to transfer genetic information which can be associated with resistance (sex pili)

103
Q

what can almost all bacteria survive on and why

A

simple organic compounds e.g. glucose

because they need little nutrients in order to survive (they have a simple metabolism)

104
Q

which ways are energy production achieved for bacteria

A
  • glycolysis
  • TCA cycle
  • oxidative phosphorylation
105
Q

what is the alternative pathway which can be used to produce energy for bacteria

A

pentose phosphate pathway

106
Q

in which conditions can facultative organisms live in and what does this determine

A

aerobic
or
anaerobic conditions
determines if the bacteria either only uses glycolysis or glycolysis & krebs cycle

107
Q

how are facultative organisms very adaptable

A

they can live with or without oxygen or it can even utilise oxygen

108
Q

how does bacteria in the absence of oxygen (anaerobes), produce energy

A

the glycolytic pathway (fermentation yielding) which goes to pyruvate, which turns into lactate or ethanol

109
Q

what do aerobes require

A

oxygen

110
Q

where are bacterial genes located

A

both within the bacterial chromosomes and extrachromosomal plasmids

111
Q

where are many antibiotic resistance genes located

A

on plasmids

112
Q

what can the transfer of genetic information occur through

A
  • transformation
  • transduction
  • conjugation
113
Q

how does the transfer of genetic information occur via transformation

A

bacteria can take up the plasmid (simple loop of DNA) and they become incorporated

114
Q

how does the transfer of genetic information occur via transduction

A

a phage (bacterial virus) is able to transfer genetic information from one bacterial cell on to another

115
Q

how does the transfer of genetic information occur via conjugation

A

a pilus connects bacterial cells together & plasmids can transfer across the pilus

116
Q

what are bacterial spores and what do they do

A

spores are highly resistant structures which are an inactive form of bacterial cells which will activate when they are ready, and a few bacteria have the ability to produce them.
spores resist a range of environments and protect against heat, radiation or desiccation

117
Q

give some examples of spore forming bacteria

A
  • clostridium tetani
    &
  • bacillus anthracis
118
Q

what spore does clostridium tetani produce

A

tetanus

119
Q

what spore does bacillus anthracis produce

A

anthrax

120
Q

what does the body act as a host to a large number of

A

microorganisms (commensals)

121
Q

how do commensals protect against infection

A

by competing with potential pathogens for nutrients
or
preventing pathogens from colonising epithelial surfaces

122
Q

what may trigger pathogenic damage and give an example

A

alterations in homeostasis.
eg a non harming staphylococcus aureus on the eyelid are harmless but if they go into the eye from a cataract surgery they can cause bad effects which can be sight threatening

123
Q

name an example of a bacteria which is entirely adapted to the pathogenic way of life in humans and are never part of the normal flora

A

M. tuberculosis

124
Q

what do some bacteria which are part of the normal flora acquire, and what do they make them, give an example

A

extra virulence factors making them pathogenic

eg S. epidermidis

125
Q

what can many free-living bacteria and components of the normal flora cause in immunocompromised patients, and what if introduced to something particular, give an example

A

disease especially if introduced into deep tissues

eg acinetobacter

126
Q

what does the virulence mean

A

degree of pathogenicity (ability to cause damage to our body cells)

127
Q

what does virulence factors mean and give examples of what triggers this

A

factors that trigger pathology e.g.

  • adherence
  • invasion
  • toxicity
128
Q

name the steps of bacterial virulence factors

A
  • exposure (first must be exposed to pathogens)
  • adherence (bacterial cell must bind to skin or mucosa to cause harm)
  • invasion (through epithelium, but is not always the case as sometimes through the toxins that those bacterial cells induce you can still have an external infection & harm comes from what bacterial cells are excreting)
  • colonisation and growth (a direct damage to tissue = production of virulence factors)
    can either go on to:
  • toxicity (toxic effects are local or systemic)
    or
  • invasivness (further growth at original site and distant sites)
    both cause tissue damage & disease
129
Q

explain how bacterial cells cause harm in blepharitis

A

blepharitis has an infective component but the bacterial cells on the eyelash doesn’t cause the blepharitis, but the toxins they release does, which produces the harm

130
Q

many bacteria synthesise toxins that serve as…

A

virulence factors, inducing damage to the host

131
Q

what mechanisms do toxins cause damage by

A
  • inhibiting protein synthesis

- damaging cell membranes

132
Q

name the two types of bacterial toxins

A
  • endotoxins

- exotoxins

133
Q

how do endotoxins work

A

they are bound to the bacterial cell surface (become a component of the bacterial cell wall) and the toxin induces damage on contact

134
Q

the do exotoxins work

A

they are excreted or released onto surrounding tissues during bacterial lysis

135
Q

list the pathogenic mechanisms of staphylococcus species

A
  • protein A activates complement and induces inflammation (local inflammatory response) and inhibits opsonisation
  • leukocidin (toxins) kills neutrophils (cells which protect us) and macrophages
  • alpha toxin causes membrane damage to many types of cell
136
Q

what do antimicrobial agents do

A

kill or inhibit bacterial growth by interfering with

  • cell wall synthesis
  • DNA synthesis
  • protein synthesis
  • folic acid metabolism
137
Q

which antimicrobial agent kills bacterial growth by interfering with protein synthesis

A

chloramphenicol

138
Q

which antimicrobial agent kills bacterial growth by interfering with cell wall synthesis

A

penecillin

139
Q

when do we test for antibiotic susceptibility

A

when broad spectrum anti biotic doesn’t work

140
Q

what is the most common test for antibiotic susceptibility in clinical laboratories

A

disk diffusion test (kirby-bauer)

141
Q

how is the disk diffusion test carried out

A
  • a bacterial isolate is inoculated uniformly onto the surface of an agar plate
  • a filter disk is impregnated with a standard amount of antibiotic is applied to the surface of the plate
  • the antibiotic is allowed to diffuse into the adjacent medium
142
Q

how do we test for antibiotic susceptibility from disk diffusion test

A
  • zones of inhibition of bacterial growth may be present around the antibiotic disk
  • the size of the zone of inhibition is dependent on the degree of sensitivity of the bacterium to the antibiotic

Pathology (20 decks)

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