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Year 2 EMS MoD > Microbiology > Flashcards

Microbiology Flashcards

1
Q

What is meant by an akaryote?

A

Without a nucleus

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2
Q

What percentage of cells within the body are human body cells?

A

10%

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3
Q

What is the difference between human commensal flora and human microbiota?

A

Theyre the same thing

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4
Q

What is the human microbiota made up of?

A

Mostly bacteria, but some fungi and protists aswell

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5
Q

Are viruses considered part of human microbiota?

A

No, as dont have a cellular structure and all they can achieve outside of a host cell is infection of another host cell

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6
Q

In what 2 ways can viruses persist in the body?

A

1) As latent infections

2) Persistent sub-clinical infections

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7
Q

Microbiota varies depending on anatomical site - what microbiota tends to be found on the teeth and what on the tongue?

A

Teeth - Streptococcus mutans

Tongue and other soft tissues of the mouth - Streptococcus salivarius

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8
Q

Which microbiota is responsible for dental caries, in which people are they most common?

A

Streptococcus mutans - microbiota found on the teeth

Common in people with a diet high in sugar

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9
Q

What 2 terms are used to describe microorganisms which may cause disease?

A

Virulent or pathogenic

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10
Q

Which vitamin would we require a constant supply of in the absence of gut commensal flora?

A

Vitamin K

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11
Q

What is Koch’s Postulates?

A

Criteria used to decide if a microorganism caused disease

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12
Q

What are Koch’s 4 postulates?

A

1) The causative organism must be isolated from every individual suffering from the disease in question
2) The causative organism must be cultivated artificially in pure culture
3) When the causative organism is inoculated from the pure culture, they typical symptoms of the infection must result
4) The causative organism must be recoverable from individuals who are infected experimentally

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13
Q

What extra postulate would possibly be added to Koch’s postulates in modern day?

A

Ab to be raised against the causative organism in natural cases and in organisms infected artficially

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14
Q

What are Koch’s postulates for genes? 6

A

1) The gene encoding the trait should be present and transcribed/translated in virulent strain
2) The gene encoding the trait of interest should not be present or should be silent in a strain that does not cause disease
3) Disruption of the gene in a virulent strain should result in formation of a strain which is incapable of causing disease
4) Introduction of the gene into a strain that previously did not cause disease should transform the strain into one that does cause disease (NB. some virulence traits may require the expression of more than one gene)
5) The gene must be expressed during infection
6) Ab raised against the gene product or the appropriate cell-mediated immunity should protect experimental subjects against disease

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15
Q

What are the 4 problems with Koch’s postulates?

A

1) Difficulty of isolating the causative agent
2) Impossible to grow some pathogens in artificial culture
3) Ethical objections
4) Animal models not sufficient

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16
Q

Name one microorganism which can be difficult to isolate, what does it cause?

A

Mycobacterium tuberculosis, causes TB is very difficult to isolate

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17
Q

Name 2 pathogenic microorganisms which cannot be grown in artificial culture, what do they cause?

A

1) Mycobacterium leprae - causes leprosy, cannot be grown in artificial culture except in the foot of the 9 banded armadillo
2) Treponema pallidum causes syphillis

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18
Q

What do viruses consist of?

A

A nucleic acid core wrapped in a protein coat - some are enveloped and some are naked

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19
Q

Do viruses have DNA or RNA core?

A

Either but not both

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20
Q

Why are retroviruses unusual in terms of their action upon infection?

A

Contain an RNA copy of a genome but on infection of host cell a cDNA copy is made using reverse transcriptase which is then incorporated into the host cell DNA

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21
Q

What is the name of the units that make up the protein coat surrounding viruses?

A

Capsomeres

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22
Q

What is the name of the class of viruses which attacks bacteria?

A

Bacteriophage

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23
Q

What is the name of viruses which infect plants?

A

Viroids

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24
Q

What (in prevailing opinion) causes spongiform encephalopathies?

A

Infectious proteins known as prions

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25
Q

Are all fungi, prokaryotes, eukaryotes or akaryotes?

A

Eukaryotes

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26
Q

What is chitin?

A

Polymer of N-acetyl glucosamine that is found in the cell walls of the majority of fungi

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27
Q

Other than fungi what other organisms is chitin found in the cell walls of?

A

Exoskeleton or arthropods

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28
Q

What are moulds?

A

Fungi that grow in mats of tiny filaments known as hyphae that form mats called mycelia

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29
Q

What is the difference between aseptate hyphae and septate hyphae?

A

Hyphae may or may not be seperated into compartments by cross walls known as septa
Septate hyphae tend to be more advanced fungi than aseptate hyphae

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30
Q

What are unicellular fungi known as?

A

Yeasts

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31
Q

Are moulds multicellular or unicellular organisms?

A

Multicellular

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32
Q

What is the most common yeast?

A

Saccharomyces cerevisiae - bakers or brewer’s yeast

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33
Q

How do yeasts grow?

A

By budding of daughter cells from mother cells

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34
Q

What is the most common yeast infection and what is it caused by?

A

Thrush - caused by candida albicans

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35
Q

Give 2 examples of infections caused by moulds are they serious?

A

Superficial infections - ringworm and athletes foot

In immune compromised individuals they can cause much more serious infections but these are rare

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36
Q

What are pseudomycelia?

A

Yeasts can develop into these under certain conditions

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37
Q

What are protists?

A

Unicellular eukaryotes

Can infect any human tissue and cause a variety of diseases

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38
Q

What are the 4 classes of protists?

A

1) Apicomlxa (formerly sporozoa)
2) Flagellate protista
3) Ciliate protista
4) Amoebae

39
Q

Name 7 infections caused by protists?

A

1) Toxoplasmosis
2) Amoebic meningitis
3) Malaria
4) Trypanosomiasis
5) Leishmaniasis
6) Amoebic dysentery
7) Diarrhoea

40
Q

Chronic persistent diarrhoea caused by what organisms is associated with the onset of AIDS?

A

Cryptosporidium spp.

or Giardia intestinalis

41
Q

Name a protist which causes vaginal infections, what are the symptoms, can men be carriers?

A

Trichomonas vaginalis
Foul-smelling vaginal discharge
Men can be asymptomatic carriers, although this protist can cause balanitis

42
Q

Is Pneumocystis jiroveci a protist or fungus?

A

For many years considered to be a protist now known to be a fungus

43
Q

Are bacteria prokaryotes or eukaryotes, why?

A

Prokaryotes- lack a membrane bound nucleus

44
Q

What 4 shapes can bacteria be?

A

1) Round - cocci
2) Rod-shaped - bacilli
3) Comma shaped
4) Spiral shaped
(Most are round or rod shaped)

45
Q

What is the fundamental difference between gram negative and gram positive bacteria?

A

Gram positive - thick peptidoglycan layer (interlinked sugar molecules with both D and L amino acids) also containing teichoic and teichuronic acids
Gram negative - very thin peptidoglycan layer, with an extra complex outer membrane

46
Q

What colours do gram positive and gram negative go in the gram test?

A

Gram positive - retain crystal violet

Gram negative - counterstain pink or red

47
Q

What is the structure of the outer membrane of gram-negative bacteria, how does this contribute to disease?

A

Inner leaflet is a normal lipid layer
Outer leaflet containing lipopolysaccharide
Contains a complex lipid known as lipid A which acts as an endotoxin and is responsible for the symptoms of Gram-negative shock

48
Q

On which kind of bacteria are fimbraie found? What are they used for?

A

Found on gram negative bacteria

Used for adhesion to surfaces

49
Q

On which kind of bacteria are sex pili found, what are they used for?

A

Gram negative - exchange material through conjugation

50
Q

Some bacteria are enclosed within a capsule, how does this aid them?

A

Protects them from being killed, even within phagocytes

51
Q

Other than fimbraie what else do some bacteria do to help them adhere to surfaces?

A

Produce slime

52
Q

How is streptococcus mutans adapted to be able to form plaque which leads to dental caries?

A

Produces slime which enables it to stick to the surface of teeth
Also allows other microorganisms to stick to the teeth
The acid produced by metabolism of sugars in the diet then etches the surface of the tooth to which the bacteria are stuck initiating dental caries

53
Q

Name a bacteria that causes infections associated with metal or plastic implanted devices and how its adapted to do so?

A

Coagulase negative staphylococci
Live on the skin
Some strains produce a slime that enables them to stick to plastics

54
Q

Can all bacteria produce endospores? What do they enable?

A

No, only a few species of bacteria can produce endospores, resist a range of hazardous environments and protect against heat, radiation and desiccation

55
Q

Give the different methods of person to person infection? 6

A

1) Airbourne - droplets
2) Faecal-oral
3) Sexually transmitted
4) Direct inoculation - eg. IDUs
5) Animals - malaria
6) Inanimate objects

56
Q

Give 5 diseases spread by the faecal oral route (by drinking water contaminated with human faeces)?

A

1) Typhoid
2) Cholera
3) Dysentery
4) Hepatitis A
5) Poliomyelitis

57
Q

Why are the pathogens that cause STIs considered to be vulnerable?

A

They rapidly die when exposed to conditions outside of the body
In order to spread they require the most intimate of human contact

58
Q

Malaria is spread by what animal and is caused by what microorganism?

A

Female anopheles mosquito

Protists of the genus Plasmodium

59
Q

What are zoo noses? Give an example?

A

Animals are reservoirs for bacteria such as Salmonella enterica, infections caused by such organisms are known as zoo noses

60
Q

What are inanimate objects that can act as vectors for disease known as?

A

Fomites

61
Q

What does control of infection involve?

A

Identifying the mode of spread

Interrupting the cycle of infection, replication and spread

62
Q

What are traits used to complete the cycle of infection frequently known as?

A

Virulence factors

63
Q

Why are intoxication illnesses such as tetanus, botulism or ergotism unusual?

A

The sufferer does not need to encounter the live microorganism because disease results from exposure to the toxin rather than a living microorganism

64
Q

Give 4 main mechanisms through which bacteria cause disease?

A

1) Production of structures that enable the microorganism to attach to the surface at which they cause disease
2) Production of one or more toxins - endotoxins or exotoxins
3) Production of aggressins
4) Initiating undesirable consequences of host defences

65
Q

Why can soluble pathogenic antigens that combine with antibodies to produce circulating immune complex be a problem?

A

Can become trapped in blood vessels compromising their function

66
Q

Glomerulonephritis can result from circulating immune complexes after infection by what microorganism?

A

Streptococcus Pyogenes

67
Q

What does rheumatic fever result from?

A

Immunological cross reactions between human tissue antigens and antigens on Streptococcus pyogenes. Ab raised against the bacterial Ag cross react with human Ag causing autoimmune disease

68
Q

What is the tubercle?

A

Characteristic lesion of TB, has a major component of giant cells made from the fusion of several macrophages

69
Q

How many microbial cells does your human body harbour?

A

10^14

70
Q

Which part of your body contains the highest number of microbial cells?

A

Colon

71
Q

What is the definition of normal flora?

A

Organisms found in a given location in a state of health

72
Q

What is meant by colonisation?

A

Establishment at a sight in the body

73
Q

What is meant by symbiosis?

A

Two or more organisms co-exist in close physical association

74
Q

What are the 4 types of symbiosis and what is meant by each?

A

1) Mutualism - both organisms benefit from symbiosis
2) Neutralism - neither organism derives benefit or harm
3) Commensalism - one organism benefits, the other derives neither benefit or harm
4) Parasitism - one organism benefits at the expense of the other

75
Q

What is the difference non-sterile and sterile sights?

A

Non-sterile sights - have normal flora

Sterile sights - have no normal flora

76
Q

What characterises a non-sterile sight?

A

Exposed to the environment either directly or indirectly

No mechanism in place to maintain sterility

77
Q

Name 5 non-sterile sights?

A

1) Conjuctiva
2) Nasopharynx
3) GI tract
4) Vagina
5) Skin

78
Q

When does aquisition of normal flora begin?

A

Until birth sterility is maintained throughout
Aquisition of normal flora begins at birth
Differences are evident in caesarean vs. birth canal and breast fed vs. bottle fed

79
Q

What are the predominant differences in the normal flora of breast fed vs bottle fed babies?

A

Breast fed - bifidobacteria and lactobacillus

Bottle-fed - Enterobacteriacea

80
Q

Through which 3 mechanisms is sterility maintained in sterile sights, and in which kind of sights does each tend to occur?

A

1) Sterility maintained by surface cleaning - in sights open to the environment
2) Sterility maintained by barriers which allow uni-directional flow - in sights adjacent to non-sterile sights
3) Sterility maintained by physical separation from non-sterile sights - eg. closed cavities

81
Q

Give an example of a sterile sight maintained by surface cleaning?

A

1) Lower respiratory tract

82
Q

Give 3 examples of sterile sights maintained by barriers allowing uni-directional flow, and what these barriers are?

A

1) Upper genital tract - barrier = cervix
2) Urinary tract - barrier = urethra
3) Middle ear - barrier = eustachian tube

83
Q

Give 3 examples of sterile sights in which sterility is maintained by physical separation?

A

1) Plural cavity
2) Peritoneal cavity
3) Spinal cord and meninges

84
Q

What is meant by microenvironments?

A

Different sites within sites

85
Q

What is meant by tissue tropism?

A

Propensity for a particular organism to grow in a particular part of the body

86
Q

What are the 5 physical variables of different sites of normal flora?

A

1) Moisture
2) Temperature
3) pH
4) O2 availability
5) Nature of surface

87
Q

What are the 6 physical properties of the skin that make it a relatively inhospitable environment for microbiota?

A

1) Variable temperature
2) Dry
3) Subject to abrasion
4) Aerobic environment
5) Nutrient - poor
6) Skin surface components

88
Q

What are the 6 physical properties of a gingival crevice in terms of as a site for microbiota?

A

1) Constant temperature
2) Moist
3) Few physical challenges (toothbrush)
4) Anaerobic environment
5) Bathed in nutrients
6) Mucosal surface components

89
Q

What should be noted about the type of bacteria on skin close to an orifice?

A

It is likely to be similar to the bacteria in that orifice

90
Q

What 3 bacteria make up the majority of skin flora?

A

1) Coagulase-negative staphylococci (staphylococcus epidermis)
2) Staphylococcus aureus (esp. in nasal cavities)
3) Propionibacterium species (propionibacterium acnes)

91
Q

How can normal mouth flora benefit us in terms of infection?

A

Mouth is exposed to a wide range of bacteria and established normal flora can prevent colonisation of pathogenic flora

92
Q

Overgrowth of what normal mouth flora can lead to tooth erosion and how?

A

Overgrowth of oral streptococci leads to biofilms on teeth, convert sugars to lactic acid which damages enamel and erodes teeth

93
Q

What are the 2 main components of normal mouth flora?

A

1) Viridans/ oral streptococci

2) Anaerobes

94
Q

In terms of nasopharyngeal flora, what 2 bacteria and mainly found in the nostrils?

A

1) Skin flora

2) Staph aureus (20% - nose is main carrier sight)

Year 2 EMS MoD (16 decks)

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