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Neural Biology 1 > Microbiology 1 > Flashcards

Microbiology 1 Flashcards

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1
Q

What is microbiology ?

A
  • the study of organisms and agents too small to be seen by the unaided eye – i.e. microorganisms
  • Its subjects include bacteria, viruses, fungi and protozoa
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2
Q

What are the size of viruses ?

A

10 - 1000nm

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3
Q

What are the size of bacteria ?

A

0.1 - 5um

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4
Q

What are the size of protozoa ?

A

5 - 200 um

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5
Q

What are the 3 main groups of microorganisms?

A

virus
bacteria
protozoa

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6
Q

What are infectious diseases caused by?

A

pathogenic microorganisms - can easily be spread from one person to another

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7
Q

What are pathogenic microorganisms ?

A

such as bacteria, viruses, parasites or fungi; the diseases can be spread, directly or indirectly, from one person to another

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8
Q

How much do infections still cause death ?

A

1/3 of all deaths worldwide and the lead cause of death mainly because of disease in developing countries

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9
Q

What is the % of deaths from infectious disease caused by only a handful of diseases?

A

90%

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10
Q

What is an ocular surface viral infection ?

A

Herpes Simplex keratitis

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11
Q

What is an ocular surface bacterial infection ?

A

Bacterial keratitis

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12
Q

What is an ocular surface chlamydial infection ?

A

Trachoma

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13
Q

What is an ocular surface protozoal infection ?

A

Acanthamoeba keratitis

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14
Q

What is an ocular surface fungal infection ?

A

Fungal keratitis

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15
Q

What are the prevention of infection ?

A

vaccination

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16
Q

What do vaccination programmes use ?

A

vaccines contained pathogen specific antigens to elicit a protective immune response in the recipient

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17
Q

What does repeated vaccination enhance ?

A

the effectiveness of the antibody response and also elicits cell mediated response
e.g for old people - vaccine needs to be altered against new variants

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18
Q

How else can we fight infection ?

A

from using antibiotics - they are most frequently prescribed

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19
Q

What do antibiotics do?

A

cure disease by killing or interfering with the growth of bacteria

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20
Q

What will other antibiotics target ?

A
  • a wider range of bacteria, these are known as broad spectrum antibiotics
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21
Q

What are spectrum antibiotics ?

A

targeting a wider range of bacteria, these are known as broad spectrum antibiotics

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22
Q

What is superbugs ?

A

often used to refer to the healthcare-associated infections (Methicillin-resistant Staphylococcus Aureus) MRSA and Clostridium difficile (C.difficile) that are resistant to commonly used antibiotics

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23
Q

how does Antibiotic resistance arise by?

A

the drug killing the defenceless bacteria and “selecting,” in biological terms–those that can resist it.

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24
Q

What is epidemic?

A

most commonly used to describe an outbreak of an illness or disease in which the number of individual cases significantly exceeds the usual or “expected” number of cases in any given population e.g. Ebola outbreak in West Africa in 2014

,

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25
Q

What is pandemic?

A

which means “all the people,” describes an epidemic which occurs in more than one country or population simultaneously. An example of a disease which has reached pandemic proportions is the AIDS/HIV virus and more recently COVID-19

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26
Q

what do large numbers of bacteria do ?

A

inhabit the human body (significantly greater than the total number of cells in the body!) with at least 800 different species

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27
Q

What amount causes disease from bacteria ?

A

small minority

28
Q

What amount causes disease from bacteria ?

A

small minority

29
Q

What are microbes ?

A

very few are always pathogenic
many are potentially pathogenic
BUT MOST are never pathogenic

30
Q

How are bacteria classified ?

A

classified according to their morphological appearance (size and shape), staining characteristics or growth requirements

31
Q

What does the advent of antibiotics allow ?

A

further classification according to drug susceptibility

Recent developments in molecular genetics have led to genotype classification

32
Q

What are the 3 shapes that bacteria adopt ?

A
  • round (cocci, diplococci), -
  • rod-shaped (bacilli)
  • spiral (spirochetes)
33
Q

What is the structure of bacteria ?

A
  • simple structures lacking a membrane bound nucleus and sub-cellular organelles (prokaryotes)
  • DNA is organised as a fibrous mass in the cytoplasm
  • 70S ribosomes consisting of 30S and 50S sub-units (different from eukaryote 80S ribosomes)
  • Cell envelope consists of a plasma membrane and a cell wall containing a special polymer called peptidoglycan
  • Some bacteria have inclusion bodies which act as an energy store
34
Q

What are the 2nd classification of bacteria ?

A
  • two sub-divisions of bacteria are distinguished according to their ability to retain a crystal-violet iodine dye complex
-Gram stain:
    Bacteria on a slide
    Air dry at room    temperature
    Stain slide with crystal violet
    Treat slide with iodine
    Decolourize with ethanol
-Different staining characteristics relate to differences in the cell wall
35
Q

What does gram positive bacteria do ?

A

-retain the Gram stain as it becomes incorporated in the thick peptidoglycan layer that surrounds the organism

36
Q

What do gram negative organisms have ?

A

Gram negative organisms have a reduced peptidoglycan layer

  • Peptidoglycan consists of a backbone of alternating units of N-acetyl glucosamine (NAG) and N-acetyl muramic acid (NAM)
  • Gram negative bacteria have a more complex cell envelope
37
Q

What is Lipopolysaccharide ?

A

Lipopolysaccharide (incorporating lipid A endotoxin) is a major component of the outer membrane of Gram negative bacteria

38
Q

What do certain Gram positive and Gram negative bacteria?

A

have a capsule external to the cell wall

This protects the bacterium (and may confer resistance to intracellular killing by phagocytes)

39
Q

What are the various appendages that can be present?

A

e.g. flagella for locomotion

40
Q

What can Gram negative organisms may be covered by?

A
  • fine hairs (fimbriae) which mediate attachment to host

- Pili can attach bacterial cells together or transfer genetic information (sex pili)

41
Q

How can bacteria survive ?

A
  • Almost all bacteria can survive on simple organic compounds e.g. glucose
42
Q

How is energy production achieved ?

A
  • Energy production is achieved through glycolysis, TCA cycle and oxidative phosphorylation
43
Q

What is another pathway that can be used ?

A
  • Alternatively pentose phosphate pathway can be used
  • Facultative organisms can live in aerobic or anaerobic conditions
  • Obligate aerobes require oxygen
  • Obligate anaerobes use a process of fermentation yielding lactate or ethanol
44
Q

Where are bacterial genes located ?

A
  • located both within the bacterial chromosome and on extrachromosomal plasmids
45
Q

Where are antibiotic resistance genes located ?

A
  • located on plasmids
46
Q

Where can transfer of genetic information occur through?

A

Transformation
Transduction
Conjugation

47
Q

What can a few species of bacteria do ?

A
  • have the ability to produce highly resistant structures known as spores
  • These resist a range of environments and protect against heat, radiation or dessication
48
Q

What are some examples of spore forming bacteria ?

A

-Examples of spore forming bacteria include: Clostridium tetani that produces tetanus and Bacillus anthracis causing anthrax

49
Q

What does the body act as?

A

-acts as host to a large number of microorganisms (commensals)

50
Q

How much bacteria does the human body house ?

A

It has been estimated that the human body houses 1012 bacteria on the skin, 1010 in the mouth and 1014 in the GI tract

51
Q

How do Commensals protect against infection by ?

A

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

52
Q

What can alterations in -homeostasis do?

A

might trigger pathogenic damage

53
Q

How are some bacteria adapted?

A
  • adapted to the pathogenic way of life in humans.
  • They are never part of the normal flora
    e. g. M . tuberculosis
54
Q

What are some bacteria which are part of the normal flora acquire ?

A

extra virulence factors making them pathogenic, e.g. E. coli

55
Q

What can some bacteria from the normal flora cause ?

A

disease if they gain access to deep tissues by trauma or surgical procedures e.g. S. epidermidis

56
Q

What happens inIn immunocompromised patients ?

A

many free-living bacteria and components of the normal flora can cause disease, especially if introduced into deep tissues, e.g. Acinetobacter

57
Q

How else can bacteria produce damage except from penetrating body tissue ?

A

Some bacteria produce damage through the colonisation of the body surface and release of toxins and only invade the tissue to a limited extent

-Some bacteria cause damage by invasion and subsequent multiplication in the tissues
Most bacterial pathogens fall between these two extremes

58
Q

What are bacterial virulence factors ?

A

Virulence = Degree of pathogenicity
Virulence factors = Factors that trigger pathology
which ARE :

Adherence
Invasion
Toxicity

59
Q

What do bacteria toxin do ?

A
  • Many bacteria synthesize toxins that serve as virulence factors, inducing damage to the host
60
Q

What can toxins do?

A

-Toxins can cause damage by a variety of mechanisms (e.g. inhibiting protein synthesis, damaging cell membranes)

61
Q

What are the 2 types of toxins ?

A

Endotoxins=bound to cell surface

Exotoxins= excreted or released during bacterial lysis

62
Q

What are antimicrobial agents?

A

Kill or inhibit bacterial growth by interfering with:

  • Cell wall synthesis
  • DNA synthesis
  • Protein synthesis
  • Folic acid metabolism
63
Q

What is the most common test for antibiotic susceptibility ?

A

is a disk diffusion test (Kirby-Bauer)

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

64
Q

What may be present around the antibiotic disk ?

A
  • Zones of inhibition of bacterial growth may be present around the antibiotic disk.
65
Q

What is the size of the zone inhibition ?

A

is dependent on the degree of sensitivity of the bacterium to the antibiotic

66
Q

Summary

A
  • Microbiology involves the study of ‘micro’ organisms: bacteria, viruses, fungi and protozoa
  • Microorganisms are a major cause of disease (including diseases of the eye)
  • Bacteria are major human pathogens and possess a number of virulence factors which determines their pathogenicity
  • Antibiotics are generally effective in treating bacterial disease however bacterial resistance is becoming increasingly prevalent

Neural Biology 1 (58 decks)

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