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1st Year - Principles > Microbiology 1 and 2 - Nature of infection, systemic bacteriology 1 > Flashcards

Microbiology 1 and 2 - Nature of infection, systemic bacteriology 1 Flashcards

1
Q

List of microorganisms in increasing size

A 
Prion proteins
Viruses
bacteria
fungi
parasites
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2
Q

What type of names do all organisms have?

A

A genus name and a species name

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3
Q

What type of diseases does prion proteins cause?

Give an example.

A

Transmissible Spongiform Encephalopathies (brain infection)

Mad cow disease (Crutzefelt Jacob Disease)

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4
Q

Problem with prion proteins?

A

Cannot be reliably removed by sterilisation

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5
Q

What type of organism is a virus?

What is it surrounded by?

A 
"obligate intracellular parasite"
A capsomere (protein coat)
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6
Q

Diagnosis of viral infections?(3)

A

PCR
Cell culture
Serology

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7
Q

Difference between the genetic material contained within viruses and bacteria?

A 
Viruses = DNA or RNA
Bacteria = DNA and RNA (one double stranded chromosome with some genetic material sometimes stored within plasmids)
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8
Q

What surrounds a bacteria in terms of walls, etc.?

A

Plasma membrane
Cell wall
Capsule (+/-)

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9
Q

What does a bacteria use for adhesion and movement?

A

Adhesion: Pilli and fimbriae
Movement: Flagellae

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10
Q

Bacterial shapes? (3)

A

Coccus
Bacillus
Spirochaetes

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11
Q

Can spirochaetes be stained using the gram method?

A

No but they have a gram negative structure

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12
Q

Gram stain reactions?

A

Gram positive = purple

Gram negative = pink

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13
Q

Difference between gram positive and gram negative?

A

Gram positive cell wall contains a thick layer of peptidoglycan compared to a thin layer between the cytoplasmic membrane and outer membrane in gram negative bacteria

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14
Q

What 2 organisms do not stain well?

A 
Mycobacterium tuberculosis (causes TB, has a waxy coat)
Treponema pallidum (spirochaete that causes syphilis)
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15
Q

Where in the body is there a natural bacterial flora? (5)

A 
URT
Lower small intestine
Large intestine
Vagina
Skin (resident and transient flora)
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16
Q

What is commensalism?

A

Where one organism benefits from the relationship without affecting the other (commensal is part of the normal flora)

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17
Q

Opportunistic pathogen?

A

An organisms that will cause infection in an immunocompromised individual

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18
Q

Virulence?

A

Degree of pathogenicity of an organism (i.e. how easily can an organism cause disease)

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19
Q

How does bacteria replicate?
What do they require to replicate? (4
)How quickly can bacteria replicate in ideal growth conditions?

A 
Binary fission
Food
Moisture
Correct temp. (usually 37 for human pathogens)
correct pH (about 7.4)
Every 20 minutes
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20
Q

3 main types of atmosphere?

A

Aerobic (growth in presence of oxygen, many aerobic organisms will also grow in anaerobic conditions but less well)
Microaerophillic (reduced O2 and enriched with CO2)
Anaerobic (no O2, “anaerobes” are strict anaerobes)

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21
Q

Why does bacteria make us ill?2 types of these?

A

Many produce toxins (enzymes)
Exotoxin (mainly gram positive, produced side cell and exported out)
Endotoxin (mainly gram negative, part of GN cell wall)

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22
Q

What do toxins produced from bacteria do?

A

Interact with cells of the immune system causing release of cytokines
Damage RBCs and WBCs, make small blood cells ‘leaky”, decrease BP, affect blood clotting and eventually lead to sepsis and septic shock

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23
Q

What type of organisms tend to form spores?2 examples

A

Gram positive bacilli (put DNA in thick coat = can’t replicate but can survive for long time)
Clostridium sp. (e.g. C. difficile)
Bacillus sp. (e.g. Bacillus anthracis)

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24
Q

How does a spore develop? (3 stages)

A

Chromosome condenses
Septum forms
Calcium dipliconate accumulates

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25
Q

Diagnostic methods for bacteria?

A

Microscopy (same day)
Culture (48 hours)
Detection of antigens (e.g. in urine)
Detection of antibodies (e.g. serology) - same day
PCR (same day) for NAATs (detection of DNA/ RNA through nucleic acid amplification tests

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26
Q

Streptococcus pneumoniae causes?

A

Pneumonia and meningitis

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27
Q

Streptococcus viridans?

A

Endocarditis

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28
Q

Streptococcus pyogenes (group A strep.)

A

Skin (e.g. necrotising fascitis), throat infecitons (e.g. tonsillitis - if rash present = scarlet fever), peurperal sepsis = severe life threatening infection in pregnant and post natal women)

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29
Q

Group B strep.?

A

Neonatal meningitis

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30
Q

Enterococcus sp.

A

Gut infections, UTI

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31
Q

Staphylococcus aureus

A

Wound, skin infections, bone and joint, food poisoning etc.

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32
Q

Coagulase negative staphylococci e.g. Staph. epidermidis

A

Skin commensal, IV line infections

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33
Q

Corynaebacterium diphtheriae

A

Diptheria

34
Q

Diptheroids

A

Skin commensal

35
Q

Listeria monocytogenes

A

Meningitis

36
Q

Bacillus cereus?

A

Food poisoning

37
Q

Bacillus anthracis

A

Anthrax

38
Q

Clostridium tetani

A

Tetanus

39
Q

Clostridium perfingens

A

Gas gangrene

40
Q

Clostridium difficile

A

Antibiotic related colitis

41
Q

How long does a TB culture take?

A

4-12 weeks

42
Q

2 types of fungi?

A

Moulds (produce spores and hyphae (allow them to invade organic tissues)
Yeasts (single cells that reproduce by budding)

43
Q

Most common mould infection in humans?

A

Aspergillus spp (do not stain)

44
Q

Most common yeast infection in humans?

A

Candida spp. (stain as large gram positive structures)

45
Q

Difference between sterilisation and disinfection?

A

Sterilisation destruct and removes 99.9% of micro-organisms and spores
Used for anything that will come into contact with a normally sterile area of the body
Disinfection removes or destructs pathogenic micro-organisms enough to make an item safe

46
Q

What might sterilisation not kill?

A

Prion proteins

47
Q

Sterilisation methods?

A

Steam under pressure (autoclave)
Dry heat in oven at 160 degrees for greater than an hour
exposure to ethylene oxide gas
Irradiation

48
Q

Disinfection methods (2)?

A

Hot water

Chemicals (e.g. hypochlorite, chlorohexidine, Povidone iodine)

49
Q

What are the genus for bacteria that are gram positive cocci?

A

Streptococcus spp.
Enterococcus sp.
Staphylococcus spp.

50
Q

Which out of streptococcus and staphylococcus and enterococcus grow in chains/ clusters?

A

Strep, entero. = chains

Staph. = clusters

51
Q

How are streptococci and enterococcus differentiated?Are they aerobic or anaerobic?

A

by type of haemolysis when grown on blood agar

Aerobic (although facultatively anaerobic)

52
Q

Types of haemolysis?

A

Alpha/ partial
Beta/ complete
gamma/ non-haemolytic

53
Q

What happens in alpha haemolysis

A

Enzymes denature haemoglobin inside RBC causing greenish discolouration around colony

54
Q

What happens in beta haemolysis

A

Enzymes (exotoxins) lyse RBC = complete clearing (most pathogenic streptococci are beta)

55
Q

Which species are alpha haemolytic

A

streptococcus pneumoniae aka “pneumococcus”

Streptococcus “viridans” (contains many different species)

56
Q

Streptococcus pneumoniae:Where is this part of the normal floraWhat are the majority of UK strains of this sensitive to

A

URT

Penicillin

57
Q

Where is streptococcus “viridian’s” part of the normal flora?

A

Vagina, bowel, URT

58
Q

How to tell the difference between the 2 alpha haemolytic gram positive cocci?

A

Streptococcus pneumoniae tends to grow in pairs or short chainsStreptococcus “viridans” grows in chains

59
Q

How are beta haemolytic streptococci differentiated

A

Based on cell wall antigenic structure

60
Q

2 types of beta haemolytic streptococci?

A

Group A strep aka strep. pyogenes

Group B strep.

61
Q

What is the most pathogenic of all the strep.why

A

Group A strep.

Produces a range of exotoxins

62
Q

What antibiotics are strep A sensitive to

A

Penicillin and amoxicillin

63
Q

What is the non-haemolytic bacteria?

A

Enterococci e.g. enterococcus faecalis, enterococcus faecium

64
Q

Where are enterococcus normally foundWhen do they cause problems

A

In the bowel flora

When they get into normally sterile sites

65
Q

what are most strains of E. faecalis sensitive to

A

Amoxicillin

66
Q

what are the antibiotic resistant strains of E. facium called

A

Vancomycin resistant enterococci

67
Q

What test is used to distinguish staph. aureus from all the other staphlococci

A

Coagulase test

68
Q

What does a positive coagulase test look like

A

Coagulase plasma clots in bottom of test tube = staph. aureus

69
Q

Are coagulase negative staph. harmfulWhen do they cause harm

A

Not usually (don’t tend to produce toxins)Produce slime (surface polysaccharide) which allows them to stick to artificial material in the body

70
Q

Where does staph. aureus colonise in about 30% of patients

A

URT

71
Q

What are 2 conditions staph. aureus can cause depending on exotoxin produced

A

Toxic shock syndrome

Panton-Valentine leukocidin (damages WBCs)

72
Q

Condition staph. aureus can cause due to enterotoxins?

A

food poisoning

73
Q

What are staph. aureus sensitive/ resistant to flucloxacillin called?

A

MSSA

MRSA (meticillin resistant staphylococcus aureus)

74
Q

Treatment for MSSA?

A

Flucloxacillin

75
Q

Bacteraemia?

A

Bacteria in the blood stream

76
Q

One of the commonest causes of bacteraemia?

A

Staph. aureus

77
Q

Microbiology tests for infection (6)

A 
blood culture
urine culture
faeces culture
swab for puss
specimen for PCR
Blood for serology
78
Q

Fever?

A

Temperature greater than 38

79
Q

In a fever, what is released to raise the body’s thermal set point
What WBC is involved in creating a fever

A

Prostoglandins

Macrophages

80
Q

What happens during sepsis?

A

Small blood vessels become leaky and loose fluid
Lower blood volume means heart has to work harder
Poor tissue oxygen perfusion means blood supply to less essential organs (e.g. skin, kidneys, liver) is shut down
Blood clotting cascade activated = clotting in tiny vessels = uses clotting factors = increased risk of haemorrhage

81
Q

Levels of sepsis

A

Sepsis
Severe sepsis
Septic shock

1st Year - Principles (37 decks)

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