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Infection and Immunity > Infectious Stuff > Flashcards

Infectious Stuff Flashcards

1
Q

Pathogen

A

Organism that causes or is capable of causing disease

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2
Q

Commensal

A

Organism which colonizes the host but causes no disease in normal circumstances

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3
Q

Opportunist Pathogen

A

Microbe that only causes disease if host defenses are compromised

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4
Q

Virulence/Pathogenicity

A

The degree to which a given organism is pathogenic

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5
Q

Asymptomatic carriage

A

When a pathogen is carried harmlessly at a tissue site where it causes no disease

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6
Q

Staphylococcus aureus - Which is the genus and which is the species ?

A

Staphylococcus (genus) aureus (species)

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7
Q

Which disease does treponema pallidum cause ?

A

Syphilis

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8
Q

Name for round bacteria

A

Coccus

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9
Q

Name for rod shaped bacteria

A

Bacillus

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10
Q

Gram positive stains

A

Purple

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11
Q

Gram negative stains

A

Pink

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12
Q

Typical features of bacterial cell (but not definitive)

A

Capsule, Cell wall, inner membrane and chromosome of circular double-stranded DNA

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13
Q

How does one stain for Mycobacterium tuberculosis

A

Ziehl-Neelsen Stain

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14
Q

Key features of Gram Positive

A

Gram Positive bacteria have -
A single phospholipid membrane and a large chunk of peptidoglycan made of AA and sugars which forms rigid structure around the cell.

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15
Q

Key features of gram negative

A

Inner phospholipid membrane
Very small layer of peptidoglycan
Outer phospholipid membrane
Layer of lipopolysaccharide (Endotoxin)

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16
Q

What is bacteria endotoxin made up of ?

A

Layer of lipopolysaccharide

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17
Q

What is a spore ?

A

When bacteria protect their DNA inside and wait until conditions are right to proliferate

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18
Q

What conditions can spores survive ?

A

120 degrees

Up to 50 years without water

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19
Q

What conditions are bacteria found ?

A

Temperature: 50 years for spores)
Light: UV

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20
Q

What are exotoxins ?

A

Secreted proteins of Gram positive and Gram-negative bacteria

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21
Q

Exotoxins are:

A 
Made of proteins with specific actions 
Dependent on correct tempreture  
Produced by gram positive and gram negative 
Can be converted to toxoid 
Strong antigenicity
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22
Q

Endotoxins

A 
Made of lipopolysaccharides 
Non-specific action 
Stable in variable heat 
Weak antigenicity 
Produced by gram negative 
No convertibility to toxoid
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23
Q

Toxoid

A

A toxin treated (usually with formaldehyde) so that it loses its toxicity but retains its antigenicity

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24
Q

Where in bacterial DNA can antibiotic resistance be found ?

A

Plasmid

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25
Q

What is bacterial conjugation ?

A

Where the plasmids are transferred through a tube called a sex pilus

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26
Q

Bacterial DNA can be shared through

A

Transformation e.g. via a plasmid
Transduction e.g. via a phage
Conjugation e.g. via a sex pilus

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27
Q

How does transformation occur

A

Via a plasmid

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28
Q

How does transduction occur ?

A

Via a phage

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29
Q

How does conjugation occur ?

A

Via a sex pilus

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30
Q

What are Obligate Intracellular Bacteria

A

Intracellular parasites are microparasites that can grow and reproduce inside the cells of a host

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31
Q

What is a disease caused by a Obligate Intracellular Bacteria ?

A

E.g. chlamydia

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32
Q

Cocci Gram Negative Bacteria

A

Neisseria -
Meningitis
Gonorrhoea

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33
Q

Cocci Gram Positive

A

Staphylococcus and Streptococcus

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34
Q

Gram Positive Rods

A

Clostridium

  • Tetanus
  • Perfringens
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35
Q

Perfringens

A

Most common cause of food poisoning

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36
Q

Gram Negative Rods

A

Vibrio e.g. cholera

Coliforms e.g. salmonella

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37
Q

Mycobacteria

A 
M. tuberculosis 
M. leprae 
M. avium-intracellulare 
M. ulcerans 
M. Kansaii 
etc
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38
Q

Bacilli =

A

Rods

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39
Q

Normal habitat for staphylococci

A

Nose and skin

40
Q

How can staphylococcus be differentiated ?

A

If they produce coagulase enzyme

41
Q

How is staphylococcus Aureus spread ?

A

Touch and aerosol

42
Q

S.aureus virulence factor

A

Pore-forming toxins (some strains)
Proteases
Toxic Shock Syndrome Toxin
Protein A

43
Q

MRSA is resistant to

A

Beta lactams and other antibiotics

44
Q

Staphylococcus aureus

Causes 2 types of infections

A

Pyogenic infections

Toxin mediated infections

45
Q

Pyogenic infections

A

Causes impetigo (bacterial infection of the skin), septicaemia, osteomyelitis, pneumonia and endocarditis

46
Q

Toxin mediated infections

A

Toxin mediated is TSS and food poisoning

47
Q

Impetigo

A

Bacterial infection of the skin

48
Q

Endocarditis

A

A rare and potentially fatal infection of the inner lining of the heart

49
Q

S.epidermidis causes

A

Opportunistic infections in debilitated, prostheses, catheters

50
Q

Main virulence factor of S.epidermidis - coagulase negative staphylococci

A

Ability to form persistent biofilms

51
Q

S.epidermidis is a

A

Coagulase negative staphylococci

52
Q

S.saprophyticus causes

A

UTI’s

53
Q

S.pyogenes

A 
Beta-haemolysis 
Wound infections 🡪 cellulitis 
Tonsillitis & pharyngitis 
Otitis media 
Impetigo 
Scarlet fever 
Complications: 
Rheumatic fever 
Glomerulonephritis 
Anti-SLO test to assess risk
54
Q

S.pneumoniae

A

Normal commensal in oro-pharynx ~ 30% of population

Causes - pneumonia, otitis media, sinusitis, meningitis

55
Q

S.pneumoniae - predisposing factors

A

Impaired mucus trapping (e.g. viral infection)
Hypogammaglobulinaemia, don’t produce good antigens
Asplenia, no spleen

56
Q

S.pneumoniae - Virulence factors:

A

Capsule
Inflammatory wall constituents
Cytotoxin e.g. pneumolysin

57
Q

S.pneumoniae in culture can be distinguished by

A

‘Draughtsman colonies’

58
Q

Viridans Group Streptococci

A

Some cause dental caries & abscesses and eventually infective endocarditis

59
Q

What forms the outer leaflet of the outer membrane in gram negative bacteria ?

A

Lipopolysaccharides

60
Q

What makes up the lipopolysaccharides of the outer leaflet of gram negative bacteria ?

A

Lipid A, the toxic portion of LPS that is anchored in the outer leaflet of the outer membrane
Core (R) antigen (core oligosaccharide), short chain of sugars, some are unique to LPS
Somatic (O) antigen (O-polysaccharide), a highly antigenic repeating chain of oligosaccharides

61
Q

What is it in gram positive bacteria that absorbs the gram stain ?

A

Peptidoglycan layer

62
Q

What are Colonisation factors when thinking about bacteria virulence ?

A

Adhesins, invasins, nutrient acquisition, defence against the host

63
Q

Name a family of Proteobacteria

A

Enterobacteriaceae

64
Q

Features of Enterobacteriaceae

A

Rods
Most are motile using peritrichous flagella (flagella all over the cell)
Facultatively anaerobic which means they will grow in oxygen or without oxygen
Some species colonise the intestinal tract (in a good or bad way)
Can cause opportunistic infections

65
Q

Conditions E. coli can cause

A

Wound infections (surgical)
UTIs (cystitis; 75-80% ♀ UTIs - faecal source or sexual activity; catheterisation - most common type of nosocomial infection)
Gastroenteritis
Travellers’ diarrhoea
Bacteraemia (sometimes leading to sepsis syndrome)
Meningitis (infants) - rare in UK

66
Q

Lactose can be used by

A

E.coli

67
Q

Lactose cannot be used by

A

Shingella.flexneri or Salmonella.enterica

68
Q

Cell Surface Antigens Of Enterobacteria

A

H antigen → flagellum
K antigen → exopolysaccharide capsule
O (somtatic) antigen LPS

69
Q

How could you distinguish between E.coli, Shingella.flexneri or Salmonella.enterica

A

E.coli can use lactose for respiration
Shigella.flexneri is not motile
E.coli and salmonaella.enterica are motile

70
Q

Features of Shigella

A

It is acid-tolerant so can pass the gastric barrier
Person-to-person spread, or spread via contaminated water & food
Entry through colonic M cells*

71
Q

What cells can Shigella infect ?

A

Shigella enters the body through M cells and then in macrophages, causing the macrophage to apoptoses

72
Q

What can Shigella cause ?

A

Bloody diarrhea (dysentery)

73
Q

Serovar

A

A distinct variation within a species of bacteria or virus or among immune cells of different individuals.

74
Q

Forms of Infections Caused by S. enterica

A

Gastroenteritis/enterocolitis
Enteric fever
Bacteraemia

75
Q

Serovars responsible for gastroenteritis/enterocolitis

A

Enteritidis and Typhimurium

76
Q

Serovars responsible for enteric fever

A

Typhi and Paratyphi

77
Q

Gastroenteritis

A 
Bacterial-mediated endocytosis 
Induction of interluekin-8 release 
Neutrophil recruitment and migration 
Neutrophil-induced tissue injury 
Fluid and electrolyte loss → diarrhoea 
Inflammation/necrosis of the gut mucosa
78
Q

Enteric Fever

A 
Bacterial-mediated endocytosis 
Transcytosis to basolateral membrane 
Survival in macrophages
Systemic spread through macrophages 
Initially little damage to gut mucosa
79
Q

Proteus Mirabilis

A

Produces urease (causes urine pH ↑) → calcium phosphate precipitation → formation of bladder/kidney stones, catheter blockage

80
Q

Klebsiella Pneumoniae

A

Opportunistic, nosocomial infections (neonates, elderly, compromised)
Colonisation of GIT (normal) and oropharynx (less frequent) is benign but can lead to:
UTI
Pneumonia (aspiration from oropharynx)
Surgical wound infections, bacteraemia → sepsis (high mortality)
Multi-drug resistant (resistant to carbapenems)

81
Q

Cholera mechanism

A

CT binds to a glycolipid receptor on epithelial cell (B subunits)
A subunit ADP-ribosylates G-protein (Gs ) → locked in ‘ON’ state
Uncontrolled cAMP production
Protein kinases activated CFTR ion transporter activity modified (loss of Cl- & Na+ into gut lumen) → massive loss of H2O

82
Q

Pseudomonas Aeruginosa acute infections

A

Opportunistic acute infections: Localised burn/surgical wounds UTI (catheters) keratitis (ii)
Systemic (bacteraemic → sepsis) neutropenic patients (leukaemia, chemotherapy, AIDS)
ICU patients (ventilators) leading cause of nosocomial pneumonia

83
Q

Pseudomonas Aeruginosa chronic infections

A

Chronic inflammation leading to progressive lung damage and deterioration of lung function that occurs following infection of the CF lung by P. aeruginosa is mainly due to the effect of the host immune system trying to clear the infection

84
Q

Legionella Pneumophila

A

Severe inflammatory pneumonia
Infection from man-made aquatic environments e.g. air-conditioning
It can survive and replicate within alveolar macrophages

85
Q

Pseudomonas Aeruginosa does not infect

A

Healthy patients

86
Q

Haemophilus influenzae

A 
Opportunistic infections
Meningitis (in children 5-10% of adult cases) 
Bronchopneumonia 
Epiglottitis 
Bacteraemia 
Pneumonia in CF COPD and HIV patients
87
Q

Diagnostic characteristics of Haemophilus influenzae

A

It is fastidious
Requires haem and NAD
Cultured on chocolate agar
It is non-motile

88
Q

Fastidious

A

Needs rich medium to grow

89
Q

Virulence determinants of Haemophilus influenzae

A

Capsule

LPS endotoxin

90
Q

Conditions caused by mycobacteria

A

TB

Leprosy

91
Q

What is the first clinical sign of TB (usually) ?

A

Coughing up of caseous material

92
Q

When typically does pulmonary tuberculosis occur ?

A

After the immune system is weakened

93
Q

What are the features of pulmonary TB ?

A

Formation of granulomas around bacilli that have settled in the apex of the lung
Necrosis results in abscess formation and caseous material is coughed up

94
Q

Stages of TB

A

Primary
Latent
Pulmonary

95
Q

Where can TB spread

A

Brain (meningitis)
Miliary (Liver and spleen)
Pleural
Bone and Joint

96
Q

How to lab test for TB ?

A

Ziehl-Neelsen stain for acid fast bacilli

97
Q

Microbiology of TB

A

Aerobic
Non-spore forming
Non motile bacillus
Cell wall with high molecular weight lipids
Can survive in low pH environments - even inside macrophages
Slow growing

Infection and Immunity (2 decks)

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