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Infectious Stuff Flashcards

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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
What is bacterial conjugation ?
Where the plasmids are transferred through a tube called a sex pilus
26
Bacterial DNA can be shared through
Transformation e.g. via a plasmid Transduction e.g. via a phage Conjugation e.g. via a sex pilus
27
How does transformation occur
Via a plasmid
28
How does transduction occur ?
Via a phage
29
How does conjugation occur ?
Via a sex pilus
30
What are Obligate Intracellular Bacteria
Intracellular parasites are microparasites that can grow and reproduce inside the cells of a host
31
What is a disease caused by a Obligate Intracellular Bacteria ?
E.g. chlamydia
32
Cocci Gram Negative Bacteria
Neisseria - Meningitis Gonorrhoea
33
Cocci Gram Positive
Staphylococcus and Streptococcus
34
Gram Positive Rods
Clostridium - Tetanus - Perfringens
35
Perfringens
Most common cause of food poisoning
36
Gram Negative Rods
Vibrio e.g. cholera | Coliforms e.g. salmonella
37
Mycobacteria
``` M. tuberculosis M. leprae M. avium-intracellulare M. ulcerans M. Kansaii etc ```
38
Bacilli =
Rods
39
Normal habitat for staphylococci
Nose and skin
40
How can staphylococcus be differentiated ?
If they produce coagulase enzyme
41
How is staphylococcus Aureus spread ?
Touch and aerosol
42
S.aureus virulence factor
Pore-forming toxins (some strains) Proteases Toxic Shock Syndrome Toxin Protein A
43
MRSA is resistant to
Beta lactams and other antibiotics
44
Staphylococcus aureus | Causes 2 types of infections
Pyogenic infections | Toxin mediated infections
45
Pyogenic infections
Causes impetigo (bacterial infection of the skin), septicaemia, osteomyelitis, pneumonia and endocarditis
46
Toxin mediated infections
Toxin mediated is TSS and food poisoning
47
Impetigo
Bacterial infection of the skin
48
Endocarditis
A rare and potentially fatal infection of the inner lining of the heart
49
S.epidermidis causes
Opportunistic infections in debilitated, prostheses, catheters
50
Main virulence factor of S.epidermidis - coagulase negative staphylococci
Ability to form persistent biofilms
51
S.epidermidis is a
Coagulase negative staphylococci
52
S.saprophyticus causes
UTI's
53
S.pyogenes
``` Beta-haemolysis Wound infections 🡪 cellulitis Tonsillitis & pharyngitis Otitis media Impetigo Scarlet fever Complications: Rheumatic fever Glomerulonephritis Anti-SLO test to assess risk ```
54
S.pneumoniae
Normal commensal in oro-pharynx ~ 30% of population | Causes - pneumonia, otitis media, sinusitis, meningitis
55
S.pneumoniae - predisposing factors
Impaired mucus trapping (e.g. viral infection) Hypogammaglobulinaemia, don’t produce good antigens Asplenia, no spleen
56
S.pneumoniae - Virulence factors:
Capsule Inflammatory wall constituents Cytotoxin e.g. pneumolysin
57
S.pneumoniae in culture can be distinguished by
'Draughtsman colonies'
58
Viridans Group Streptococci
Some cause dental caries & abscesses and eventually infective endocarditis
59
What forms the outer leaflet of the outer membrane in gram negative bacteria ?
Lipopolysaccharides
60
What makes up the lipopolysaccharides of the outer leaflet of gram negative bacteria ?
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
What is it in gram positive bacteria that absorbs the gram stain ?
Peptidoglycan layer
62
What are Colonisation factors when thinking about bacteria virulence ?
Adhesins, invasins, nutrient acquisition, defence against the host
63
Name a family of Proteobacteria
Enterobacteriaceae
64
Features of Enterobacteriaceae
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
Conditions E. coli can cause
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
Lactose can be used by
E.coli
67
Lactose cannot be used by
Shingella.flexneri or Salmonella.enterica
68
Cell Surface Antigens Of Enterobacteria
H antigen → flagellum K antigen → exopolysaccharide capsule O (somtatic) antigen LPS
69
How could you distinguish between E.coli, Shingella.flexneri or Salmonella.enterica
E.coli can use lactose for respiration Shigella.flexneri is not motile E.coli and salmonaella.enterica are motile
70
Features of Shigella
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
What cells can Shigella infect ?
Shigella enters the body through M cells and then in macrophages, causing the macrophage to apoptoses
72
What can Shigella cause ?
Bloody diarrhea (dysentery)
73
Serovar
A distinct variation within a species of bacteria or virus or among immune cells of different individuals.
74
Forms of Infections Caused by S. enterica
Gastroenteritis/enterocolitis Enteric fever Bacteraemia
75
Serovars responsible for gastroenteritis/enterocolitis
Enteritidis and Typhimurium
76
Serovars responsible for enteric fever
Typhi and Paratyphi
77
Gastroenteritis
``` 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
Enteric Fever
``` Bacterial-mediated endocytosis Transcytosis to basolateral membrane Survival in macrophages Systemic spread through macrophages Initially little damage to gut mucosa ```
79
Proteus Mirabilis
Produces urease (causes urine pH ↑) → calcium phosphate precipitation → formation of bladder/kidney stones, catheter blockage
80
Klebsiella Pneumoniae
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
Cholera mechanism
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
Pseudomonas Aeruginosa acute infections
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
Pseudomonas Aeruginosa chronic infections
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
Legionella Pneumophila
Severe inflammatory pneumonia Infection from man-made aquatic environments e.g. air-conditioning It can survive and replicate within alveolar macrophages
85
Pseudomonas Aeruginosa does not infect
Healthy patients
86
Haemophilus influenzae
``` Opportunistic infections Meningitis (in children 5-10% of adult cases) Bronchopneumonia Epiglottitis Bacteraemia Pneumonia in CF COPD and HIV patients ```
87
Diagnostic characteristics of Haemophilus influenzae
It is fastidious Requires haem and NAD Cultured on chocolate agar It is non-motile
88
Fastidious
Needs rich medium to grow
89
Virulence determinants of Haemophilus influenzae
Capsule | LPS endotoxin
90
Conditions caused by mycobacteria
TB | Leprosy
91
What is the first clinical sign of TB (usually) ?
Coughing up of caseous material
92
When typically does pulmonary tuberculosis occur ?
After the immune system is weakened
93
What are the features of pulmonary TB ?
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
Stages of TB
Primary Latent Pulmonary
95
Where can TB spread
Brain (meningitis) Miliary (Liver and spleen) Pleural Bone and Joint
96
How to lab test for TB ?
Ziehl-Neelsen stain for acid fast bacilli
97
Microbiology of TB
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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