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YR2: MCD Microbiology > Community Acquired Bacterial Infections > Flashcards

Community Acquired Bacterial Infections Flashcards

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Biology 101 flashcards
1
Q

Define virulence factor.

A

Molecules produced by pathogens that contribute to the pathogenicity of the organism

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2
Q

List 5 common bacterial virulence factors and include their function.

A

Flagella: movement + attachment
Pili: adherence factors
Capsule: protects against phagocytosis
Endospores: metabolically dormant forms of bacteria – they are heat, cold, desiccation + chemical resistant
Biofilms: organised aggregates of bacteria embedded in a polysaccharide matrix, antibiotic resistant

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3
Q

Give examples of bacteria that possess the following virulence factors:

a. Capsule
b. Endospores
c. Biofilms

A

Capsule: S. pneumoniae
Endospores: Bacillus + Clostridium
Biofilms: P. aeruginosa + S. epidermidis

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4
Q

What are exotoxins?

A

Toxins released by a living bacterial cell into its surrounding

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5
Q

What are the 4 different types of exotoxin? Give examples of bacteria that produce such toxins.

A

Neurotoxins: Botulinum toxin, Tetanus
Enterotoxins: Infectious diarrhoea –Vibrio cholerae, E. coli, Shigella
+ Food poisoning –Bacillus cereus, S. aureus
Pyrogenic toxins: S. aureus, S. pyogenes
Tissue invasive toxins: S. aureus, S. pyogenes

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6
Q

What is an endotoxin? What is the pattern of release?

A

Lipid A moiety of lipopolysaccharide found on outer membrane of Gram-negative cells
Shed in steady amounts from living bacteria

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7
Q

Why can treating patients with Gram-negative infection sometimes worsen their condition?

A

Antibiotics can cause lysis of bacteria, releasing endotoxins into the circulation in large quantities
This can trigger an immune response that leads to septic SHOCK

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8
Q

What is an outbreak?

A

A greater than normal/ than expected number of individuals infected with a particular infection in a given time period or place

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9
Q

How can an outbreak be identified?

A

Surveillance

Good + timely reporting systems are necessary

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10
Q

What was the 2011 E. coli outbreak in Germany caused by?

What were the symptoms of infection?

A

Enteroaggregative shiga toxin producing E. coli

Gastroenteritis + Haemolytic uraemia syndrome

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11
Q

What was special about the E. coli strain that caused the 2011 outbreak?

A

It was an EAEC strain that had acquired the ability to produce shiga toxin
Shiga toxin production is a feature of EHEC
Thus, produced a new strain = EAHEC

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12
Q

Describe the structure of shiga toxin.

A

An A subunit non-covalently associated with a pentamer of protein B

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13
Q

Describe the action of shiga toxin.

A

Subunit A = enzymatically active domain
Subunit B = binds host cell membrane
Subunit A cleaves 28S ribosomal RNA in eukaryotic cells thus inhibiting protein synthesis
Bacterial ribosomes are also a substrate for subunit A so it can lead to decreased proliferation of susceptible bacteria (e.g. commensals)

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14
Q

How was the shiga toxin gene transferred between bacteria?

A

Bacteriophage

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15
Q

What is the important virulence factor in EAEC?

A

Aggregative adherence fimbriae (AAF): required for adhesion to enterocytes

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16
Q

What type of bacterium is Legionella pneumophila and what is the route of infection?
Which cells does it infect and grow in?

A

Gram negative
Transmitted through inhalation of contaminated aerosols
Grows in Alveolar Macrophages

17
Q

What is the important virulence factor for L. pneumophila? Describe this

A

Type IV secretion system

Allows injection of toxic proteins from cytoplasm into vacuoles of macrophages

18
Q

What feature of Mycobacterium tuberculosis makes it more difficult to treat?

A

Mycolic acid outer membrane; prevents normal antibiotics from getting into the cell

19
Q

State 3 bacterial sexually transmitted diseases including the species of bacteria that cause the diseases. What type of bacteria are these?

A

Chlamydia: Chlamydia trachomatis
Syphilis: Treponema pallidum
Gonorrhoea: Neisseria gonorrhoeae
All gram negative

20
Q

What is a major consequence of Chlamydia in the developing world?

A

Blindness (due to eye infection)

21
Q

How does N. gonorrhoeae establish infection in the urogenital tract?

A

Interacts with non-ciliated epithelial cells in urogenital tract

22
Q

What are the important virulence factors of N. gonorrhoeae?

A

Pili allow adhesion

Antigenic variation: escapes detection + clearance by the immune system

23
Q

What is the most commonly reported infectious GI disease in the EU?

A

Campylobacter jejuni

24
Q

What is the route of infection of Campylobacter and Salmonella?

A

Ingestion of undercooked poultry

25
Q

State 4 important virulence factors of Campylobacter jejuni.

A

Adhesion + invasion factors
Flagella motility
Type IV secretion system
Toxin

26
Q

Which subset of the population has the highest incidence of Salmonella and Campylobacter infection?

A

Young children (0-4 years)

27
Q

What is an important virulence determinant of Salmonella sp.?

A

Type III secretion system

Allows injection of toxic proteins into eukaryotic cells

28
Q

What are the important virulence factors of Vibrio cholerae?

A

Cholera toxin

Type IV fimbria

29
Q

Explain how cholera toxin works.

A

Has A + B subunits
A = active toxin
B = allows entry of toxin into epithelial cell
A subunit activates adenylate cyclase, thus increasing production of cAMP
cAMP binds to CFTR + causes Cl- efflux
Water follows ion movement
Results in massive movement of water into intestinal lumen

30
Q

Which subsets of the population are at risk of infection by Listeria monocytogenes?

A

Immunocompromised
Elderly
Pregnant + their foetus

31
Q

What are some special features of Listeria?

A

Can enter non-phagocytic cells + cross tight barriers (e.g. intestinal barrier, BBB + maternal-foetal barrier)

32
Q

Name 2 bacterial vector-borne diseases.

A

Q fever

Plague

33
Q

List 6 vaccine-preventable diseases caused by bacteria

A 
Diphtheria  
Invasive pneumococcal infections  
Invasive meningococcal infections  
Invasive Haemophilus influenzae
Pertussis  
Tetanus
34
Q

What is the mode of action of each type of exotoxin?

A

Neurotoxins act on nerves/ motor endplates
Enterotoxins act on GI tract
Pyrogenic exotoxins stimulate release of cytokines
Tissue invasive exotoxins allow bacteria to destroy + tunnel through tissue

35
Q

What are the usual consequences of Salmonella and Campylobacter infection?

A

Salmonella sp. can cause outbreaks

Campylobacter tends to be sporadic cases

36
Q

What is cholera? What can it lead to?

A

Acute, severe diarrhoea disease

Without prompt dehydration, leads to death within hours

YR2: MCD Microbiology (8 decks)

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