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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 some common bacterial virulence factors and include their function.

A

Flagella – movement and attachment
Pili – adherence factors
Capsule – protects against phagocytosis
Endospores – metabolically dormant forms of bacteria – they are heat, cold, desiccation and 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

a. Capsule
S. pneumoniae

b. Endospores
Bacillus sp.
Clostridium sp.t

c. Biofilms
P. aeruginosa
S. epidermidis

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4
Q

What are exotoxins?

A

A toxin released by a living bacterial cell into its surrounding

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5
Q

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

A 
Neurotoxins 
 Botulinum toxin
 Tetanus
Enterotoxins 
 Infection 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
 C. perfringens
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6
Q

What is an endotoxin?

A

This is the lipid A part of lipopolysaccharide that is found on the outer membrane of Gram-negative cells
NOTE: so ONLY Gram-negative cells can produce endotoxins

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7
Q

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

A

Antibiotics can cause lysis of the bacteria meaning that the endotoxins are released 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 or greater than expected number of individuals infected or diagnosed with a particular infection in a given time period, or a particular place, or both

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9
Q

How can an outbreak be identified?

A

Surveillance

Good and timely reporting systems are necessary

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10
Q

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

A

Enteroaggregative shiga toxin producing E. coli

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11
Q

What were the symptoms of infection by this bacterium?

A

Gastroenteritis

Haemolytic uraemia syndrome (acute renal failure + haemolytic anaemia + thrombocytopenia

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12
Q

What was special about the bacterial strain that caused by outbreak?

A

The bacterial strain was an enteroaggregative E. coli strain (EAEC) that had acquired the ability to produce shiga toxin (through phagetransfer)
Shiga toxin production is a feature of Enterohaemorrhagic E. coli(EHEC)
This produced a new strain called Enteroaggregative haemorrhagic E. coli (EAHEC

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13
Q

Describe the structure of shiga toxin.

A

There is an A subunit that is non-covalently associated with a pentamer of protein B

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14
Q

Describe the action of shiga toxin.

A

Subunit A is the enzymatically active domain
Subunit B is responsible for binding to the 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. commensal microflora of the gut)

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15
Q

How was the shiga toxin gene transferred between bacteria?

A

Bacteriophage

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16
Q

What is the important virulence factor in EAEC?

A

Aggregative adherence fimbriae (AAF) – this is required for adhesion to enterocytes

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17
Q

What type of bacterium is Legionella pneumophila and what is the route of infection?

A

Gram negative

It is transmitted through inhalation of contaminated aerosols

18
Q

Which cells within the human host does L. pneumophila infect and grow inside?

A

Alveolar macrophages

19
Q

What is the important virulence factor for L. pneumophila?

A

Type IV secretion system

20
Q

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

A

It has a mycolic acid outer membrane – this prevents normal antibiotics from getting into the cell

21
Q

State three bacterial sexually transmitted diseases including the species of bacteria that cause the diseases.

A

Chlamydia - Chlamydia trachomatis
Syphilis –Treponema pallidum
Gonorrhoea –Neisseria gonorrhoeae

22
Q

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

A

Blindness (due to eye infection)

23
Q

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

A

It interacts with non-ciliated epithelial cells

24
Q

What are the important virulence factors of N. gonorrhoeae?

A

Pili

Antigenic variation escapes detection and clearance by the immune system

25
Q

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

A

Campylobacter jejuni

26
Q

What is the route of infection of Campylobacter and Salmonella?

A

Ingestion of undercooked poultry

27
Q

State some important virulence factors of Campylobacter jejuni.

A

Adhesion and invasion factors
Type IV secretion system
Toxin
Flagella motility

28
Q

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

A

Young children (0-4 years)

29
Q

What is an important virulence determinant of Salmonella sp.?

A

Type III secretion system

NOTE: Salmonella sp. can cause outbreaks whereas Campylobactertends to be sporadic cases

30
Q

What are the important virulence factors of Vibrio cholerae?

A

Cholera toxin

Type IV fimbria

31
Q

Explain how cholera toxin works.

A

It has A and B subunits
A is the active toxin
B allows entry of the toxin into the epithelial cell
The A subunit activates adenylate cyclase, thus increasing the production of cAMP
The cAMP then binds to CFTR and causes Cl- efflux
Water follows the ion movement so you get massive movement of water into the lumen of the intestine

32
Q

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

A

Immunocompromised
Elderly
Pregnant and their foetus

33
Q

What are some special features of Listeria?

A

They can enter non-phagocytic cells and cross tight barriers (e.g. BBB and maternal-foetal barrier)

34
Q

Name some bacterial vector-borne diseases.

A

Q fever

Plague

35
Q

List some vaccine-preventable diseases. Identify which are viral.

A 
Diphtheria  
Invasive pneumococcal infections  
Invasive meningococcal infections  
Pertussis  
Tetanus  
Invasive Haemophilus influenzae
Measles * -V
Mumps*  V
Rubella* -V
Polio* 
Rabies
36
Q

What do neurotoxins act on?

A

Nerves or motor endplate

37
Q

What do enterotoxins act one?

A

GI tract

38
Q

How do pyrogenic toxins act?

A

Stimulate release of cytokines

39
Q

How do tissue invasive exotoxins work

A

enzymes that allow bacteria to tunnel through tissue:

40
Q

What is the success rate for TB

A

72% new cases, 54% for second infection

Microbiology (3 decks)

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