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Y2 Micro (MCD) > Community Acquired Bacterial Infections > Flashcards

Community Acquired Bacterial Infections 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.

c. Biofilms
Pseudomonas aeruginosa
Staphylococcus 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? Briefly describe what they do

A

Neurotoxins - act on nerves or motor endplate to cause paralysis

Enterotoxins - act on the GI tract to cause diarrhea and vomiting

Pyrogenic exotoxins - stimulate release of cytokines to cause rash, fever and toxic shock

Tissue invasive toxins - allow bacteria to destroy and tunnel through tissue

Miscellaneous exotoxin - specific to becterium/function not well understood

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6
Q

What is an endotoxin?

A

This is the lipid A part of lipopolysaccharide (LPS) that is found on the outer membrane of Gram-negative cells

Gram negative bacteria shed this all the time

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 was special about the bacterial strain that caused by 2011 E.coli outbreak in Germany?

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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12
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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13
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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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) – this is 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?

A

Gram negative

It is transmitted through inhalation of contaminated aerosols

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17
Q

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

A

Alveolar macrophages

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18
Q

What is the important virulence factor for L. pneumophila?

A

Type IV secretion system

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19
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

Incredibly slow growing

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20
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

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21
Q

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

A

Blindness (due to eye infection)

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22
Q

How does Neisseria gonorrhoeae establish infection in the urogenital tract?

A

It interacts with non-ciliated epithelial cells

23
Q

What are the important virulence factors of Neisseria gonorrhoeae?

A

Pili

Antigenic variation escapes detection and clearance by the immune system

24
Q

What are the 2 most commonly reported infectious GI diseases in the EU?

A

Campylobacter jejuni

Salmonella sp.

25
Q

What is the route of infection of Campylobacter and Salmonella?

A

Ingestion of undercooked poultry

26
Q

State some important virulence factors of Campylobacter jejuni.

A

Adhesion and invasion factors

Type IV secretion system

Toxin

27
Q

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

A

Young children (0-4 years)

28
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

29
Q

What are the important virulence factors of Vibrio cholerae?

A

Cholera toxin

Type IV fimbria

30
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

31
Q

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

A

Immunocompromised

Elderly

Pregnant and their foetus

32
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)

33
Q

Name some bacterial vector-borne diseases and the becteria that cause them

A

Q fever (Coxiella burnetti; Gram –)

Plague (Yersinia pestis; Gram-)

34
Q

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

A 
Diphtheria  
Invasive pneumococcal infections  
Invasive meningococcal infections  
Pertussis  
Tetanus  
Invasive Haemophilus influenzae
Measles * 
Mumps* 
Rubella* 
Polio* 
Rabies
35
Q

Where does Staphylococcus epidermidis populate?

A

Normally a commensal on the skin

Can form biofilms on catheters

36
Q

Give 2 examples of bacteria that produce neurotoxins

A

Tetanus or Botulinum toxins

37
Q

Give examples of bacteria that produce the 2 sub-groups of enterotoxins

A

1) Infectious diarrhea
i. e. Vibrio cholera, Escherichia coli, Shigella dysenteriae and Campylobacter jejuni

2) Food poisoning i.e. Bacillus cereus or Staphylcoccus aureus

38
Q

Give 2 examples of bacteria that produce pyrogenic exotoxins

A

Staphylcoccus aureus or Streptococcus pyogenes

39
Q

Give 3 examples of bacteria that produce tissue invasive exotoxins

A

Staphylococcus aureus,

Streptococcus pyogenes

Clostridium perfringens

40
Q

Give 2 examples of bacteria that produce misc exotoxins

A

Bacillus anthracis

Corynebacterium diphtheriae

41
Q

What is Hemolytic-uremic syndrome

A

acute renal failure,

hemolytic anemia

thrombocytopenia

42
Q

What normally causes Hemolytic-uremic syndrome?

A

Shiga toxin producing E. coli

EHEC strains - enterohemorrhagic E. coli

43
Q

What group is Hemolytic-uremic syndrome most common in?

A

Children

44
Q

What does SHIGA

TOXIN PRODUCING ESCHERICHIA COLI (STEC) cause?

A

Diarrhoea and heamolytic uremic syndrome

45
Q

What is the difference between where enterohaemorrhagic E. coli (EHEC) and enteroaggegrative E. coli (EAEC) can colonize?

A

EHEC can only colonize the large bowel

EAEC can colonize the small and large bowel so causes more widespread pathology

46
Q

What are the 6 catagories of Communicable diseases in Europe?

A

1) Respiratory tract infections
2) Sexually transmitted infections, including HIV and blood-borne viruses
3) Food- and waterborne diseases and zoonoses
4) Emerging and vector-borne diseases
5) Vaccine-preventable diseases
6) Antimicrobial resistance and healthcare-associated infections

47
Q

State two bacterial respiratory tract infections including the species of bacteria that cause the diseases.

A 
Legionnaires’ disease (legionellosis)
Legionella pneumophila (Gram -)
Tuberculosis
Mycobacterium tuberculosis (Gram +)
48
Q

What is significant about treatment of TB?

A

Antibiotic treatment takes at least 6 months

72% success rate of treatment of new cases

Treatment success rate for second infection is 54%

Multi drug resistant (MDR) treatment success rate in is 32%

49
Q

What kind of bactieria is Neisseria gonorrhoeae?

A

Gram- negative

50
Q

Name and describe the pathogen that causes anthrax

A

Bacillus anthracis
Gram +
Zoonoses from hoofed animals (often contracted from eating meat)

51
Q

Name and describe the pathogen that causes botulism

A

Clostridium botulinum
Gram +
Found in soil and untreated water, survives in canned food disease

52
Q

Name and describe the pathogen that causes Brucellosis

A

Brucella spp.
Gram -
Caused by ingestion of unsterilized milk or meat

53
Q

Name and describe the pathogen that causes Cholera

A

Vibrio cholera
Gram -
Colonizes poorly sanitised food and water

Y2 Micro (MCD) (8 decks)

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