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Flashcards in Community Acquired Bacterial Infections Deck (53)
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1

Define virulence factor.

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

2

List some common bacterial virulence factors and include their function.

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

3

Give examples of bacteria that possess the following virulence factors:
a. Capsule
b. Endospores
c. Biofilms

a. Capsule
S. pneumoniae

b. Endospores
Bacillus sp.
Clostridium sp.

c. Biofilms
Pseudomonas aeruginosa
Staphylococcus epidermidis

4

What are exotoxins?

A toxin released by a living bacterial cell into its surrounding

5

What are the five different types of exotoxin? Briefly describe what they do

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

6

What is an endotoxin?

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

7

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

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

8

What is an outbreak?

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

9

How can an outbreak be identified?

Surveillance
Good and timely reporting systems are necessary

10

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

Enteroaggregative shiga toxin producing E. coli

11

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

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

12

Describe the structure of shiga toxin.

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

13

Describe the action of shiga toxin.

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)

14

How was the shiga toxin gene transferred between bacteria?

Bacteriophage

15

What is the important virulence factor in EAEC?

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

16

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

Gram negative

It is transmitted through inhalation of contaminated aerosols

17

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

Alveolar macrophages

18

What is the important virulence factor for L. pneumophila?

Type IV secretion system

19

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

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

Incredibly slow growing

20

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

Chlamydia - Chlamydia trachomatis

Syphilis –Treponema pallidum

Gonorrhoea –Neisseria gonorrhoeae

21

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

Blindness (due to eye infection)

22

How does Neisseria gonorrhoeae establish infection in the urogenital tract?

It interacts with non-ciliated epithelial cells

23

What are the important virulence factors of Neisseria gonorrhoeae?

Pili

Antigenic variation escapes detection and clearance by the immune system

24

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

Campylobacter jejuni

Salmonella sp.

25

What is the route of infection of Campylobacter and Salmonella?

Ingestion of undercooked poultry

26

State some important virulence factors of Campylobacter jejuni.

Adhesion and invasion factors

Type IV secretion system

Toxin

27

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

Young children (0-4 years)

28

What is an important virulence determinant of Salmonella sp.?

Type III secretion system

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

29

What are the important virulence factors of Vibrio cholerae?

Cholera toxin

Type IV fimbria

30

Explain how cholera toxin works.

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

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

Immunocompromised

Elderly

Pregnant and their foetus

32

What are some special features of Listeria?

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

33

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

Q fever (Coxiella burnetti; Gram –)


Plague (Yersinia pestis; Gram-)

34

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

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

35

Where does Staphylococcus epidermidis populate?

Normally a commensal on the skin

Can form biofilms on catheters

36

Give 2 examples of bacteria that produce neurotoxins

Tetanus or Botulinum toxins

37

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

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

Give 2 examples of bacteria that produce pyrogenic exotoxins

Staphylcoccus aureus or Streptococcus pyogenes

39

Give 3 examples of bacteria that produce tissue invasive exotoxins

Staphylococcus aureus,

Streptococcus pyogenes

Clostridium perfringens

40

Give 2 examples of bacteria that produce misc exotoxins

Bacillus anthracis

Corynebacterium diphtheriae

41

What is Hemolytic-uremic syndrome

acute renal failure,

hemolytic anemia

thrombocytopenia

42

What normally causes Hemolytic-uremic syndrome?

Shiga toxin producing E. coli

EHEC strains - enterohemorrhagic E. coli

43

What group is Hemolytic-uremic syndrome most common in?

Children

44

What does SHIGA
TOXIN PRODUCING ESCHERICHIA COLI (STEC) cause?

Diarrhoea and heamolytic uremic syndrome

45

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

EHEC can only colonize the large bowel

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

46

What are the 6 catagories of Communicable diseases in Europe?

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

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

Legionnaires’ disease (legionellosis)
Legionella pneumophila (Gram -)

Tuberculosis
Mycobacterium tuberculosis (Gram +)

48

What is significant about treatment of TB?

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

What kind of bactieria is Neisseria gonorrhoeae?

Gram- negative

50

Name and describe the pathogen that causes anthrax

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

51

Name and describe the pathogen that causes botulism

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

52

Name and describe the pathogen that causes Brucellosis

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

53

Name and describe the pathogen that causes Cholera

Vibrio cholera
Gram -
Colonizes poorly sanitised food and water