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Microbio > Hospital and community acquired infections > Flashcards

Hospital and community acquired 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

Capsule
S. pneumoniae

Endospores
Bacillus sp.
Clostridium sp.

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

Misc Toxin
Bacillus anthracis
Corynebacterium diphtheriae

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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 e.coli?

A

Gastroenteritis

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

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12
Q

What was special about the E.coli strain that caused the 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

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18
Q

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

A

Alveolar macrophages

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19
Q

What is the important virulence factor for L. pneumophila?

A

Type IV secretion system

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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

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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

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22
Q

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

A

Blindness (due to eye infection)

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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

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 Campylobacter tends 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 
Rabies

Measles *
Mumps*
Rubella*
Polio*

36
Q

Define the following:

a. Antimicrobial
b. Antibacterial
c. Antibiotic

A

a. Antimicrobial
Interferes with growth and reproduction of a microbe

b. Antibacterial
Commonly used to describe agents that reduce or eliminate harmful bacteria

c. Antibiotic
Type of antimicrobial that is used as medicine for humans and animals

37
Q

What is a health-care associated infection?

A

Infections that occur after exposure to healthcare Infection starts >48 hours after admission to hospital

38
Q

Why do health-care associated infections cost money to the healthcare system?

A

They increase the length of stay at hospital

39
Q

List some medical interventions that can increase the risk of infection.

A 
Catheterisation 
Intubation 
Lines (e.g. central venous lines) 
Chemotherapy 
Prosthetic material
40
Q

State some other factors that increase the risk of infection in the hospital setting.

A

Dissemination by healthcare staff

Concentration of ill patients

41
Q

What are the ESCAPE pathogens?

A 
Enterococcus faecium 
Staphylococcus aureus 
Clostridium difficile 
Acinetobacter baumanii 
Pseudomonas aeruginosa 
Enterobacteriaceae

NOTE:
ESC are Gram-positive
APE are Gram-negative

42
Q

What is the main problem with the escape pathogens?

A

They are antibiotic resistant

43
Q

What is the most frequent cause of bacteraemia by a Gram-negative bacterium?

A

E. coli

44
Q

What does E. coli frequently cause?

A

UTI

45
Q

Which antibiotics is E. coli resistant to in many countries?

A

Cephalosporins

46
Q

Which antibiotics is E. coli still sensitive to?

A

Carbapenems

47
Q

State the target proteins and the method of resistance to the following classes of antibiotics:

a. Cephalosporins
b. Carbapenems
c. Methicillin
d. Vancomycin

A

Cephalosporins
Target: Penicillin binding proteins (PBP)
Resistance: Extended-Spectrum Beta-Lactamase (ESBL)

Carbapenems
Target: PBP
Resistance: Carbapenemase enzymes

Methicillin
Target: PBP
Resistance: alternative target (PBP2A), which has low affinity for methicillin and can function in its presence

Vancomycin
Target: peptidoglycan precursor
Resistance: synthesis of a different peptidoglycan precursor

48
Q

What is ESBL encoded on?

A

Plasmid

49
Q

What are carbapenemases encoded on?

A

Transposon

50
Q

What types of infections does Klebsiella pneumoniae tend to cause?

A

UTI

Respiratory tract

51
Q

Which group of patients are at risk of Klebsiella infection?

A

Immunocompromised

52
Q

Which classes of antibiotics are Klebsiella widely resistant to?

A

Cephalosporins, fluoroquinolones and aminoglycosides

Carbapenem resistance in the US

53
Q

Which group of patients are at risk of P. aeruginosa infection?

A

Immunocompromised

54
Q

Which class of antibiotics is P. aeruginosa widely resistant to?

A

Carbapenems

55
Q

What is the most important cause of antimicrobial resistant infection in the world?

A

MRSA

56
Q

What is Enterococcus faecium widely resistant to?

A

Vancomycin

NOTE: causes blood stream infections

Microbio (7 decks)

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