4: Community Acquired Bacterial Infections

Question 1

List virulence factors of bacteria

Answer 1

Secretion systems
Flagella
Pili
Capsule (Strep pneumoniae)
Endospores (Clostridium sp.)
Biofilms (Pseudomonas aeruginosa)

Question 2

List exotoxins secreted by bacteria

Answer 2

Neurotoxins (Tetanus)
Enterotoxins (Vibrio cholera)
Pyrogenic exotoxins - release of cytokines (S.aureus)
Tissue-invasive exotoxin - destroy/tunnel through tissue (S.aureus)
Miscellaneous exotoxins

Question 3

Features of endotoxins

Answer 3

Only produced by gram-NEGATIVE bacteria
NOT proteins
Lipid A moiety of the lipopolysaccharide strucure (outermost membrane)
SHED in steady amounts

Treatment patient with gram-negative bacterial infection with antibiotics -> lysis -> lots of endotoxin released -> SEPTIC SHOCK

Question 4

What is an outbreak?

Answer 4

Greater than normal/expected no. of individuals infected/diagnosed with particular infection in a given period of time and/or a particular place

Question 5

How do you identify an outbreak?

Answer 5

Surveillance systems provide opportunity to identify outbreaks
Good/timely reporting systems ESSENTIAL

Question 6

Give 2 examples of Resp infections

Answer 6

1. Mycobacterium tuberculosis (gram +)
   Infects lungs
   Spread through air droplets
2. Legionella pneumophila (gram -) Legionnaire’s disease
   INHALATION of contaiminated aerosol
   Infects alveolar macrophages
   Type 4 secretion system
   Replicate in a Legionella containing vacuole

Question 7

Examples of STIs

Answer 7

Chlamydia trachomatis (gram -)
Most frequent STI in Europe
Obligate intracellular pathogen (can’t culture outside host cell)
Eye infection

Neisseria gonorrhoeae (gram -)
Interacts with non-ciliated epithelial cells in urogenital tract
Pili + antigenic variation

Treponema pallidum (gram -)
Cause of syphilis

Question 8

List 4 food and water-borne diseases

Answer 8

Campylobacter sp. (mostly C. jejuni)
Most common GI disease in Europe
Usually sporadic, not outbreaks
small children 0-4 highest risk
Most likely via uncooked chicken
Virulence factors: flagella, type 4 secretion, adhesion factors

Salmonella sp. (gram -)
Undercooked chicken
Outbreaks
Small children highest risk
Type 3 secretion system encoded on pathogenecity islands

Vibrio cholerae (gram -)
Acute severe diarrhoea
Death if not rehydrated
Virulence factor: cholera toxin, Type 4 fimbria
Cholera toxin = AB type molecule, enters cell, activates A cyclase, opens chloride channels

Listeria monocytogenes (gram +)
Can cross BBB, intestinal barrier and maternal/fetus barrier (propels by formation of actin tails)
Risk group = immuno-compromised, elderly, pregnant and their fetus

Question 9

Emerging/vector-borne diseases

Answer 9

Plague - Yersinia pestis (gram -)

Q fever - Coxiella burnetti (gram -)

Question 10

Vaccine preventable diseases

Answer 10

Diptheria - Clostridium diptheriae (+)
Invasive disease - Haemophilus influenzae (-)
Invasive meningococcal disease - Neisseria meningitidis (-)
Invasive pneumococcal disease - Strep. pneumoniae (+)
Pertussis - bordetella pertussis (-)
Tetanus - Chlostridium tetani (+)

Question 11

2011 E.coli outbreak in Germany

Answer 11

Cause: Shiga-toxin producing E.coli
Illness: Gastroenteritis, hemolytic uremic syndrome