Community acquired bacterial infections

Question 1

What are the main groups of bacterial shapes

Answer 1

Cocci (spherical)
Bacilli (rod)
Budding and appendaged bacteria
Others

Question 2

Give examples of cocci shapes

Answer 2

Coccus (single)
Diplococci (double) + encapsulated (pneumococcus)
Streptococci (chain)
Staphylococci (rows)
Sarcina (four, two layers)
Tetrad (four)

Question 3

Give examples of bacilli shapes

Answer 3

coccobacillus (oval shaped)
Bacillus (single)
Diplobacilli (double)
Palisades (side by side lengthways)
Streptobacilli (chain)

Question 4

Give examples of Budding + appendaged bacteria shapes

Answer 4

Hypha

Stalk

Question 5

Give examples of common bacterial virulence factors

Answer 5

Secretion systems
Flagella
Pili
Capsule
Endospores
BIolfilms

Question 6

Explain how the following contribute to virulence:
Secretion systems
Flagella
Pili
Capsule
Endospores
BIolfilms

Answer 6

Diverse secretion systems - as they move molecules towards the exterior of cells -

Flagella - movement and attachment

Pili (smaller, hair-like projections) - attachment

Capsule - protection against phagocytosis e.g. Streptococcus pneumoniae

Endospores - resistant to heat and cold, desiccation - (dryness) and chemicals

Biofilms - antibiotic resistant

Question 7

What is a biofilm

Answer 7

organised aggregates of bacteria embedded in a polysaccharide matrix which is antibiotic resistant e.g. Pseudomonas aeruginosa, Staphylococcuqs epidermidis

Question 8

What are endospores

Answer 8

metabolically dormant forms of bacteria, resistant to heat and cold, desiccation - (dryness) and chemicals e.g. Bacillus sp. (species), Clostridium sp.

Question 9

What are exotoxins and what are the types

Answer 9

proteins released as free molecules by bacteria:
Neurotoxins
Enterotoxins

Question 10

What do neurotoxins act on and give examples of bacteria that might produce them

Answer 10

act on nerves or motor endplates e.g. Clostridium tetani or C. botulinum toxins

Question 11

What do enterotoxins act on and what pathologies may they cause (+ examples of bacteria that may cause each)

Answer 11

act on the GI tract, causing infectious bacteria diarrhoea (bacteria are alive - E. coli) or food poisoning (bacterial toxins from food were not destroyed by cooking - S. Aureus)

Question 12

What are the two types of exotoxins (other than neurotoxins and enterotoxins)

Answer 12

Pyrogenic exotoxins - stimulate release of cytokines, e.g. Strep. pyogenes, Staph. aureus

Tissue invasive exotoxins -enzymes that allow bacteria to destroy and tunnel through tissue e.g. - Strep. pyogenes, Staph. aureus, Clostridium perfringens

Question 13

What are endotoxins

Answer 13

Endotoxins are antigens that the immune system responds to to combat such bacteria

Question 14

Which grams stain bacteria can produce endotoxins and why

Answer 14

Endotoxins can only be produced by Gram-negative bacteria, because they’re not free molecules but rather the lipid A moiety of lipopolysaccharides from bacterial outer membranes. They are shed steadily from living bacteria

Question 15

What are the risks of endotoxins

Answer 15

Lysing the bacteria (e.g. with antibiotics) can cause sudden release of large quantities of endotoxin, thus worsening any septic shock.

Question 16

Define outbreak

Answer 16

A greater-than-normal or greater-than-expected number of individuals infected or diagnosed with a particular infection in a given period of time, or a particular place, or both

Question 17

What is important in the identification of an outbreak

Answer 17

Good, timely reporting systems are instrumental for identifying outbreaks.
After reporting, the cause of an outbreak must be confirmed and it must be ensured that there are no other causes.

Question 18

What are the 6 categories of communicable diseases in Europe

Answer 18

• respiratory tract infections
• sexually-transmitted infections, including blood-borne viruses
• food- and water-borne diseases and zoonoses
• emerging and vector-borne diseases
• vaccine-preventable diseases
• drug-resistance and healthcare-associated infections

Question 19

Give examples of respiratory tract infections

Answer 19

Influenza (swine and bird)
Mycobacterium tuberculosis
Legionella pneumophilia

Question 20

Describe mycobacterium tuberculosis

Answer 20

(called Gram-positive but has another lipid layer in its cell
- wall, making treatment difficult)
Can also become dormant, leading to ‘latent tuberculosis’
Where immunological evidence of current infection exists without clinical signs or symptoms

Question 21

Describe legionella pneumophilia

Answer 21

lives in ponds, lakes, and air conditioning units, and infects hosts - via inhalation of contaminated aerosols.
Its type IV secretion system then allows Legionella to survive and replicate in vacoles inside alveolar macrophages (causes Legionnaires’ disease)

Question 22

Give examples of sexually-transmitted infections

Answer 22

Chlamydia trachomatis
Neisseria gonorrhoea
Treponema pallidum (syphillis)
Hep B and C
HIV

Question 23

Describe chlamydia trachomatis

Answer 23

Most common STI in Europe
Responsible for more than 3% of world blindness, infecting tens of millions of people’s eyes
An obligate intracellular pathogen so cannot be cultured outside the host cells.

Question 24

Describe neisseria gonorhoae

Answer 24

Establishes infection of the urogenital tract via non-ciliated epithelial cells
Important virulence factors are its pili and the antigenic variation that help it escape immune detection and clearance.

Question 25

Give examples of food and water-borne diseases and zoonoses

Answer 25

``` Campylobacter Salmonella Cholera toxin (from vibrio cholerae) Listeria monocytogenes Escherichia coli Clostridium botulinum Shigella dysenteriae Bacillus anthracis Giardia (parasite) - traveller's diarrhoea ```

Question 26

Describe campylobacter

Answer 26

Most commonly reported GI infection in the EU. Cases are usually sporadic rather than outbreaks, and tend to affect 0-4 year-olds. Undercooked poultry is the most likely source. It has many important virulence factors.

Question 27

Describe salmonella

Answer 27

sp. infects small children mostly via undercooked poultry, but outbreaks of it do occur. Type III secretion systems on pathogenicity islands are crucial virulence factors.

Question 28

Describe cholera toxin

Answer 28

causes upregulation of a Cl- channel (CFTR) in the GI epithelium, causing severe, acute dehydration. The most recent outbreak was in Haiti.

Question 29

Describe listeria monocytogenes

Answer 29

Can enter non-phagocytic cells and cross tight barriers, allowing it to penetrate the intestinal barrier, blood-brain barrier, and placenta. Listeria’s intra- and intercellular movement (which creates ‘comet trails’ of actin) is a popular research topic.

Question 30

What is typhoid fever caused by

Answer 30

Salmonella enterica enteric of the serotype 'typhi'

Question 31

Give examples of emerging and vector-borne diseases

Answer 31

``` Malaria Plague(there are three types of the plague, bubonic is just one) SARS (severe acute respiratory syndrome) Smallpox West Nile fever Yellow fever ```

Question 32

What is malaria caused bu

Answer 32

Plasmodium parasite

Question 33

What was plague caused by

Answer 33

Yersinia pestis

Question 34

Give examples of vaccine-preventable diseases

Answer 34

``` Corynebacterium diphtheriae (diphtheria) Clostridium tetani (tetanus) Bordetella pertussis (pertussis) Neisseria meningitidis (meningitis) Haemophilus influenzae measles mumps rubella poliomyelitis (polio) rabies ```