Community acquired bacterial infections Flashcards
What are the main groups of bacterial shapes
Cocci (spherical)
Bacilli (rod)
Budding and appendaged bacteria
Others
Give examples of cocci shapes
Coccus (single) Diplococci (double) + encapsulated (pneumococcus) Streptococci (chain) Staphylococci (rows) Sarcina (four, two layers) Tetrad (four)
Give examples of bacilli shapes
coccobacillus (oval shaped) Bacillus (single) Diplobacilli (double) Palisades (side by side lengthways) Streptobacilli (chain)
Give examples of Budding + appendaged bacteria shapes
Hypha
Stalk
Give examples of common bacterial virulence factors
Secretion systems Flagella Pili Capsule Endospores BIolfilms
Explain how the following contribute to virulence: Secretion systems Flagella Pili Capsule Endospores BIolfilms
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
What is a biofilm
organised aggregates of bacteria embedded in a polysaccharide matrix which is antibiotic resistant e.g. Pseudomonas aeruginosa, Staphylococcuqs epidermidis
What are endospores
metabolically dormant forms of bacteria, resistant to heat and cold, desiccation - (dryness) and chemicals e.g. Bacillus sp. (species), Clostridium sp.
What are exotoxins and what are the types
proteins released as free molecules by bacteria:
Neurotoxins
Enterotoxins
What do neurotoxins act on and give examples of bacteria that might produce them
act on nerves or motor endplates e.g. Clostridium tetani or C. botulinum toxins
What do enterotoxins act on and what pathologies may they cause (+ examples of bacteria that may cause each)
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)
What are the two types of exotoxins (other than neurotoxins and enterotoxins)
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
What are endotoxins
Endotoxins are antigens that the immune system responds to to combat such bacteria
Which grams stain bacteria can produce endotoxins and why
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
What are the risks of endotoxins
Lysing the bacteria (e.g. with antibiotics) can cause sudden release of large quantities of endotoxin, thus worsening any septic shock.
Define outbreak
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
What is important in the identification of an outbreak
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.
What are the 6 categories of communicable diseases in Europe
- 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
Give examples of respiratory tract infections
Influenza (swine and bird)
Mycobacterium tuberculosis
Legionella pneumophilia
Describe mycobacterium tuberculosis
(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
Describe legionella pneumophilia
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)
Give examples of sexually-transmitted infections
Chlamydia trachomatis Neisseria gonorrhoea Treponema pallidum (syphillis) Hep B and C HIV
Describe chlamydia trachomatis
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.
Describe neisseria gonorhoae
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.
Give examples of food and water-borne diseases and zoonoses
Campylobacter Salmonella Cholera toxin (from vibrio cholerae) Listeria monocytogenes Escherichia coli Clostridium botulinum Shigella dysenteriae Bacillus anthracis Giardia (parasite) - traveller's diarrhoea
Describe campylobacter
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.
Describe salmonella
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.
Describe cholera toxin
causes upregulation of a Cl- channel (CFTR) in the GI epithelium, causing severe, acute dehydration.
The most recent outbreak was in Haiti.
Describe listeria monocytogenes
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.
What is typhoid fever caused by
Salmonella enterica enteric of the serotype ‘typhi’
Give examples of emerging and vector-borne diseases
Malaria Plague(there are three types of the plague, bubonic is just one) SARS (severe acute respiratory syndrome) Smallpox West Nile fever Yellow fever
What is malaria caused bu
Plasmodium parasite
What was plague caused by
Yersinia pestis
Give examples of vaccine-preventable diseases
Corynebacterium diphtheriae (diphtheria) Clostridium tetani (tetanus) Bordetella pertussis (pertussis) Neisseria meningitidis (meningitis) Haemophilus influenzae measles mumps rubella poliomyelitis (polio) rabies
