Kelly 34 - Emerging and Re-emerging Infectious Diseases Flashcards
Give the 5 main reasons why we have been identifying “new” pathogens or have been seeing re-emergences of previously controlled diseases
- changes to the environment; urbanisation (increase in insect borne viral diseases), global warming (increase in vector borne diseases), deforestation (Ebola)
- changes to the pathogen; high mutation rates (HIV), acquiring toxic genes
- poor food handling; inadequate cooking, bacteria colonising meat during large scale meat production
- new pathogens associated with old diseases (H. pylori) or new epidemic outbreaks associated with new pathogens
- natural disasters/public health breakdowns; nautral disasters - leading to poor fresh water supply eg cholera, MMR vaccine scare leading to increased measles cases
Give 2 example of re/emerging infectious diseases and state thier source
- gastritis/ulcers, Helicobacter pylori, isolated as new pathogen. Source - humans
- Legionnaires’ Diseases, Legionella pneumophila, new bacteria isolated as new disease Source - water systems
What were gastric ulcers originally thought to be caused by and name an old treatment for them
caused by stress, diet, hereditary factors
short term symptomatic releife when excess stomach acid production inhibited, ulcers returned following stopping of treatemnt (zantac)
How was H. pylori determined to be the cause of gastric ulcers and state 3 other things infection causes
- after link between ulcers & H. pylori rejected by medical commuity, Barry Marshall drank pure culture of H. pylori (previously hard to gorw a pure culture) and developed stomach ulcers
- gastritis, duodenal ulcers, gastric cancer
Describe the properties of H. pylori
- gram -ve , rod shaped bacteria
- small genomes and highly adapted to host , cant live outside host
- transmission = per;per
- microaerophillic - grow under high CO2 (5%) and low O2 (5-10%)
- highly motile (flagella) and chemotaxis
- production of urease
Give the reaction that urease catalyses and state its function
- urea -> CO2 and NH3
- neutralises the gastric acid so can survive
What is the function of the flagella in H. pylori?
swim through the mucus layer. chemotaxis also helps to direct the bacteria to the epithelial cells in the stomach lining to colonise
Draw a diagram to illustrate the different virulence factors of H. pylori’s pathogenecity island
Give the 3 main outcomes of infection w/ HP
- 80% normal - no ulcers etc
- 10-15% - duodenl ulcers
- 2-5% - gastric ulcers/gastric cancers
Describe the treatment of HP and state how successfu this treatment is
combination of 3 drugs - 2 antibiotics, 1 to stop acid production
90% success rate
Name the diseases that have been on the raise since treatment of HP was implemented and give a reason as to why this is the case
- esophogeal cancers, gastro-esophageal reflux disease (GERD) all increasing
- HP said to have protective effect against these - is hP a commensal?
How was Legionella pneumophila discovered?
outbreak of pneumonia in hotel in which 15% of infected died. analysis of Legionnaires’ lungs in autopsy showed spiral shaped bacteria. later found that passed through air conditioning events
What are the main soures of growth for LP?
air cooling towers
air conditioning
shower heads
- all produce AEROSOLS in which bacteria transferred
Give the 3 locations where LP can survive
- intracelllary - in amoebae in water sources
- biofilms in aquatic environments
- human macrophages
How does LP survive in macrophages?
- T4SS passes effector proteins into macrophage cytosol after phagocytosis of LP by macrophage
- proteins prevents phagolysosome production and LP can replicate in phagosome
- now called Legionella containing vesicle
