Infectious diseases 17/10/22 Flashcards
(43 cards)
What is an infectious disease?
Causes pathological effect.
Caused by an infectious agent.
Can be passed between people easily.
What is the microbiome?
All the genomes from microorganisms in an environment.
What is the microbiota?
All the microorganisms in an environment.
How many microorganisms are there in and on us?
There are 38 trillion cells.
What are the different microorganisms?
Bacteria - single celled prokaryote.
Virus - non-cellular or living + survive in host.
Fungi - eukaryote.
Protozoa - single celled eukaryote.
Prions - protein that can make other proteins fold abnormally.
Helminths - parasitic worms that are large non microbial.
Arthropods - eukaryotic invertebrate animals such as insects.
Archaea - single celled prokaryotes and have no infectious agent identified.
What is commensal?
Relationship where one benefits and the other is unaffected.
What is mutualistic?
Both benefit.
What are the different types of pathogens?
Opportunistic - when conditions alter and permit infection (thrush)
Obligate - always cause disease (colds)
What is an infection?
An infection is when there is damage to tissues or cells leading to symptomatic disease.
What is a causative agent?
Microscopic microorganism or microbes that causes infection.
The etiological agent is a substances that contain the infectious microorganism.
Who invented the microscope?
Robert Hooke in 1664.
Who discovered the germ theory?
Robert Koch, 1843-1910. German microbiologist.
Germ theory of disease - certain diseases caused by single species of bacteria. Discovered Bacillus anthracis as causing Anthrax in mice in 1876. Developed precursor of Ziehl-Neelson stain to view Mycobacterium tuberculosis to observed in lung tissue (mycolic acids in cell wall structure). Developed solid media with glass plates to culture and isolate single species/strains.
What is the historical context of infectious disease?
Not always possible to culture microorganism to obtain pure species (e.g., Treponema palladium which causes syphilis, bejel, and yaws).
Not always a suitable animal model of disease available (e.g., Epstein Barr Virus mice with reconstituted human immune system components (HIS mice)).
Some infections may be polymicrobial, or have additive effects (e.g., V. Cholera. Some infectious agents may be present but not cause disease).
What was the discovery of helicobacter pylori?
- Gram negative corkscrew shaped bacilli
- No animal model
- Had been thought that gastric ulcers were caused by lifestyle factors
- In 1982, Barry Marshall deliberately infected himself with H. pylori before and after gastric biopsy for evidence of cause of acute gastric illness.
- Barry Marshall and Robin Warren – 2005, Nobel Prize in Physiology or Medicine
- Colonizes human stomach 90% of duodenal ulcers and 70-80% of gastric ulcer
What are the routes of transmission?
Aerosol - by inhalation of air droplets containing microorganism
Oral - by ingestion of contaminated food or water
Direct contact - contact with infected individual tissues or bodily fluids, via entry sites, e.g., eyes/mouth/nose or wound (e.g., bite/scratch)
Fomite transmission - contaminated surfaces of inanimate objects e.g cages/door handles/medical equipment
Vector-borne - by other living organisms e.g., mosquitoes, ticks
Zoonotic - originating from other animal species through routes above
What is bacillus anthracis?
First described by Robert Koch in 1864.
Gram positive bacilli
Endospore forming
In the environment (soils, water, contaminated animal products e.g., wool, hides, or hair).
Depending on transmission route:
Cutaneous anthrax - contamination of wound with spores from environment or contaminated animal products
Inhalation anthrax - breathing in of spores from contaminated animal products such as workers in wool mills, tanneries
Gastrointestinal anthrax - spores with meat from an animal infected with anthrax
Injection anthrax - resulting from contaminated needle, this is the least common form of anthrax
What are the differences in bacillus anthracis depending on where the bacilli is located in the body?
Cutaneous anthrax:
1 - 6 days from exposure
Swelling, skin ulcer with black centre
20% fatality rate if untreated
100% survival with treatment
Inhalation anthrax:
1 week - 2 months
Fever and chills, sweating, headache, body aches, cough, chest discomfort, shortness of breath, nausea, vomiting, stomach pains, extreme tiredness
100% fatality rate if untreated
55% survive with treatment
Gastrointestinal anthrax:
Diarrhoea or bloody diarrhoea, stomach pain, swelling of abdomen, headache, fainting, flushing (red face) and red eyes
If untreated >50% fatality rate
If treated 60% survival
What is influenza syndrome?
Causative agent - Influenza virus
Segmented –ve sense ssRNA genome
Pleomorphic nucleocapsid
Signs and symptoms:
* Fever
* Cough
* Sore throat
* Congestion
* Muscle/body aches
* Fatigue
* Vomiting and diarrhoea
Acute:
Contagious via airborne transmission/indirect contact. Respiratory tract infection, symptoms felt throughout body. Epidemics occur seasonally, typically low fatality, pandemics more deadly less frequent. Genome structure means it is highly changeable, infect multiple species (humans, pigs, birds). Concerns for avian flu led to new pandemic H1N1 & H5N1
What are the phases of infectious disease?
Phases of an infectious disease:
* Duration of infectious disease
* Location of infectious disease
* Timing of infectious disease
* Stages in infection
What are the phases of infectious disease?
Incubation period - time between infection and the appearance of signs and symptoms
Prodromal phase - mild, non-specific symptoms that signal onset of some diseases
Clinical phase - a person experiences typical signs and symptoms of disease
Decline phase - subsidence of symptoms
Recovery phase - symptoms have disappeared, tissues heal, and the body regains strength
What is the duration of infectious disease?
Acute – develops and progresses quickly
Chronic – develops slowly and less severe but long lasting
Latent – characterised by no symptoms between outbreak and illness
What are the locations of infectious disease?
Local – confined to a specific area of the body
Systemic – infects across multiple body sites and across tissues
What are the timings of infectious diseases?
Primary – initial infection in a previously healthy person
Secondary – infection that occurs in a person weakened by a primary infection
What is an example of an acute infection?
Ebola - ebola virus,
Single - ve sense ssRNA
Helical nucleocapsid
Direct contact, bodily fluids,
Symptoms onset ~5-9 days
Ebola haemorrhagic fever
* Early – fever, fatigue
* Later – vomiting, diarrhoea, rash, haemorrhaging, bleeding or bruising
Fatality rate, 50% (95%)
FDA approved 2020, Inmazeb, three monoclonal antibodies and Ebanga, single monoclonal antibody 2019 Vaccine rVSV-ZEBOV (recombinant vesicular stomatitis virus–Zaire Ebola virus), glycoprotein.
