Activities of Pathogens Flashcards
What are microbes?
Microbes are tiny organisms (need a microscope to be seen). Many are healthy and are essential for live on earth (eg microbes in soil, the commensal bacteria in our gut) however many are disease causing.
The disease causing microbes include bacteria, viruses, prions, fungi and parasites.
What is the difference between a bacteria and a virus? (and also a bacterial infection and a viral infection)
Bacteria are much bigger with a rigid cell wall and cytoplasm etc and can survive on their own and thrive in many environments.
Viruses are much tinier than bacteria and they rely on invading the cells and taking over the machinary in order to reproduce. They just consist of a protein coat that encloses the genetic material (DNA or RNA).
Only a small percentage of bacteria is disease causing whereas most viruses are disease causing.
The treatment of bacterial infections is relatively simple with antibiotics however these are becoming harder to treat due to antibiotic resistance.
Viruses cannot be treated with an antibiotic and instead require an antiviral drug.
What are the two ways in which viruses can cause symptoms can disease?
- Direct damage to the host cell during its replication (cytopathic). eg cause the cell to lyse
- Alarming of the immune system can result in the immune system attacking the virus infected cells and cause necrotic tissue/ other tissue damage by cytokine release
What does a humans skin flora do?
Prevent foreign bacteria invasion into the body - mostly by competition. eg Staph Epidermidis
What is the bodies flora?
The bacteria that is normally found on the human body (in gut, mucosal surfaces, skin) etc that does not cause disease.
What is colonisation?
Where a bacteria or microbe invades the body and makes it its new home but it dosent cause an immune response in the host and dosent cause any symptoms.
This colonisation may however cause disease later on.
What is a pathogen?
A disease causing microbe.
What is the difference between infection and colonisation?
Infection is where a microbe invades and causes an immune response. Note infections do not have to result in disease if the infection is cleared by the immune system.
Colonisation is where a microbe invades and does not cause an immune response.
Note: Staph aureus can cause both colonisation (primarily in the nose) and infection (noticeable in the skin)
What is the difference between a clinical infection and subclinical infection?
A clinical infection is where the host has signs and symptoms of the disease whereas a subclincal infection is where the host has no symptoms.
What is an endogenous infectious disease compared to an exogenous infectious disease?
Endogenous = an infectious disease arising from inside the body eg colonising gut flora or other bacteris. example would be urinary tract infection.
Exogenous = an infectious disease arising from outside the body eg flu - the microbe comes from the environment/other person
What is zoonosis?
An infectious disease transmitted from an animal host.
What is the difference between a primary pathogen, a principle pathogen and an opportunistic pathogen?
Primary = always causes disease
Principle = most often/usually causes disease in otherwise well people
Opportunistic = only causes disease in people whose immune defenses are down. eg already sick people or young or old people
Infections can occur in the community or the healthcare setting. How can we reduce the spread of healthcare associated infections?
WASH HANDS.
Otherwise wear gloves, decontaminate spills, dispose of needles appropriately, wear face masks where appropriate.
What is an arbovirus?
An infection spread by an insect
How can serology be used to diagnose a viral infection?
Serology is the study of the antibodies in the blood serum.
If there are antibodies against a pathogen it can often be used for diagnosis but for things like influenza where we already have antibodies against it we may need to monitor the level of antibodies after a 2 or 3 week period.
