Human Microbe Relationship Flashcards
What is mutualism?
In a mutualistic relationship both organisms benefit.
Ruminococcus sp. can be found in significantly high numbers in the gut microbiome. They break down cellulose in the gut, helping with digestion.
What is commensalism?
In commensalism, one organism benefits whilst the other neither benefits nor suffers as a result of the relationship.
•The human body provides shelter and food for the bacteria
•Escherichia coli and Bacteroides species in the colon
•These organisms are often referred to as the commensal microbiome
What is parasitism?
In a parasitic relationship only the parasite benefits and the host is usually harmed
•The parasitic bacteria live and multiply within or on the human body causing damage in the process - disease
What is the commensal microbiome?
The commensal microbiome is the microorganisms that live on the human body - in the gut for example.
What is colonisation of the commensal microbiome?
The ability of a microorganism to remain at a particular site within the human and multiply there
What are the two types of colonisation?
●Permanent colonisation
- always present and generally don’t cause disease
●Transient colonisation
- usually survive less than 24 hours, removed with washing
- can cause infection (opportunistic pathogens)
Factors which affect the commensal microbiome
- Age
- Diet
- Personal hygiene
- State of health
- Antibiotics
Advantages of the commensal microbiome
Produce substances that inhibit pathogenic disease causing bacteria; eg colicins
•Modify the environment such as to suppress the growth of other microorganisms; eg vaginal tract
•Overgrow throughout the environment such that other microorganisms are unable to establish a foot-hold; eg intestinal tract
•Stimulates a healthy immune system
Disadvantages of commensal microbiome
•Potential for the commensal microbiome to gain access to sites that would not normally be inhabited
•Changes in the balance of the host-commensal relationship leading to parasitism
What is an exogenous infection?
Caused by pathogens from outside the body, such as from the hospital environment or from a healthcare worker. For example, poor infection control practices by a healthcare worker can spread an infection.
What is an endogenous infection?
Caused by the body’s own microorganisms, such as the normal flora that live on the skin, in saliva, and in the gastrointestinal tract. These microorganisms can become invasive if conditions are favorable.
What is a pathogen?
An organism that causes disease
Do opportunistic pathogens cause disease? Name 3
Do not normally cause disease
•Viridans group streptococci (endocarditis)
•Pseudomonas aeruginosa (burn and wound infection)
•Candida albicans (oral candidiasis)
Does a primary/strict pathogen cause disease? Name three
A strict pathogen is always associated with disease
•Mycobacterium tuberculosis (tuberculosis)
•Neisseria gonorrhoeae (gonorrhoea)
•Salmonella typhi (typhoid)
What is an infection?
Invasion and multiplication of microorganisms in body tissues, which may or may not present with symptoms of disease
