Microbial Ecology Flashcards
(19 cards)
How are microbes ubiquitous in nature?
- Interact w/ hosts ( Humans, animals, plants etc )
- Diverse ( viruses, fungi, bacteria etc )
- Tolerate different temperatures, utilize different nutrients & produce different metabolites
Define Host-Microbe relationship :
- How host microorganisms sustain themselves within host organisms
Define Microbial ecology :
Study of interactions between microbes & their environment
What is symbiosis? Give an example.
- Interaction between host & organism
- Example: Human/animal skin & mucous membranes generate an environment for microorganisms
What are the three forms of symbiotic relationships ?
- Mutualism
- Commensalism
- Parasitism
What is Mutualism? Give an example.
- Both the microorganism & the body work together w/out causing harm to each other.
- E.coli in the human intestine
What is Commensalism? Give an example.
- Either the body or the microorganism benefits, while the other is not affected.
- Microrganisms that inhabit the eyes.
What is Parasitism? What do they use in the human body?
- One organism benefits at the expense of the other.
- Gastrointestinal tract of humans.
What are the two types of Microorganisms with relation to disease?
- Parasitic pathogens (microbes that cause disease)
2. Non-parasitic non-pathogens (microbes that do not cause disease)
What are biofilms?
- community of microbial cells attached irreversibly to the substrate @ the interface or to each other
- embedded in an exopolysaccharidic matrix
What role do biofilms play?
- Implant of medical devices, such as intravascular catheters
- What are the 5 steps of biofilm formation called?
- Reversible attachment
- Irreversible attachment
- Colonization
- Maturation
- Dispersion
Explain the 5 steps of biofilm formation :
- Individual cells population the surface ( initial attachment )
- Extrapolymeric substances (EPS) are produced & attachment becomes irreversible
- Saturation
- Biofilm architecture develops & matures
- Single cells are released from the biofilm
What is the clinical significance of biofilms?
- Infection of medical implants & devices
- Cause recurrent & difficult to treat infections
- Device-associated infections usually resistant to antibiotics, immune to defense mechanisms
- Biofilm bacteria release antigens & stimulate production of antibodies, yet bacteria residing in biofilms are resistant to these defense mechanisms
- This above immune response may even cause damage to the surrounding tissue
What are the bacteria associated with biofilms?
- Gram-Positive bacteria :
- Enterococcus faecalis
- Staphylococcus aureus
- Staphylococcus epidermis
- Streptococcus viridans
- Bacillus cereus
- Candida albicans
- Gram-negative bacteria :
- Escherichia coli
- Klebsiella pneumoniae
- Proteus mirabillis
- Pseudomonas aeruginosa
- Salmonella enterica
Describe the infectious disease cycle:
- The pathogen : organism causing infection
- The host : Infected person or animal
- The entry : Method pathogen used to enter host
- Transmission : How pathogen goes from host to host
- Environment : Where transmission of pathogen takes place
- Exit : Method pathogen uses to leave body of host
What are the two types of pathogens? Define them & give examples.
- Primary pathogens : Always cause disease
- Vibrio cholerae, M. Tuberculosis, Treponema pallidum
- Opportunistic pathogens : Resident or transient flora that can cause disease under certain conditions
- Staphyloccus aureus, Escherichia coli
What determines potential pathogenicity?
- Number of pathogens
- virulence
- nature & magnitude of host defenses
Define Host defenses & give examples :
- A microorganism will not be able to invade unless it overcomes an animal’s/individual’s host defenses.
- Skin & mucosal secretions
- Non-specific local responses (pH)
- Non-specific inflammatory responses
- Specific immune responses ( lymphocytes )
