Microbial Interactions with Humans Flashcards
What are the 8 sites known to host a microbiome
- Skin and adjacent mucous membranes
- Upper respiratory tract
- Gastrointestinal tract (including mouth)
- Outer portion of urethra
- External genitalia
- Vagina
- External ear canal
- External eye (lids, conjunctiva)
What are the 6 newly discovered sites that host a microbiome?
- Lungs (lower respiratory tract)
- Bladder (and urine)
- Breast and breast milk
- Amniotic fluid and fetus
- Brain (DNA detected)
- Bloodstream (DNA detected)
What are the sites that only DNA has been detected?
Brain, Bloodstream
What is virulence?
The relative severity of a disease caused by a particular microbe
What are the 5 steps of infection?
- Portal of entry
- Attachment interactions
- Surviving host defense
- Damaging the host/causing disease
- Exiting the host
Describe the Portal of entry step
The route that a microbe takes to enter the tissues of the body to initiate an infection.
: Through mucous membrane, skin, parenteral route
Exogenous - Organisms coming from OUTSIDE the body
Endogenous - Organisms coming from somewhere in the same human
Describe the Attachment interactions step
Use ADHESION which is a process which microbes gain a more stable foothold on host tissues.
Bacterial, fungal and protozoal pathogens attach most often through fimbrae, surface proteins and adhesive slimes or capsules.
Viruses attach by specialized receptors
Explain the surviving host defenses step
Antiphagocytic factors are used by some pathogens to avoid phagocytes (white blood cells)
Some like Streptococcus and Staphylococcus produce leukocidins which are toxic to WBC
OR some microbes secrete a capsule or slime layer to prevent being engulfed
or they can survive within the WBC
What are the 3 ways a microbe can damage their host?
- Directly through the action of enzymes or toxins (both endo and exotoxins)
- Microbial enzymes and exo- endotoxins disrupt host cell structure or connections between host cells. - Indirectly by inducing the hosts defenses to respond excessively or inappropriately
- Epigenetic changes made to host cells by microbe (such as histones, altering the host genes that are expressed)
What are exotoxins and what do they cause?
They’re secreted proteins that are the most potent toxins produced by microbes
Damaging the cell membrane and causing lysis or disrupting intracellular function.
Describe the exiting the host step
Pathogens depart through the portal of exit
What do exoenzymes do?
They break down and inflict damage on tissues, other enzymes dissolve the host’s defense barriers and promote the spread or microbes to deeper tissues.
What are enterotoxins?
Bacterial toxins that affect the GI tract (small intestine)
What are endotoxins
Also lipopolysaccharides (LPS) on gram-negative bacteria, initiates a host inflammatory response cause fever, diarrhea, decreased number of immune cells
What is an infectious dose?
The minimum number of microbes necessary to cause an infection to proceed.
Whats the 7 difference between exotoxins and endotoxins
Exotoxins -
- Proteins from gram + and -, toxic in small amounts
- SPECIFIC mode of action (binds to a specific cell receptors or structures)
- HIGHLY toxic
- Can be converted to a toxoid: FORMALDEHYDE will DESTROY toxicity
- Can be killed by antitoxins
- Does NOT cause Fever
- unstable
Endotoxins -
- LPS only on Gram -, released on cell lysis
- GENERAL/SYSTEMIC : fever, diarrhea, vomiting
- RARELY fatal
- Immune réponse not sufficient to neutralize toxin
- No toxoid potential
- INDUCES fever in host
- stable
What is a toxoid?
a chemically modified toxin from a pathogenic microorganism, which is no longer toxic but is still antigenic and can be used as a vaccine.
What are the 4 cardinal signs of inflammation?
- Redness (blood flow to an area)
- Pain
- Heat (local area, fever)
- Swelling
What is a reservoir?
The primary habitat in the natural world where a pathogen makes its home
What are examples of reservoirs?
Living:
Animals, humans (carriers),
Arthropods
Nonliving: Soil Air Water The built environment
When is a host communicable?
When an infected host can transmit the infectious agent to another host and establish infection in that host.
What does it mean for an agent to be contagious?
Highly communicable , especially through direct contact