Host parasite relationships Flashcards
What is the term microbiota?
Normal flora basically
What is medical microiology?
Study of dyamins interaction between microbes and the human host
What is a symbiosis?
Close and prolonged association between 2 or more organisms of different species
What is commensalis?
Host gets no benefits to symbiosis, but is not harmed either
What is mutualism?
Both host and microorganisms benefit
What is parasitism?
Microorganisms benefits, but the host is harmed
What is a niche?
A shelter/physical space in the body that provides nutrients
What is the normal microbiota?
Commensal or mutual symbionts that are adapted to specific niches
True or false: the normal microbiota tend to avoid directly injuring the host?
True
What are bacteriosins?
Toxins that bacteria produce that are toxic only to other bacteria
What type of microrganisms in the lungs?
None, usually considered sterile
How much bacteria do the stomach and the esophagus have?
Very little
Why do PPIs change the microbiota?
Change the pH, change the bacteria
True or false: fetueses are generally sterile?
True
Where do the bacteria come from just after birth?
Either from the vagina, or from the environment
True or false: The urinary bladder is generally considered sterile
True for boards, but not really
Why does the normal microbiota change as we grow?
Developing immunity, then decreasing
What are resident vs transient members of the microbiota?
Resident- long term occupation of niches
Transient = opposite
Why are some bacteria transient members?
Competition from resident bacteria
Immune system target
Chemical changes in the body
Where does staphloccous epidermidiis live? Gram positive or negative? Cocci or baccili?
Skin, nose, ears
Gram +, cocci
What are group A streptococcus pyogenes?Gram positive or negative? Cocci or baccili?
Gram + cocci in chaines that colonize the oropharynx of children
Causative agent of strep throat
What are pathogens?
Microorganisms that have the ability to cause disease
What are strict pathogens?
Organisms that are always associated with disease
What are opportunistic pathogens?
normal micobiota that take advantage of preexisiting
Are most infectious disesaes caused by opportunistic infections or by strict pathoges?
Opportunistic infections
What is pathogenicity?
The ability of a microorganisms to cause disease
What is virulence?
A measurement of pathogenicity
What are virulence factors?
Factors produced by organisms that enable it to infect, cause disease, and/or kill a host
UIs are generally caused by what bacteria?
E.coli
What is the causative agaent of pseudomembrane colitis? Cause?
C. diff, (normal microbiota)
Abx use kills microbiota
What is the cause of OM? (3)
Strep pneumonia, haemophilus influenza, and moraxella catarrhalis
Why do children develop OM?
Tensor veli palatini muscle is not develop, and cannot close the eustaian tube
What is a carrier?
An asmptomatic individual but has the ability to transmit the pathogens to others
Can you be a permanent carrier of disease?
Yes
What is a zoonotic entry into a human?
Animal to human
What is a vector?
Like an asymptomatic carrier
What are the commensal barriers to entry into a host?
niche bacteria killing off bad bacteria through competition
What is the first step that a pathogen does in order to infect?
Adhesion through adhesins or attachment proteins on pilli
Why do pathogenic bacteria only infect a certain area of the body?
Specific adhesion molecules only in certain areas in the body
What is plaktincally?
Free moving in solution. Most bacteria are not free–they are stationary
What are biofilms?
Bacteria encased in an exopolmeric substance of their own making
What is the source of dental caries?
Biofilm that turns to acid
How do biofilms protect bacteria from abx?
Slows the diffusion of abx, increased genetic exchange
True of false: biofilms play a small role in infections?
False
What are the sites that are considered sterile in the human body? (4)
Internal organs
Upper urogenital tract
Lungs
Circulatory system
What are the three factors that prevent transient bacteria from becoming resident members?
- Immune responses
- Competition from bacteria
- Chemical changes
What is the causative agent of strep throat? Is this a normal member of the microbiota?
Streptococcus Pyogenes
What determines the tropism of a bacteria?
The specific adhesion molecules it has
True or false: The majority of bacteria in nature do not live planktonically (i.e. freely moving or swimming
True
What are the factors that bacteria in a biofilm have that prevents them from being affected by abx? (3)
- Lower metabolism
- Increase in genetic exchange
- Slow diffusion of chemicals through the biofilm
What are intracellular pathogens?
Bacteria that replicate inside a host cell
What are the ways in which bacteria are toxic to a host?
- Release toxins
2. Byproducts of growth
What are exotoxins?
are bacterial proteins that directly harm tissue or lead to destructive biological activities
What is the AB binding toxin family?
An AB toxin is comprised of an A subunit that possesses the toxic activity and a B subunit that is responsible for binding to a host cell recepto
What are endotoxins? What type of bacteria posses these?
Toxins on the outer surface leaflet of gram-negative bacteria
What is the effect of a capsule on the bacteria’s ability to evade the host immune system?
Increases it since the polysaccharide makes a poor antigen
What is antigenic mimicry?
When bacteria produce/coat themselves in compounds that the host immune system recognizes as self
Where are staph aureus bacteria usually found on the human body?
Nose, skin
Where are staph aureus epidermisusually found on the human body?
Nose, skin,
Where are diptheroids bacteria usually found on the human body?
Nose, urethra and vagina, skin,
Where are streptococci bacteria usually found?
nose, mouth, throat, skin, urethra and vagina
Where are strep mutans bacteria usually found on the human body?
teeth
Where are strep viridan, pyogenes, and pneuumoniae bacteria usually found on the human body?
Throat
Where are neisseria bacteria usually found on the human body?
Throat
Where are haemophilus influenzae bacteria usually found on the human body?
Throat
Where are pseudomonas aeruginosa bacteria usually found on the human body?
skin
Where are Torulopsis bacteria usually found on the human body?
skin
Where are Pityrosporum bacteria usually found on the human body?
skin
Where are candida usually found on the human body?
mouth, skin,
What are the bacteria that are found in the staomach?
Lactobacilli
What are the bacteria that are found in the duodenum, jejunum, and ileum? (4)
Lactobacilli
Streptococci
Enterobacteria
Baceroides
What are the bacteria that are found in the large bowel? (10)
Strep E.coli bacteroides fusobacterium lactobacillus clostridium Staph auerues enterobacteria pseudomonas Salmonella
Infections with staph epidermis are associated with what?
Prosthetic devices and IV catheters
What are the opportunistic infections that are associated with IV catheters?
Staph epidermis Staph aureus (MRSA)
What are the opportunistic infections associated with wound/surgical site infections?
Staph auerus
Klebsiella pneumoniae
Pseudomonas aeruginosa
What are the opportunistic infections associated with bacterial endocarditits?
Strep viridans
What are the opportunisitic infections associate with aspiration pneumonia?
Polymicrobial
What types of bacteria are responsible for OM? (3)
Step penumoniae
Haemophilus influenza
Moraxella catarrhalis
True or false: bacteria only produce pathology at the sites of infection
False- can produce toxins that disseminate
How can bacteria evade IgA antibodies?
Secreting proteases
How can bacteria resist complement?
By preventing complement from directly interacting with the membrane (capsule, long O-antigen on LPS) or through degradation of complement components.
What is the MOA of diptheria toxin?
AB protein binds to cell surface, and inhibits EF-2
What is the MOA of cholera?
AB binding protein increases adenylate cyclase activity by biding the G proteins and preventing inactivation of the cAMP producing protein
What is the MOA of C. tetani?
Produce tetanospasmin that inhibits inhibitory transmitter release (tense paralysis)
What is the MOA of c. botulinum?
Release toxin that blocks the release of ACH (flacid paralysis)
What are superantigens?
Proteins that bind to MHC class II without requiring an antigen, and provoke an anaphylactic response
What is antigenic variation?
Bacteria that quickly change their antigenic makeup, due to many recombination of silent and active genes
What is quorum sensing?
A way for bacteria to sense the size of their population by secreting chemicals at appropriate times
What are the ways that bacteria can escape phagocytic clearance?
Inhibit opsonization Inhibit chemotaxis Kill phagocyte Inhibit lysosomal fusion Escape lysosome Resistant antibacterial lysosomal action
