Microbial Pathogenesis Flashcards
What are enterotoxins?
Exotoxins that cause GI signs and symptoms
What is meant by antigenic variation?
The bacteria changes the antigens on its surface (epitopes)
This makes it hard to build long term immunity and initiates new cycle of disease
What is “disease?”
Abnormal condition of body structure/function that occurs when interaction leads to pathogenesis.
Results in damage to the host.
What are the 5 stages of disease?
- Incubation (Preclinical)
- Prodromal (Warning)
- Acute (Clinical Illness)
- Decline
- Convalescent
What are the 3 types of adhesins?
Glycocalyx-capsule and slime layers (make biofilms)
Fimbriae and pili
Afimbiral adhesins- NOT fimbriae/pili, they are proteins associated with cell wall/membrane
What are superantigens?
Toxins that activate up to 40% of T cells in the absence of antigen (?)
Results in massive release of cytokines.
Immune system gets overworked and you are in really bad shape
What is a major limitation of Koch’s postulates?
Inability to grow isolated cultures in the lab
What happens during the incubation/preclinical stage?
An infectious amount of a pathogen has entered the body, but the innate immune system has not been activated, and there are NO signs or symptoms
What happens during the decline stage of disease?
Illness is apparent, but signs and symptoms dwindle
Immune system activity is reduced (antibodies have been formed)
Pathogen gets cleared from the host
What is bacterial “infection”?
Microbial growth that MAY manifest disease (not yet causing symptoms)
What is an example of a bacteria that can encapsulate itself and block phagocytosis?
S. Pneumoniae
Are you contagious during the preclinical/incubation phase?
No! (Not many germs present)
What happens during the prodromal (Warning) stage?
Non-specific signs/symptoms appear due to activation of the innate immune system (slight fever, dry cough, just not feeling good)
Numbers of bacteria are increasing
What are Koch’s postulates?
- The suspected germ must be present in every case of the disease
- The germ must be isolated and grown in pure culture
- The cultured germ must cause the disease when it is inoculated into a healthy susceptible host
- The same germ must be reisolated from the diseased experimental host
What are two examples of bacteria that can inactivate our antibodies?
S. Pneumoniae secretes protease that degrade IgA
S. Aureus binds to the Fc region of IgG
What are A-B Exotoxins?
Toxins that have 2 domains- an A and a B
After B Binds to the host cell, A Attacks the host cell by going inside it
(Can form toxoids)
What is antigenic shift?
2 or more strains get remixed and made into something new
Ex:if a cell is infected with 2 strains of Influenza A they can mix together and make a new flu pandemic
What are invasins/“spreading factors”?
Enzymes that act locally to damage host cells. They soften tissue and allow the microbe to invade it deeper (away from blood flow and immune system)
What happens during the acute/clinical illness stage of disease?
Pt experiences characteristic signs and symptoms
Acquired immune system has been activated
Pathogen numbers are STATIONARY
Can be Acute or Chronic
What are adhesins?
Virulence factors that help the bacteria stick to receptors on host cells and tissues. They usually bind to carbohydrate moieities (glycoproteins)
Can somone in the decline stage of disease be contagious?
They can be if they become a carrier
(Whatever that means….his example was someone with a lot of antibodies to malaria who feels ok that can still spread it)
What are virulent pathogens?
Organisms that are strictly pathogens. They are never part of the normal flora, and are always associated with disease
What is bacterial ”colonization”?
Microbial growth that has NO interference with normal body functions
What is the difference between endotoxins and exotoxins?
Endotoxins: secreted
Endotoxins: inside the cell and only cause problems when the cell is lysed
What are exotoxins?
Proteins that are secreted into the extracellular fluid to are on the bacteria’s surface.
They are directly toxic to cells and bind to host cell receptors
At what stage of disease are people “asymptomatic carriers”?
Prodromal/warning
Although they are having some nonspecific signs and symptoms
Can “disease” occur without the presence of a microbe?
YES*****
Toxins from microbes can cause intoxications
Ex: clostridia and staph species
(Botox injections )
Is the patient contagious during the convalescent stage of disease?
No
What are membrane active exotoxins?
Toxins that cause lots of tissue damage. 3 kinds:
Protease-destroy protein in host’s cell membranes
Lipases- destroy lipids in cell membranes
Hemolysins- poke holes in RBCs and phagocytes
What is a potential problem with using PCR?
Normal flora
What is “chronic” disease?
Symptoms persist, and it is slow to move to the decline phase
Ex: TB
What is the difference between signs and symptoms?
Signs: objective evidence that a clinician can observe ex: redness, edema
Symptoms: subjective evidence that the patient experiences ex: pain, itching
What stage of disease is the innate immune system activated?
Prodromal/warning
Are people contagious during the prodromal/warning stage?
YES
~~asymptomatic carriers~~
What is “acute” disease?
Symptoms develop rapidly, peak and decline
What happens during the convalescent stage of disease?
Patient returns to full health and symptoms disappear
No immune system activity to pathogen
Pathogen is cleared from host
How do metabolites increase a bacteria’s virulence?
They are acids, gases, or other byproducts of metabolism that serve to directly damage host tissues
What is an example of a bacteria that lives INSIDE our cells and escapes detection?
M. Tuberculosis
In AB Exotoxins, will A or B by themselves have a toxic effect?
No
What is a toxoid?
Inactivated toxin
Ex: just one part of an A-B exotoxin. Can still cause an antigenic effect, but is no longer toxic
What are opportunistic pathogens?
Pathogens that do not produce disease in the normal setting, but can establish disease when introduced to an unprotected site (blood, tissues), or if the immune system is compromised
(May be part of the patient’s normal flora)
What are 4 mechanisms of bacterial virulence?
Metabolites
Invasins
Adhesins
Toxins
What is antigenic drift?
Small genetic mutations over time forms antigenically distinct strains of the bacteria
Ex: E. Coli O157:H7
Influenza virus- minor mutations in the proteins and envelop necessitate yearly flu vaccines
What is antigenic switching?
Results from genetic shuffling from recombination within a group of genes
Results in new surface antigen, but no change in biological function
Ex: pili, fimbriae, surface glycoproteins
Pili of N. Gonorrgoeae always present, but antigenic structure changes
What is PCR?
Identifying the cause of a disease using a single copy of DNA or RNA from a blood/tissue sample
