Unit 2- Determinants of Pathogenicity Flashcards
What is a niche
a compartment with unique properties (ie. temperature, pH, nutrients)
What proportion of body cells do microbes make up?
90%
When do microbes start colonizing the human body
at birth and throughout lifetime
What is commensalism?
One organism benefiting without harming the other
What is mutualism?
Two organisms cooperating to both benefit (ie. bacteria in the grass cows eat help the cow digest grass)
What is parasitism?
One organism benefiting at the expense of another (harm is done to one)
How long does colonization of a baby take after birth?
8-12 hours
What protects the womb from vaginal microbes?
Fetal membranes
What microbes are exposed to bottle-fed babies?
coliforms, lactobacilli, enteric strepotococci, staphylococci
What microbes are exposed to breast-fed babies?
bifidobacterium
Where in the body do normal flora microbes colonize?
Skin, mucous membranes, upper respiratory tract, gastrointestinal tract, outer opening of urethra, external genitalia, vagina, external ear and canal, external eye (lids, lash follicles)
What are microbes that are temporary in the body called
Transients
What are long term/permanent microbes called?
Residents
Pathogen?
Parasitic microbes with the potential to cause disease
What a true/primary pathogens?
Those likely to cause disease in people with normal immune system
What are opportunistic pathogens?
They cause disease in immunocompromised people
What factors weaken host defenses and increase susceptibility to infection?
Old age, extreme youth, genetic defects or acquired defects in immunity, surgery and organ transplants, organic disease (liver, cancer, diabetes), chemotherapy/immunosuppressive drugs, physical and mental stress and other infections
Invasion?
Microbes enter into germ-free tissues or cells
Infection
Microbe spreads throughout the tissues and body
Virulence
degree of harm caused by pathogen
virulence factors
Intrinsic characteristics of pathogens that contribute to virulence
infectious dose (ID)
minimum number of microbes required to cause illness
lethal dose (LD)
minimum number of microbes needed to cause death
Virulence factors of E. coli?
1) toxins to break down gut lining 2) rapid growth 3) ability to enter gut lining (ingesting as little as 10 cells may cause illness)
Virulence factors of Vibrio cholera
1) produces cholera toxin (which draws salts and water into intestine, causing diarrhea) (ingesting 10^6-10^11 cells are needed to cause illness)
ID50?
minimum amount of microbes required to infect 50% of a given population
LD50
amoutn of microbes needed to kill 50% of a given population
the ____the ID50 and LD50, the more virulent the pathogen
lower
Adhesion?
adsorption to host cells and tissues
Adhesion mechanisms of bacteria
Fimbrae (non-specific), capsule
Adhesion mechanisms of viruses
Glycoproteins (specific), Hemagglutinin (non-specific)
Evasion?
Antiphagocytic factor, prevent being eaten from immune cell
3 strategies to avoid phagocytosis?
1) Capsule- slimy layer preventing phagocytosis
2) Toxins- defense against phagocytic cells
3) Leukocidins- toxins that directly kill WBCs
Intracellular Microbes do what?
hide inside host cells, and ecrete molecules into a target cell to make it easier to enter
Evasive factors of H. pylori?
1) urease produces NH4 to neutralize stomach acid
2) flagella
