Host/Parasite

Question 1

commensals on skin

Answer 1

• S. epidermidis

- C. albicans

Question 2

opportunistic pathogen on skin

Answer 2

• S. aureus

- attacks when skin is broken

Question 3

commensals in nose and throat

Answer 3

-Strep, Staph, Neisseria
-problems with S pyogens, N meningitidis, S aureus
infections-meningitis

Question 4

commensals in mouth

Answer 4

• S mutans in mouth in plaque causes cavities or lead to endocarditis if dental hygiene is poor
• anaerobic bacterial in grooves of teeth can cause trouble when aspirated
• actinomyces
• HACEK endocarditis

Question 5

GI tract bacteria

Answer 5

• stomach often clear of bacteria
• SI has strep, lactobacilli, yeasts
• colon is totally full of a huge variety of bacteria-20% by mass of stools, most anaerobes
• will cause serious problem if colon is punctured
• bacteroides, bifidobacterium, eubacterium, coliforms, enterococci, bactobacilli, clostridium
• some cases of mutualism-bacteria gets food and we get nutrients we can use
• also can be thrown off by antibiotics/ gut injured
• pseudomembranous colitis-C diff
• sepsis

Question 6

vagina flora

Answer 6

• lactobacillus-symbiote- maintains low pH
• candida overgrowth follows rising pH
• uropathogenic e coli may set up stubborn colonizations of the area leading to recurring UTIs
• 15-20% of women carry group B strep, can cause sepsis and meningitis of newborns if delivered vaginally without antibiotics
• 5% colonized by s. aureus-predisposes to TSS

Question 7

symbiotes in normal flora

Answer 7

• GI tract

- lactobacillus in vagina

Question 8

pathogenisis

Answer 8

• when assumptions of commensal relation ship are violated
• tissue damage allows commensals to escape their proper compartment
• host becomes immunosuppressed so that a commensal organism overgrows
• use of antibiotics throws off the balance among the commensal organisms
• several microorganisms tolerated by immunocompetent vaccinated adults remain very dangerous to newborns

Question 9

colonization resistance

Answer 9

• all the good spots are taken, fewer nutrients and physical locations for pathogens to set up residence
• see flow chart

Question 10

Innate immunity-barriers

Answer 10

• skin
• mucus
• flushing action
• bacteria need wet, stagnant conditions to grow

Question 11

innate-chemical

Answer 11

• acid pH on skin and in stomach-and rapid change in upper GI tract
• lysozyme-in tears and saliva
• defensins-in secretions

Question 12

innate-microbiological

Answer 12

• normal flora

- colonization resistance

Question 13

innate-immunochemical

Answer 13

• fever-helps WBCs work more efficiently

- interferon-tells neighboring cells to protect against virus invasion-paracrine signal

Question 14

innate-cellular

Answer 14

• complement

- phagocytosis

Question 15

Koch’s postulates

Answer 15

• to know that a disease is really caused by a pathogen, we must do 4 things
  1. observe pathogen in sick animal and its symptoms
  2. grow a pure culture of pathogen
  3. infect a new animal from pure culture
  4. observe same disease in new animal and obtain pure culture of same pathogen from new animal
• this is different than how humans are treated-they report symptoms, tests uncover potential pathogens, patient is treated-might get better from that or by chance–not proof