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Flashcards in Micro 1 Deck (145)
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0

What organisms naturally colonize the skin?

Yeast and gram + organisms

1

What organisms naturally colonize the large intestine?

Anaerobes - bacteroides (10^11 /g fecal mater)

2

What organisms naturally colonize the mouth?

anaerobes - density sim to lg. intestine

3

What organisms colonize the nose and pharynx?

Gram + and - cocci (Neisseriae and Moraxella)
Gram + rods (Corynebacterium)

The rest of the respiratory tract is sterile

4

What organisms normally colonize the urogenital tract?

Urethra - transiently colonized
Vagina - changes w/ age: gram + cocci (staph, strep) before puberty; Lactobacillus Acidophilus after puberty (reduces pH and maintains uniform flora)

5

What is the procedure for gram staining?

Heat fix
Crystal Violet - then rinse
Iodine - then rinse
Acetone or Isopropyl alcohol - then rinse
Safranin - rinse then dry

6

What is the mechanism of Gram staining?

Iodine - crystal violet complex is too large to wash out of gram +

7

Describe acid fast bacteria

Mycobacterium (TB)
Cell walls contain long chain fatty (mycolic) acids, do not gram stain well.
Stain w/ carbol fuchsin, decolorize w/ 3% HCl and ETOH - acid fast will remain red

8

What is lipoteichoic acid and where is it found?

Part of gram + cell wall - strengthens
Endotoxin - can evoke immune response from humans

9

Where are gram - toxins housed?

Periplasmic space - between inner cell membrane and peptidoglycan cell wall
ex: cholera toxin

10

Cell wall components

Disaccharide-pentapeptide subunits
N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)
Peptide bridges between NAM cross link subunits (determine thickness of wall)
Gram +: pentaglycine links D-ala and lysine
Gram -: direct link between D-ala and diaminopimelic acid

11

What is mycolic acid?

Component of Acid Fast Bacteria cell wall
resistant to phagocyte killing and drying

12

What are components of gram - outer membrane?

Lipopolysaccharides (LPS) and phospholipids
LPS: virulence factor (endotoxin), mediates inflammation, septic shock
LPS composed of
-O antigen: repeating sugars - used for typing bacteria
-core sugars
-fatty acid moieties - bioactive portion of LPS

13

What is a bacterial capsule?

Both Gram + and - bacteria
High MW polysaccharides or amino acids
production depends on enviro and growth conditions
Virulence factor
Protection from complement mediated killing

14

What are pili and what are they made of?

proteinaceous structures extending from cell membrane
made of pilin, tipped w/ adhesins which bind host tissue (receptors) - virulence factor- antigenic
1. common type: mediate adhesion to host eukaryotic cells
2. sex type: join conjugating bacteria

15

What are flagella made of? Are they antigenic?

Flagellin
highly antigenic - H antigen

16

3 spore forming bacteria and assoc. diseases

clostridium tetani - tetanus
bacillus anthracis - anthrax
clostridium botulinum - botulism

17

How do Beta-Lactams work?

Inhibit final step of cell wall synthesis - transpeptidation by Penicillin Binding Proteins (PBPs)

18

What is the mechanism of penicillinase resistance in resistant penicillins?

Bulky side chains - sterically hinder B-lactamase binding

19

What coverage do beta-lactam / beta-lactamase inhibitor combo drugs offer?

Improved gram (-) and anaerobe
MSSA

20

What classes of bacteria are highly resistant to pecinillins?

aerobic gram - bacilli
anaerobes

21

What are beta-lactamase inhibitors?

Suicide inhibitors
Bind beta-lactamase -> inactive compound

22

What are common side-effects of Penicillin drugs?

Allergic reaction - from a rash to anaphylaxis
-may be due to B-lactam ring or to side chains

Acute Interstitial Nephritis - allergic rxn in kidney
-fever, rash, eosinophilia
-non-oliguric renal failure, may progress to anuria and kidney failure
-eosinophilic cells and tubular damage seen on biopsy

23

Probenecid

Gout medication given to prolong effect of Penecillin - blocks renal elimination
Used for persistent infections - syphillis

24

What do cephalosporins NOT have activity against?

Enterococcus

25

What drugs would most likely be used to treat community acquired intra-abdominal infections or for surgical prophylaxis?

2nd gen cephalosporins - cephamycins
Cefotetan or Cefoxitin

26

What is the drug of choice for community acquired pneumonia (s.pneumo)?

Cephtriaxone - 3rd gen cephalosporin

27

What are the SPICE organisms?

Serratia, Providencia, Indole (+) Proteus, Citrobacter, Enterobacter
-all have B-lactamase
-lab may say susceptible to 3rd gen Cephalosporin, but use may select resistant strain
-usually use cefepime or carbapenems

28

What cephalosporins have activity against anaerobic bacteria?

Cefotetan, Cefoxitin - 2nd gen (2B or GI) cephamycins

29

Ceftaroline

Advanced generation cephalosporin
Binds PBP2A and 2X
MRSA - first B-lactam w/ activity against.
Gram (-) activity between 2nd and 3rd gen