Intro to Bacteriology and Antibiotic Strategies Flashcards Preview

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Flashcards in Intro to Bacteriology and Antibiotic Strategies Deck (32):
1

Gram positive cocci in pairs?

Pneumococcus = S. pneumoniae

2

Gram positive cocci in chains?

Streptococcus pyogenes = Group A Strep

3

Gram positive cocci in clusters?

Staphylococcus

4

Gram Positive Rods

Bacillus species

5

Gram Negative Cocci

Neisseria (meningitis)

6

Gram Negative Rods

Campylobacter (bacterial gastroenteritis)

7

Can spirochetes be visualized with the gram stain?

No

8

Do bacteria have organelles?

No, have one supercoiled circular chromosome and small plasmids. Smaller ribosomes

9

Gram negative cell wall

Inner lipid bilayer, thin cell wall, outer lipid bilayer

10

Gram positive cell wall

Inner lipid bilayer, thick peptidoglycan cell wall

11

Components of the peptidoglycan cell wall

N-acetyl glucosamine and N-acetyl muramic acid, NAG and NAM, form parallel structures which are cross linked by peptide strands.

12

Porin Channels

Located on outer membrane of gram negative bacteria, allow nutrients to flow in.

13

Lipopolysaccharide

An endotoxin that is part of the outer bilayer of a gram negative bacteria, causes a cytokine cascade in host when released upon death of the organism.

14

Normal bacteria of the skin

Staphylococcus epidermidis

15

Normal bacteria of the upper respiratory tract

anaerobic cocci, viridans streptococci

16

Environmental Factors of Infection

Overcrowding, climate, antibiotic use

17

Host Factors of Infection

Immunocompromised state, extremes of age, breach in barriers

18

Inhibitors affecting peptidoglycan synthesis

Penicillin, cephalosporin, carbapenems, monobactams

19

How does penicillin work?

Inhibits cross-linking of peptidoglycans on the cell wall, causes a fragile outer coat, guts spill out.

20

How does the structure of penicillin cause it to work?

Beta lactam (peptide bond with 4 membered ring). Has 2 alanines hidden in the molecule, which will bind to active site of transpeptidase, which is built for 2 alanines.

21

Beta-lactamase

An enzyme that confers penicillin resistance buy cutting open the beta lactam ring.

22

Transposition of drug resistance genes

A drug resistance gene can be flanked by insertion elements where endonucleases will cut. This will create a circular piece of DNA that can be transported to a new plasmid. Polygenic plasmids can be created this way, leading to MDR plasmids.

23

Vancomycin, bacitracin

Also affects peptidoglycan synthesis by inhibiting the polymerization of NAG and NAM. Recognizes the double-alanine sequence for binding.

24

Resistance to vancomycin

1) Decrease the penetration of vancomycin to its target (gram negativity, vanc. can't pass outer membrane).

2) Alter the target of the antibiotic. Bacteria have Vanc receptor which causes D-ala-D-lactate formation instead of Ala-Ala. Vancomycin has no target.

25

Inhibitors affecting cell wall membranes

Polymyxins (cationic detergent), polyene antibiotics (amphotericin B, binds to sterols), azoles (depletes cell of ergosterol)

26

Resistance mechanism to tetracyclines

Moved out to the cell

27

Resistance to aminoglycosides

Transport in to cell is dependent on ETC, so anaerobes are resistant. Most commonly, aminoglycosides can be inactivated by an enzyme encoded in a plasmid or on the chromosome.

28

Inhibitors affecting DNA-dependent DNA polymerase activity

Quinolones (inhibit gyrase/topoisomerase), Nalidixic acid (gyrase inhibitor), Mitomycin (cross-links DNA), Metronidazole (damages DNA with free radicals)

29

Inhibitors affecting DNA-dependent RNA polymerase activity

Rifampicin, actinomycin D

30

Folic acid antimetabolites

Sulfonamides and trimethorprim, cells need folate to build amino acids and DNA.

31

Synergy, Indifference, Antagonism

Look this up.

32

What is necessary for aminoglycosides to work?

Protein synthesis. Administer streptomycin with a protein synthesis inhibitor and antagonism occurs.