Intro to Bacteriology and Antibiotic Strategies

Question 1

Gram positive cocci in pairs?

Answer 1

Pneumococcus = S. pneumoniae

Question 2

Gram positive cocci in chains?

Answer 2

Streptococcus pyogenes = Group A Strep

Question 3

Gram positive cocci in clusters?

Answer 3

Staphylococcus

Question 4

Gram Positive Rods

Answer 4

Bacillus species

Question 5

Gram Negative Cocci

Answer 5

Neisseria (meningitis)

Question 6

Gram Negative Rods

Answer 6

Campylobacter (bacterial gastroenteritis)

Question 7

Can spirochetes be visualized with the gram stain?

Answer 7

No

Question 8

Do bacteria have organelles?

Answer 8

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

Question 9

Gram negative cell wall

Answer 9

Inner lipid bilayer, thin cell wall, outer lipid bilayer

Question 10

Gram positive cell wall

Answer 10

Inner lipid bilayer, thick peptidoglycan cell wall

Question 11

Components of the peptidoglycan cell wall

Answer 11

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

Question 12

Porin Channels

Answer 12

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

Question 13

Lipopolysaccharide

Answer 13

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.

Question 14

Normal bacteria of the skin

Answer 14

Staphylococcus epidermidis

Question 15

Normal bacteria of the upper respiratory tract

Answer 15

anaerobic cocci, viridans streptococci

Question 16

Environmental Factors of Infection

Answer 16

Overcrowding, climate, antibiotic use

Question 17

Host Factors of Infection

Answer 17

Immunocompromised state, extremes of age, breach in barriers

Question 18

Inhibitors affecting peptidoglycan synthesis

Answer 18

Penicillin, cephalosporin, carbapenems, monobactams

Question 19

How does penicillin work?

Answer 19

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

Question 20

How does the structure of penicillin cause it to work?

Answer 20

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.

Question 21

Beta-lactamase

Answer 21

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

Question 22

Transposition of drug resistance genes

Answer 22

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.

Question 23

Vancomycin, bacitracin

Answer 23

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

Question 24

Resistance to vancomycin

Answer 24

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.

Question 25

Inhibitors affecting cell wall membranes

Answer 25

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

Question 26

Resistance mechanism to tetracyclines

Answer 26

Moved out to the cell

Question 27

Resistance to aminoglycosides

Answer 27

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.

Question 28

Inhibitors affecting DNA-dependent DNA polymerase activity

Answer 28

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

Question 29

Inhibitors affecting DNA-dependent RNA polymerase activity

Answer 29

Rifampicin, actinomycin D

Question 30

Folic acid antimetabolites

Answer 30

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

Question 31

Synergy, Indifference, Antagonism

Answer 31

Look this up.

Question 32

What is necessary for aminoglycosides to work?

Answer 32

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