cell wall II

Question 1

Structurally, the cephalosporins have a ___ membered ring attached to the beta-lactam moiety in contrast to the 5-membered ring of the penicillins.

Answer 1

6

Question 2

cephalosporins are

Answer 2

bactericidal- inhibit bacterial cell wall synthesis exhibiting time-dependent killing

Question 3

cephalosporins activity against enterococci

Answer 3

not active

Question 4

which cephalosporins is the only one active against MRSA

Answer 4

5th generation- ceftaroline

Question 5

1. Active against gram positive cocci
2. Gram negative coverage: active against some Escherichia coli, Proteus spp., Klebsiella spp.
3. oral form is cephalexin
4. Cephalosporin of choice for S. aureus that is not Methicillin resistant
   Used in PCN (oxacillin) allergic patients

Answer 5

Cefazolin

Question 6

_____ today is most commonly used to treat gram positive infections such as skin and soft tissue infections or bacteremias caused by susceptible S. aureus in patients who are allergic to oxacillin and for surgical antibiotic prophylaxis when MRSA is of low concern.

Answer 6

Cefazolin

Question 7

when should we never use cephalosporins in a patients

Answer 7

history of pcn anaphylaxis

*** caphalosporins have a cross-reactivity rate with penicillins of approx. 5-8%

Question 8

What organisms are considered part of the skin microbiota?

Answer 8

S. epididermis

Question 9

• Active against gram positive cocci
• Active against β-lactamase producing Haemophilus influenzae
• Active against Eschericia coli, Klebsiella, Proteus (some gram (-))

Answer 9

cefuroxime- 2nd generation

Question 10

• Slightly less active than first generation against gram + cocci
• Active against gram negative organisms including E. coli, Proteus, Klebsiella
• **True strength is activity against Bacteroides fragilis (bowel anaerobe)

Answer 10

cefoxitin- second generation

Question 11

• Less active against S. aureus than first generation cephalosporins
• Excellent activity against Streptococci
• Excellent activity against gram neg. rods - (more stable to beta-lactamases)
• ****More effective penetration into CNS
• Modest activity against bowel anaerobes
• No activity against Pseudomonas

Answer 11

ceftriaxone- 3rd generation

Question 12

Ceftraixone has good activity against streptococcus pneumoniae and gram negatives but not to

Answer 12

yep but NOT pseudomonas

Question 13

cefrtriaxone may complex with calcium leading to

Answer 13

precipitation- stones

** associated with formation of biliary sludge/ pseudo biliary pseudolithiasis

Question 14

BROAD Spectrum:
- Active against gram positive organisms

• Active against gram negative organisms including Pseudomonas aeurginosa
• No anaerobic activity

Clinical Use
Hospital acquired infections
Hospitalized neutropenic patients with fever and we don’t know the organism

Answer 14

cefepime- 4th generation

Question 15

• Poor gram positive activity
• NO anaerobic activity
• ****Special role is in infections due to Pseudomonas aeruginosa (gram negative rod)
• Excellent penetration into central nervous system

Answer 15

ceftazidime- 3rd generation

Question 16

ceftraixone but with MRSA activity

Answer 16

ceftaroline

Question 17

what types of tox associated with cefepime if you have renal failure

Answer 17

neurotoxicity

Question 18

________ binds PBP 1-4 and has a high affinity for PBP2a (mecA) which is associated with methicillin resistance
Little clinical experience with VRE

Broad gram positive activity with some gram negative activity

Answer 18

Ceftaroline

Question 19

weird factor of ceftaroline and positive direct Coombs test

Answer 19

positive but not hemolysis

Question 20

cephalosporins is associated with what type of infection

Answer 20

C. difficile

Question 21

Aztreonam- is a monocyclic beta lactam – beta lactam ring is not fused to another ring

1. excellent activity against ___ thus it is

Answer 21

excellent activity against gram negative esp. P. aeruginosa thus it is a narrow spectrum agent

Question 22

aztreonam is usually reserved for

Answer 22

PCN allergic patients with GNR infections

Question 23

carbapenems are broad or narrow spectrum activity

Answer 23

broad

Question 24

carbapenems are active against MRSA

Answer 24

nope- active against gram negative, gram positive and anaerobes but not MRSA

Question 25

Carbapenems share common beta-lactam ring with penicillins

Answer 25

yes however clinical studies have shown low rate of cross-reactivity

Question 26

Non-Beta Lactam Cell Wall and Cell Membrane Inhibitors (2)

Answer 26

1. vancomycin

2. daptomycin

Question 27

vancomycin is a bactericidal that has a narrow spectrum oonly active against

Answer 27

gram positive esp. those that are resistant to other antibiotics

Question 28

MOA of Vancomycin

Answer 28

Blocks peptidoglycan synthesis, prevents cross linking
however note mechanism of action is distinct from that of beta lactams. vancomycin binds D-ala-D-ala preventing binding of transpeptidase and cross linking

while beta lactams inhibit transpeptidases

Question 29

vancomycin is only used orally to treat for

Answer 29

C. difficile colitis

Question 30

Red man syndrome

Answer 30

it is a adverse effect of vancomycin caused by a fast infusion

Question 31

tox. associated with vancomycin

Answer 31

kidney tox

Question 32

MOA of daptomycin

Answer 32

binds to the bacterial cell membrane and forms a potassium channel leading to an efflux and destroys the gradient causing cell death

*** cell membrane potential is inhibited

Question 33

daptomycin is not used to treat pneumonia… why?

Answer 33

it is inactivated by alveolar surfactant

Question 34

daptomycin is used against

Answer 34

gram positive organisms

Question 35

very good for resistant GNRs (ESBL) and anaerobes

Answer 35

imipenem-cilastatin

Question 36

Which beta lactams is able to bind Penicillin Binding Protein 2a?

Answer 36

ceftaroline