8.1 PCN

Question 1

In general, how do B-lactam’s function?

Answer 1

Target’s PBP- binds there instead, causes NAG/NAM to fall apart –> breaks cell wall

Question 2

What are the subclasses of B-lactam?

Answer 2

Penicillins
Cepharlosporins
Carbapenems
Monobactam

Question 3

How do bugs become resistant?

6 Ps

Answer 3

Penetration – PCN poorly penetrate into intracellular
Bacteria hide in this compartment (i.e. Rickettsia and Legionella)
Porins – “sieving” system prevent PCN to get into periplasmic space
Some G(-) – E. Coli, Proteus M, Salmonella, and Shigella
Pumps – Efflux pump – prevent accumulation
Pseudomonas aeruginosa
Penicillinases (beta-lactamase) – G+ and G-
PBPs – mutated – not binding to penicillins
Peptidoglycan – Do not make peptidoglycan PCN ineffective (i.e. Mycoplasma, and Chlamydia)

Question 4

What are the natural PCN meds on the market? Route?

Answer 4

PCN-G IV

PCN-V PO

Question 5

What is the mechanism of anti-staph penicillins?

Answer 5

Bulky side chain prevent binding to beta-lactamases

Question 6

What are examples of anti-staph PCNs?

Answer 6

Nafcillin, Oxacillin, and Dicloxacillin

Methicillin- no longer available

Question 7

What bugs do anti-staph penicillins treat?

Answer 7

S. aureus, S. epidermidis

BUT NOT MRSA/MRSE

Question 8

Are anti-staph penicillins useful for streptococci or enterococci?

Answer 8

No

Question 9

What is the mechanism of aminopenicillins?

Answer 9

Amino group-> increase hydophilicity

Interferes with NAG/NAM

Question 10

What bugs are targets of aminopenicillins?

Answer 10

E coli
P mirablis
Shigella

Question 11

How does resistance to aminopenicillins form?

Answer 11

Drug is susceptible to beta-lactamse

Bugs with this modification defeat med

Question 12

What are 2 examples of aminopenicillins?

Answer 12

Amoxicillin, ampicillin

Question 13

What is the mechanism of aminopenicillins and b-lactamase inhibitors?

Answer 13

Inhibitors mimic penicillin –> bind to beta-lactamases –> enzyme inactivation
Then interferes with NAG/NAM

Question 14

What are examples of aminopenicillins and b-lactamase inhibitors?

Answer 14

Ampicillin + Sulbactam (Unasyn) – IV

Amoxicillin + Clavulanate (Augmentin) – PO

Question 15

What is the mechanism of extended-spectrum PCN?

Answer 15

Polar side chain allows greater penetration into G- bacteria

More resistant to G- beta-lactamases than aminopenicillins

Question 16

What coverage do you get wth extended-spectrum PCN?

Answer 16

More active against G- bacilli including Pseudomonas
Have modest activity against anaerobes
Still susceptible to beta-lactamases of staph

Question 17

What is the fullest potential of PCN?

Answer 17

Extended spectrum penicillin + beta-lactamase inhibitors

Question 18

What are examples of extended-spectrum PCN?

Answer 18

Piperacillin + tazobactam (Zosyn)- broader

Ticarcillin + clavunate (Timentin)

Question 19

What is the coverage of extended-spectrum PCN (e.g. zosyn)

Answer 19

Cover staph, aerobic G-, almost all anaerobic (except C. diff.)

Question 20

What are the toxicities of PCN?

Answer 20

N/V/D
Drug fever, rash
Hepatotoxicity
Neurologic toxicity
Urticaria
Angioedema

Question 21

What is the coverage of antistaph PCN?

Answer 21

cover G+, but no G- activity

Question 22

What is the coverage of natural PCN?

Bugs?

Answer 22

G+ plus few G- activity (i.e. N. meningitidis, H. influenza)

Question 23

What is the coverage of Amino PCN? Bugs?

Answer 23

G+ plus H. influenza, E. Coli, N. meningitidis, P. mirabilis, S. enterica, Shigella…

Question 24

What is the coverage of ES-PCN? Bugs?

Answer 24

G+ plus H. influenza, E. Coli, N. meningitidis, P. mirabilis, S. enterica, Shigella, AND PSEUDOMONAS

Question 25

What is the coverage of ES-PCN w/ b-lactamase inhibitor? Bugs?

Answer 25

Broadest, cover most enteric G- bacilli

PSUDOMONAS