beta-lactam inhibitors - penicillin Flashcards Preview

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Flashcards in beta-lactam inhibitors - penicillin Deck (47):
1

Vary in resistance to gastric acid
 Vary in their oral bioavailability
 Polar compounds
 Not metabolized extensively

penicillins

2

penicillins are excreted unchanged or changed

unchanged

3

penicillins Excreted unchanged in urine via

 Inhibited by probenecid

 Glomerular filtration
 Tubular excretion

4

Tubular excretion of penicillin is Inhibited by ---

probenecid

5

Major antibiotics that inhibit cell wall synthesis

Penicillins
Cephalosporins

6


 Partly excreted in bile

Ampicillin and nafcililin

7

penicillins are Derivatives of ?

6-aminopenicillanic acid

8

Plasma half-life of penicillins vary from --

30 min to 1 h

9

Given intramuscularly
Long half-lives
Drug is released slowly
Cross blood-brain barrier when meninges are inflamed

Procaine and benzathine penicillin G

10

penicillin inhibit cell wall synthesis by the following steps

1. Binding of the drug to specific receptors (penicillin-binding proteins [PBPs]) located in the bacterial cytoplasmic membrane
2. Inhibition of transpeptidase enzymes that act to cross-link linear peptidoglycan chains
3. Activation of autolytic enzymes that cause lesions in the bacterial cell wall

11

? hydrolysis of the beta-lactam ring results in the lost of antibacterial activity

Enzymatic

12

 Penicillinases
 Formed by most staphylococci and gram (-) organisms

beta lactamases

13

 Major mechanism for bacterial resistance

beta lactamases

14

Another mechanism of bacterial resistance
responsible for:
 Methicillin resistance in staphylococci
 Penicillin G resistance in pneumococci

Structural changes in target PBPs

15

 Contribute to resistance by impeding access of penicillin to PBPs
 Resistance in some gram (-) rods like P. aeruginosa

Changes in the porin structure in the outer membrane

16

3 types of resistance to penicillin

beta lactamases
Structural changes in target PBPs
Changes in the porin structure in the outer membrane

17

 Prototype Narrow-spectrum penicillinase-susceptible agents

penicillin G

18

PENICILLIN G
 Prototype of narrow-spectrum penicillinase-susceptible agents
 Parenteral
 Limited spectrum of activity
 Susceptible to beta-lactamases

PENICILLIN G

19

 For infections caused by
 Streptococci
 Meningococci
 Gram (+) bacilli
 Spirochetes

PENICILLIN G

20

 Drug of choice for syphilis
 Activity against enterococci is enhanced by aminoglycoside

PENICILLIN G

21


 Oral drug
 Oropharyngeal infections

PENICILLIN V

22

Very-narrow-spectrum penicillinase-resistant agents (3)

METHICILLIN (prototype), NAFCILLIN, OXACILLIN

23

 Treatment of known or suspected staphylococcal infections
 Methicillin-resistant S. aureus (MRSA) and S. epidermidis (MRSE) are resistant to other members of this subgroup and often to multiple antimicrobial drugs

METHICILLIN (prototype), NAFCILLIN, OXACILLIN

24

3. Wider spectrum penicillinase-susceptible agents

ampicillin and amoxicillin
PIPERACILLIN and TICARCILLIN

25

 Wider spectrum than pen G
 Susceptible to penicillinases
 Uses similar to pen G
 Enterococci L. monocytogenes
 E. coli P. mirabilis
 H. influenzae M. catarrhalis
 Enhanced activity in combination with inhibitors of penicillinases
 Synergistic (1+1=3) with aminoglycosides in enterococcal and listerial infections

ampicillin and amoxicillin

26


 Activity against gram (-) rods
 Pseudomonas
 Enterobacter
 Some cases of klebsiella species
 Synergistic action with aminoglycosides
 Susceptible to penicillinases
 Enhanced activity in combination with inhibitors of penicillinases

PIPERACILLIN and TICARCILLIN

27

toxcity of penicillin

allergy
GI disturbances

28

toxcity of penicillin

allergy
GI disturbances

29

can cause neutropenia

Nafcillin

30

causes maculopapular rashes

Ampicillin

31

causes interstitial nephritis more than other penicillins

Methicillin

32

cross-allergenicity (complete or not)

Complete

33

GI disturbances are caused by

 Oral penicillins especially ampicillin

34

specific GI disturbances

nausea and diarrhea

35

Pseudomembranous colitis
Maybe caused by (2)

direct irritation or by overgrowth of gram (+) organisms or yeasts

36

An antimicrobial drug that can eradicate an infection in the absence of host defense
mechanisms; kills bacteria

bactericidal

37

An antimicrobial drug that inhibits antimicrobial growth but requires host defense
mechanisms to eradicate the infection; does not kill bacteria

Bacteriostatic

38

Drugs with structures containing a beta-lactam ring: includes the penicillins, cephalosporins
and carbapenems. This ring must be intact for antimicrobial action

Beta-lactam antibiotics

39

Bacterial enzymes (penicillinases, cephalosporinases) that hydrolyze the beta-lactam ring of
certain penicillins and cephalosporins

Beta-lactamases

40

Potent inhibitors of some bacterial beta-lactamases used in combinations to protect
hydrolyzable penicillins from inactivation

Beta-lactam inhibitors

41

Lowest concentration of antimicrobial drug capable of inhibiting growth of an organism in a
defined growth medium

Minimal inhibitory concentration (MIC)

42

Bacterial cytoplasmic membrane proteins that act as the initial receptors for penicillins and
other beta-lactam antibiotics

Penicillin-binding proteins (PBPs)

43

Chains of polysaccharides and polypeptides that are cross-linked to form the bacterial cell wall

Peptidoglycan

44

More toxic to the invader than to the host; a property of useful antimicrobial drugs

Selective toxicity

45

Cross allergenicity with penicillins (complete, incomplete, partial) is assumed

Complete cross allergenicity must be assumed

46

T or F: 5-10% of patients with history of allergic rxns to penicillin will have the same rxn when given again

True

47

Bacterial enzymes involved in the cross-linking of linear peptidoglycan chains, the final step in
cell wall synthesis

Transpeptidases

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