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Beta Lactams Flashcards

1
Q

What are the antibiotic molecular targets?

A

DNA synthesis

RNA Synthesis

Protein Syntheis

Peptidoglycan synthesis

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2
Q

What are the quick characteristics of a Gram positive?

A

Very thick murein (peptidogylcan cell wall)

No outer membrane

Teichoic acid

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3
Q

What are the quick characteristics of a gram negative cell wall?

A

Thin murein wall (peptidoglycan)

Contain outer membrane in addition to cytoplasmic

Porins

LPS

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4
Q

Describe the basic mechanism of peptidoglycan synthesis that can be interrupted by antibiotics.

A

Two peptidoglycan chains need to cross link to be a stable wall.

Attached to each NAM are a series of amino acids ending in D-Alanine - D-Alanine

A transpeptidase enzyme connects the first D-Alanine to the Lys of the adjacent peptidoglycan chain with a L-Glycine

The result is a D-Ala - L-Gly crosslink

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5
Q

What is the basic structure of penicillins?

A

A beta lactam ring with secondary amino group and a thiazolidine ring

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6
Q

What is the basic structure of cephalosporin?

A

Similar to penicillin but instead of a thiazolidine ring it has a 6 carbon ring

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7
Q

What is the mechainism of action of penicillin?

A

It inhibits transpeptidation reaction of cell wall synthesis

Beta lactams are structural analogs of natural D-alanyl-D-alanine substrate.

The beta lactam covalently binds to the active site of the transpeptidases

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8
Q

Why is penicillin considered bactericidal?

A

The interference of the cross linking increases the osmotic instability with the cell leading to cell lysis via osmotic pressure causing it to burst or activation of autolysins

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9
Q

What are autolysins?

A

Degenerative enzymes produced by many bacteria (particullar gram positive cocci) that participate in normal remodeling of the bacterial cell wall.

In the pressence of penicillins, the autolysisn continue in the absence of cell wall syntehsis and further degrade the cell wall.

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10
Q

What infectious agents are penicillins targeted for?

A

Only rapidly replicating bacteria with a cell wall.

No activity against mycobacteria, protozoa, fungi and viruses

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11
Q

What are the components of the cell wall?

A

Comprised of cross-linked polymers of:
polypeptides
peptidoglycans
polysaccharides: N-acetylglucosamine and N-acetylmuramic acid

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12
Q

What drugs are of the class Penicillin?

A

Penicillin G (benzylpenicillin)

Penicillin V

Benzathine

Procain penicillin G

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13
Q

Procaine Penicillin G

A

Procaine benzylpenicillin (rINN), also known as procaine penicillin, is a form of penicillin which is a combination of benzylpenicillin and the local anaesthetic agent procaine

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14
Q

Penicillin G

A

Benzylpenicliin or penicillin G (G referring to the Gold standard)

Non-beta-lactamase staphylococci

Streptococcus (pneumo,pyogenes, and viridans)

Gram (+) bacilli (Bacillus anthracis, corynebacterium diphtheriae)

Gonorrhea (neisseria gonnorrhoeae/meningitidis)

Syphilis (treponema palligum)

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15
Q

What are the class of extended-spectrum penicillins?

A

Amoxicillin

Ampicillin

Piperacillin

Ticarcillin

Ampicillin and Amoxicillin (identical spectrum and activity) active against:

Gram-positive bacilli (Listeria Monocytogenes)

Gram negative rods (Escherichia coli, Hameophilus influenzae, proteus mirabilis, salmonella typhi)

AMP AMOX good for Penicillin resistant pneumococci

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16
Q

What are the Anti-staphylococcal penicillins?

A

Beta-lactamase resistant

Nafcillin

Methicillin

Oxacillin

Cloxacillin

Dicloxacillin

OCD (PO) used for mild to moderate localized staphylococcal infections

NO (Nafcillin and Oxacillin; IV) for serious systemic staphylococcal infections (like MSSA - methicillin susceptible Staphylococcal Aureus)

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17
Q

What are the routes of administration for penicillins?

A

Oral - absorption is impaired by food (given 1-2 hours before or after meal)

Parenteral - absoprtion complete and rapid

IV preferred over IM

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18
Q

Which penicillin can be given with food?

A

Amoxicillin (an extended spectrum antibiotic)

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19
Q

Which penicillin when given intramuscularly are leached slowly?

A

Benzathine and procaine

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20
Q

How are most ‘Beta-lactamse resistant’ penicillins excreted?

A

both biliary and renal routes

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21
Q

What affect does treament of gout have on the role of penicillins?

A

Probenecid is use to treat gout.

Probenecid impairs renal tubular secretion of weak acids which increase blood levels of beta-lactams

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22
Q

How are most beta-lactams excreted?

A

All except for anti-staph (beta-lactamase resistant penicillins) are readily exreted through urine

Anti-staph are exreted via urine and biliary

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23
Q

What is the most determinant criteria for penicillin dosage?

A

Adjustments base on renal failure

24
Q

Can penicillins be used to treat menigitis?

A

Yes, the inflammed meninges allows for greater permeability of penicillin into the CSF

25
Benzathine penicillin G (BPG) clinical use
Beta-hemolytic streptococcal pharyngitis (pyogenes ) or syphilis (treponema palidum) Given IM yield low but prolonged drug levels
26
Procaine penicillin G clinical use
former DOC for uncomplicated pneumococcal pneumonia or gonorrhea Rarely used\*\*\*low yield\*\*\*
27
Drug of choice for Listeria Monocytogenes
Ampicillin
28
Ticarcillin and Piperacillin
Extended spectrum Penicillins **Antipseudomonals**, other gram negative rods **UTIs** P. Aeruginosa can lead to pneumonia, UTIs and Bacteremia (often given in comibnation with other antibiotics (aminogrlycosides or fluroquinolones) for infections outside the urinary tract)
29
What are the beta-lactamase inhibitors?
Potent inhibitors of Beta-lactamases \* Clavulanic acid \* Sulbactam \* Tazobactam Extends the activity of penicillins to include β-lactamase-producing strains of S. aureus and some strains of β-Lactamase-producing gram negative bacteria
30
Augmentin
Amoxicilin (extended spectrum) and clavulanic acid (resemble beta-lactamase) Synergistic
31
Zosyn
Piperacillin (extended spectrum; antipseudomonas) + Tazobactam (resembles beta-lactam)
32
What are the adverse effects of Penicillins?
Most common: Rash and Diarrhea Serum sickness: urticaria (hives), fever, joint swelling, angioneurotic edema, intense pruritus and respiratory embarrassment Nephritis: due to an autoimmune reaction to a penicilliin-protein complex in patients with renal failure, penicillins may cause seizures
33
What is the basic of methicillin resistance in staphlococci and penicillin resistance in penumoccoci and enterococci?
Modifications of the PBPs (transpeptidase)
34
What is the most common ways for penicillin resistance? What are the others
Most common: Inactivation by beta-lactamases Others: **Modification of transpeptidases** Poor drug penetration to peptidases (gram negative species; alteration of porins) Efflux pumps eject drugs from periplasmic space (gram negatives)
35
What are the main differences of cephalosporins from penicillins?
Still beta lactams but have two R groups; Have broader spectrum of activity More stable to many bacterial beta-lactamases Divided into generations that are determined by spectrum of activity
36
What are the first generation cephlosporins?
**Cef/Ceph\_adroxil,azolin,alexin,or radine** Cefadroxil, Cefazolin, Cephalexin, Cephradine Effective against: Gram-positive cocci except MRSA Gram-negative activity: Proteus mirabilis, E.Coli, K.Pneimoniae **(PEcK)** Anaerobic cocci activity: Peptococcuc and peptostreptococcus but NOT Bacteroides Clinical Uses:
37
What are the second generation cephalosporins?
Cef\_aclor, furoxime, foxitin, otetan Cefaclor Cefuroxime Cefoxitin# Cefotetan# Active against organisms inhibited by 1st generation PLUS extended gram negative activity Gram positives: Streptococcus Pneumoniae, Streptococcus Pyogenes, Anaerobic streptococci (#) Gram Negatives: Neisseria gonorrhea, enterobacter aerogenes, Escherichia coli, Hameophilus influenzae, Klebsiella pneumoniae, PRoteus Mirablilis Cephamycins (#) have good anaerobe activity
38
What are the third generation cephalosporins?
**Cef\_ Tax, Traix, or taz** Cefotaxime Ceftazidime Ceftriaxone **"Tax and Triax"** can cross the blood brain barrier Have expanded Gram-negative coverage compared to 2nd generation ( adds Pseudomonas aeruginosa)
39
What are the fourth generation cephlasporins?
**Cef\_prime** Cefipime Good activity against P. aeruginosa, **enterobacteriaceae**, S. aureus, and **S. pneumoniae** Highly active against haemophilus and neisseria Penetrates the CSF
40
What are the clinical uses of second generation cephalosporins?
Cefuroxime (fur) - sinusitis, otitis, and lower respiratory tract infections (active against influenzae or Moraxella catarrhalis) Community acquired pnbeumonia (H influenzae, K pneumoniae and peniccilin-resistant pneumococci) Cefoxitin, Cefotetan (fox & tea) - mixed anaerobic infections (bacteroides fragilis)
41
What is the empirical therapy for third geenration
Empirical therapy for **sepsis of unknown cause**: Immunocompetent and immunocompromised Treatment of infection where cephalosporins are the least toxic drug available In neutropenic, febrile, immunocompromised patients, 3rd generation are used in combination with an aminoglycoside
42
What are the excretion patterns of cephalosporins?
Renally and require a does adjustment in the case of renal insufficiency (except 3rd generation; ceftriaxone)
43
What organisms are not cover by cephalosporins?
LAME Listeria Monocytogenes Atypicals (chlamydia, mycoplasma) Methicillin-resistant staphylococcal aureus Enterococci Psuedomonas is covered by Cephs but NOT UNTIL 3rd generation (Ceftazidime and Cefoperazone are the only two with useful activity).
44
What are the adverse effects of cephalosporins?
May induce hypersensitivity reactions identical to penicillins however, **if no anaphylaxis**, Individuals with penicillin allergies may tolerate cephalosporins cefotetan can cause **Hypoprothrombinemia** and bleeding disorders (reaction with vitamin K which is needed for the clotting cascade Avoid alcohol and alcohol containing medications
45
Aztreonam
Specturm: Similar to 3rd generation cephalosporins Resistant to most β-lactamases Can be given to penicillin-allergic patients without reaction Can treat pneumonia, meningitis and sepsis caused by Gram-negative pathogens
46
Imipenem
Acts like penicillin Resistant to most beta lactamases Inactivated by dehydropeptidase in renal tubules Administered with cilastatin to inhibit dehydropeptidase Given to resistant strains of p. aeruginosa, enterobacter, MSSA, MSS(trep), anaerobes, intrabdominal infections, LRTI, gynocological, UTIs, **ATOM BOMB of Penicillins**
47
Adverse effects of imipenem
N/V/D Skin rashes, seizures in patients with renal insufficiency **MUST MONITOR RENAL FUNCTION** Avoided in patients with histroy of seizures
48
Vancomycin resistanct?
The terminal D-ala becomes D-lactate\*\*\*\* Modifies the structure reducing the ability of vancomycin to bind to the target Vancomycin-resistant Staphylococcus aureus (VRSA) Vancomycin-resistant enteroccal species will be common
49
Spectrum of activity of Vancomycin
Bactericidal for Gram-positive No gram negatives MRSA treatment
50
Clinical uses of Vancomycin
**Sepsis or endocarditis** caused by MRSA. Reserved for serious infections In combination with cefotaxime or ceftriaxone for treatment of meningitis caused by highly penicillin-resistant pneumococcus
51
key words associated with Vancomycin
Redman syndrome MRSA NEPHROTOXICITY
52
How is vanco administered and cleared?
Oral if for enterorcolitis; Slow IV otherwise excreted via the Kidneys and must be monitored in patients with renal insufficiency
53
Adverse effects of vancomycin
Ototoxicity and Nephrotoxicity are both increased when given with other drugs (ex: aminoglycosides) that also produce these side effects Fever Chills Flushing (redman syndrome) Pain (phlebitis)
54
Bacitracin
-Bacitracin: Only used topically. Active against Gram +ve bacteria. Works by interfering with the lipid carrier that transfers peptidoglycan subunits to the growing cell wall. Not given internally. C. Diff
55
Fosfomycin
-Fosfomycin: Inhibits cell wall synthesis by inhibiting enolpyruvate transferase, preventing formation of UDP-N-Acetylmuramic acid, the precursor of NAM. Approved for single use 3g does of uncomplicated UTIs in women. Safe for use in pregnancy.
56
Cycloserine
-Cycloserine: Structural analog of D-alanine, inhibits alanine racemase (converts L-ala to D-ala). Used to treat tuberculosis when 1st line drugs have failed. Serious dose-related CNS side-effects.

MSKIII (2 decks)

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