Cell Wall Synthesis Inhibitors

Question 1

What are antimicrobials?

Answer 1

Antimicrobials are therapeutic substances used to prevent or treat infections. They include antiseptics, antibiotics, antivirals, antifungals and antiparasitics.

Question 2

What are antibacterials?

Answer 2

Used internally and externally for bacteria infection.

e.g. Ampicillin/cloxacillin (Ampiclox)

Question 2

What are antibiotics?

Answer 2

Antibiotics are substances which kill or inhibit the growth of bacteria within a living tissue. They may be synthetic, semi-synthetic or naturally-produced by microorganisms.

Question 3

What are disinfectants?

Answer 3

Disinfectants are antimicrobial agents applied to non-living surfaces.

Chloroxylenol (Dettol)

Question 4

What are antifungals?

Answer 4

Used internally and externally for fungal infections.

Griseofulvin (Fulcin), Clotrimazole (Canesten)

Question 5

What are antivirals?

Answer 5

Used internally and externally for viral infections.

Acyclovir (Zovirax)

Question 6

What are antiprotozoans?

Answer 6

Antiprotozoal drug, any agent that kills or inhibits the growth of organisms known as protozoans.

Artemether/lumefantrine (Coartem)

Question 7

What are antiseptics?

Answer 7

Used externally on living tissue

Chlorhexidine (SavlonR)

Question 8

Who discovered the first antibiotic?

Answer 8

Alexander Fleming in 1928

Question 9

What are the classification of antibiotics based on mechanisms of action?

Answer 9

1. Antibiotics that Inhibit Cell Wall Synthesis
2. Antibiotics that affect nucleic acid synthesis
3. Antibiotics that act on ribosomes and inhibit protein synthesis
4. Antimetabolites

Question 10

Antibiotics that target cell wall synthesis

Answer 10

Cycloserine
Vancomycin
Bacitracin
Beta-lactams (Penicillins, Cephalosporins, Monobactams, Carbapenems)
Antimycobacterials (Isoniazid, Ethambutol)

Question 11

Antibiotics that target DNA gyrase

Answer 11

Quinolones (Nalidixic acid and Ciprofloxacin)
Novobiocin

Question 12

Antibiotics that target RNA elongation

Answer 12

Actinomycin

Question 13

Antibiotics that target DNA-directed RNA polymerase

Answer 13

Rifampin
Streptovaricins

Question 14

Antibiotics that target protein synthesis (50S inhibitors)

Answer 14

Macrolides (Erythromycin)
Chloramphenicol
Clindamycin
Lincomycin

Question 15

Antibiotics that target protein synthesis (30S inhibitors)

Answer 15

Tetracyclines
Spectinomycins
Streptomycin
Gentamicin
Kanamycin
Amikacin
Nitrofurans

Question 16

Antibiotics that target protein synthesis (RNA)

Answer 16

Mupirocin
Puromycin

Question 17

Antibiotics that target cytoplasmic membrane structure

Answer 17

Polymyxins
Daptomycin

Question 18

Antibiotics that target folic acid metabolism

Answer 18

Trimethoprim
Sulphonamides

Question 19

What is the mechanism of action of Penicillin?

Answer 19

Penicillins interfere with cell wall synthesis by inhibiting the transpeptidase enzyme that cross-links the peptide chains attached to the backbone of the peptidoglycan.

The final bactericidal event is the inactivation of an inhibitor of autolytic enzymes in the cell wall, leading to lysis of the bacterium.

Question 20

Classifications of penicillin

Answer 20

1. Natural penicillin (benzylpenicillin)
2. Broad-spectrum penicillin (Amino penicillin e.g. ampicillin, amoxicillin)
3. Broad-spectrum penicillin with antipseudomonal activity (ticarcillin , carbenicillin)
4. B-lactamase (penicillinase) resistant penicillin e.g. flucloxacillin.

Question 21

Uses of penicillins

Answer 21

Typhoid fever and other susceptible bacteria infections

Question 22

Adverse effects of penicillins

Answer 22

Hypersensitivity, nausea and vomiting

Question 23

Are penicillins bactericidal or bacteriostatic?

Answer 23

Bactericidal

Question 24

Penicillins have greater beta-lactam activity than cephalosporins. True or False?

Answer 24

False

Question 25

What is the mechanism of action of cephalosporins?

Answer 25

They interfere with bacterial cell wall synthesis by reducing stability of the cell wall which leads to lysis of the cell membrane.

Question 26

Are cephalosporins bactericidal or bacteriostatic?

Answer 26

Bactericidal

Question 27

Classifications of cephalosporins

Answer 27

1st Generation: Cefazolin, Cefalexin, Cephradine 2nd Generation: Cefuroxime, Cefoxitin, Cefaclor 3rd Generation: Cefixime, Ceftriaxone, Cefpodoxime 4th Generation: Cefepime, Cefepirole 5th Generation: Ceftolozane, Ceftaroline

Question 28

What trend increases down the generations of cephalosporins?

Answer 28

Increased potency against Gram negative bacteria and decreased potency against Gram positive bacteria (except the 4th generation)

Question 29

Uses of cephalosporins

Answer 29

Septicaemia (cefuroxime) Meningitis (ceftriaxone) UTI Sinusitis.

Question 30

Mechanism of action of carbapenems

Answer 30

They kill bacteria by binding to penicillin-binding proteins, thus inhibiting bacterial cell wall synthesis.

Question 31

Examples of carbapenems

Answer 31

Meropenem Ertapenem Doripenem Imipenem Tebipenem M-E-D-I-T

Question 32

Arrange the following by antibiotic activity: Carbapenems, Penicillins, and Cephalosporins

Answer 32

Carbapenems > Cephalosporins > Penicillins

Question 33

What are the advantages of carbapenems over other classes of beta-lactams?

Answer 33

They have activity against anaerobes and beta-lactamase producing organisms

Question 34

Uses of carbapenems

Answer 34

They are reserved for multi-drug resistant infections. Pneumonia, complicated urinary tract infections, and blood stream infections.

Question 35

Adverse effects of carbapenems

Answer 35

Skin rash

Question 36

What are monobactams?

Answer 36

Monobactams are monocyclic beta-lactam antibiotics with b-lactam rings that are not fused to another ring.

Question 37

Monobactam activity spectrum

Answer 37

They are effective against aerobic Gram negative bacteria only.

Question 38

Mechanism of action of monobactams

Answer 38

They kill bacteria by inhibiting synthesis of the bacterial cell wall via blockage of peptidoglycan crosslinking.

Question 39

Examples of monobactams

Answer 39

Aztreonam Tigemonam

Question 40

Uses of monobactams

Answer 40

Pneumonia Urinary tract infections Bone infections Intraabdominal infections Sepsis Endometritis

Question 41

Adverse effects of monobactams

Answer 41

Skin rash

Question 42

What is vancomycin?

Answer 42

Vancomycin is a glycopeptide antibiotic administered intravenously.

Question 43

What is the spectrum of activity of vancomycin?

Answer 43

It is a last resort medication for the treatment of sepsis and lower respiratory tract, skin, and bone infections caused by Gram-positive bacteria

Question 44

Mechanism of action of vancomycin

Answer 44

Vancomycin acts by inhibiting proper cell wall synthesis in Gram-positive bacteria.

Question 45

Why is vancomycin ineffective against Gram negative bacteria?

Answer 45

Vancomycin is not active against G-ve organism due to the different mechanism by which G-ve bacteria produce their cell walls and the various factors related to entering the outer membrane of G-ve organisms

Question 46

Uses of vancomycn

Answer 46

Methicillin resistant Staphylococcus aureus (MRSA) infections Clostridium difficile colitis Meningitis Complicated skin infections Bone and joint infections Endocarditis

Question 47

Adverse effects of vancomycin

Answer 47

Hearing loss Low blood pressure Allergic reactions Bone marrow suppression Nephrotoxicity (rarely) Also causes "red man syndrome" or sometimes "red neck syndrome," clinically referered to as Vancomycin Flushing Syndrome

Question 48

What is vancomycin flushing syndrome?

Answer 48

It is the presentation of side effects resulting from histamine release when vancomycin is infused too rapidly: a red rash, hypotension, tachycardia, angioedema, etc.