Cell Wall Synthesis Inhibitors Flashcards
What are antimicrobials?
Antimicrobials are therapeutic substances used to prevent or treat infections. They include antiseptics, antibiotics, antivirals, antifungals and antiparasitics.
What are antibacterials?
Used internally and externally for bacteria infection.
e.g. Ampicillin/cloxacillin (Ampiclox)
What are antibiotics?
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.
What are disinfectants?
Disinfectants are antimicrobial agents applied to non-living surfaces.
Chloroxylenol (Dettol)
What are antifungals?
Used internally and externally for fungal infections.
Griseofulvin (Fulcin), Clotrimazole (Canesten)
What are antivirals?
Used internally and externally for viral infections.
Acyclovir (Zovirax)
What are antiprotozoans?
Antiprotozoal drug, any agent that kills or inhibits the growth of organisms known as protozoans.
Artemether/lumefantrine (Coartem)
What are antiseptics?
Used externally on living tissue
Chlorhexidine (SavlonR)
Who discovered the first antibiotic?
Alexander Fleming in 1928
What are the classification of antibiotics based on mechanisms of action?
- Antibiotics that Inhibit Cell Wall Synthesis
- Antibiotics that affect nucleic acid synthesis
- Antibiotics that act on ribosomes and inhibit protein synthesis
- Antimetabolites
Antibiotics that target cell wall synthesis
Cycloserine
Vancomycin
Bacitracin
Beta-lactams (Penicillins, Cephalosporins, Monobactams, Carbapenems)
Antimycobacterials (Isoniazid, Ethambutol)
Antibiotics that target DNA gyrase
Quinolones (Nalidixic acid and Ciprofloxacin)
Novobiocin
Antibiotics that target RNA elongation
Actinomycin
Antibiotics that target DNA-directed RNA polymerase
Rifampin
Streptovaricins
Antibiotics that target protein synthesis (50S inhibitors)
Macrolides (Erythromycin)
Chloramphenicol
Clindamycin
Lincomycin
Antibiotics that target protein synthesis (30S inhibitors)
Tetracyclines
Spectinomycins
Streptomycin
Gentamicin
Kanamycin
Amikacin
Nitrofurans
Antibiotics that target protein synthesis (RNA)
Mupirocin
Puromycin
Antibiotics that target cytoplasmic membrane structure
Polymyxins
Daptomycin
Antibiotics that target folic acid metabolism
Trimethoprim
Sulphonamides
What is the mechanism of action of Penicillin?
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.
Classifications of penicillin
- Natural penicillin (benzylpenicillin)
- Broad-spectrum penicillin (Amino penicillin e.g. ampicillin, amoxicillin)
- Broad-spectrum penicillin with antipseudomonal activity (ticarcillin , carbenicillin)
- B-lactamase (penicillinase) resistant penicillin e.g. flucloxacillin.
Uses of penicillins
Typhoid fever and other susceptible bacteria infections
Adverse effects of penicillins
Hypersensitivity, nausea and vomiting
Are penicillins bactericidal or bacteriostatic?
Bactericidal
Penicillins have greater beta-lactam activity than cephalosporins. True or False?
False
What is the mechanism of action of cephalosporins?
They interfere with bacterial cell wall synthesis by reducing stability of the cell wall which leads to lysis of the cell membrane.
Are cephalosporins bactericidal or bacteriostatic?
Bactericidal
Classifications of cephalosporins
1st Generation: Cefazolin, Cefalexin, Cephradine
2nd Generation: Cefuroxime, Cefoxitin, Cefaclor
3rd Generation: Cefixime, Ceftriaxone, Cefpodoxime
4th Generation: Cefepime, Cefepirole
5th Generation: Ceftolozane, Ceftaroline
What trend increases down the generations of cephalosporins?
Increased potency against Gram negative bacteria and decreased potency against Gram positive bacteria (except the 4th generation)
Uses of cephalosporins
Septicaemia (cefuroxime)
Meningitis (ceftriaxone)
UTI
Sinusitis.
Mechanism of action of carbapenems
They kill bacteria by binding to penicillin-binding proteins, thus inhibiting bacterial cell wall synthesis.
Examples of carbapenems
Meropenem
Ertapenem
Doripenem
Imipenem
Tebipenem
M-E-D-I-T
Arrange the following by antibiotic activity: Carbapenems, Penicillins, and Cephalosporins
Carbapenems > Cephalosporins > Penicillins
What are the advantages of carbapenems over other classes of beta-lactams?
They have activity against anaerobes and beta-lactamase producing organisms
Uses of carbapenems
They are reserved for multi-drug resistant infections.
Pneumonia, complicated urinary tract infections, and blood stream infections.
Adverse effects of carbapenems
Skin rash
What are monobactams?
Monobactams are monocyclic beta-lactam antibiotics with b-lactam rings that are not fused to another ring.
Monobactam activity spectrum
They are effective against aerobic Gram negative bacteria only.
Mechanism of action of monobactams
They kill bacteria by inhibiting synthesis of the bacterial cell wall via blockage of peptidoglycan crosslinking.
Examples of monobactams
Aztreonam
Tigemonam
Uses of monobactams
Pneumonia
Urinary tract infections
Bone infections
Intraabdominal infections
Sepsis
Endometritis
Adverse effects of monobactams
Skin rash
What is vancomycin?
Vancomycin is a glycopeptide antibiotic administered intravenously.
What is the spectrum of activity of vancomycin?
It is a last resort medication for the treatment of sepsis and lower respiratory tract, skin, and bone infections caused by Gram-positive bacteria
Mechanism of action of vancomycin
Vancomycin acts by inhibiting proper cell wall synthesis in Gram-positive bacteria.
Why is vancomycin ineffective against Gram negative bacteria?
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
Uses of vancomycn
Methicillin resistant Staphylococcus aureus (MRSA) infections
Clostridium difficile colitis
Meningitis
Complicated skin infections
Bone and joint infections
Endocarditis
Adverse effects of vancomycin
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
What is vancomycin flushing syndrome?
It is the presentation of side effects resulting from histamine release when vancomycin is infused too rapidly: a red rash, hypotension, tachycardia, angioedema, etc.
