Intro to Antibacterial Agents Flashcards
Definition of Antibiotics
Chemical products of microbes that kill or inhibit other organisms.
Definition of Antimicrobials agents
(usually) synthetic compounds that kill or inhibit organisms - includes, antibiotics, antifungal, antiviral ect…
* *Antimicrobial and Antibiotic are terms used interchangeably
Definition of Bacteriostatic
Inhibit bacterial growth (protein synthesis inhibitors)
Definition of Bactericidal
Kill Bacteria (Cell wall active agents)
Definition of Minimum Inhibitory Concentration (MIC)
The minimum conc of antibiotic at which visible growth is inhibited.
Definition if Synergism
Activity of two antimicrobials given together is greater than the sum of their activity if given separately.
Definition of Antagonism
One agent that diminishes the activity of another
Definition of Indifference
Activity unaffected by the addition of another agent
The combination of which 2 drugs is used in the treatment of streptococcal endocarditis?
Synergism of:
- beta lactam
- aminoglycoside
*Streptococcal endocarditis is the infection of the endocardial surface of the heart.
Name 5 targets of antibacterial agents
- Cell wall (only present in bacteria not in eukaryotes so ideak for selective toxicity)
- Protein Synthesis
- DNA synthesis
- RNA Synthesis
- Plasma Membrane
What is the major component of a bacterial cell wall?
Peptidoglycan :
- it is present in both Gram positive and Gram negative bacteria
- it is a polymer of glucose derivatives.
(N-acetyl muramic acid (NAM) and N-acetyl glucosamine (NAG) )
What makes up peptidoglycan?
N-acetyl muramic acid (NAM)
N-acetyl glucosamine (NAG)
what drugs inhibit cell wall synthesis?
- beta-Lactams
- Glycopeptides
what type of drug is Benzylpenicillin?
beta-lactam antibiotic
*was the first true antibiotic in clinical practice
How do beta-lactam antibiotics work?
The are characterised by the beta-lactam ring.
They interfere with the function of “penicillin binding proteins”.
(inhibit with transpeptidase enzymes involved in peptidoglycan cross linking)
Name 4 types of beta-lactam antibiotics
- Penicillins (narrow spectrum)
- Cephalosporins (broad spectrum)
- Carbapenems (extremely broad spectrum)
- Monobactams (gram negative bacteria only)
Give an example of a penicillin
- Benzylpencillin (PEN)
- Amoxicillin
- Flucloxacillin
(penicillin is a relatively narrow spectrum beta-lactam antibiotic)
Give an example of a cephalosporin
- Cefuroxime (CXM)
- ceftazidime
(cephalosporin is a relatively broad spectrum beta-lactam)
give an example of a carbapenem
- Meropenem (MER)
- Imipenem
(Carbapenem is an extremely broad spec beta-lactam antibiotic)
give an example of a Monobactam
-Aztreonam (AZT)
Monobactams are a beta-lactam that are effective only on gram negative bacteria
How do glycopeptides work?
they are large molecules that inhibit the binding of transpeptidades and therefore prevents peptideoglycan cross-linking
*effective on gram positive bacteria (can’t penetrate gram negative bacteria)
give an example of glycopeptides
- Vancomycin
- Teicoplanin
describe how protein synthesis takes place in bacteria
Translation of RNA takes place on a ribosome.
Ribosome complexes catalyse peptide bond formation and synthesise polypeptides in 4 stages:
-INITIATION (ribosome attaches to mRNA)
- ELONGATION (amino acids join to form polypeptide chain)
- TERMINATION (stop codon reached and ribosome releases polypeptide)
- RIBOSOME RECYCLING (70S ribosome splits into 50S and 30S subunits)
Name 4 Protein synthesis inhibitors
- Aminoglycosides
- Macrolides, Lincosamides, Streptogramins (MLS)
- Tetracyclines
- Oxazolidinones
Give an example of an aminoglycoside
- Gentamicin
- amikacin
how to aminoglycosides inhibit protein synthesis?
bind to 30S ribosomal subunit
Give an example of a MLS (macrolides, Lincosamides, Steptogramins)
- Erythromycin, clarithromycin (macrolides)
- Clindamycin (lincosamide)
How to MLS drugs inhibit protein synthesis?
- Bind to 50S ribosomal subunit
- inhibit protein elongation
How do tetracyclines inhibit protein synthesis?
- bind to 30S ribosomal subunit.
- Inhibit RNA translation by interfering with the binding of tRNA to rRNA.
Give a example of an Oxazolidinone
Linezolid
How to Oxazolidinone inhibit protien synthesis?
Bind to 50S ribosomal subunit
-inhibits assembly of initiation complex therfore inhibits initiation of protein synthesis
How do trimethoprim and sulfonomides work?
- They inhibit DNA synthesis.
- Inhibit folate synthesis. (folic acid is a purine synthesis precursor)
- Trimethoprim inhibits Dihydrofolate reductase
- Sulfonamides inhibit Dihydropteroate synthetase.
How do quinolones and fluoroquinolones work?
inhibit DNA synthesis :
- inhibit DNA gyrase
- inhibit topoisomerase IV
(these enzymes are involved in remodelling DNA during replication ie supercoiling and strand separation)
give an example of a Quinolone / fluoroquinolone
Ciprofloxacin
How does Rifampicin work
Rifampicin works as an RNA synthesis inhibitor:
- inhibits RNA polymerase
- prevents synthesis of mRNA
How does Daptomycin work?
Daptomycin is a plasma membrane agent.
only effective on gra positive bac
What are the adverse effects specific to aminoglycosides?
-Reversibel renal impairment
what are the adverse effects specific to beta lactams
Allergic reactions
Nausea / rash / anaphylaxis
what are the adverse effects of linezolids?
Bone marrow depression
What beta-lactam drugs are safe to use on a patient with a non-severe penicilin allergy?
- cephalosporins
- carbapenems
-AZTREONAM is safe to use with ANY penicillin allergy
what type of bacteria is Vancomycin used to treat?
Gram positive
What type of bacteria is Metronidazole used to treat?
Anaerobes
what type of bacteria is cephalosporins used to treat?
Gram negative bacilli
what is Flucloxacillin used to treat?
Staphylococcus aureus (not MRSA)
what is used to treat streptococcus pyogenes?
benzylpenicillin
what are cephalosporins used to treat?
Gram positive and negative bacteria
What is metronidazole used to treat?
Anaerobes
What is vancomycin used to treat?
Gram-positive bacteria
MRSA
What are the 3 reasons for combination antibiotics therapy?
- To increase efficacy
- To provide adequately broad spectrum
- To reduce resistance
