Antimicrobial agents Flashcards
Mechanism of action and resistance
These agents cause cell lysis, thus killing bacteria. These agents “attack” microbes by affecting the cell wall, lipids, enzymes, or protein synthesis within the cell – sometimes even completing a combination of these mechanisms
Bactericidal agents
- By disrupting the cell wall structure of existing cells and inhibiting the formation of new cells, bactericidal substances cause bacterial cells to die off, therefore decreasing the amount found in the individual affected.
These agents cause cell lysis, thus killing bacteria. These agents “attack” microbes by affecting the cell wall, lipids, enzymes, or protein synthesis within the cell – sometimes even completing a combination of these mechanisms
Bactericidal agents
- By disrupting the cell wall structure of existing cells and inhibiting the formation of new cells, bactericidal substances cause bacterial cells to die off, therefore decreasing the amount found in the individual affected.
These agents inhibit the growth and multiplications of bacterial cells, rather than directly killing them.
Bacteriostatic agents.
-they can achieve this by obstructing the metabolic mechanisms of the bacterial cell, in most cases targeting the protein synthesis. While doing this does not cause outright cell death, it does effectively inhibit further growth and DNA replication of the bacterial cells.
Examples of bactericidal agents
- Penicillin, cephalosporins, and vancomycin
Examples of bacteriostatic agents
- Tetracycline, sulfonamides, and erythromycin
Antibacterial agents can be categorized into two spectrum: _______ and ________
-Narrow and Broad spectrum
These refer to antibiotics with limited spectrum and target only few types of bacteria
e.g: Penicillin G which is effective against gram negative bacteria only
-Narrow spectrum antibiotics
also Vancomycin since it is a very large molecule it cannot penetrate the outer membrane of gram-positive bacteria so it is also effective only in gram negative bacteria
These antibiotics have an antimicrobial spectrum which includes some gram-positive and some gram-negative organisms, as well as certain rickettsiae, larger viruses, protozoa, and pleuropneumonia-like organisms. Antibiotics with a wide range effect
Broad spectrum antibiotics
True or false: Narrow-spectrum antibiotics are more likely to lead to bacteria that resist drugs. This leads to infections that last longer and cost more to treat.
False.
-it should be broad spectrum antibiotics
True or false: Broad spectrum antibiotics may inhibit and destroy normal flora — a new infection may appear (superinfection) as a result of antibiotic treatment
True
Aminoglycosides, 2nd and 3rd generation cephalosporins, and quinolones are examples of what type of antibiotic?
-Broad spectrum antibiotics
Antibiotics mechanism of action targets:
- bacterial cell wall biosynthesis
- cell membrane function
- protein synthesis
- RNA and DNA synthesis
- Metabolic processes
An antimicrobial agent that binds enzymes transpeptidase/ penicillin binding proteins. They contain 4-membered nitrogen-containing beta-lactam ring at the core of their structure.
Beta-Lactams
Give the 4 beta-lactam class
- Penicillin, Cephalosporins, Monobactam, and Carbapenems
Penicillin were found to inhibit the growth of what bacteria?
Streptococcus aureus
- discovered by Alexendar Fleming in 1928
On what year do humans first started the use of Penicillin?
1941
- from the mold penicillum notatum
To be effective Penicillin must:
- penetrate the bacterial cell wall
- keep its beta-lactam ring intact
- binds to transpeptidase
How can bacteria develop resistanc to penicillins?
- by producing penicillinase that binds to C-N bond of the beta-lactam ring
What bacterial structure provide antibiotics resistance gene to the cell?
- Plasmids
The “first true antibiotic”
Penicillin
- Fleming discovered that the mold penicillum notatum can inhibit S. aureus
These antibiotics are structurally similar to penicillin but can more withstand the action of beta-lactamase and are more modifiable
Cephalosporins
-Beta-lactams bind to and block the activity of enzymes responsible for making peptidoglycan, resulting in cell wall death.
What is beta-lactamase? and how do they inactivate antibiotics?
Beta-lactamases are enzymes produced by bacteria that provide multi- resistance to β-lactam antibiotics
-The beta-lactamase enzymes inactivate beta-lactam antibiotics by hydrolyzing the peptide bond of the characteristic four-membered beta-lactam ring rendering the antibiotic ineffective.
This antibiotic only has 1 beat-lactam ring, its ring is alone and not fused to another ring (in contrast to other beta-lactams which have at least two rings).
Monobactam
- can kill tough hospital acquired, MDR bacteria
This antibiotics can work only against aerobic gram-negative bacteria. They are actually referred to as “magic bullet” for gram-negative aerobic bacteria.
Monobactam
