Antimicrobrial chemotherapy- mechanisms of action Flashcards
What are antibiotics active against?
bacteria
What is a bactericidal?
antimicrobial that kills bacteria
What is M.B.C?
minimal bactericidal concentration - minimum conc of antimicrobial needed to kill a given organism
What is bacteriostatic?
they do not kill bacteria but they inhibit the growth
What is MIC?
minimal inhibitory concentration- minimum concentration of antibiotic you need in order to inhibit the growth of the specific organism
What are the different routes of antibiotic administration?
topical: applied to surface
systemic: taken internally
parenterally: administered intravenously or intramuscularly
What are the classifications of sypherical, cocci bacteria?
diplococci, streptococci, staphylococci
What are the classifications of rod, bacilli bacteria?
chain of bacilli, flagellate rods, spore former
What are the classifications of spirals bacteria?
vibrios, spirilla, spirochettes
What are gram negative cocci?
neisseria
morasella
What are gram positive cocci?
staphylococcus
streptococcus
enterococcus
pneumococcus
What are gram negative bacilli?
escherichia coli
shigella
salmonella
What are gram positive bacilli?
corynebacterium
clostridium
listeria monocytogenes
What are the gram negative spirals?
vibrio cholerae
helicobacter pylori
How do the antibiotics work when they want to kill or inhibit the growth of specific bacteria?
Antibiotics may inhibit or kill bacteria by acting at three different areas of metabolic activity.
-inhibition of cell wall synthesis
-inhibit protein synthesis
-inhibition of nucleic acid synthesis
Why do antibiotics not interfere with human cells?
Human cells do not have any kind of cell wall
What antibiotics inhibit the cell wall synthesis?
Beta-lactams- Penicillins and Cephalosporins
Give characteristics of beta lactam antibiotics?
-bactericidal antibiotics
-effective mostly against Gram-positive bacteria
Why are penicillin and cephalosporins classified as beta lactams?
chemical structure of drugs contain a beta lactam ring (square)
Why are many gram negative organisms resistant to benzyl penicillin?
inability to penetrate gram negative cell wall
Describe how glycopeptides (bactericidal antibiotics) are able to inhibit the cell wall synthesis?
-prevent two peptidoglycans to join
together to create a more stable cell wall
-vancomycin (glycopeptide) is going to prevent the two peptidoglycans to link to each other
-cell wall is disrupted
Describe how penicillins and cephalosporins inhibit cell wall synthesis?
interfere with the specific kind of enzyme involved in the cross link between peptidoglycan bridges and cell wall. On the enzyme itself there is a specific binding site for the penicillin drug. Penicillin will interact with enzyme and inhibit it. Cell wall less strong
How would you administer glycopeptides?
-can’t be given orally as cannot be absorbed by gastrointestinal tract, only given parentally
What are the kind of antibiotics that are able to inhibit the protein synthesis of bacteria?
aminoglycosides
Give characteristics of aminoglycosides?
inhibit the protein synthesis
concentration-dependent bactericidal antibiotics
useful in the treatment of serious Gram-negative infection
How do aminoglycosides work?
antibiotic going to interfere with protein synthesis and prevent proper protein to be created.
There are some differences between the ribosome structure in the bacteria and the mammalian ribosome. This makes antibody specific for bacteria, as antibody can discriminate between ribosomes. Targets 70S ribosome
Give example of aminoglycoside?
gentamicin
Give characteristics of macrolides?
useful alternatives to penicillins in treatment of Gram positive infections in patients who are penicillin allergic.
Give name of a macrolide that can be used instead of penicillin?
erythromycin
Give characteristics of tetracyclines?
bacteriostatic antibiotics
treatment of gram positive infections
What bacteria is resistant to tetracycline?
percentage of bacteria like staphylococcus aureus, streptococcus pyogenes and streptococcus pneumonia that are actually resistant to the tetracycline.
Give characteristics of oxazolidinones?
bacteriostatic or bactericidal
treatment of gram positive infections
last resort
Give an example of an oxazolidinones?
linezolid
Give characteristics of cyclic lipopeptides?
strong bactericidal antibiotics
treatment of gram positive
Give example of a cyclic lipopeptide?
daptomycin
How does the specific antibiotic, trimethoprim work?
inhibition of purine synthesis
bacteriostatic alone but when combined with antibiotics- bactericidal
inhibition of DNA synthesis either directly, or indirectly by interrupting the supply of precursors for DNA synthesis
When is trimethoprim used?
treatment of urinary tract and chest infections
Give another example of inhibitor of purine synthesis?
sulphamethoxazole
What is co-trimoxazole a combination of?
trimethoprim and sulphamethoxazole
Give characteristics of fluoroquinolones?
bactericidal antibiotics
particularly effective against gram negative
inhibiting enzyme involved in DNA synthesis
used orally as well as parenterally
Give examples of fluroquinolones?
ciprofloxacin
levofloxacin- can be used against gram pos
