Antibiotics Flashcards
Define Antibiotic
compound made by microorganism (or chemically made) that kills or inhibits growth of bacteria
Define Antimicrobial
synthetic compound that kills all microorganisms
3 Reasons why infectious diseases declined
1) increased hygiene and sanitation
2) use of antibiotics
3) childhood vaccination programs
Sterile
no living organisms present
Aseptic
no harmful organisms present
Bacteriocidal
kills bacteria by stopping reproduction
Bacteriostatic
inhibits microbial growth (microbes still present)
What should an antibiotic do?
1) Target selectively (kills microorganism w/o harming pt)
2) Microbes should not easily acquire resistance
3) Broad spectrum antibiotics (targets many types) vs narrow spectrum antibiotic (targets few bacteria)
2 types of antibiotic
1) minimal inhibitory concentration
2) minimal bacteriocidal concentration
Beneficial combined antibiotic therapies
Define Additive
Define Synergistic
Define Antagonistic
Additive - sum of effect of 2 chemicals taken separately
Synergistic - combined equals greater effect than sum of their separate effect at same dose
Antagonistic - interferes with physiological effect of other
5 modes of antibiotic action
1) inhibition of cell wall synthesis
2) inhibition of bacterial enzymes
3) inhibition of nucleic acid metabolism
4) inhibition of protein synthesis
5) disruption of membrane function
Vancomycin
treats gram positive infections
binds to D-Ala-D-Ala
where can cell wall synthesis be blocked?
1) cytoplasm
2) cytoplasmic membrane
3) perimplasm/cell wall
define Transglycosidases
link monomers into chains
define Transpeptidases
crosslink chains to create a meshwork
Fosfomycin
is a bacterial cell wall synthesis inhibitor of the cytoplasm that blocks the addition of phosphoenolpyruvate which blocks NAG to form NAM. Effect for gram + and gram -. also inhibits bacterial enzymes.
What are the 4 B-lactam antibiotics?
Penicillins
Cephalosporins
Carbapenems
Monobactams
What do different R groups lead to on B-lactams?
leads to improved permeability and increased resistance to B-lactamases
What do bacterial B lactamases inhibit?
B lactamases inhibit B-lactam antibiotics
Which enzyme do bacteria produce to destroy the B lactam ring?
B lactamases
Where can protein synthesis be inhibited?
30S rRNA subunit - Aminoglycosides, Tetracyline
50S rRNA subunit - Chloramphenicol, Macrolide
List 5 Bacteriocidal drugs
Penicillins Cephalosporins Vancomycin Aminoglycosides Ciprofloxacin
List 3 Bacteriostatic drugs
Sulphonamides
Tetracyclines
Chloramphenicol
Inhibition of nucleic acid metabolism
- bacterial toposomerase/Gyrase - block dna replication
- rna polymerase- block mrna synthesis
- Folate metabolism- block nucleotide synthesis
antibiotic resistance
Innate resistance- due to lack of target or impermeability
Acquired resistance - due to plasmid based or chromosomal mutation
how does bacteria become Vancomycin resistant?
the bacteria alters their peptidoglycan synthesis so there’s no D-Ala-D-Ala intermediate
Where do Antibiotics come from?
synthesized by chemicals or occurring naturally in mold
What do Antibiotics do?
they kill or neutralize bacteria by interrupting cell wall synthesis or interfering with protein synthesis while leaving human cells unharmed.
Which bacteria is resistant to b-lactam antibiotics like penecillin, oxocyllin, and methacylin?
MRSA
It has a protein that makes its cell wall unimpeded
how is salmonella resistant to b-lactam antibiotics
salmonella produces b-lactamases to break down antibiotics
how do bacteriostatic antibiotics stop bacterial growth?
Stopping DNA replication
Stopping metabolism AG enzyme activity
stops protein production
How do bactericidal antibiotics kill bacteria?
by preventing bacteria making cell wall
Do Antibiotics work on viruses?
NO because they have a different structure than bacteria
Viruses do not have a cell wall and uses human cell as host
how does penecillin kill bacteria?
by breaking down the cell wall
erythromycin
stop protein synthesis by binding to specific rna
where do b-lactamases come from?
Some bacteria have dna that allows them to make those enzymes
what do beta-lactams inhibit?
transpeptidases and therefore cell wall synthesis
what does antibiotic cycloserine target?
Alanine racemase which is needed to convert L-Alanine to D-alanine which is what builds the cell wall
what do B-lactam antibiotics and vancomysin target?
vancomysin targets D-Ala-D-Ala substrate for crosslinking and penecillin binds to (PBP) Penecillin Binding protein.
what does vancomysin block?
blocks addition of peptidoglycan subunits to the glycan chain
how does bacteria become vancomysin become resistant?
it alters its peptidoglycan synthesis so there is no D-Ala D-Ala intermediate for it to bind to and interfere cell wall synthesis by inhibitig crosslinking of peptidoglycans.
it changes its peptidogylcan synthesis so vancomysin does not inhibit crosslinking of peptidoglycan
what bacteria are penecillins used against?
staphlococcus
streptococcus
STDs
what are synergistic compounds used?
B-lactamase inhibitors and penicillins
sulfanilamide and trimethoprim (for traveler’s diarrhea)
is chloramphenicol bacteriostatic?
yes
most common mechanism for resistance?
lipopolysaccharide
how do antibiotics disrupt membrane function?
in gram - bacteria, hydrophobic tails insert into membranes which increases permeability
what do beta lactam antibiotics inhibit?
Transpeptidase and therefore bacterial wall synthesis
what are catalase microorganisms?
facultatie anaerobes (can grow with some O2)
