Module 16 - Part 2 Flashcards
Penicillin
- Discovered by?
- Mechanism of action?
- Net result?
- Antibiotic type?
- Effective against which type of bacteria?
Sir Alexander Fleming
Inhibits Transpeptidases and activates autolysins
Causes breakdown of the cell wall, influx of water and lysis of the bacterium
Bactericidal
Effective against gram positives due to large cell wall
What are the two PBPs?
PBPs = penicillin binding proteins
Transpeptidase
Autolysin
Enzymes that function to form cross-bridges between the peptidoglycan strands, therefore making the cell wall strong.
Transpeptidases
Bacterial enzymes that degrade the peptidoglycan cell wall
Autolysins
How may penicillin resistance come about?
Inability to reach its target (see efflux/uptake)
Inactivation of penicillin
Mutations in PBPs making them have low affinity for penicillins (e.g. MRSA)
Predominant mechanism of resistance against penicillins.
Beta lactamases
What are the different classes of penicillins?
Narrow spectrum penicillins
Narrow spectrum penicillinase resistant penicillins
Broad spectrum penicillins
Extended spectrum penicillins
Narrow spectrum penicillins:
- Effective against what?
- Administration and reasoning behind it.
- Effective in treating what infections?
- Adverse effect profile
Effective against gram positives
Administered by IV or IM since some are destroyed by gastric acid
Effective in treating pneumonia and meningitis
Drug allergy is the primary side effect
How are narrow spectrum penicillinase resistant penicillins resistant to penicillinase?
Have an altered side chain that makes them not susceptible to inactivation by beta-lactamase enzymes
Why aren’t narrow spectrum penicillinase resistant penicillins always used?
Less effective against non-penicillinase producing bacteria
Narrow spectrum penicillinase resistant penicillins:
Effective against?
No effective against?
What bacteria are resistant?
Effective against penicillinase producing Staphylococci
Less effective vs. non penicillinase producing bacteria
Not effective in treating abscesses or penetrating into bone
MRSA
Broad spectrum penicillins:
Effective against?
Reason for being broad spectrum (i.e. mechanism)?
Inactivated by?
Effective against both gram +ve and -ve bacteria
Able to penetrate the outer membrane of gram negatives and are thus broader in spectrum
Readily inactivated by beta lactamases
Have the same mechanism of action as penicillins.
Cephalosphorins - inhibit transpeptidases and activate autolysins
Cephalosporins:
- Antibiotic type (i.e. bacteri______)
- As we move from 1st generation to the 4th generation, what occurs?
- Most frequently reported side effect?
- Why are these used when a person has an allergy to penicillin?
Bactericidal (same as penicillins)
1st –> 4th = drugs tend to increase in terms of their activity against gram negative bacteria, increase their ability to penetrate CSF and increase their resistance to beta-lactamase enzymes
Allergy
Cross reactivity of people with penicillin allergy is very rare, thus cephalosporins can be used in penicillin allergic persons
When is vancomycin used?
Potentially toxic drug - used only to treat resinous infections such as those caused by MRSA, including osteomyelitis, meningitis, pneumonia and septicemia
What is the mechanism of action of vancomycin?
Binds to precursors of cell wall synthesis to block transglycosylation in cross-bridge synthesis
What are the side effects of vancomycin?
Ototoxicity
Rapid infusion - red person syndrome (extreme flusing, rash, itching, HTN] [infuse slowly to avoid)
Describe the mechanism of action of Tetracyclines.
Bind to the 30S ribosomal subunit and prevent amino acid addition to the peptide chain
Tetracyclines:
- Antibiotic type?
- Spectrum?
- Effective in treatment of?
- Adverse effects?
Broad spectrum, bacteriostatic (only block translation)
Effective in treating typhus fever, chlamydia, cholera
Adverse effects:
- GI irritation
- photosensitivity (mus always wear sunblock)
- susceptible to superinfection (since broad spectrum)
Mechanism of action of macrolide antibiotics?
Block the 50S ribosomal subunit and block the addition of amino acids to the peptide chain
Macrolide:
- Antibiotic type
- Adverse effects
Broad spectrum, bacteriostatic
Adverse effects:
- GI upset, QT interval prolongation
Mechanism of action of oxazolidinones?
Bind to a specific region of the 50S ribosomal subunit to inhibit protein synthesis
Oxazolidinones
- antibiotic type
- effective in treating what?
Narrow spectrum (effective against gram positives), bacteriostatic Effective in treating MRSA and VRE - reserved for this use
Mechanism of action of aminoglycosides?
Bind to the 30S ribosomal subunit to prevent protein synthesis
Rapidly lethal to bacteria
Aminoglycosides:
- Antibiotic type?
- adverse effects?
bactericidal, narrow spectrum (gram negative)
Irreversible ototoxicity, reversible nephrotoxicity
Mechanism of action of sulfonamides and trimethoprim?
These antibiotics (although acting at different stages), block the synthesis of folic acid
Often, these drugs are given in combination and result in bactericidal action.
Trimethoprim, sulfonamides
If humans also use folic acid, how come sulfonamides and trimethoprim do not affect us?
We obtain folic acid from our diet
What is the common use of sulfonamides and trimethoprim?
Treatment of UTIs
Adverse effects of sulfonamides and trimethoprim?
Hypersensitivity reactions (fever and photosensitivity) Small risk of severe hypersensitivity called Steven-Johnson syndrome
Mechanism of action of Fluoroquinolones?
Inhibit DNA gyrase and topoisomerase IV - block DNA replication
Fluoroquinolones:
- Antibiotic type?
- Effective in treating?
- Adverse effects?
Bactericidal, broad spectrum
- Treatment of UTIs, osteomyelitis, soft tissue infections
- AEs: GI symptoms (nausea, vomiting, diarrhea)
Primary treatment for TB.
Isoniazid (only effective in treating TB)
Mechanism of action of isoniazid?
Inhibit the synthesis of mycolic acid.
Adverse effects of isoniazid?
peripheral neuropathy and hepatotoxicity
