Microbiology - Antimicrobials Flashcards
What are the 4 major sites of antibacterial activity in the bacterial cell?
- Inhibitors of cell wall synthesis
- Inhibitors of protein synthesis
- Inhibitors of DNA/RNA synthesis
- Inhibitors of folic acid reduction
How does Penicillin work and what organisms is it typically used for?
Blocks peptidoglycan cross-linking.
Used against gram positive organisms, some gram negative (n. meningitidis) and spirochetes (t. pallidum).
How does Ampicillin/Amoxicillin work and what organisms is it typically used for?
Blocks peptidoglycan cross-linking and is penicillinase resistant.
“HHELPSS” penicillin
H. influenzae, H. pylori, E. coli, L. monocytogenes, P. mirabilis, Salmonella, Shigella.
List the beta-lactamase inhibitors.
“CAST”
Clavulanic acid, Avibactam, Sulbactam, Tazobactam.
Organisms not covered by the 1st-4th Generation Cephalosporins are?
“LAME”
Listeria, Atypicals (Chlamydia, Mycoplasma), MRSA, Enterococci
How do 1st Generation Cephalosporins work and what organisms are they typically used for?
Inhibit cell-wall synthesis. Less susceptible to Penicillinases.
Gram positive + PEcK
Proteus, E. coli, Klebsiella
How do 2nd Generation Cephalosporins work and what organisms are they typically used for?
Inhibit cell-wall synthesis. Less susceptible to Penicillinases.
Gram positive + HENS PEcK
H. influenza, Enterobacter aerogenes, Neisseria, Serratia
Proteus, E. coli, Klebsiella
How do 3rd/4th Generation Cephalosporins work and what organisms are they typically used for?
What property do they have over 1st and 2nd gen?
Inhibit cell-wall synthesis. Less susceptible to Penicillinases.
3rd Gen can cross BBB - meningitis
Both add cover of Pseudomonas.
What do 5th Generation Cephalosporins cover?
Listeria, MRSA, Enterococcus faecalis.
Cephalosporins increase the nephrotoxicity of?
Aminoglycosides.
Monobactams are good only for?
Gram negative bacilli.
Synergistic with aminoglycosides.
Vancomycin is only good for?
What are the common adverse effects?
What is an uncommon adverse effect?
Gram positive bacteria only, including MRSA.
Nephrotoxicity, Ototoxicity, Thrombophlebitis.
Red man syndrome (give slowly and with histamine)
What is the mechanism of Vancomycin resistance?
Enterococcus modifies AAs to D-Ala-D-Ala to D-Ala-D-Lac
“Pay back 2 D-Alas for Vandalising Vancomycin”
Where do the protein synthesis inhibitors work?
List them.
Specifically target the small bacterial ribosome (70S; made of 30S and 50S), leaving human ribosome 80S unaffected.
buy AT 30, CEL at 50
Aminoglycosides, Tetracyclines
Chloramphenicol, Clindamycin, Erythromycin, Linezolid.
What are the common Aminoglycosides?
How do they work?
What are the common side effects?
“mean GNATS cNNOT kill anaerobes”
Gentamicin, Neomycin, Amikacin, Tobramycin, Streptomycin.
Bactericidal inhibition of 30S ribosomal subunit.
Nephrotoxicity, NM blockade, Ototoxicity, Teratogen.
Which antibiotic is useful in renal failure and why?
Doxycycline.
It is faecally eliminated.
How do Macrolides work?
What are their adverse effects?
Azithromycin, Clarithromycin, Erythromycin.
Inhibit protein synthesis by blocking translocation; bacteriostatic.
MACRO:
Motility issues, Arrhythmia due to long QT, Cholestasis, Rash, Eosinophilia.
What are the anti-mycobacterial drugs?
How is Leprosy treated?
“RIPE for treatment”
Rifampin, Isoniazid, Pyrazinamide, Ethambutol.
Add Dapsone and Rifampin +/- Clofazimine for Leprosy.
What are the Rifamycins and how do they work?
What are the 4 Rs of Rifampin?
Rifampin, Rifabutin.
RNA polymerase inhibitor
Ramps up cytochrome pP-450
Red/Orange body fluids
Rapid resistance if used alone
Rifampin ramps up cytochrome P-450 but Rifabutin does not.
What is the mechanism of action of Isoniazid?
What are its clinical uses?
What are the adverse effects and what special step should be taken?
Reduces synthesis of mycolic acids.
Can treat TB and is the only agent for prophylaxis.
INH Injures Neurons and Hepatocytes so administer with B6 (pyridoxine).
Which antibiotic, and for which bug, would you give an HIV+ patient with a CD4+ count of less than 200?
TMP-SMX
Pneumocystis pneumonia
Which antibiotic, and for which bug, would you give an HIV+ patient with a CD4+ count of less than 100?
TMP-SMX
Pneumocystis pneumonia and toxoplasmosis
Which antibiotic, and for which bug, would you give an HIV+ patient with a CD4+ count of less than 50?
Azithromycin or Clarithromycin
Mycobacterium avid complex.
How does Amphotericin B work?
What are the common side effects?
“AmphoTEARacin”
Binds ergosterol (unique to fungi); forms (tears) membrane pores that leak electrolytes.
“Shake and Bake” + Nephrotoxicity + Arrhythmias
