L26 Miscellaneous Antibiotics Flashcards
What are the three Tetracyclines? What is the one Glycylcyline?
- Tetracycline
- Doxycycline
- Minocycline
- Tygecycline
What is the MOA of tetra/glycylcyclines?
Protein synthesis inhibition via REVERSIBLE binding to the 30S ribsomal subunit; this inhibits binding of aminoacyl tRNA, preventing addition of amino acids
Tetra/glycylcyclines are ___ (cidal/static).
Static, but can be cidal at higher concentrations against susceptible organisms
What are the mechanisms of resistance for tetra/glycylcyclines?
- Efflux pumps
- Ribosomal protection proteins
- Enzymatic inactivation
Tigecycline is resistant to this resistance
Discuss the spectrum of activity of Tetracyclines broadly.
- Gram positive aerobes
- Gram negative aerobes
- Anaerobes
- Other bacteria
What are the most important Gram positive bacteria Tetracyclines have activity against?
MSSA
Also: PSSP, Bacillus, Listeria, Nocardia
What are the most important Gram negative bacteria Tetracyclines have activity against?
B. pseudomallei
Also: N. gonorrhea, H. influenzae, H. ducreyi, Campylobacter jejuni, H. pylori, V. cholera, V. vulnificus
What are the most important anaerobic bacteria Tetracyclines have activity against?
Actinomyces and Propionibacterium
What are the most important other bacteria Tetracyclines have activity against?
Legionella, Chlamydophila, Chlamydia, Mcyoplasma, Ureaplasma, Rickettsia
Also: Bordetella, Brucella, Pasteurella, Borrelia, Trepenoma, Leptospira, Coxiella, M. fortuitum, Bartonella
Discuss the absorption, distribution, and elimination of Tetra/glycylcyclines.
Absorption: impaired by di- and trivalent cations
Distribution: wide, synovial fluid, prostate, seminal fluid, minimal CSF
Elimination: renal (tetra), metabolic (doxy, mino), biliary (tige)
What are the clinical uses of Tetra/glycylcylines?
RMSF, respiratory infections, CA pneumonia (doxy), pertussis, STDs, malaria, Q fever, Lyme disease, Burcellosis, Bartonellosis, plague, Tularenmia, chanchroid, anthrax, H. pylori, acne, SIADH
Also: Polymicrobial infections (tige)
What are the major adverse effects of tetra/glycylcylcines?
GI (nausea, vomiting), photosensitivity, Fanconi-like syndrome (outdated tetra), contraindicated in pregnancy
Also: diarrhea, pseudomembranous colitis, hypersensitivity, reversible diabetes insipidus, hepatic enzyme elevation
Discuss the spectrum of activity of Glycylcyclines broadly.
- Gram positive aerobes
- Gram negative aerobes
- Anaerobes
What are the most important Gram positive bacteria Tigecycline has activity against?
MSSA, MRSA, VRE, VSE (NOT for bacteremias or UTIs)
What are the most important Gram negative bacteria Tigecycline has activity against?
NOT Proteus or P. aeruginosa
A. baumannii, A. hydrohpila, Citrobacter, E. coli, Klebsiella S. marcescens, S. maltophila
What are the most important anaerobes Tigecycline has activity against?
Bacteroides
Also: C. perfringens
What is the MOA of sulfonamides?
Inhibition of dihydropteroate synthetase (inhibits incorporation of PABA into tetrahydropteroic acid)
Sulfonamides are ___ (static/cidal).
Bacteriostatic
What are the 4 short/medium-acting sulfonamides?
- Sulfisoxazole
- Sulfamethoxazole
- Sulfadiazine
- Sulfamethizole
What is the 1 long-acting sulfonamide?
Sulfadoxine
What is the MOA of trimethoprim?
Inhibition of dihydrofolate reductase (interferes with conversion of dihydrofolate to tetrahydrofolate)
Trimethoprim is ___ (static/cidal).
Bacteriostatic
TMP-SMX is ___ (static/cidal).
Bactericidal
Describe the steps of the pathway at which Sulfamethoxazole and Trimpethoprim act to inhibit metabolism.
PABA is converted to Dihydrofolic acid via Dihydropterate Synthetase (Sulfamethoxazole acts here). Dihydrofolic acid is converted to tetrahydrofolic acid via Dihydrofolate reductase (trimpethoprim acts here).
What are the mechanisms of resistance of Sulfonamides?
- PABA overproduction
- Structural change of Dihydropteroate synthetase
- Drug resistant DHPS or decreased cell wall permeability
What are the mechanisms of resistance of Trimethoprim?
- Production of resistant dihydrofolate reductase
2. Changes in cell permeability
Discuss the spectrum of activity of TMP-SMX broadly.
- Gram-positive
- Gram-negative
- Other bacteria
What are the most important Gram positive bacteria TMP-SMX have activity against?
S. aureus (MRSA)
Also: S. pyogenes, Nocardia, Listeria
What are the most important Gram negative bacteria TMP-SMX have activity against?
S. maltophilia
Also: Acinetobacter, Enterobacter, E. coli, K. pneumoniae, Proteus, Salmonella, Shigella, Haemophilus, N. gonorrheae
What are the most important otherbacteria TMP-SMX have activity against?
Pneumocystis carinii
Discuss the absorption, distribution, and elimination of TMP-SMX.
- Rapidly and completely absorbed; IV, PO
- Good distribution (lungs, urine, prostate, CSF)
- SMX is 70% protein bound
- Liver and kidney elimination
What are the clinical uses of TMP-SMX?
- UTI (acute, chronic, recurrent)
- Bacterial prostatitis (acute/chronic)
- Skin infections due to CA-MRSA
Also: bacterial sinusitis, Stenotrophomonas, Toxo, Listeria, Nocardia
What are the major adverse effects of TMP-SMX?
GI (nausea, vomiting, diarrhea, glossitis, jaundice, hepatic necrosis), Hematologic (leukopenia, thrombocytopenia, eosinophilia, acute hemolytic anemia, aplastic anemia, agranulocytosis, megaloblastic anemia), Hypersensitivity (rash, urticaria, epidermal necrolysis, Steven-Johnson, drug fever), CNS (headache, aspecti meningitis, seizures), renal toxicity (tubular necrosis,, interstitial nephritis), drug-induced lupus, serum sickness-like syndrome, cyrstalluria
What are the major drug interactions of TMP-SMX?
- Phenytoin (increased phenytoin levels)
- Warfarin (increased anti-coagulant effect)
- Methotrexate (decreased renal clearance)
True or false - Chloramphenicol is not used in the U.S.
True
What is the MOA of chloramphenicol?
Binds to 50s subunit of 70s ribosome, prevents peptide bond formation
Chloramphenicol is ___ (cidal/static) except for…
Static; H. influenzae, S. pneumoniae, N. meningitidis
What are the mechanisms of resistance of Chloramphenicol?
- Reduced permeability or uptake
- Ribosomal mutation
- Acetyltransferase inactivation
Discuss the absorption, distribution, and elimination of Chloramphenicol.
- Well-absorbed by the GI tract
- Lipid soluble, not highly protein bound, CSF levels
- Metabolized by the liver, excreted by the kidneys; decrease dose in liver failure, no adjustment in renal failure
Discuss the spectrum of activity of Chloramphenicol broadly.
- Gram positives (unreliable against S. aureus, not active against Enterococci)
- Gram negatives (not against P. aeruginosa)
- Anaerobes
What are the most important other bacteria Chloramphenicol have activity against?
Rickettsiae sp., Spirochetes, Chlamydia, Mycoplasma
What are the clinical uses of Chloramphenicol?
Third and developing world: pneumonia, bacterial meningitis, typhoid fever
RMSF
What are the major adverse effects of Chloramphenicol?
- Gray baby syndrome (abdominal distention, vomiting, flaccidity, cyanosis, circulatory collapse/death)
Also: hematologic (reversible bone marrow suppression, aplastic anemia), optic neuritis, hypersensitivity reaction, anaphylaxi, GI intolerance, stomatitis, porphyria
What are the two major urinary tract agents?
- Nitrofurantoin
2. Methenamine
What is the MOA of nitrofurantoin?
Binds to ribosomal proteins, inhibits translation, inhibits bacterial respiration and pyruvate metabolism
What is the MOA of methenamine?
Converted in acid pH to ammonia and formaldehyde, which is a non-specific denaturant of proteins and nucleic acids
What are the mechanisms of resistance of Nitrofurantoin?
Poorly understood - development of resistance is rare; E. coli shows production of nitrofuran reductase
What are the mechanisms of resistance of Methenamine?
Alkaline urine; no bacterial resistance to formaldehyde itself
Discuss the absorption, distribution, and elimination of Nitrofurantoin.
- 40-50% absorption following oral administration, occurs in small intestine, enhanced with food
- Large urine concentrations, low serum concentration, no prostate distribution
- Urine elimination, some biliary
Discuss the absorption, distribution, and elimination of Methenamine.
- Rapid absorption after oral adminsitration, may be degraded by stomach acid
- Broad distribution
- Renal excretion
What are the clinical uses of Nitrofurantoin?
- Acute uncomplicated UTIs
NOT pyelonephritis, complicated UTI
What are the clinical uses of Methenamine?
- Suppression or prophylaxis of recurrent UTIs
NOT established infections, prophylaxis against CAUTI
What is the spectrum of activity of Nitrofurantoin?
E. coli, Citrobacter, GBS, S. saprophyticus, Enterococcus (VRE)
What is the spectrum of activity of Methenamine?
No antimicrobial activity; may not be effective against urease producing organisms (Proteus)
What are the major adverse effects of Nitrofurantoin?
GI intolerance, rashes, acute pulmonary symptoms, subacute/chronic pulmonary reaction
What are the major adverse effects of Methenamine?
Generally well-tolerated, GI, rash, pruritis, bladder irritaiton, hemorrhagic cystitis, peripheral sensory neuropathy, hepatitis, hemolytic anemia, leukopenia, aplastic anemia, megaloblastic anemia, eosinophilia