Antibiotics 2 Flashcards
What 2 classes of Abs are cell wall inhibitors?
penicillins and cephalosporins
What are the 2 classes of protein synthesis inhibitors?
tetracyclines and macrolides
What is the 1 class of DNA synthesis inhibitors?
fluoroquinolones
Targeting the synthesis of _____ is one of the most widely effective and least toxic antibiotic strategies
bacterial cell walls
What are cell wall inhibitors only effective against?
actively growing bacteria
How does penicillin inhibit cell wall synthesis?
it inhibits transpeptidase that forms cross links between peptidoglycan chains that are essential for cell wall integrity
- causes osmotic pressure on the cells resulting in cell lysis
What enzyme does gram positive bacteria product to break down the cell wall?
- produces autolysins
Without active cell wall synthesis ____ can damage the cell
autolysins
What are the 2 examples of penicillinase resistant penicillins
- methicillin and cloxacillin
What are the 2 examples of extended spectrum penicillins
- ampicillin and amoxicillin
Are penicillins bactericidal or bacteriostatic?
Bacteriocidal
Penicillin V and Amoxicillin are only available as ______
oral preparations
Pipercillin must be through the _____ route
IV/IM
Why do penicillins affect the composition of the intestinal flora?
- because they are incompletely absorbed
Absorption of penicillinase resistant antibiotics are ___ by food in the stomach and must be administered ______
reduced
- before a meal or 2-3 hours after
Does penicillin cross the placenta? What abut the bone or CNS?
- does cross the placenta
- does not penetrate the bone or CNS
Where is penicillin excreted?
- in the urine and breast milk
What are the most common adverse effects of penicillins?
- GI effects relatively common but are seldom severe due to the disruption of normal intestinal microflora
- allergy to its metabolite penicilloic acid relatively common (rash, swelling, anaphylaxis)
- cross allergy within the penicillin class
- no negative birth effects
_____ is a concern in patients receiving anticoagulants also also on penicillin
Reduced coagulation
What are the 4 antibiotics that fall under the class of cephalosporins?
cephalxin, cephalothin, cepazolin, cefepime
Which cephalosporins are the only 2 Abs administered orally?
- cephalexin and cefixime
____ penetrates the bone
cefazolin
____ crosses the BBB
cefuroxime
____ and _____ penetrate the cerebrospinal fluid
cefotaxime and ceftriaxone
Where are most cephalosporins excreted?
- most are eliminated in the urine
cefriaxone is excreted in the bile- longest t1/2 of all cephalosporins
How do protein synthesis inhibitors work?
Bind to 70S ribosomes (in bacterial cells) opposed to the 80S ribosomes that are in mammalian cells
- effective against gram positive and gram negative bacteria as well as other micro organisms
What are the 5 classes of antibiotics that fall under the protein synthesis inhibitors class?
- tetracyclines
- amino-glycosides
- macrolides
- chloramphenicol
- clindamycin
How do tetracyclines act as a protein synthesis inhibitor?
- binds irreversible to the 30S ribosome
- blocks acyl-tRNA access to the ribosome
Tetracyclines are considered ____ spectrum and are bacterio____
broad
bacteriostatic
What is the naturally occurring tetracycline?
tetracycline
What is the semi-synthetic tetracyclines?
- doxycycline
- methacycline
- minocycline
Absorption PO of tetracycline is reduced by the consumption of ____ and ____
dairy foods and antacids
Describe the distribution of tetracyclines. Where do they concentrate? What do they cross?
- distribution is throughout the body and body fluids
- concentrates in the liver, kidney, and spleen
- crosses the placenta and penetrates the bone and teeth
Where are tetracyclines excreted?
- metabolized and conjugated to form glucuronides by the liver and secreted in the bile and enters the urine via glomerular filtration
- excreted as well in the breast milk
What are the adverse effects of tetracyclines?
- GI discomfort- overcome by consuming food with the pills
- deposition in bones and teeth of growing children
- hepatotoxicity
- sunburn (increased sensitivity to UV rays)
- dizziness, nausea and vomiting
(minocycline and doxycycline concentrate in the inner ear) - headache/blurred vision
- superinfection: resistance is common
- not recommended or patients with kidney/liver disease or pregnant/lactating women
How do aminoglycosides act as a protein synthesis inhibitor?
- binds irreversibly to the 30S ribosome
- blocks functional assembly of the ribosome
Amino glycosides are effective against _______
aerobic gram negative bacteria
Is aminoglycosides bacteriocidal or bacteriostatic
bacteriocidal
What Abs are derived from streptomyces?
streptomycin
kanamycin
What Abs are derived from micromonospora?
gentamicin
amikacin
Molecular properties of aminoglycosides prevent ____ absorption
oral
Describe the distribution of aminoglycosides in the body?
- levels achieved in most tissues are low
- concentrates in the renal cortex and the inner ear
- low penetration into the cerebrospinal fluid
- crosses the placenta and enters the fetal circulation