Antibiotic Therapy Flashcards
What are antibiotics?
A drug used to treat or prevent infection caused by bacteria
What does bacteriostatic describe?
Inhibiting the growth of bacteria
If something is bactericidal, what does it do?
Kill bacteria
What is the spectrum?
The range of micro-organisms an antibiotic can act on (ie how broad/narrow)
What are the characteristics of an ideal antibiotic?
Selective toxicity (to minimise host damage), tidal, long half life, appropriate tissue distribution, no adverse side effects/drug interactions and oral & parenteral preparations
What are the main antibiotic targets?
Cell wall, ribosomes, DNA replication, DNA gyrases and metabolic pathways - really want to find something in bacteria that isn’t in humans (to help prevent toxicity to humans)
What are the 2 types of antibiotics that target cell walls?
Beta-lactams - (Penicillins and cephalosporins) and glycopeptides
What is the main issues with penicillin?
Allergy (hypersensitivity), rapid excretion via kidneys (need many doses) and resistance
What do cephalosporins do different from penicillins?
Wider spectrum and more resistant to beta-lactamases
What does the cell wall protect the cell from?
Internal osmotic pressure (bursting)
What are the targets of beta-lactams?
Penicillin Binding Proteins (PBPs)
What is the role of beta-lactams?
A suicide substrate which halts the cell wall synthesis = compromised wall
What are the benefits to penicillin?
Safe (few side effects), variety, range from narrow to broad spectrum, rapid excretion via kidneys and safe in pregnancy
What are the benefits to amoxicillin?
Safe (well tolerated by body), well absorbed (when given orally), low binding to plasma proteins, good tissue distributions
What are the problems with amoxicillin?
Effectiveness challenged by spread of beta-lactamases and resistance
What does clavulanic acid do?
Inhibits the action of beta-lactamases (microbial enzyme) - nb it has no antibiotic properties of its own
What antibiotic is commonly used for staph and strep skin infections?
Flucoxacillin
What does temocillin work against?
Extended spectrum beta-lactamases and ampC beta-lactamases. (usually restricted to coliforms)
What is the problem with cephalosporins?
Kill off gut bacteria and so allow the overgrowth of clostridium difficile = gastroenteritis
What are the main issues with glycopeptides?
Not absorbed so requires hospitalisation (excreted via kidneys and urine - problem for people with kidney disease as can’t leave body causing toxic build up) and activity limited to gram +ve cell walls
How do antibiotics that inhibit protein synthesis work?
Attach to bacterial ribosomes (structurally different from mammalian ribosomes) - usually protein synthesis continues when bacteria is removed (antibiotics are bateriostatic - except aminoglycosides = bactericidal)
What is the problem with aminoglycosides?
Toxic - cause kidney damage and VIII cranial nerve damage = need to monitor blood levels
How do tetracyclines get into the cell?
Active transport by binding to 30S subunit
What are the problems with tetracyclines?
Destruction of normal intestinal flora = secondary infection and increasing resistance
