Antibiotics Flashcards
What is selective toxicity?
Ability of the drug to target the invader and not the host
Define Bactericidal
Drug which kills the bacteria
Define Antibacterial
Drug which kills or inhibits the growth of bacteria
Define minimum [bactericidal]
Lowest [drug] to kill bacteria
Define minimum [inihbitory]
lowest [drug] to inhibit growth of bacteria
Define bacteriostatic
drug which prevents growth of bacteria
Define Empirical treatment
antibiotic therapy used before a specific bacteria has been identified
How are antibacterials selected?
What is the pathogen? Bacteriostatic or bactericidal? Pharmacokinetics? Dose? Route of admin? Contraindications? Allergies? Side effects? Need for monitoring?
What are the mechanisms of action of antibacterials?
Selective toxicity
How do cell wall targetting antibiotics work?
Inhibit the 2 enzymes which catalyse the formation of the cell wall (transglycosylase and transpeptidase). Transglycosylase likes the glycan portion of the cell wall together and transpeptidase the peptide portion
Which group of drugs target the cell wall synthesis?
Beta-Lactams - inhibit transpeptidase function competitively by mimicing AA structure
Vancomycin - inhibits transpeptidase by covering the peptide chain
What are the 4 beta-lactam classes?
Penicillins, Carbapenems, Cephalosporins, Monobactams
How do polymyxins work?
They disrupt the cell membrane and cause lysis. Not very selective
How do protein synthesis inhibitors work?
Chloraphenicol - binds to 50S portion and inhibits formation of peptide bond
Erythromycin - Binds to 50S portion and prevents translocation along mRNA
Tetracyclines - interfere with attchment of tRNA to mRNA
Streptomycin - Changes shape of 30S portion causing mRNA misreads
How do folate inhibitors work?
Sulfonamides target the enzyme which catalyses PABA to Folate
How do antibacterials affect DNA/RNA formation?
Quinolones - inihibit topoisomerases which prevents supercoiling
Nitroimidazoles - Causes DNA fragmentation
Nitrofurantoin - Causes DNA and RNA fragmentation
Rifampicin - inhibits DNA-dependant RNA polymerase (prevents mRNA synthesis)
What are the mechanisms of antibiotic resistance?
Efflux pump - removes the drug from the bacterial cell
Alteration of enzyme pathways
Alteration of drug binding site
Production of enzyme which inactivates the drug
Class, mechanism of action, selective toxicity, functions and limitations of Benzyl penicillin
Beta-lactam - penicillin Competitive inhibition of transpeptidase Targets cell wall of bacteria Throat infections, Pneumonia, Cellulitis Side effects - Diarrhoea, nausea, vomiting
Class, mechanism of action, selective toxicity, functions and limitations of flucloxacillin
Beta-lactam - penicillin Competitive inihibition of transpeptidase Targets cell wall of bacteria Pneumonia, chest infections Nausea, vomiting, indigestion
Class, mechanism of action, selective toxicity, functions and limitations of amoxicillin
Beta-lactam - penicillin Competitive inihibition of transpeptidase Targets cell wall of bacteria Chest infections, dental abscesses, UTIs Diarrhoea, nausea
Class, mechanism of action, selective toxicity, functions and limitations of co-amoxiclav
Beta-lactam - penicillin
Competitive inihibition of transpeptidase
Targets cell wall of bacteria
Middle ear infections, Respiratory tract infections, UTIs, Joint and bone infections, Dental infections
Diarrhoea, itching/redness of mouth, armpits, genitals, nausea/vomiting
Class, mechanism of action, selective toxicity, functions and limitations of ceftriaxone
Beta-lactam - Cephalosporin
Competitive inihibition of transpeptidase
Targets cell wall of bacteria
Pneumonia, UTI, intra-abdominal infections
Diarrhoea, dizziness, abdominal pain
Class, mechanism of action, selective toxicity, functions and limitations of ceftazidime
Beta-lactam - Cephalosporin Competitive inihibition of transpeptidase Targets cell wall of bacteria Septicaemia, pneumonia, meningitis Abdominal pain, diarrhoea, dizziness
Class, mechanism of action, selective toxicity, functions and limitations of erythromycin
Macrolide
Binds to 50S portion and prevents translocation along mRNA
Targets bacterial ribosomal function
Chest infections, skin problems (acne), STIs
Nausea, vomiting, stomach cramps, loss of appetite, indigestion
Class, mechanism of action, selective toxicity, functions and limitations of ciprofloxacin
Fluoroquinolones
Inhibits DNA replication by binding to DNA topoisomerase
Bacterial DNA
Pneumonia, Gonorrhoea, typhoid fever
Tendon damage (tendonitis), nausea, diarrhoea
Class, mechanism of action, selective toxicity, functions and limitations of doxycycline
Tetracycline Interferes with tRNA/mRNA attachment Bacterial ribosome Malaria, chest infections, STIs Headaches, nausea/vomiting, sensitive to sunlight
Class, mechanism of action, selective toxicity, functions and limitations of trimethoprim
Sulfonamides Prevents folic acid synthesis PABA to Folate does not occur in humans UTIs, Acne, chest infections Nausea, diarrhoea, headaches
Class, mechanism of action, selective toxicity, functions and limitations of metronidazole
Nitroimidazole
DNA fragmentation
Targets Bacterial DNA
Skin infections, Bacterial vaginosis, pelvic inflammatory disease
Class, mechanism of action, selective toxicity, functions and limitations of meropenem
Beta-lactam - carbapenem Competitive inhibition of transpeptidase Cell wall synthesis Meningitis, pneumonia, anthrax Diarrhoea, abdominal pain, headache
Class, mechanism of action, selective toxicity, functions and limitations of Clarithromycin
Macrolide
Binds to 50S portion and prevents translocation along mRNA
Targets bacterial ribosomal function
Chest infection, stomach ulcers, cellulitis
Class, mechanism of action, selective toxicity, functions and limitations of gentamicin
Aminoglycoside
Binds to 30S region of ribosome and causes misreading of bacterial proteins
Bacterial ribosomes
Meningitis, pneumonia, UTIs
Class, mechanism of action, selective toxicity, functions and limitations of vancomycin
Glycopeptide Prevents Ala-Ala elongation of peptides Bacterial ribosome Colitis, Diarrhoea, Intestinal infections Dizziness, nausea
