Principles antibiotic module Flashcards
Define bacteriocidal.
Antibiotics which kill bacteria.
Define bacteriostatic.
Antibiotics which inhibit the growth of bacteria.
Name an issue with oral administration of antibiotics.
In oral antibiotic administration, antibiotics are absorbed from the small intestine and spread to all parts of the body. However, large amounts are excreted unchanged in the faeces,
How do antibiotics work?
Act on bacterial cell wall, bacterial ribosomes and bacterial DNA.
Give features of penicillins.
Penicillins are bactericidal, and inhibit cell wall synthesis. They are safe in pregnancy and excreted rapidly by kidneys.
Give features of cephalosporins.
Cephalosporins are bactericidal and inhibit cell wall synthesis by preventing cross-linking of peptidoglycan. They are excreted in the urine by the kidneys.
Give features of glycopeptides.
Glycopeptides, e.g. vancomycin IV. They are bactericidal, weakening bacterial cell wall by interfering with peptidoglycan synthesis. They are active only against gram positive organisms. Toxic levels may cause kidney damage.
Give features of macrolides.
Macrolides, e.g. erythromycin, clarithromycin and azithromycin inhibit bacterial protein synthesis. They are excreted by the liver.
Give features of aminoglycosides.
Aminoglycosides, e.g. gentamicin IV. Are bactericidal, binding to ribosomes to inhibit protein synthesis. They are mainly active against gram-negative aerobic organisms, e.g. coliforms and pseudomonas aeruginosa. Excreted in urine.
What is the 2nd line antibiotic in the treatment of serious staph. and strep. infections (particularly in penicillin allergic patients)?
Clindamycin. It is also active against true anaerobes and inhibits protein synthesis,
Describe tetracyclines.
Tetracyclines inhibit bacterial protein synthesis, They are bacteriostatic. They are excreted by the liver. Useful in treating atypical pneumonia and chest/skin infections in the penicillin allergic.
Describe metronidazole.
Metronidazole acts by causing strand breakage of bacterial DNA. It is used in true anaerobe infection and protozoa infection.
Describe trimethoprim.
Trimethoprim inhibits bacterial folic acid synthesis by interfering with bacterial enzymes. May be given with sulphamethoxazole as co-trimoxazole. Active against both positive and negative gram bacteria. Excreted in urine.
Describe fluoroquinolones.
Fluoroquinolones interact with topoisomerases (enzymes responsible for supercoiling and uncoiling of bacterial DNA) to prevent bacterial replication. They are bactericidal. Only antibiotics that may be given orally to treat pseudomonas infection. Oral is as effective as IV. Excreted in the urine. Use is severely restricted.
Describe ciprofloxacin
Ciprofloxacin may be given IV or oral. It is used for complicated UTI and sometimes UTIs in young men.
