Antibiotic Classes Flashcards
What are the 3 main ways antibiotics kill bacteria?
Acting on the bacteria cell wall
Acting on the bacterial ribosome
Acting on bacterial DNA
Antibiotics are “selectively toxic”, what does this mean?
They kill bacteria without damaging host cells
What does bactericidal mean?
Kills bacteria
What does bacteriostatic mean?
Inhibits growth of bacteria
What does narrow spectrum mean?
Antibiotic acts on a limited range of bacteria
What does broad spectrum mean?
Antibiotic acts on a wide range of gram +ve and -ve bacteria
Where in the GI tract are antibiotics absorbed?
Small intestine
Which 3 classes of antibiotics act on the cell wall?
Penicillins
Glycopeptides
Cephalosporins
How are penicillins excreted from the body?
Via the kidneys (rapidly)
Are penicillins safe in pregnancy?
Yes
If an antibiotic contains “cilia” it’s name, which antibiotic class does it belong to?
Penicillins!
How do penicillins kill bacteria?
Inhibit cell wall synthesis (bactericidal)
If antibiotics contains “ceph” or “cef” in it’s name, is it a ….?
Cephalosporin
How do cephalosporins kill bacteria?
Inhibit cell wall synthesis by preventing cross-linking of peptidoglycan (bactericidal)
How are cephalosporins excreted?
Via kidneys and urine
Are cephalosporins safe in pregnancy?
Yes
How do glycopeptides kill bacteria?
Binds to the end of the growing pentapetide chain during peptidoglycan synthesis, preventing cross-linking and weakening the bacterial cell wall
How are glycopeptides administered?
IV
Not absorbed orally
Give examples of glycopeptides?
Vancomycin
Teicoplanin
How are glycopeptides excreted?
Via kidneys and urine
Why should precautions be taken when prescribing vancomycin for patients with kidney failure?
Toxic levels of vancomycin can build up in the blood of patients with kidney failure causing further kidney damage
Vancomycin is only active against gram +ve or -ve?
Gram +ve
NO activity against Gram -ve
Vancomycin can only be given orally for which infection?
C. Diff
acts topically on the gut lumen
Name 3 classes of antibiotics that inhibit protein synthesis?
Macrolides
Aminoglycosides
Tetracyclines
How do antibiotics inhibit protein synthesis?
Attach to bacterial ribosomes
Protein synthesis can resume when antibiotic is removed (bacteriostatic= inhibits growth but does not kill bacteria, bacteria then killed by WBC)
Why are ahminoglycosides the exception to the rule for antibiotics that inhibit protein synthesis?
Aminoglycoside group bind to ribosomes which is lethal
Give examples of macrolides
Erythromycin
Clarythromycin
Azithromycin
How are macrolides excreted?
Via the liver, biliary tract and guy
not urine
Macrolides are useful for treating infections that “hide” from the host’s immune system, how?
Macrolides are lipophilic and can pass through cell membranes easily to attack the bacteria hiding in the host’s cells
Which macrolide is safe for pregnancy?
Erythromycin
Give an example of an aminoglycoside
Gentamicin
How should gentamicin be administered?
IV
Not absorbed by gut
How does gentamicin kill bacteria?
Binds to ribosomes inhibiting protein synthesis but also bactericidal
Which antibiotic is mainly active against Gram negative?
Gentamicin
Which antibiotic is used for coliforms?
Gentamicin
Which antibiotic can be used for pseudomonas aeruginosa?
Gentamicin
How is gentamicin excreted?
Urine
How are tetracyclines excreted?
Liver and biliary system
Why should tetracyclines not be given to under 12s?
Stains their teeth
Which antibiotic can be used against “true” anaerobes?
Clindamycin
Name two other antibiotics that inhibit protein synthesis
Clindamycin and chloramphenicol
Give an example of a tetracycline
Doxycycline
What can doxycycline be used to treat?
Some chest + skin infections for pts with Pen allergy
Treating bacteria without a proper cell wall (atypical pneumonias)
Name 3 antibiotics that act on bacterial DNA
Metronidazole
Trimethoprim
Fluoroquinolones
How do antibiotics act on bacterial DNA?
Acts by causing strand breakage of bacterial DNA
Metronidazole can treat?
Infection caused by “true” anaerobes
Some infections caused by protozoa (single-celled parasites)
What is the mode of action for fluoroquinolones?
Inhibits bacterial folic acid synthesis Inhibits topoisomerase (enzymes responsible for the supercoiling and uncoiling of DNA), thus bacteria can no longer replicate
Are fluoroquinolone bactericidal?
Yes
Which antibiotics are the only antibiotics that can be given orally to treat Pseudomonas infection?
Fluoroquinolones
How are fluoroquinolones excreted?
Urine
Give examples of fluoroquinolones
Ciprofloxacin
Levofloxacin
How can you use ciprofloxacin to treat?
Complicated UTIs
Sometimes UTIs in younger men (<60y/o)
What must levofloxacin only be used to treat?
ONLY for severe community-acquired pneumonia in Pen allergy pts
What are the 3 forms of penicillin available?
Benzylpenicillin (Penicillin G, IV)
Phenoxymethyl penicillin (Penicillin V, oral)
Long-acting penicillin (IM)
Which penicillin treats Gram positive?
Flucloxacillin
Which penicillins treat Gram negative?
Amoxicillin
Co-amoxiclav
Tazocin (Piperacillin/Tazobactam)
Which organisms is flucloxacillin only used for due to a very narrow spectrum?
Staph and Strep ONLY
Which penicillin is the most commonly prescribed?
Flucloxacillin as staph and strep are skin infections
What infections does flucloxacillin treat?
Skin and soft tissue
Wound infection
Cellulitis (soft tissues under the skin)
Staph. aureus infections
How is amoxicillin administered?
Can be given orally as this is well-absorbed
How effective is amoxicillin compared to other penicillins?
Less effective over the years, many organisms produce beta-lactamase (enzyme that destroys beta- lactam ring)
What is co-amoxiclav a combination of?
Combination of amoxicillin (antibiotic) + clavulanic acid (beta-lactamase inhibitor)
This combination extends the range of bacteria that can be treated
What is tazocin a combination of?
Piperacillin (antibiotic) + Tazobactam (beta-lactamase inhibitor)
AKA pip-tazobactam
How can tazocin only be administered?
IV not absorbed orally
Pip-tazobactam will treat which type of bacteria?
Gram negative including pseudomonas
Name a 1st gen cephalosporin
Cefalexin (UTI)
Name a 2nd gen cephalosporin
Cefuroxime (used very little)
Name 3rd gen cephalosporins
Cefixime (Gonorrhoea)
Ceftriaxone (meningitis)
Ceftazidime (Pseudomonas sp)
What can macrolides been used for treating?
Intracellular organisms (e.g. Legionella infection) Bacteria without a proper cell wall (mycoplasma and chlamydia)
