Antibiotics - Pt 1 Flashcards
What ae antibiotics?
Chemical compound made by another microorganism which inhibits or kills bacteria
Majority derived from bacterial species - steptomyces
What is the function of bactericidal antibiotics?
Kill the bacteria
What is the function of bacteriostatic antibiotics?
Prevent bacteria multiplying
What are some types of bactericidal antibiotics?
Penicillin, gentamicin, vancomycin, ciprofloxacin and metronidazole
What are some types of bacteriostatic antibiotics?
Doxycycline, clarithromycin, azithromycin and linezolid
What are the mechanisms of action for antibiotics?
Inhibition of Cell wall synthesis, Protein synthesis, DNA gyrase and Folic acid metabolism
What are some antibiotics which inhibit cell wall synthesis?
Penicillin, cephalosporins, carbapenems, vancomycin and aztreonam
What are some antibiotics which inhibit protein synthesis?
Gentamicin, doxycycline, clarithromycin, erythromycin, clindamycin, chloramphenicol and linezolid
What are some antibiotics which inhibit DNA synthesis?
Metronidazole and fluoroquinolones
What are some antibiotics which inhibit folic acid synthesis?
Trimethoprim and co-trimoxazole
What are the groups which target bacterial cell wall?
Beta lactams
Glycopeptides
Describe beta-lactams
3 carbon and 1 nitrogen ring - beta-lactam ring
Bactericidal
Bind to penicillin binding proteins in cell wall or cytoplasm - inhibit cell wall formation
Inhibition by beta lactamases
Describe penicillin
Beta-lactam
Penicillium moulds
Composition - beta lactam and thiazolidine ring, plus Acl side chain
Wide spread of activity
What is the bacteria which benzylpenicillin and phenoxymethylpenicillin is active against?
Streptococcus pneumoniae - mainly
Beta-haemolytic - Streptococcus sp.
Alpha-haemolytic - Neisseria meningitis and Clostridium perfringes
What bacteria is amoxicillin and ampicillin active against?
Same as benzylpenicillin
E. coli
Enterococcus faecalis
Listeria monocytogenes
What bacteria is flucloxacillin active against?
Meticillin sensitive
Staph. aureus (MSSA)
Beta haemolytic - streptococcus
What bacteria is temocillin active against?
No gram positive activity
Enterobacteriaceae including AmpC and ESBL producers - Burkholderia cenocepacia
Describe the structure of cephalosporins
Beta-lactam ring
Dihydrothiazine ring
R1 and R2 side chains
Describe 1st class of cephalosporins
Active against gram positive
Cefazolin and cefalexin
Describe 2nd class cephalosporins
Enhanced gram negative activity and varying gram positive activity
Cefuroxime
Describe 3rd class cephalosporins
Markedly improved gram negative activity
Variable gram positive activity
Ceftriaxone and cefotaxime
Describe 4th class cephalosporins
Broad gram positive and negative activity
Cefepime
What do cephalosporins all cover?
Group A, B and C streptococci
Viridians group streptococci
E. coli
Klebsiella
Proteus mirabilis
What do cephalosporins not cover?
LAME
Listeria, Atypical, MRSA and Enterococcus
Describe carbapenems
Broad spectrum
Imipenem, Ertapenem and Meropenem
Fused beta lactam ring to 5 membered carbon only ring - stable against beta lactamases
IV only
When is meropenem used?
Active against gram positive, gram negative and pseudomonas
Severe infections - unresponsive to other antibiotic and haematology patients
Lung infections in CF patients
What are some mild adverse reactions to beta lactams?
Rash and fever
What are some severe adverse reactions to beta lactams?
Anaphylaxis, angioedema, facial swelling, breathing difficulties and Steven Johnstone’s reaction
What is the interaction between carbapenems and valproate?
Decreased valproate levels - increased risk of seizures
Clinically significant
Avoid concurrent use
What is the interaction between carbapenems and probenecid?
Increased levels of ertapenem and imipenem
Caution and rarely used
What is the interaction between all beta lactams and typhoid vaccine?
Prevents multiplication and reduces immune response achieved
Clinically significant and should be stopped 3 days before until 3 days after vaccine is given
Describe beta lactamase inhibitors
Restore antibacterial activity of antibiotics - amoxicillin and piperacillin
Clavulanic acid and tazobactam - potent beta lactam inhibitors
What bacteria is co-amoxiclav and piptazobactam active against?
Co-amoxiclav - meticillin sensitive - staph. aureus, klebsiella spp., proteus and anaerobes
Piptazobactam - pseudomonas and same as co-amoxiclav
Describe glycopeptides
Bactericidal - Vancomycin and teicoplanin
Gram positive organisms
Inhibits peptoglycans in the cell wall - weakens cell wall and leakage of intracellular components
Large molecules - poor oral absorption
Describe vancomycin use
MRSA
1st line for gram + infections in individuals with penicillin allergy
Used for skin and soft tissue infections, streptococcus meningitis and infective endocarditis
Clostridium difficile - oral vancomycin
What is a side effect of vancomycin?
Red man syndrome - flushing, erythema, pruritus, affecting upper body, neck and face, myalgia, dyspnoea and hypotension
What is the management for red man syndrome?
Stop infusion
Administer antihistamine
Can restart at slower rate once symptoms resolve
Describe vancomycin dose monitoring
Target is 10-20mg/l
If too high then stop vancomycin until trough <20mg/l then restart at increased dose intervals
If too low then reduce dose interval then dose
