Antimicrobials Flashcards
what drug do you use to treat giadia infection that causes diarrhoea?
Tinidazole or metronidazole
what drug do you use to treat clostridium difficile infection causing pseudomembranous colitis?
metronidazole
What antibiotics and antivirals would you give post transplant
Bactrim (pcp) and valgancyclovir (cmv) and niostatin (anti fungals)
What antimicrobials are nephrotoxic?
Gentamicin, sulfonimides, penicillins, rifampicin, acyclovir
A 13 year-old female presented to the emergency department looking unwell and septic. She was started on ceftriaxone IV. A diagnosis of pyelonephritis was subsequently made, with no evidence of obstruction on ultrasound.
You are notified by the microbiology lab that her urine culture results are consistent with a urinary tract infection, with a pure culture of Enterobacter cloacae that is sensitive to ceftriaxone. Would you prescribe ceftrioxone?
No. enterobacter cloacae are part of the ESCAPPM organisms that develop resistance to ceftriaxone.
They all share a chromosomally-encoded cephalosporinase (a type of beta-lactamase) that is inducible. Thus they tend to develop cephalosporin resistance during treatment.
What drug would you use for an Ecoli UTI?
Trimethoprim
what drug do we use for PCP
bactrim= co trimoxole
what would you use if a patient needed penicillin but was hypersensitive to it? (think alternatives)
ceftriaxone
as you move from first gen cephalosporins to 3rd gen, what organisms do you increase cover of?
First gen–> mostly staph; then by the time you get to 3rd gen you get more gram negative cover
what groups of antibiotics are bacteriocidal in general?
those that target the bacterial cell wall or membrane, as well as those that interfere with bacterial enzymes
e.g. penicillin, cephalosporins, polymyxins, aminoglycosides and sulfonamides
what groups antibiotics are bacteriostatic?
those that target protein synthesis. For example, macrolides, and tetracyclines
give an example of an amino glycoside, and tell me how it works.
Gentamycin, tobramycin, neomycin. Aminoglycosides have strong gram negative cover, and inhibit bacterial protein synthesis
what does penicillin, carbapenams, cephalosporins and monobactams have in common?
beta lactam ring
what is another name for benzylpenicillin?
penicillin G
give examples of macrolides?
erythromycin, azithromycin. Inhibit cytochrome p450 system
what are some SEs of tetracyclines
oesophagitis, enamel decay
what are the narrow spectrum penicillins?
benzylpenicillin IV, benzathine penicillin IM, phenoxymethylpenicillin PO
which cephalosporins treat enteroccocus?
only 5th generation cephalosporins
what are the antimicrobials that inhibit DNA synthesis
trimethoprim, sulfonamides, metronidazole
first generation of cephalosporins?
cephazolin –> good for MSSA
what is an example of 3rd gen cephalosporins?
ceftriaxone –> not good for staph, but more for gram negatives
what kind of drug is vancomycin
glycopeptide antibiotic therapy
contraindication to bactrim?
G6PD deficiency and pregnancy
SE of bactrim?
steven johnson syndrome
how do fluoroquinolones work?
interfere with DNA gyros, prevents bacterial replication
Se of fluoroquinolones?
tendonitis
How does nitrofurantoin? what is it used for?
It inhibits enzymes and DNA activity. Prophylactic measures for UTIs
what SE is due to nitrofurantoin?
pulmonary fibrosis
what does hydronephritis
dilation of the urinrary collecting system
what do you think if you saw a younger male with gas in the urinary system?
emphysematous pyelonephritis
what are the classical features of acute pyelonephritis?
temp, fever, loin pain +/- dysuria frequency and urgency
what are some SE of ethambutol?
Optic neuritis
And changes to colour vision
side effects of pyrazinamide?
Gout Hepatic toxicity GIT upset Fever Malaise
how does isoniazid work
Inhibits synthesis of mycolic acid in cell wall of mycobacterium
what kind of drug is metronidazole?
nitroimidazole. Used to be an antiprotozoal drug but now used for anaerobic bacteria
what would you want to advise a patient who is about to commence metronidazole
abstain from alcohol
how do quinolones work
inhibit topoisomerase II (a bacterial DNA gyrase)
what are some adverse effects of chloramphenicol?
pancytopenia and grey baby syndrome and HS reaction
what is the difference between gentamicin and chloramphenicol in terms of how they inhibit ribosomal protein synthesis?
chloramphenicol (and macrolides) inhibits 50s subunit, gentamicin inhibit 30s subunit
are tetracyclines bacteriostatic or bactericidal?
bacteriostatic
how do sulphonamides work?
they have a structural analogue to PABA. PABA is needed for folate synthesis. So they inhibit folate synthesis (by competing for the same Dihydropterate synthetase enzyme as PABA) and thus interfere with DNA synthesis and replication
how do trimethoprim work?
inhibits enzyme dihydrofolate reductase in folate synthesis pathway
SE of vancomycin?
- Ototoxicity
- Nephrotoxicity
- Red man syndrome- dosing consideration
How does vancomycin work? how does resistance to Vancomycin develop?
- Acts on GRAM POSITIVE BACTERIA ONLY- MRSA usually
- BINDS TO D-ALA, D-ALA preventing crosslinking of NAM/NAG polymers that make up the backbone of peptidoglycan cell wall
RESISTANCE TO VANCOMYCIN:
D-ALA gets converted to D-LAC so vancomycin cannot bind.
name the beta lactams
• Penicillins • Cephalosporin's • Antipseudomonals • Carbapenams Monobactams
how do beta lactams work?
Inhibit the synthesis of bacterial cell walls by inhibiting penicillin binding proteins, i.e. enzymes transpeptidase and carboxypeptidase.
how does resistance to beta lactams occur?
- beta lactamase enzyme encoded in plasmid
2. change in penicillin binding proteins
what is a haematological consideration you would have before prescribing antimalarials?
A patient with G6PD deficiency–> as it can cause oxidative haemolysis
what drug protocol do we use for Multi drug resistant TB?
• Pyrazinamide, Ethambutol • 5 active agents • Injectable AMIKACIN • Moxifloxacin --> treat for 2 years
What empirical therapy do we give for severe CAP?
Severe CAP- ceftriaxone (cephalosporin) IV daily + AZITHROMYCIN (macrolide)
What antibiotic do you prescribe for an infective exacerbation of COPD without consolidation on CXR?
doxycycline
What empirical antibiotics for a man who presents with LIF abdo pain and fever? (worried about perforated diverticulitis)
Tazocin OR Ampicillin, metronidazole, gentamicin
When would tazosin be contraindicated
Contraindicated when there is a hx of jaundice or liver problems
Adverse effects of clindamycin?
TEN, taste disturbance, C. difficile colitis
what constitutes tazocin?
Piperacillin + tazobactam
why might you prescribe flucloxacillin and rifampicin?
for staphyloccocal dermatitis infections and osteomyelitis. Rifampicin reduces the amount of flucloxacillin required
