Antibiotics Flashcards
Antibiotic classes
Beta lactams (Penicillin Cephalosporin Monobactams Carbapenems)
Glycopeptides (eg Vancomycin)
Aminoglycosides (eg Gentamicin)
Macrolides (eg Erythromycin )
Tetracyclines (eg Doxycyclin)
Fluoroquinolones (eg Ciprofloxacin)
Others trimethoprim, sulfamethoxasole, metronidazole, clindamycin
cell wall agents
Betalatams and glycopeptides
ribosomal agents
Macrolides, aminoglycosides, tetracyclines and clindamycin
DNA
Fluoroquinolones
Bacteriacidal agents
Betalactam drugs Vancomycin Fluoroquinolones Metronidazole Nitrofruantoin
Aminoglycosides (high dose)
Co-trimoxazole
Bacteriostatic agents
Trimethoprim Sulfamethoxazole Tetracyclines Macrolides Clindamycin Aminoglycosides (low dose)
4 big categories of bacteria
Gram positive
Gram negative
Anaerobes
Atypical
Coagulase positive staph =
S. aureus, only one coagulase producing staph in human infection. Coagulase makes them stick in big number
Coagulase negative staph =
All other staph, eg staph epidermidis. They are bunched up in 4-8 cocci, unlike the picture.
All staph became resistant to penicillin due to
penicilinase production
What can be used as synergic agent?
Aminoglycoside for synergic effect
What if pt gets a rash with penicillin?
Rash with penicillin -> use first gen cephalosporin like cefazolin. Cephalosporins have some resistance to penicilinase
What if anaphylaxis?
If anaphylaxis -> avoid all beta lactam drugs. Use macrolides, clindamycin, vancomycin, fluoroquinolones instead
Anti-staph penicillin
Oxacillin, cloxacillin, dicloxacillin and nefcillin
In NZ flucloxacillin
Penicillinase resistant
Don’t work on gram negatives
MRSA is basically resistant to all beta lactam drugs
by altering penicillin binding protein. Any antibiotics works in other ways are ok.
Glycopeptide (Vancomycin)
+ Aminoglycosides/clindamycin/fusidic acid for synergic effect
When do we use methicillin?
NEVER! It causes allergic (eosinophilic) nephritis -> renal failure
Methicillin is the first penicillin invented with penicilinase resistance
Vancomycin
Glycopeptides
Inhibits cell wall synthesis differently
Don’t work as well as penicillin
Steven-Johnson syndrome
Penicillin
Cell wall agent
Covers gram positives
Usually the first line agent of choice
They work!
syphillis, Strep pyogenes
Penicillin G
Penicillin G dosent have much gram negative activity because it doesn’t get into the cells.
Penicillin G has poor bioavailability whereas amoxi has good oral bioavailablity (one of the reason why its used a lot in primary care setting)
extended gram negative cover penicilin
Ampicillin/amoxicillin
Good pseudomonas cover penicillin
Piperacillin extended gram negative
Penicillinase resistant penicillin
fluclox
Cephalosporins
First gen:
G +ve + PEcK (Proteus, E. coli, Klebisiella) eg Cefazolin
Cephalosporins
Second gen:
G+ve + HEN (Haemophillus, Enterobacter and Neisseria) + PEcK eg Cefaclor
Cephalosporins
Third gen:
Antipseudomonal
more G-ve eg Ceftriaxone
Ceftazidime
Third gen have poor oral bioavailability -> given IV or IM
Third gen crosses BB barrier -> good agent for meningitis
Cefotaxime excreted primarily in urine
Ceftriaxone excreted primarily by liver
Cephalosporins
Fourth gen:
Good G +ve and –ve + anti pseudomonal eg Cefepine
Carbapenems
Broadest spectrum betalactam drug
G +ve and –ve + anaerobes
Covers pseudomonas
No intracellular coverage e.g. Chlamydia
Betalactamase resistant
Good empiric therapy for invasive disease eg sepsis
Emerging resistance. E. Coli, enterococcus
Gram positive bacilli
Claustridia –
difficile, botulinum, tetani (GI tract)
Metronidazole because anaerobes
Gram positive bacilli Listeria monocytogenes (pneumonia)
Resistant to all cephalosporines
Amoxi to treat
Gram positive bacilli
Corynebacterium – diptheria
Penicillins, macrolides, fluoroquinolones
Enterococcus faecalis
Gram positive bacilli
Multi-drug resistant
Amoxi if sensitive. Vancomycin, linezolid, daptomycin
Gram negative cocci
3 medically relevant species
All diplococci
Moraxella is common cause of respiratory tract infection and occasinally UTI
Moraxella catarrhalis Neisseria gonorrhoeae Neisseria meningitidis IV Ceftriaxone if meningitis Rifampicin for prophylaxis
Gram negative cocci
Moraxella catarrhalis
Amoxi is ok but high betalactamase prevalence
Gram negative cocci
Neisseria gonorrhoeae
IM Ceftriaxone 250mg single dose
Gram negative cocci
Neisseria meningitidis
IV Ceftriaxone if meningitis
Rifampicin for prophylaxis
Gram negative bacilli
GI + UTI
E. coli Salmonella Shigella Vibrio Yersinia Proteus Campylobacter Pseudomonas
Gram negative bacilli
Don’t need Abx for diarrhoea unless invasive
Invasive diarrhoea means
blood and fever
the most common cause of UTI
E. Coli
BPAC recommends trimethoprim as first line
The term Urosepsis is used because of high likelihood of …
Another organism to keep in mind in urosepsis is
gram –ve organism involvement, especially E coli.
Enterococcus faecalis, G +ve bacilli because E. coli and E. faecalis have high prevalence of resistance + multidrug resistance.
Gram negative bacilli
Invasive pathogens
Salmonella
Shigella
Yersinia
Chamylobacter
Ascending cholangitis, cholecystitis, peritonitis
usually caused by
Gram negative bacilli Invasive pathogens Salmonella Shigella Yersinia Chamylobacter
Gram negative bacilli drug of choice
Aminoglycosides Carbapenems Fluoroquinolones 3rd and 4th cephalosporines Monobactams
Psudomonas
G –ve bacilli, aerobic
Difficult to treat!! Why?
Multiple mechanisms of Abx resistance biofilm Thick wall Active pump Extended spectrum betalactamase
CFS, intubated, wound
Psudomonas G-ve vacilli, aerobic
antibiotics
Aminoglycosides, tazocin, carbapenem, ceftazedime, fluoroquinolone
Tazocin contains piperacillin and tazobactam – tazobactam must be used due to betalactamase
Atypicals
Cannot gram stain
Spirochetes Syphilis – Penicillin G Borrelia (lyme’s disease) -Doxy Mycoplasma - Macrolide Chlamydia - Macrolide Mycobacterium – 4 Tb meds Rikettisia - Doxy
4 Tb meds RIPE, and side effects
Rifampin R for red, it stains all ur body fluid red/orange colour.
Isoniazid isoNiazid, N for neuropathy
Pyrazinamide P for Pain in the joint
Ethambutol E for eye, causes retionopathy
Anaerobes
C. difficile, botulinum, tetani Bacteroids - gut Actinomyces – mouth -> lungs Disruption of normal flora, poor blood supply and necrosis -> Abscess Mixed organisms in abscess Debridement/surgical drainage
Anaerobes antibiotics
Metronidazole, clindamycin, a penicillin + betalactamase inhibitor, carbapenem, fluoroquinolone
Clindamycin for above diaphragm. ie dental and lung
Bacteroids, Claustridia, actinomyces
Aminoglycosides
Gentamicin and tobramycin
Good gram –ve cover including pseudomonas
Renal and ototoxic
Don’t cross blood brain barrier
Prolonged exposure > 10mcg/ml should be avoided.
Use ideal body weight for calculating the dose
Check the trough level, should be < 2mcg/ml
Dosing interval 8 hours
Tetracyclines
Only doxycycline G +ve and –ve + anaerobe Good for intracellular organisms Malaria Chlamydia Gonorrhoea Rickettisia Low dose therapy for acne Stains bone and teeth, avoid in pregnancy Oesophagitis Photosensitivity
Macrolides
Erythro, azithro, roxithro and clarithromycin
Similar spectrum to amoxicillin
Atypical pneumonia – Chlamydia, mycoplasma and legionella
Good for Campylobacter
Long half life
GI upset + disulfiram like action
Potent CYP3A4 inhibitor except azithromycin
Bad if pt is on statin
Fluoroquinolones
Old – Ciprofloxacin New – Levo, gemi and moxifloxacin Good G +ve and –ve coverage Good tissue penetration Cipro – best gram negative potency Fist line for pyelonephritis Moxi has good anaerobic cover
GI upset
Elevate BSL especially with gati
Neuropathy – central and peripheral
Trimethoprim
First line agent for uncomplicated UTI
Doesn’t cover proteus (Don’t use it if pH is high!!)
Bad in pregnancy
Sulfamethoxazole increases the potency
Covers proteus
Used in uncomplicated paediatric UTI
Prophylaxis for PCP and toxo infection in HIV +ve pt with CD4 cell < 200 cell/microL or 200 x 10^6/L
Nitrofurantoin
UTI
Safe in pregnancy unless close to term 36-42 weeks
Possible haemolytic anaemia in neonate
Gram positive
Penicillin
Staph – Anti-staph penicillin
MRSA – Vancomycin
Gram negative
Aminoglycosides Fluoroquinolones Carbapenems Monobactam Penicillin and cephalosporines
Atypicals
Macrolides or fluoroquinolones for pneumonia
Otherwise depends
Anaerobes
Metronidazole
Clindamycin (above diaphragm)
For 5th year exam
Nitrofurantoin for UTI during pregnancy if the bug is resistant to amoxicillin
Penicillin G for syphilis
Amoxicillin for Listeriosis
Macrolides for atypical pneumonia
Azithromycin 1g PO stat for chlamydia
Metronidazole for C. difficile, bacterial vaginosis and Giardia
Ceftriaxone for meningitis unless in neonates and pregnancy
Co-trimoxazole for PCP and Toxo prophylaxis
Quadruple therapy for tuberculosis + their side effects
No antibiotics for non bloody diarrhoea
Gentamicin pharmacokinetics
Ceftriaxone is not used for meningitis in babies or pregnant women
because of possible listeria infection. Listeria is resistant to all cephalosporins
Cotrimoxazole =
bactramrim = trimethoprim + sulfamethoxasol
Nitrofurantoin is not recommended in pregnancy 37-42 weeks due to
possible haemolytic anaemia in neonate
