Antimicrobial use in Lung Infection 1 Flashcards
what are the modes of action of antimicrobial compounds
- DNA replication
- RNA synthesis
- protein synthesis
- cell wall synthesis
- antimetabolites
what are short acting tetracyclines
tetracylcine
chlortetracylcine
oxytetracycline
what are long acting tetracyclines
doxycycline
minocycline
what is the mode of action of tetracyclines
- bacteria uptake –> diffuse across outer cell membrane, active carrier mediated process through inner cell membrane
- bind reversibly to bacterial ribosomes
- inhibit bacterial protein synthesis
how are tetracyclines classified
bacteriostatic broad-spectrum antimicrobials
how do tetracyclines cause adverse effects
may bind to mammalian ribosomes
what is the mechanism of action of tetracycline
tetracycline binds to ribosome –> A site of 30S (small one) where mRNA template is found –> competes with protein translation and causes the polypeptide chain to not grow anymore

list 5 pharmacokinetics of tetracycline
- oral absorption is low (except Dox and Min) –> given IM or IV
- oral absorption is further lowered by food (tetracyclines chelate metal ions Ca, Mg, Fe, Al)
- enter most tissues and body fluids (min and dox are best)
- generally don’t get into brain
- cross placenta and secreted in milk
how are chlor-, oxy- and tetracycline metabolized and excreted
metabolism: minimal –> excreted unchanged in urine (and to lesser extent bile)
undergo some enterohepatic recirculation (increases half life to 6-10h)
glomerular filtration: urinary excretion and impaired renal function will increase half life
long acting formulations persist at injection site (often in oily vehicle)
list 2 pharmacokinetics of minocycline and doxycycline
semi synthetic derivatives of tetracyclines –> more lipid soluble
- better penetration into brain, ocular tissue and broncial secretions
- good absorption after oral admin
what is the metabolism and excretion of minocycline and doxycycline
mino: some metabolism and excreted in bile and feces (used in GI infections)
doxy: no renal excretion (may be good for animals with renal impairment)
enter intestine via bile and direct diffusion (may cause probelms in horses)
list 7 signs of tetracycline toxicity
- broad spectrum suppression of intestinal flora can lead to super-infection with resistant pathogens in horses (oral admin)
- idiosyncratic liver damage in some animals if there is renal impairement
- renal tubular damage (storage)
- irritant (long acting esp.)
- anaphylaxis when IV (give slow)
- deposited at active sites of ossification and in teeth
- photosensitivity
why is tetracycline widely used
widely used because broad spectrum activity (aerobic/anaerobic, gram - and gram +, local/systemic), low cost, ease of admin and difficulties in practice in ID of causative microorganism
when are tetracyclines particularly useful
mixed bacterial infections
dox and min also have anti-inflammatory properties
what are indications of tetracycline use in cattle (6)
- resp infections in calves
- bovine pneumonia (feedlots, feed)
- anaplasmosis
- infectious keratoconjunctivitis
- parenteral admin for serious udder infection
what are indications of tetracyclines in sheep
- Q fever
- enzootic abortion (chlamydophilla abortus)
- prevent pasteurella hemolitica pneumonia
- foot rot
- with streptomycin for brucella ovis
what are indications of tetracycline use in pigs
- atrophic rhinitis
- lower resp disease
- eradicate leptospira
what are the indications of tetracycline use in horses
limited spectrum
what are indications of tetracycline use in cat and dogs (6)
- urinary tract infections
- Echlirchia canis, Rickettsia rickettsii
- otitis externa
- chlamydial infection in cats
- upper resp tract
- conjunctiva
what are the indications of tetracycline use in poultry
- enteric and resp infection
largely administered in feed
what is the spectrum of macrolides
mainly gram +
some gram - (Pasteurella spp)
mycoplasmas
some rickettsiae
moderate activity against anaerobes
what are macrolides
bacteriostatic
what are some examples of macrolides
erthyromycin
tilmicosin
tylosin
spiramcyin
tulathromycin
what is the the structure of erythromcyin
macrocyclic lactone nucleus with one or more deoxy-sugars
