antimicrobial agents Flashcards
what are antimicrobial agents
chemicals that are used to prevent or treat infections
- interfere with the growth of organisms
- exert selective toxicity
what do antimicrobial agents target?
- cell wall
- ribosomes
- enzymes
two things about peniciliin
- alexander fleming (1928)
- antibiosis
what are antibiotics
a sustance produced by a microorganism (bacteria or fungi) that interferes with:
- microbial growth (bacteriostatic)
- microbial survival (bacteriocidal)
what is a soil bacterium that is filamentous and produces a number of antibiotics?
streptomyces sp.
are synthesized antibacterial drugs ‘true; antibiotics?
no
what are the 4 uses of antimicrobials in animals?
- therapy
- prophylaxis (treatment of healthy animals before the onset of disease)
- metaphylaxis (treatment of clinically healthy animals in a herd AFTER the onset of the disease)
- growth promotion (improved weight gain and feed efficiency)
what are narrow spectrum antimicrobials?
affect gram positive or gram negative bacteria
what are broad spectrum antibiotics?
affect gram positive and gram negative, mycoplasma, rickettsia, and chlamydia
what are the three broad spectrum antibiotics?
- fluoroguinolones
- phenicols
- tetracyclines
why are some antibiotics narrow and some broad spectrum?
- porins - pore size
- outer membrane - lipophilic antiobiotics will not penetrate
what is the advantage of narrow spectrum antibiotics?
selective inhibition
what is the advantage of broad spectrum antibiotics?
if the pathogen identity is not know
what is a disadvantage of broad spectrum antibiotics?
may inhibit normal flora, which could lead to opportunistic infection (superinfection)
what is the mechanism of action of bactericidas
kills bacteria
-MBC: minimum concentration needed to kill
what is the mechanism of action of bacteriostatics
inhibits growth
- host defense could then kill bacteria
- MIC: minimum concentration needed to inhibit
what does static vs cidal depend on?
concentration
-cidal at high and tatic at low
organism
-cidal to one, static to the other
what antimicrobials inhibit cell wall sythesis?
-peniciliins, bacteriacinm cephalosporinsm, vancomycin, carbapenams
what are the beta-lactam antibiotics?
- penicillins
- cephalosporins
- carbapenams
what are penicillins active against?
gram positive bacteria
how do penicillins work?
they inhibit the cross-linknig between glycan molecules in the peptidoglycan by binding to transpeptidase
what is transpeptidase aka?
penicillin-binding proteins (PBP)
are pencillins produces naturally or semisynthetically?
both
what produces natural penicillins?
a fungus called penicillium
how do some bacterias break down pencillin?
the bacteria produce penicillinase (beta-lactamase) which breaks down the pencillin
what produces cehpalosporins?
a fungus called cephalosporium
how do cephalosporins work?
they inhibit the cross-linknig between glycan molecules in the peptidoglycan by binding to transpeptidase
what spectrum are semisynthetic cephalosporins?
broad spectrum
what is ceftiofur used for?
a broad spectrum antibiotic used to treat respiratory infections of cattle, swine, and horses,
-also foot rot in cattle
what is MRSA?
-methicillin-resistant staphylococcus aureus
what is significant about MRSA?
- resistant to all beta-lactams
- most often skin infections
- could be zoonotic
what are beta lactamase inhibitors
irreversibly bind to beta-lactamases
-either have no or weak antimicrobial activity
what are carbapenams?
beta-lactam antibiotics derived from streptomyces spp
what is the spectrum for carbapenams?
broad spectrum activity
what is a widely used human medicine to treat multi-drug resistant bacterial infections?
carbapenams
what are two carbapenams used in small animals (extra label)
imipenam and meropenam
why is there a worry about resistance to carbapenams?
because of production of carbapenamase
what produces vancomycin?
streptomyces orientalis
how does vacomycin work?
inhibits cell wall synthesis by blocking cross links
what is vancomycin primarily effective against?
gram positive bacteria
what does vancomycin treat?
MRSA infections
what are aminoglycosides primarily effective against?
gram negative bacteria
why doesnt aminoglycosides work against anaerobes?
because it requires oxygen transport into the cell
aminoglycosides are synergists with what/
beta-lactams
neomycin is what?
an aminoglycosides
resistance to what is widespread?
streptomycin
what is the only aminocylitol used in ver med?
spectinomycin
what is spectinomycin used for?
- treat upper respiratory infections in catle
- treat E. coli in pigs
- avian salmonellosis
which macrolides are naturally produced?
erythromycin
spiromycin
tylosin
what are macrolides primarily effective against?
gram positive bacteria
what is macrolide resistance caused by?
erm class of genes (plasmid or chromosome-mediated)
what produces tylosin?
streptomyces fradiae
what is tylosin used for in swine?
- growth promotion
- prevention and treatment of swine dysentery
what is tylosin use for in cattle?
-treat pneumonia, foot rot, metritis, pink eye, and mastitis
what is tylosin used for in feedlot cattle
-included in the feed to prevent liver abscesses
how is tilmicosin produced?
semisynthetic
what product is tilmicosin in?
mycotil
what is tilmicosin used to treat?
repiratory infections in cattle and swine
how do you prophylactically treat cattle on arrival to feedlot?
single does of tilmicosin
what happens if humans take tilmicosin
they die
what are semisynthetic macrolides?
- azithromycin
- clarithromycin
- gamithromycin
- tulathromycin
- tildipirosin
- tylovalosin
what product has azithromycin in it?
zithromax
who is the extra label use for of azithromycin?
small animals and horses
what product had tulathromycin?
draxxin
what product had gamithromycin?
zactran
what product had tildipirosin in it?
zuprevo
what product has tylvalosin in it?
aivlosin
what type of spectrum is tylvalosin?
broad spectrum
what produces tetracyline?
strepomyces
whawt type of bacteria are tetracycines effective against?
gram positive and gram negative bacteria
what tetracyclines have longer retention time in the body?
doxycycline
minocycline
what is a naturally produced phenicol?
chloramphenicol
what produces chloramphenicol?
streptomyces venezuelae
what phenicol is a synthetic analog?
florfenicol
how do phenicols work?
they inhibit protein synthesis
what kind of spectrum does chloramphenicol have?
broad
what does chloramphenicol toxicity cause in humans?
- aplastic anemia and neutropenia
- inhibits protein synthesis in bone marrow cells
- prohibited in food animals
is there resistance to chloraphenicol?
yes, by both gram positive and gram negative bacteria
what is the synthetic analog of chloramphenicol?
florfenicol
what kind of spectrum is florfenicol?
broad
what does florfenicol treat?
respiratory infections (Nuflor)
what is pleuromutilins used for?
active against anaerobes and mycoplasma; primarily in swine
how does pleuromutilin work?
inhibits protein synthesis
-bacteriostatic
what semisynthetic antibiotic is derived from pleuromutilin?
tiamulin
what animals do you use tiamulin on?
pigs - swine dysentery, porcine proliferative enteropathy, mycoplasma pneumonis
