Antibacterial Agents Flashcards
what is the germ theory of disease?
Proposes that microorganisms cause disease
what was the first effective treatment for syphilis?
Arsphenamine (Salvarsan)
what was the first widely available antimicrobial?
Prontosil
what marks the goldern era of antibiotics?
alexander flemming discovering penicillin
what is an antibiotic?
chemical substance that has capacity to inhibit growth of or kill bacterial cells
what is an antimicrobial?
agents that act against all types of microorganisms not just bacteria
what is the difference between a narrow spectrum and broad spectrum antibiotic?
narrow spectrum - effective against limited number
broad spectrum - effective against wider array
what is a con of broad spectrum bacteria?
increased development of resistance
disrupts normal microbiome
define bactericidal
kills bacteria
define bacteriostatic
inhibits growth of bacteria
what is selective toxicity?
antibiotic that is more harmful to bacterial cells than to host cells
what are the properties of an effective antibiotic?
selective toxicity, soluble in bodily fluids, toxicity not easily altered, nonallergenic, stability, bacterial resistance not easily acquired, reasonable cost
what are the 5 classes of antibiotics?
- inhibition of cell wall synthesis
- disruption of cell membrane function
- inhibition of protein synthesis
- inhibition of nucleic acid synthesis
- action as antimetabolites
what class are the following antibiotics in - B-lactams, vancomycin, and bacitracin?
inhibitors of cell wall synthesis
How are bacterial cell walls synthesized?
NAG and NAM get AA added to them > transported across cell membrane > AA side chains cross linked by transpeptidase > membrane formed
Are antibiotics that inhibit cell wall synthesis bactericidal or bacteriostatic?
bactericidal
How does cell wall inhibitors have selective toxicity?
prokaryotic cells dont have cell walls
What type of antibiotics are penicillin and cephalosporins?
B-lactam
what is the mode of action of B-lactam antibiotics?
binds to and blocks activity of transpeptidases, preventing cross-linking of peptidoglycan layers
what is the mode of action of vancomycin?
blocking transglycosylation and transpeptidation steps of peptidoglycan synthesis
which cell wall inhibitor antibiotic is a glycopeptide antibiotic?
vancomycin
what is the mode of action of bacitracin?
prevents dephosphorylation of bactoprenol (lipid carrier), preventing assembly and transport of NAG-NAM
how is bacitracin applied? why?
topical use only due to toxicity
what antibiotic disrupts the cell membrane?
polymyxins
what is the mode of action of polymyxin?
cationic detergent, disrupting membrane structure
how is polymyxin administered? why?
topical or ophthalmic use only - poor selectivity toxicity
what are the two ribosomal subsunits in bacterial protein synthesis?
30s and 50s
what is the mode of action of Aminoglycosides?
irreversibly bind to 30s subunit and block initiation complex, causing misreading and premature release of mRNA from ribosome - halts protein synthesis
what antibiotic is ototoxic and nephrotoxic to cats and dogs?
aminoglycosides
what is the mode of action of tetracycline?
bind to 30s subunit to prevent attachment of aminoacyl-tRNA to RNA-ribosome complex
which antibiotic is toxic to the human mitochondria?
amphenicol
what is the mode of action of amphenicol?
bind to 50s subunit, inhibiting peptidyl transferase
what is the mode of action of macrolides?
bind to 50s subunit, blocking formation of initiation complex and translocation
what is the mode of action of lincosamides?
binds to 50s subunit
what is the mode of action of streptogramins?
bind to different sites on the 50s ribosomal subunit, inhibition of protein synthesis at different steps
which ribosome inhibitor is toxic to rodents?
lincosamides
what is the mode of action of Quinolones/Fluoroquinolones?
inhibit DNA gyrase (topoisomerase II) and topoisomerase IV, preventing bacteria DNA from unwinding and duplicating
what is the mode of action of rifamycins?
inhibits DNA-dependent RNA polymerase > prevents transcription of messenger RNA
what is the mode of action of metronidazole?
pro-drug
reduction of nitro group of metronidazole creates active drug that covalently binds DNA, causing DNA breaks > pieces of DNA get destroyed
what is the mode of action of sulfonamides and diaminopyrimidines?
interferes with folic acid synthesis (needed for DNA synthesis)
what are the pros and cons of antibiotic use?
pros - gain 4%-5% more body weight, livestock live longer, containment of potentially large-scale epidemics
cons - multidrug-resistant pathogens
