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what makes an appropriate microbial compound
needs to remain in the system long enough to be effective
must be broken down and secreted by the host
kill or inhibit the microorganism without simultaneously damaging the host tissue
goal of selective toxicity
to target specific function or structure in the pathogen that is not present in the host
-cell wall (not present in humans)
70S ribosome (some toxicity to mitochondria)
harder to have selective toxicity with some pathogens (fungi, helminths, and viruses)
worked into antimicrobial compounds
-used an arsenic based drug that was toxic to cause syphilis
origins of antimicrobial drugs
antibiotics are common metabolic products of aerobic spore-forming bacteria and fungi
Targets of antimicrobial drugs
-inhibition of cell wall synthesis
-inhibition of nucleic acid synthesis, structure or function
-inhibition of protein synthesis
-disruption of cell membrane structure or function
Penicillin and cephalosporins
react with one or more nzymes that synthesize/complete the cell wall, causing the cell to lyse
blocks the peptidase enzymes that link the cross bridges between the glycans in peptidoglycan
Drugs that inhibit nucleic acid synthesis
may block synthesis of nucleotides, inhibit replication, or stop transcription
sulfonamides and trimethoprim
block enzymes required for tetrahydrofolate synthesis needed for DNA and RNA synthesis.
-these drugs are competitive inhibitors called metabolic analogs
an additive effect, achieved by multiple drugs working together, requiring a lower dose of each
insert on sites on the 30S subunit and cause misreading of mRNA
Drugs that disrupt cell membrane function
-cell with a damaged membrane dies from disruption in metabolism or lysis
-these drugs have specificty for a particular microbial group, based on differences in types of lipids in their cell membranes
Penicillin consist of 3 parts
-variable sidechain dictates microbial activity
-account for majority of all antibitics administered
-beta-lactam ring that can be altered
impair ribosome function
-comosed of 2 or more amino sugarsand an aminocyclitol (6C ring)
inhibit protein synthesis especially useful against gram-negtive rods and certain gram-positive bacteria
needs to be taken 2 hours after eating to prevent binding with food
-also inactivated by antacids
side effects tetracycline antibiotics
-potential damage to developing bones of a fetus
-discoloration of teeth in children
-sensitivity to light
rickettsial & chlamydial infections
reserved for serious infections
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