Introduction to Antimicrobial Therapy Flashcards
Antimicrobial
Defined as any agent, natural or synthetic, that has the ability to kill or suppress microorganisms.
Antibiotic
Means “destructive to life,” and strictly speaking, an antibiotic is a chemical that is produced by one microorganism and has the ability to harm other microbes
Chemotherapy
Term was first defined as the use of chemicals against invading microorganisms (e.g., bacteria, viruses, fungi).
Today the term is applied to the treatment of cancer and to the treatment of infection
Spontaneous Mutation Resistance Mechanisms
Results in random changes in a microbe’s DNA.
such mutations confer resistance to only one drug.
Development of multiple drug resistance would require multiple mutations, which is very rare.
Conjugation Resistance Mechanisms
Process by which extrachromosomal DNA is transferred from one bacterium to another.
Extrachromosomal DNA in bacteria are called plasmids.
Plasmids can be exchanged from one bacterium to another
Primarily gram-negative bacteria
Mechanisms of antibiotic resistance
Enzymatic inactivation
Antibiotic uptake reduction
Increased antibiotic removal
Alteration of bacterial target sites
Beta-lactamases
Bacterial enzymes that split the beta-lactam ring of penicillin, cephalosporins, carbapenems and monobactams
Usually plasmid mediated
Aminoglycoside, ciprofloxacin and trimethoprim-sulfamethoxazole resistance often all on same plasmid
Beta-lactam resistance
Penicillins and cephalosporins are also referred to as Beta-lactam antibiotics because these antibiotics have a beta-lactam ring
The beta-lactam ring is essential for the activity of the antibiotic against a pathogen
Antibiotics, such as penicillin are oftentimes not effective against these enzyme producing bacteria
MIC (Minimum inhibitory concentration)
Lowest concentration of antimicrobial that inhibits growth of bacteria.
Breakpoint
The MIC that is used to designate between susceptible and resistant.
Inhibition of an Enzyme MOA
The sulfonamide drugs suppress bacterial growth by inhibiting an enzyme required to produce folic acid from PABA.
Disruption of the Bacterial Cell Wall MOA
Several kinds of drugs (penicillin’s, cephalosporin’s, others) act to weaken the cell wall and thereby promote bacterial lysis.
Disruption of Bacterial Protein Synthesis MOA
It is possible for drugs to disrupt the function of bacterial ribosomes while having little or nor affect on ribosomes of the host.
Protein Synthesis inhibitors: Inhibit 30s Subunits Aminoglycosides
Gentamicin
Tobramycin
Amikacin
Protein Synthesis inhibitors: Inhibit 30s Subunits Tetracyclines
Tetracycline
Doxycycline
Minocycline
