Antimicrobial Therapy 1 Flashcards
Antibiotic definition vs. Antimicrobial definition
antibiotic- “destructive to life” , a chemical that is produced by one microorganism and tha the ability to harm other microbes
antimicrobial- any agent, natural or synthetic, that has the ability to kill or suppress microorganisms.
Why are antibiotics selectively toxic?
If they weren’t the drugs would not only kill the infecting microbes, but also the host cell and therefore have no therapeutic utility.
What is one of the major causes of antibiotic abuse?
Overtreatment of acute pharyngitis
What is the only drug that have direct public health consequences for persons other than the one who received the medication?
Antibiotics
How do microorganisms become resistant?
by alterations in the function or structure
- spontaneous mutation: random changes in a microbes DNA, usually results in resistance to only one drug
- Conjugation/plasmid transfer: process by which extrachromosomal DNA (plasmid) is transferred from one bacterium to another. Primarily in gram negative bacteria
- enzymatic inactivation
- antibiotic uptake reduction
- increased antibiotic removal: efflux pumps remove abx from intracellular space
- alteration of bacterial target sites: the binding site on bacterial cell membrane is altered
**Use of antibiotics promotes the emergence of drug-resistant microbes
What is the role of a beta lactamase?
to split the beta lactam ring of penicillin, cephalosporins, carbapenems, monobactams
What are three strategies for delaying emergence of resistant?
- antimicrobial agents should be used ONLY when actually needed.
- narrow-spectrum agents should be be employed whenever possible
- Newer antibiotics should be reserved for situations in which older drugs are no longer effective.
What is MIC?
What is breakpoint?
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.
How do you use breakpoint to determine susceptibility?
Breakpoint has to be greater than MIC and the greater the difference between them, the more susceptible the organism is to that antibiotic.
ex.
gentamicin: MIC=2, breakpoint=4 —>susceptible
Pip/tazo: MIC=8, breakpoint=32—> susceptible
Pip/tazo is a better choice
What is empiric therapy?
assuming what the organism is based on pt history and site in the body.
It is your best guess!
*once the identity and drug sensitivity of the infecting organism has been determined, the patient can be switched to a more selective antibiotic.
To be effective, the antibiotic must be present at the site of infection in a concentration (less/greater) than the MIC.
greater
*drug levels 4 to 8 times the MIC are often desirable
