Week 3 - Antibacterial Drugs - Prunuske Flashcards
What is the difference between bactericidal and bacteriostatic drugs? When would you prefer to use bactericidal drugs?
Bacteriostatic drugs tend to stop bacteria from multiplying a lot so that you immune cells can catch up and take them out. (ex ribosome inhbitor)
Bactericidal drugs are out to kill bacteria. You need to use bactericidal when the patient is immunocompromised because their immune system can’t help the drugs fight off the infection. (ex. cell wall inhibitor)
Basic considerations of pharmacokinetics?
Absorption- movement of drug into blood
Distribution- transfer of drug from intravascular to extravascular, blood brain barrier presents challenge
Metabolism- irreversible transformation of parent compound into metabolites, often in liver
Excretion- elimination of the drug through urine or feces
Must treat with right drug, right dose, right route, and right duration to to eliminate the infection.
What is the difference between prophylactic, pre-emptive, empiric, suppressive, and definitive therapy??
Prophylaxis- treat an infection that has not yet developed in individuals at a high risk
Pre-emptive- lab test indicating infection but no symptoms.
Empiric Therapy- take cultures, patients have an infection with serious potential consequences but the organism not identified (use broad spectrum)
Definitive Therapy- pathogen identified (use monotherapy, narrow spectrum)
Suppressive Therapy- after initial disease is controlled therapy is continued at a lower dose
How do pathogens develop resistance to drugs?
Bacteria cahnge their DNA (mutate) or acquire new DNA resulting in drug resistance
NOT the drug itself that causes it. The new trait is just selected for because it helps it survive.
What kinds of strategies can limit the development of drug resistance?
- Vaccines
- take out catheters
- target pathogen
- dont treat colonization
- avoid using Vanco, unless necessary
- stop treatment when cured
What does selective toxicity mean?
Antibiotics injure the invading organism while causing minimal problems to the host!
Good to exploit the differences in cell biology between out species and that of the pathogens!
Why should doctors pay attention to the therapeutic index?
A high theraeutic index means fewer adverse effects while still targeting the problem microbe.
Why shouldn’t you give antibiotics for “any old thing?”
- Need to minimize the development of antibiotic resistant microorganisms
- Minimize harm to the patient caused by toxicity due to the use of an unnecessary or inappropriate drug.
- Provide cost effective treatment. Hospital purchases of antibiotics usually represent 25-30% of the drug budget.
What test can tell the difference between streptococci and staphylococci?
The Catalase test
Monitors degradation of H2O2 which differentiates between:
staphylococci (present) and
streptococci (absent)
What are the different hemolytic results that can help differentiate bacterial strains?
α-hemolytic - form green ring
β-hemolytic - clearing around colonies on agar plates
γ-hemolysis - no hemolysis
What if the patient is elderly? How will this affect the excretion?
Older people’s kidneys don’t work as well so they won’t excrete things as fast. Higher chance of adverse effects.
Describe 4 main methods of drug resistance in bacteria:
1- Increased elimination of the drug by an efflux pump
2- Drug-inactivating enzyme is used
3- Alteration created in the drug’s target molecule
4- Porin proteins prevent entry into cell
How does DNA-mediated transformation occur?
- DNA enters the cell
- combines with recipient cell’s DNA by homologous recombination
- strand it replaced will be degraded
- new genome will be passed to daughter cells
What is a consequence of an overly broad antibiotic treatment?
SUPERINFECTION!
Can actually kill a lot of friendly bacteria on accident and allow harmful bacteria to take over
ex. in the bowel with clostridium dificille. (C-diff)
