Ch 41 - intro to antimicrobial drugs Flashcards
What are 4 critical factors that determine the selection of an antimicrobial drug?
- Identity of the organism
- Safety of the drug
- Site of infection
- Patient´s medical history
Identity of the organism
usually identified through Gram´s stain or culture
Site of infection
for example some drugs cross the blood-brain barrier whereas others don´t
Patient´s medical history
allergies, immune status, renal and hepatic conditions, pregnancy, and lactation status
Name 4 large classes of antimicrobial agents, give examples of each, and describe their mechanisms of action:
- Cell wall synthesis inhibitors
- Protein synthesis inhibitors
- DNA synthesis inhibitors
- Cell membrane disrupters
- Cell wall synthesis inhibitors
- E.g: Penicillins, cycloserine, cephalosporins, vancomycin.
- These drugs block the cross-linking peptidoglycan chains, which is the final step in bacterial cell wall synthesis.
- Protein synthesis inhibitor
- E.g: Tetracycline, aminoglycosides, erythromycin, clindamycin, chloramphenicol.
- These agents bind to bacterial ribosomes.
- DNA synthesis inhibitors
- E.g: Quinolones and fluoroquinolones block nucleic acid synthesis by inhibiting DNA gyrase.
- Rifampin inhibits DNA-dependent RNA polymerase.
- The Sulfonamides inhibit synthesis of folate, which is a critical component of DNA
- Cell membrane disrupters
Polyene antimicrobials such as amphotericin B bind to components of fungal CM
What do bacteriostatic drugs do?
they arrest the growth and replication of bacteria, thus giving the body immune system the chance to destroy and remove the pathogens
What do bactericidal drugs do?
kill bacteria outright
Which drugs are considered bactericidal?
- Aminoglycosides
- Quinolones
- cycloserine
- Vancomycin
- Carbapenems
- Penicillins
- Cephalosporins
- Trimethoprim- sulfamethoxazole
Which drugs are considered bacteriostatic?
- Chloramphenicol
- Nitrofurantoin
- Clindamycin
- Tetracyclin
- Erythromycin
- Lincomycin
What is meant by chemotherapeutic spectrum of an antibiotic?
- the term “chemotherapeutic spectrum” refers to the types of microorganisms affected by a given agent.
- thus, a broad-spectrum agent affect a wide variety of microorganisms
What is drug resistance?
the term “drug resistance” refers to the ability of a microorganism to withstand a drug that was previously toxic to it
Name the 4 basic mechanisms by which microorganisms can become resistant to antibiotics (and give an example of each: not written in the flashcards)
- Production of drug-inactvating enzyme
- Changes in drug penetration
- Changes in receptor structure
- Alterations of metabolic pathways
What is meant by empiric therapy?
early intervention through the use on an antibiotic before pathogen is identified
What is the benefit of empiric therapy?
- Because early intervention usually helps to improve the outcome of an infection, antibiotics are sometimes used before a Gram´s stain or culture of the pathogens is obtained.
- Physicians use information from the history, physical examination, and any other completed diagnostic tests to determine which antibiotics to use.
What is meant by antimicrobial prophylaxis?
- Antimicrobial prophylaxis is the use of antibiotics to PREVENT disease.
- Examples include prevention of tuberculosis among individuals who are in close contact with infected patients with artificial heart valves who are undergoing dental procedures
