Ch 41 - intro to antimicrobial drugs

Question 1

What are 4 critical factors that determine the selection of an antimicrobial drug?

Answer 1

• Identity of the organism
• Safety of the drug
• Site of infection
• Patient´s medical history

Question 2

Identity of the organism

Answer 2

usually identified through Gram´s stain or culture

Question 3

Site of infection

Answer 3

for example some drugs cross the blood-brain barrier whereas others don´t

Question 4

Patient´s medical history

Answer 4

allergies, immune status, renal and hepatic conditions, pregnancy, and lactation status

Question 5

Name 4 large classes of antimicrobial agents, give examples of each, and describe their mechanisms of action:

Answer 5

1. Cell wall synthesis inhibitors
2. Protein synthesis inhibitors
3. DNA synthesis inhibitors
4. Cell membrane disrupters

Question 6

1. Cell wall synthesis inhibitors

Answer 6

• E.g: Penicillins, cycloserine, cephalosporins, vancomycin.
• These drugs block the cross-linking peptidoglycan chains, which is the final step in bacterial cell wall synthesis.

Question 7

2. Protein synthesis inhibitor

Answer 7

• E.g: Tetracycline, aminoglycosides, erythromycin, clindamycin, chloramphenicol.
• These agents bind to bacterial ribosomes.

Question 8

3. DNA synthesis inhibitors

Answer 8

• 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

Question 9

4. Cell membrane disrupters

Answer 9

Polyene antimicrobials such as amphotericin B bind to components of fungal CM

Question 10

What do bacteriostatic drugs do?

Answer 10

they arrest the growth and replication of bacteria, thus giving the body immune system the chance to destroy and remove the pathogens

Question 11

What do bactericidal drugs do?

Answer 11

kill bacteria outright

Question 12

Which drugs are considered bactericidal?

Answer 12

• Aminoglycosides
• Quinolones
• cycloserine
• Vancomycin
• Carbapenems
• Penicillins
• Cephalosporins
• Trimethoprim- sulfamethoxazole

Question 13

Which drugs are considered bacteriostatic?

Answer 13

• Chloramphenicol
• Nitrofurantoin
• Clindamycin
• Tetracyclin
• Erythromycin
• Lincomycin

Question 14

What is meant by chemotherapeutic spectrum of an antibiotic?

Answer 14

• 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

Question 15

What is drug resistance?

Answer 15

the term “drug resistance” refers to the ability of a microorganism to withstand a drug that was previously toxic to it

Question 16

Name the 4 basic mechanisms by which microorganisms can become resistant to antibiotics (and give an example of each: not written in the flashcards)

Answer 16

1. Production of drug-inactvating enzyme
2. Changes in drug penetration
3. Changes in receptor structure
4. Alterations of metabolic pathways

Question 17

What is meant by empiric therapy?

Answer 17

early intervention through the use on an antibiotic before pathogen is identified

Question 18

What is the benefit of empiric therapy?

Answer 18

• 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.

Question 19

What is meant by antimicrobial prophylaxis?

Answer 19

• 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