Introduction to Antibacterial drugs

Question 1

What is an antibiotic

Answer 1

Biggest class of systemic antimicrobial drugs .

Natural chemical substance to kill microbes

Question 2

Factors affecting bacterial infection treatment

Answer 2

1. Drug retention problems : Elimination from host and inactivation by host
2. Wrong drug ( wrong spectrum of activity)
3. Drug delivery: (Oral > poor reuptake)
   * (IV /IM > inconvenient )
   * (Topical > poor tissue uptake )
4. Side effects ( toxicity to host ,allergic reaction ,normal flora disruption )
5. Development of resistance eg mutation
6. Toxins ( Gram - neg septicemia ,antibiotics treatment can make it worse )

Question 3

Key terms

Answer 3

Chemotherapy : Use of natural / synthetic chemicals to kill bacteria ,viruses ,fungi, protozoa ,helminths within the body or inhibit their growth also chemicals whereby cells with abnormal growth patterns are treated

Disinfectants( Used on sterile objects) and Antiseptics(Used on skin and mucous membrane ) are agents that kill or inhibit the growth of microbes in high concentrations ,they are toxic to cells ,should not be administered systematically

Question 4

What is resistance

Answer 4

When a microbes is no longer affected by anti microbial drug

Question 5

How to prevent resistance

Answer 5

Resistance can be prevented by :

• using when only necessary
• at sufficiently high doses
• for sufficient long periods

Question 6

4 Main resistance mechanisms bacteria develops

Answer 6

1. Production of an enzyme that inactivates the drug
2. Alteration of drug sensitive or drug binding site
3. Decreased drug accumulation in bacterium
4. Development of a pathway that bypasses the reaction inhibited by the antibiotic

Question 7

How to choose an antibiotic rationally

Answer 7

Should be based on :

• known infective microorganisms
• site of infection
• safety of agent
• immune status of the patient
• renal and hepatic function
• cost of therapy
• severity of infection
• co-morbid disease

Question 8

3 different types of therapy

Answer 8

1. Empiric : stating treatment before the microorganism causing infection
2. Definitive : based on results of microbial tests and in vitro anti microbial susceptibility tests
3. Prophylactic : preventative

Question 9

Causes for development of resistance

Answer 9

• Unnecessary prescribing
• subminimal dose ad duration of the therapy
• Late initiation
• Inappropriate combination
• Longer duration of treatment

Question 10

When can empiric therapy be used

Answer 10

• critically ill patients
• broad spectrum agents that cove gram pos and neg and anaerobic bacteria
• for polymicrobial infection

Question 11

Combined therapy

Answer 11

A single therapy using narrow spectrum drug is optimal .

• Combined therapy is used in recommended cases ,thus care must be give in hoe drugs interact with each other
  1. Antagonist interaction : The effect of 1 drug is diminished in the prescence of another eg bactericidal (beta lactam ) and bacteriostatic ( tetracycline)

Additive interaction : Combined effect of 2 drugs is equal to the sum of the individual effects of the drugs eg Beta lactam + beta lactam

Synergistic interaction : The combined effect of 2 drugs is more than the sum of their individual effects ( beta lactam + aminoglycoside )

Question 12

Complications of therapy

Answer 12

Hypersensitivity , superinfection , direct toxicity