Lesson D1 - Antibacterial, Antifungal, Antiviral & Antimalarial Agents

Question 1

Define antibiotic

Answer 1

An antibiotic is a chemical substance produced by microorganisms that suppress the growth of
other microorganisms and may eventually destroy them

Question 2

Thus, strictly speaking, synthetic chemicals such as __________ are not antibiotics, but are antimicrobial compounds.

Answer 2

sulfonamides, antimicrobial compound

Question 3

How are bacteria classified?

Answer 3

• By their colour after a treatment know as Gram’s stain
• Bacteria that have taken up colour = gram-positive
• Bacteria that are decolourised = gram-negative

Question 4

What are 2 current issues of antibiotic use?

Answer 4

• micro-organisms mutate to have different properties and become resistant to antibiotics
• Antibiotics take advantage of differences between bacterial and human cells (selective toxicity), and we have exploited the obvious differences and are now seeking new differences where the selective toxicity may be less than desired, hence more toxicity.

Question 5

What are the 2 ways that antibiotics are classified?

Answer 5

1. Narrow or broad spectrum

2. Bactericidal or Bacteriostatic

Question 6

Give an example of a narrow spectrum antibiotic and what does it act on?

Answer 6

• Penicillin G

Question 7

Give a couple of broad spectrum antibiotics and what do they act on?

Answer 7

• Tetracyclines and chloramphenicol

- Act on both gram- positive and gram-negative bacteria.

Question 8

What are Bactericidal antibiotics and what is an example?

Answer 8

• Antibiotics that destroy microorganisms

- Penicillin G

Question 9

What are Bacteriostatic antibiotics and what is an example?

Answer 9

• Antibiotics that prevent multiplication of microorganisms, thus facilitating the ability of the natural defence system of the body (the immune system) to destroy the bacteria
• Tetracycline

Question 10

Penicillin G destroys what type of bacteria and what are a couple examples of this bacteria?

Answer 10

• Gram-positive

- Pneumococcus and Streptococcus

Question 11

Penicillin G is good to treat what infections caused by the gram-positive bacteria Pneumococcus and Streptococcus?

Answer 11

Pneumoniae, middle ear infection, skin infection, and meningitis (inflammation of the meninges, the covering of the brain and spinal cord). It is also very useful in the treatment of syphilis.

Question 12

Why does Penicillin V have an advantage over Penicillin G?

Answer 12

• Because it is more acid stable and therefore, less is destroyed by stomach acid when it is taken orally
• Higher blood levels are achieved

Question 13

Why when a penicillin is required for oral administration in some infections, penicillin V will be prescribed rather than penicillin G.

Answer 13

• Because higher blood levels are achieved with penicillin V

Question 14

What is one of the ways bacteria become resistant to penicillin G and some other penicillin?

Answer 14

By producing an enzyme called penicillinase which breaks down the penicillin molecule and inactivates it.

Question 15

What advantage does Cloxacillin have over some other Penicillins? When is it used?

Answer 15

• Resistant to the attack by penicillinase

- Used particularly against penicillinase-producing Staphylococcus aureus

Question 16

What are some characteristics of semisynthetic penicillins? Name a couple.

Answer 16

• Ampicillin and Amoxacillin
• Have a broader spectrum of antibacterial activity than penicillin G, and are active against several gram-negative bacteria such as Escherichia coli (E. Coli).

Question 17

What is Ampicillin and Amoxacillin good to treat?

Answer 17

• Urinary tract infection due to E.Coli

- Useful in the treatment of gram-negative bacteria

Question 18

What is the advantage of Carbenicillin?

Answer 18

• Has an even broader spectrum of antibacterial activity than Ampicillin and Amoxacillin
• Effective in severe infections caused by the gram-negative bacterium, Pseudomonas aeruginosa.

Question 19

What is augmentin?

Answer 19

• Combination of amoxacillin and clavulinic acid
• ## Effective against penicillinase-producing strains of bacteria such as Staphylococcus aureus and Haemophilus influenzae.

Question 20

The inhibitor of penicillinase does not have _________________ of its own.

Answer 20

antibacterial activity

Question 21

What is the most common adverse reaction to penicillin? What are the symptoms?

Answer 21

• Allergic reaction

- Rash, diarrhea, face and tongue swelling, and an eruption of itching wheels (urticaria)

Question 22

What will happen if a person is allergic to a penicillin preparation? Will they be allergic to all penicillins preparations?

Answer 22

• They will be allergic to all penicillin preparations

Question 23

How many % of the population are allergic to penicillin

Answer 23

1-10%

Question 24

What are the symptoms of rare cases of an allergic reaction to penicillin?

Answer 24

• Severe difficulty in breathing and a marked fall in blood pressure.
• Deaths do occur in some of these rare cases and individuals are recommended to wear a Medic Alert tag if allergic to penicillin.

Question 25

What are Cephalosporins? Why are they better? Give a characteristic

Answer 25

• Chemically similar to penecillins
• More resistant to penicillinase than is the penicillin group
• Cephalosporins are also selective inhibitors of bacterial cell wall synthesis

Question 26

Cephalosporins are divided into ____________________ depending on their spectrum of antimicrobial activity

Answer 26

• Four generations

Question 27

Give an example of a first generation cephalosporins drug and what is it good for?

Answer 27

• Cephalothin

- Good activity against gram-positive microorganisms and moderate activity again gram-negative microorganisms

Question 28

Give an example of a second generation cephalosporins drug and what is it good for?

Answer 28

• Cefamandole

- Increased activity against gram-negative microorganisms.

Question 29

What are the characteristics of third generation cephalosporins

Answer 29

• less active than the first generation against gram- positive microorganisms, but are more active against gram-negative microorganisms.

Question 30

It is of considerable importance that third generation cephalosporin drug are active against ___________________________

Answer 30

Pseudomonas aeruginosa

Question 31

Give a couple examples of third generation cephalosporin drugs and what are they used for?

Answer 31

• Ceftriaxone is the drug of choice for treatment of gonorrhea
• ceftriaxone and cefotaxime –> drugs of chose for the treatment of meningitis

Question 32

Some third-generation cephalosporins are useful for therapy of ________

Answer 32

Meningitis

Question 33

Give an example of a 4th generation cephalosporins and why is this generation good?

Answer 33

• Cefepine

- It has increased stability to penicillinase and a broader spectrum of activity than the third generation.

Question 34

What are some of the disadvantages of using antibiotics in combination? (4 reasons)

Answer 34

1. Unnecessary additional cost if a single antibiotic is effective.
2. Increased chance of encountering toxicity. Moreover, when toxicity is encountered, the physician does not know which antibiotic is responsible and has to cease therapy with the combination. This could lead to the patient being deprived of therapy.
3. Using a combination of antibiotics enhances the opportunity for resistant bacteria to arise and take over from susceptible bacteria.
4. A combination of antibiotics will decrease the number of normal populations of different bacteria and remove their inhibitory influence on potentially dangerous bacteria. Thus, a new dangerous infection, referred to as a superinfection, could arise.

Question 35

List 4 reasons why clinicals sometimes use antibiotic combinations.

Answer 35

1. Therapy of a severe infection where it is not known what microorganism is responsible. The infection is so dangerous that one cannot wait to determine by laboratory tests which microorganism is responsible.
2. Treatment of a mixed bacterial infection where no single antibiotic could eliminate all the different bacteria responsible for the infection.
3. When treating tuberculosis, emergence of resistant tubercle bacilli is an important hazard. Treatment, therefore, is always carried out with a combination of antitubercular drugs to decrease the change of emergence of resistant tubercle bacilli.
4. Two drugs may in some infections be effective where a single antibiotic may not. For example, a combination of a penicillin and an aminoglycoside is required to treat inflammation of the endocardium (inner lining of the heart) caused by bacteria known as enterococci. The penicillin damages the cell wall of the enterococci, allowing the aminoglycoside to penetrate and inhibit bacterial protein synthesis.

Question 36

Approximately _________prescriptions are written for antibiotics

Answer 36

• 1 in 5

Question 37

What is the reason that anti-biotics are sometimes over-prescribed?

Answer 37

1. A great deal of pressure is exerted on physicians by their patients to prescribe antibiotics when the physician does not believe that it is in the best interest of their patient. For example, parents will sometimes demand by telephone that a physician prescribe for a child without even examining the child.
2. A great deal of pressure is exerted on physicians by their patients to prescribe antibiotics when the physician does not believe that it is in the best interest of their patient. For example, parents will sometimes demand by telephone that a physician prescribe for a child without even examining the child.
3. Physicians are visited on a regular basis by representatives of the pharmaceutical industry who market the new antibiotics introduced by their companies. Moreover, physicians will receive “educational” material on the drugs from these representatives. This type of promotion of antibiotics undoubtedly influences physician prescribing.
4. Physicians are visited on a regular basis by representatives of the pharmaceutical industry who market the new antibiotics introduced by their companies. Moreover, physicians will receive “educational” material on the drugs from these representatives. This type of promotion of antibiotics undoubtedly influences physician prescribing.

Question 38

Why is the tetracyclines family of antibiotics less affective than when they were first introduced?

Answer 38

• Because these antibiotics were over-prescribed.

- A physician may be tempted to prescribe a broad spectrum antibiotic as a substitute for diagnostic judgement

Question 39

Can you used anti-biotics on viruses?

Answer 39

• No

- Viruses are not susceptible to antibiotics.