CHAPTER 5: Lesson 16: Antimicrobial Therapy and Resistance

Question 1

is defined as that which minimizes the
development of resistance as well as resulting in a therapeutically successful
outcome

Answer 1

successful antimicrobial therapy

Question 2

can be initiated as soon as specimens are collected

Answer 2

Chemotherapy

Question 3

can, if necessary, be modified when laboratory data are at hand

Answer 3

empirical chemotherapy

Question 4

arising from chemotherapy require careful
consideration in some species and also in young animals

Answer 4

Inherent Toxicity or Side Effects

Question 5

Legal regulations in some
countries may prohibit the use of certain antibiotics, such as ________ in
food-producing animal

Answer 5

chloramphenicol

Question 6

Classification of Antimicrobial Drugs

Answer 6

1. Spectrum of activity against class of microorganism
2. Antibacterial activity
3. Bacteriostatic or bactericidal
4. Pharmacodynamic activity
5. Mechanism of action

Question 7

are narrow spectrum because they inhibit only bacteria

Answer 7

Penicillins

Question 8

are broader because they inhibit both bacteria and protozoa.

Answer 8

sulfonamides, trimethoprim, and
lincosamides

Question 9

only inhibit fungi.

Answer 9

Polyenes

Question 10

Some antibiotics are __________ in that they inhibit only
gram-positive (bacitracin and vancomycin) or mainly gram negative bacteria
(polymyxin)

Answer 10

Narrow Spectrum

Question 11

Some antibiotics are narrow spectrum in that they inhibit only
gram-positive (bacitracin and vancomycin) or mainly gram negative bacteria. Give an example(s) of each type of bacteria.

Answer 11

*gram-positive (bacitracin and vancomycin) *gram negative bacteria
(polymyxin)

Question 12

such as tetracyclines inhibit both gram positive and gram-negative bacteria

Answer 12

broadspectrum drugs

Question 13

Example of a broadspectrum drug that inhibits both gram positive and gram-negative bacteria.

Answer 13

tetracyclines

Question 14

Other drugs such as _____________ are most active against gram-positive bacteria but will inhibit some
gram-negatives.

Answer 14

Penicillin G or lincosamides

Question 15

This distinction is an approximation that depends on
drug concentrations and the organism involved

Answer 15

Bacteriostatic or bactericidal

Question 16

This drug is bactericidal
at high concentrations and bacteriostatic at lower ones.

Answer 16

penicillin

Question 17

The distinction between
bactericidal and bacteriostatic is critical in certain circumstances, such as the
treatment of the _____________.

Answer 17

meningitis or of septicemia in neutropenic patients

Question 18

: Antibacterial action is concentration or time dependent

Answer 18

Pharmacodynamic activity

Question 19

: Like pharmacodynamic activity, this is dependent on the
drug class. This is probably the most useful of the classifications, since it determines
the previous four classification approaches

Answer 19

Mechanism of action

Question 20

Narrow Spectrum & Broader Spectrum

Answer 20

Spectrum of activity against class of microorganism

Question 21

Narrow Spectrum for either gram positive or gram negative bacteria
Broad Spectrum for both gram positive and gram negative bacteria

Answer 21

Antibacterial activity

Question 22

Mechanism of Action of Antimicrobial Drugs

Answer 22

(1) inhibition of cell wall synthesis
(2) damage to cell membrane
function (3) inhibition of nucleic acid synthesis or function, and
(4) inhibition of protein synthesis

Question 23

Purine synthesis

Answer 23

Sulfonamides trimethoprim

Question 24

Example of drugs that Inhibit Cell Wall Synthesis

Answer 24

penicillins and cephalosporins (β-lactam antibiotics), bacitracin,
and vancomycin

Question 25

It inhibits cross-linkage between peptidoglycans in the cell wall,
inhibiting division, and creating weak points during active growth and cell division.

Answer 25

Inhibition of Cell Wall Synthesis [penicillins and cephalosporins (β-lactam antibiotics), bacitracin,
and vancomycin.]

Question 26

The cross-linkage between _________ gives the cell wall remarkable strength.

Answer 26

peptidoglycans

Question 27

Antibiotics that damage the cell membrane function include

Answer 27

polymyxins,
monensin, and the antifungal polyenes (amphotericin, nystatin) and imidazoles
(fluconazole, itraconazole, ketoconazole, miconazole)

Question 28

The ________ lies
beneath the cell wall, enclosing the cytoplasm

Answer 28

cell membrane

Question 29

It controls the passage of materials
into or out of the cell. If its function is damaged, cellular contents (proteins,
nucleotides, ions) can leak from the cell and result in cell damage and death.

Answer 29

Cell membrane

Question 30

Examples of Drugs That Inhibit Nucleic Acid Function are

Answer 30

*nitroimidazoles,
*nitrofurans,
“nalidixic acid,
“flfluoroquinolones (ciproflfloxacin, danoflfloxacin,
diflfloxacin, enroflfloxacin, orbiflfloxacin, saraflfloxacin),
*novobiocin,
*rifampin,
*sulfonamides,
*trimethoprim, and
*5-flflucytosine

Question 31

mechanisms of these are similar in all cells

Answer 31

Nucleic
acid Synthesis, Replication, and Transcription

Question 32

drugs affecting
_________ function have poor selective toxicity

Answer 32

Nucleic Acid

Question 33

Drugs with greater selective toxicity

Answer 33

sulfonamides and trimethoprim

Question 34

which inhibits the synthesis of folic acid

Answer 34

sulfonamides and trimethoprim

Question 35

Examples of drugs that inhibit protein synthesis

Answer 35

• tetracyclines;
• aminoglycosides (amikacin, gentamicin, kanamycin, neomycin, streptomycin,
  tobramycin, and others);
• aminocyclitols (spectinomycin);
• chloramphenicol;
• lincosamides (clindamycin, lincomycin); and * macrolides (azithromycin, clarithromycin, erythromycin, tylosin, tiamulin)

Question 36

Antibiotics affecting protein synthesis can be divided into those affecting the _________

Answer 36

• 30S
  ribosome (tetracyclines, aminoglycosides, aminocyclitols) and those affecting the
• 50S ribosome (chloramphenicol, macrolides, lincosamides).

Question 37

are matters relevant to the veterinarian and the owner.

Answer 37

Route and frequency of administration of the drug,
cost of treatment, adverse effects on the host and public health aspects of treatment

Question 38

pathogenic bacteria that commonly exhibit drug resistance ,

Answer 38

staphylococci, members of the Enterobacteriaceae and pseudomonads

Question 39

Anti-microbial Drug Interaction
Combination of the use of antimicrobial drug may produce a different effect
from that achieved by the individual drugs used separately such as:

Answer 39

Indifference
Additive
Synergism
Antagonism

Question 40

: where the combined action is no greater than that of the more
effective drug used alone

Answer 40

Indifference

Question 41

: where the combined action is equivalent to the sum of the actions of
each drug when used alone

Answer 41

Additive

Question 42

: where the combined action is significantly greater than the sum of
both effects

Answer 42

Synergism

Question 43

: where the combined action is less than that of the more effective
agent when used alone. Ex: bacteriostatic drugs (chloramphamicol or a
tetracycline) and bactericidal drugs (penicillin or an aminoglycoside).

Answer 43

Antagonism

Question 44

ANTAGONISM DRUGS

Answer 44

Ex: bacteriostatic drugs (chloramphamicol or a
tetracycline) and bactericidal drugs (penicillin or an aminoglycoside).

Question 45

Forms of Antimicrobial Synergy

Answer 45

1. Two drugs may sequentially block a microbial metabolic pathway
2. One drug may prevent the inactivation of a second drug by microbial
   enzymes
3. One drug may promote the uptake of a second drug thereby increasing the
   overall antimicrobial effect
4. One drug may affect the cell membrane and facilitate the entry of a second
   drug.
5. A drug combination may also prevent the emergence of resistant
   populations.

Question 46

Two drugs may sequentially block a microbial metabolic pathway. Ex:

Answer 46

sulphonamide with
trimethoprim (Folate antagonists)

Question 47

(synthesis of dihydrofolate needed for the growth of bacteria)

Answer 47

sulphonamide

Question 48

(Folate antagonists)

Answer 48

trimethoprim

Question 49

One drug may prevent the inactivation of a second drug by microbial
enzymes. Ex:

Answer 49

Inhibition of beta-lactamases by clavulanic acid

Question 50

can protect
penicillin G or other susceptible antibiotics from inactivation by bacteria that
produce beta-lactamase.

Answer 50

Inhibition of beta-lactamases by clavulanic acid

Question 51

One drug may promote the uptake of a second drug thereby increasing the
overall antimicrobial effect.Ex:

Answer 51

Penicillins

Question 52

It enhance aminoglycosides by for the
treatment of enterococcal endocarditis.

Answer 52

Penicillin

Question 53

One drug may affect the cell membrane and facilitate the entry of a second
drug. Ex:

Answer 53

Amphotericin B

Question 54

may be synergistic with flucytosine against
Cryptococcus neoformans.

Answer 54

Amphotericin B

Question 55

A drug combination may also prevent the emergence of resistant
populations. Ex:

Answer 55

erythromycin-rifampicin

Question 56

Drug against Rhodococcus equi infection in
foals.

Answer 56

erythromycin-rifampicin

Question 57

erythromycin-rifampicin against ________ infection in
foals.

Answer 57

Rhodococcus equi

Question 58

Considerations when administering two antimicrobial drugs

Answer 58

1. Drugs are not antagonistics to each other;
2. Treatment of mixed bacterial infections, where each drug has activity against
   one of the pathogens;
3. Treatment of severe infections of uncertain aetiology;
4. Use of synergistic combinations with documented efficacy against specific
   infections.

Question 59

Take note of the inherent disadvantages in combined antimicrobial treatment
regimens such as ___________ from the drugs used

Answer 59

additive toxic effect

Question 60

disadvantages in combined antimicrobial treatment
regimens such as increased risk of
superinfection with overgrowth of fungi or resistant bacteria and a danger of
enhanced spread of __________.

Answer 60

R plasmids