Antibiotics

Question 1

What are antibiotics?

Answer 1

Substances produced by
microbes, fungi, animal-based and plant-based organisms that have a powerful antibacterial, antimycotic, partially also antiviral and anti-tumour activity.

Question 2

Chemotheraphy

Answer 2

A systematic administration of substances with an antimicrobial effect.

Question 3

MIC

Answer 3

Minimum inhibitory concentration,
the lowest concentration of
antibiotics that inhibits the growth of microorganisms. Measured in micrograms per ml.

Question 4

Superinfection

Answer 4

The action of antibiotics, a portion of the normal microflora will also die.
Microbes that are otherwise in
balance/inhibited, will start to grow (such as Candida albicans).

Question 5

Hospital-acquired infection

Answer 5

An infection caused by the microbes existing in the hospital environment.

Question 6

Mechanisms of actions

Answer 6

1. Inhibit cell wall synthesis (bactericidal)
2. Inhibit cell membrane functions (bactericidal)
3. Inhibit microbial protein synthesis (bacteriostatic)
4. Impact microbial nucleic acid metabolism (bacteriostatic)

Question 7

Resistance

Answer 7

Microbes adapt to the substances that ae harmful to them, result of selection or adaption.
Capable of passing from one generation of bacteria to the next and from one type to another.

Question 8

Reasons for failures in ab treatment

Answer 8

Infection caused by resistant strain.
Transfer of resistant gene from one bacteria to another.
Treatment without bacterial diagnosis.

Question 9

Natural resistance

Answer 9

Natural barriers to certain ABs

Question 10

Aquired resistance

Answer 10

Mutations in bacterial chromosome

Question 11

Cross-resistance

Answer 11

Microbes resistant to one ab can be resistant to other AB with same action mechanism.

Question 12

Acquisition of Antimicrobial resistance

Answer 12

Mutation of genes involved in normal physiological processes and cellular structures.

Question 13

Transmission of resistant genes

Answer 13

Transformation, transduction, conjugation.
Plasmids: Extrachromosomal self-replicating elements which carry resistant genes.
Transposons: Fragments of DNA, cannot replicate themselves.
Integrons: Carried in plasmids

Question 14

Tetracyclines

Answer 14

Bacteriostatic, prevents protein synthesis.
Resistance occurs relatively quickly.
Cross-resistance with penicillins.

Pharmacokinetics:
Well absorbed in all administration routes. Penetrate the barriers of the organism well.
Accumulate into bones, forming a stable complex with calcium -> not recommended to young animals.
Eliminated through kidneys and in bile.

Toxicity:
Irritates - oral & injection
Vomiting, pain at injection site. Animal may collapse if administrate into vein.
Horses: diarrhea and enterocolitis.

Question 15

Chloramphenicol, thiamphenicol and florfenicol

Answer 15

Broad-spectrum, bacteriostatic, suppress the metabolism of microbes.
Chemically similar while toxicity and pharmacokinetics are different.

Chloramphenicol:
Most toxic existing ab drug, do not administer with other abs.
Do not use with barbiturates, phenylbutazone, xylazine and ketamine -> death.
Use locally due to extremely high toxicity -> eye & ear infections.
Toxicity: damages to bone marrow, suppress immune system.
Well absorbed in all adm. routes.

Thiamphenicol:
Chloramphenicol derivative, but lower toxicity and activity.
Absorbed and distributed well.

Florfenicol:
Derivate of thiamphenicol. Prolonged use may lead to bm damage.

Question 16

Fluoroquinolones

Answer 16

Broad spectrum
Bactericidal, inhibit DNA synthesis of microbes, resistence occurs relatively quickly.

Pharmacokinetics:
Well absorbed and distributed in all adm. routes. Metabolized in liver. May lead to joint cartilage erosions -> not rec. to youngs.

Question 17

Nitrofurans and nitroimidazoles

Answer 17

Bactericidal, toxic. Nitrofurans also carcinogenic and mutagenic. Dont use either one in farm animals.

Question 18

Rational use of antibiotics

Answer 18

1. Make sure it’s bacterial infection, ideally take a sample.
2. Select one narrow spectrum ab that acts against this specific agent
3. Broad spectrum abs are reserve preparations (if others are ineffective), used in case of mixed infections
4. Course of treatment should have optimal duration
   5.Correct doses and administration intervals
5. Correct combination

Question 19

Complex approach in the farm

Answer 19

1. Avoid unnecessary use of AB
2. Decrease necessity to treat
3. Avoid infections
4. When treatment necessary, do the best
5. Monitore the use of AB and antimicrobial resistance.

Question 20

Penicillin

Answer 20

Easily hydrolysable -> main reason for inactivation. It can happen either in syringe or in stomach.

Classification:
Natural and synthetic broad spectrum penicillins

Spectrum activity:
Streptococci, staphylococci, some G+ and G- bacteria

Absorption quick when adm. into muscle or subcutaneous.
Elimination and excretion mainly with urine.

Pharmacodynamics:
Bactericidal, inhibit microbial cell wall synthesis, outcome is lysis of the cell. Primarily act against gram+.

Toxicity lowest among abs. Most common side effect is allergy, hives, hypersalivation, vomiting, cramps.

Question 21

Macrolides and lincosamides

Answer 21

Macrolides:
Used if microbe is resistant to beta-lactam ABs. Bacteriostatic, bactericidal in large concentrations.

Pharmacokinetics, metabolism:
Absorbed well via all routes, distributed evenly. MB in liver.

Toxicity:
If adm. orally -> vomiting, diarrhea, hypersalivation, horses have most serious side effects

Lincosamides:
Chem similar to macrolides, bacteriostatic, acts against many G+ microbes.

Pharmacokinetics:
Abs. and distr. well if adm. orally or in muscle. MB in liver.

Toxicity:
Diarrhea in horses and rabbits
Cattle; lack of appetite, diarrhea, ketosis, decreased milk production

Question 22

Aminoglycosides

Answer 22

Bactericidal, against G- and some mycobacteria and mycoplasma.

Absorptionpoor in GI, good from muscle, short half life. Excreted through kidneys, accumulates there.

Interactions:
Synergistic activity with beta-lactam abs

Toxicity:
Some of the most toxic abs. Ototoxicity (hearing and balance problems) and nephrotoxicity (kidney weakening). Treatment must be a short as possible.

Question 23

Aminocyclitols: spectinomycin

Answer 23

Act against G-.
Less toxic compared to aminoglycosides.
Increased potency of neuromuscular blockade.

Question 24

Beta-lactams

Answer 24

Penicillin, cephalosporins, carbapenems, monobactams

Question 25

Cephalosporins

Answer 25

Semisynthetic ABs, bactericidal, adm. orally or parenterally

5 generations, 5th not used in vetmed.
1st gen: for streptococci, staphylococci, e. coli; narrow spectrum
2-4 broad spectrum

Low toxicity, allergy at injection site may occur.