Antimicrobial Use in Diseased Animals

Questions and Answers

What is a characteristic of bacteriostatic agents?

They are always more effective than bactericidal agents.

They inhibit bacterial growth and require the immune system to eliminate bacteria. (correct)

They kill all types of bacteria instantly.

They work independently of the patient's defense mechanism.

What can happen when bacteriostatic agents are given at very high doses?

They have no added effect on bacterial infection.

They trigger an immediate immune response.

They become ineffective against all bacterial strains.

They may exhibit bactericidal properties. (correct)

Which mechanism of action is NOT associated with bacteriostatic agents?

Inhibitors of cell wall synthesis

Inhibitors of nucleic acid functions

Inhibitors of protein synthesis

Inhibitors of toxin production (correct)

Which of the following statements regarding bacteriostatic agents is true?

They can kill susceptible bacteria in certain conditions. Signup and view all the answers

What is a potential consequence of using agents that kill normal bacterial flora?

Higher risk of superinfection due to loss of bacterial inhibition. Signup and view all the answers

What defines intrinsic resistance in bacteria?

Resistance due to lack of antimicrobial target sites Signup and view all the answers

Which antibiotic is produced by Streptomyces griseus?

Streptomycin Signup and view all the answers

How is acquired resistance different from intrinsic resistance?

It occurs due to genetic alterations through mutations or gene transfer. Signup and view all the answers

What is the primary purpose of using antimicrobial drugs at subtherapeutic concentrations in animals?

To promote growth and improve feed efficiency Signup and view all the answers

What is an example of a mechanism through which acquired resistance occurs?

Sharing of genetic material via plasmids Signup and view all the answers

Which of the following best describes prophylaxis in the context of antimicrobial use in animals?

Use of antimicrobials in healthy animals to prevent infection Signup and view all the answers

Which antibiotic is known to be ineffective against Gram-negative bacteria?

Penicillin Signup and view all the answers

Which of the following is correctly matched to its producing organism?

Neomycin - S. kanamyceticus Signup and view all the answers

Which mechanism of action is NOT suggested for how subtherapeutic antibiotics enhance growth?

Increase of harmful metabolites in the gut Signup and view all the answers

What is the significance of Gram-negative bacteria having intrinsic resistance to certain antibiotics like penicillin?

They possess a resilient cell wall structure. Signup and view all the answers

What does the term 'metaphylaxis' refer to in antimicrobial use?

Use in animals vulnerable to outbreaks after exposure Signup and view all the answers

Which of the following antibiotics is produced by Penicillium notatum?

Penicillin Signup and view all the answers

What is the Chemotherapeutic Triangle in relation to antimicrobial therapy?

The interrelationships among the host, pathogen, and drug Signup and view all the answers

Which of the following is an independent effect of using subtherapeutic antimicrobial drugs?

Anti-inflammatory effects unrelated to gut microbiota Signup and view all the answers

Why is the exact mechanism by which subtherapeutic antibiotics enhance growth poorly understood?

Multiple potential modes of action complicate understanding Signup and view all the answers

Which of the following factors is NOT considered in effective antimicrobial therapy?

The socioeconomic status of the animal owner Signup and view all the answers

What type of antibiotic is bacitracin categorized as?

A branched, cyclic decapeptide antibiotic Signup and view all the answers

Which mechanism allows bacitracin to kill bacteria?

Inhibition of peptidoglycan synthesis Signup and view all the answers

What is a common side effect related to the administration of certain antibiotics mentioned in the context?

Gastrointestinal disturbances Signup and view all the answers

Which dosage is recommended for cefotaxime in dogs and cats?

25-50 mg per kg Signup and view all the answers

What is required for bactericidal activity of bacitracin?

Presence of divalent cations like zinc Signup and view all the answers

Which cephalosporin antibiotic retains efficacy despite bacterial β-lactamase production?

Ceftiofur Signup and view all the answers

What is the maximum recommended dosage of cefadroxil for dogs and cats?

22 mg per kg Signup and view all the answers

Which adverse effect is associated with intravenous injection of certain antibiotics?

Thrombophlebitis Signup and view all the answers

Which type of antimicrobial use is primarily focused on disease prophylaxis in feedlot calves?

Metaphylactic use Signup and view all the answers

What is the primary route of administration for therapeutic antimicrobial use?

Injection Signup and view all the answers

Which type of antimicrobial use is intended for growth promotion in healthy animals?

Subtherapeutic use Signup and view all the answers

In what scenario might some non-diseased animals be included in therapeutic antimicrobial use?

During metaphylactic treatment of groups Signup and view all the answers

What is the goal of prophylactic antimicrobial use?

To prevent the onset of disease Signup and view all the answers

Study Notes

Antimicrobial Use Types

Therapeutic Use: Treatment of clinically ill animals; includes preventing/control of disease.
Metaphylactic Use: Disease prophylaxis in vulnerable animals, often conducted during outbreaks; typically given by injection or in feed/water.
Prophylactic Use: Prevention of diseases in groups; often applied to healthy populations at risk but may include subclinical animals.
Subtherapeutic Use: Enhances growth and feed efficiency groupwise; does not show evident disease resistance.

Mechanism of Subtherapeutic Use

Enhances growth likely through:
- Suppression of normal intestinal bacteria increasing nutrient availability.
- Reduction of harmful bacterial metabolites.
- Thinning of the intestinal wall for better nutrient absorption.
- Anti-inflammatory effects unrelated to gut microbiota.
- Inhibition of subclinical diseases.

Chemotherapeutic Triangle

Effective therapy requires understanding:
- Interactions between host animal, pathogen, and drug.
- Use of antimicrobials may disrupt normal bacteria, leading to superinfections.

Bacteriostatic vs. Bactericidal

Bacteriostatic Agents: Inhibit bacterial growth; require the host's immune response to eliminate bacteria.
May temporarily antagonize some bactericidal drugs but can be effective at high doses or in high concentrations.
Mechanisms of Action:
- Inhibition of cell wall synthesis.
- Disruption of cell membranes.
- Interference with protein synthesis.
- Inhibition of nucleic acid functions.
- Inhibition of folate cofactor synthesis.

Common Antibiotics and Their Origins

Gentamicin: Micromonaspora purpurea
Kanamycin: S. kanamyceticus
Penicillin: Penicillium notatum; P. chrysogenum
Oxytetracycline: Streptomyces rimosus
Streptomycin: Streptomyces griseus

Bacterial Resistance Mechanisms

Intrinsic Resistance: Natural characteristics of bacteria that prevent susceptibility to certain antibiotics (e.g., gram-negative bacteria’s resistance to penicillin).
Acquired Resistance: Results from genetic alterations; resistance genes can be acquired through mutations or horizontal gene transfer via plasmids.

Antibiotic Side Effects and Toxicities

Gastrointestinal issues such as nausea, vomiting, diarrhea.
Local irritation, pain from injections, and complications like thrombophlebitis from IV administration.

Dose Rates for Penicillins

Cefadroxil: Dogs/cats 22 mg, Horses 25 mg.
Cephalexin: Dogs/cats 22 mg; Horses 22-33 mg.
Ceftiofur: Cattle 1 mg by IM; intervals vary by species.

Bacitracin

Cyclic decapeptide antibiotic; Bacitracin A is the most active form.
Mechanism: Inhibits bacterial cell wall synthesis and function by blocking phosphorylase reactions.
Requires divalent cations like zinc for bactericidal activity.

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Description

This quiz covers the types, purposes, and methods of antimicrobial administration in diseased animals. It includes therapeutic uses and various routes of administration such as injection, feed, and water. Test your knowledge on this critical aspect of veterinary medicine.