Antibiotics Overview Quiz

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Questions and Answers

What is the primary mechanism by which chloramphenicol exerts its antibacterial effect?

Inhibition of bacterial cell wall synthesis

Inhibition of bacterial folate synthesis

Disruption of bacterial DNA replication

Interference with bacterial protein synthesis (correct)

Which of the following is a major concern associated with the use of chloramphenicol?

Potential for serious and fatal aplastic anemia (correct)

Development of severe allergic reactions

Significant gastrointestinal upset and diarrhea

High risk of bacterial resistance development

What is the primary route of excretion for chloramphenicol in cats?

A combination of kidneys and bile (correct)

Through the kidneys

Through the bile

Through the liver

Which of the following is TRUE regarding the pharmacokinetics of chloramphenicol in horses?

The half-life is longer in foals than in adult horses (C) Signup and view all the answers

What is the primary reason for the limited use of chloramphenicol in food animals?

Potential for residues in meat and milk (A) Signup and view all the answers

Which of the following groups of bacteria is NOT typically susceptible to chloramphenicol?

Mycoplasma (B) Signup and view all the answers

What is the primary difference between chloramphenicol and florfenicol?

Florfenicol is a thiamphenicol derivative, while chloramphenicol is not (A) Signup and view all the answers

When administered intramuscularly, what is a potential side effect of florfenicol?

Local tissue reaction (B) Signup and view all the answers

Which of these are considered "old" tetracyclines?

Oxytetracycline (B), Tetracycline (C) Signup and view all the answers

What is the primary concern with tetracycline chelation?

It can decrease the effectiveness of the drug (B) Signup and view all the answers

What is the primary advantage of "new" tetracyclines over "old" tetracyclines?

They have a wider range of effective bacterial targets (C) Signup and view all the answers

Which route of administration is most reliable for achieving consistent concentrations of oxytetracycline?

Intramuscular (D) Signup and view all the answers

What unique quality of tetracyclines makes them well-suited for tackling certain infections?

They can directly penetrate and kill bacteria that reside within mammalian cells (B) Signup and view all the answers

Which of the following is a potential side effect of injecting Zeleris® in a location other than the neck?

More severe tissue reaction at the injection site (C) Signup and view all the answers

Which of these are targets for tetracyclines' antimicrobial activity?

Rickettsial diseases (A), Protozoa (C) Signup and view all the answers

What is a significant concern when using tetracyclines in young animals?

Injury to developing tooth enamel (B) Signup and view all the answers

Which of the following tetracyclines is specifically mentioned as being used to treat Rocky Mountain Spotted Fever?

Doxycycline (D) Signup and view all the answers

Which of the following is a major concern when administering aminoglycosides?

Nephrotoxicity associated with Gentamycin (B) Signup and view all the answers

Neomycin is primarily administered via which route?

Parenterally (B) Signup and view all the answers

Which of the following formulations is recommended for large animals?

Liquamycin® (B) Signup and view all the answers

What effect do aminoglycosides have on bacterial cells?

Primarily bactericidal, inhibiting protein synthesis (D) Signup and view all the answers

Which of the following is a characteristic of doxycycline as a second-generation tetracycline?

Effective against hemobartonella infection (B) Signup and view all the answers

What is an important precaution to take when using tetracyclines in horses?

Never give intravenously to horses (A) Signup and view all the answers

What was the suspected cause of the cat's elevated BUN and creatinine levels after administration of gentamicin?

Gentamicin nephrotoxicosis (C) Signup and view all the answers

Which condition did necropsy reveal following the euthanasia of the cat?

Necrosis of the proximal convoluted tubule (A) Signup and view all the answers

What was the consequence of administering gentamicin directly onto the wound and subcutaneously?

Increased plasma concentrations of gentamicin (D) Signup and view all the answers

What is a necessary precaution when administering gentamicin to prevent nephrotoxicity?

Keeping the animal well-hydrated (C) Signup and view all the answers

What alternative was used in place of gentamicin after suspected nephrotoxicosis was indicated?

Ampicillin (C) Signup and view all the answers

Which of the following is NOT a common aminoglycoside?

Rifampin (D) Signup and view all the answers

What significant appearance can be expected in urine when using rifampin?

Red-orange color (A) Signup and view all the answers

Which administration route is NOT applicable for Amikacin sulfate?

Orally (B) Signup and view all the answers

Which class of drugs inhibits bacterial protein synthesis and can be either bacteriostatic or bactericidal?

Lincosamides (D) Signup and view all the answers

What is a common use for Erythromycin in veterinary medicine?

Management of respiratory diseases (C) Signup and view all the answers

Why are rifamycins like Rifampin administered in combination with other antimicrobials?

To reduce the risk of antibiotic resistance development (A) Signup and view all the answers

Which Lincosamide is particularly effective for antibiotic-resistant bacteria?

Clindamycin (A) Signup and view all the answers

What condition is Tylosin primarily used to manage in dogs and cats?

Colitis (C) Signup and view all the answers

What is a characteristic of Macrolides in terms of their action on bacteria?

They can be bacteriostatic. (B) Signup and view all the answers

What is the primary application of Tilmicosin?

Control of respiratory disease in cattle and sheep (C) Signup and view all the answers

Which Gram-positive bacteria can develop resistance to rifamycins rapidly?

Mycobacteria (A) Signup and view all the answers

Which class of drugs is known to be synergistic with lincomycin?

Macrolides (B) Signup and view all the answers

What is a primary concern when using Erythromycin in livestock?

Potential hepatotoxicity (B) Signup and view all the answers

Study Notes

Antibiotics

Chloramphenicol
- Interferes with microbial protein synthesis, attaching to ribosomes, preventing vital protein production.
- Bacteriostatic at low doses, inhibiting the action of penicillins and cephalosporins.
- Bactericidal at high doses (high concentrations).
- Major concern: affects mitochondrial function in bone marrow cells, causing serious and fatal aplastic anemia in humans.
- Not used in food animals.
- Poor liver metabolism in cats, excreted via kidneys/bile.
Tetracyclines
- Bacteriostatic, inhibits bacterial protein synthesis.
- Resistance is common.
- Synergistic with other antibiotics, like tetracycline.
- Variable absorption among different types.
- Older tetracyclines are hydrophilic.
- Newer tetracyclines are lipophilic.
- Tetracycline & oxytetracycline can be chelated (bound to minerals).
Aminoglycosides
- Inhibit protein synthesis, causing bacterial cell division inhibition.
- Mostly bactericidal (dose-related).
- All administered parenterally (except neomycin).
- Major concerns include nephrotoxicity (100% excreted via kidney), and ototoxicity (rare, increased risk with diuretics).
- Mostly remain in extracellular fluid.
Rifamycins
- Not an aminoglycoside, but used mostly in horses.
- Combined with b-lactams and doxycycline.
- Resistance to rifampin is common.
- Red-orange coloration of urine, tears, and saliva in horses.
- Wear gloves when handling.
Aminocyclitols: Lincosamides and Macrolides
- Inhibit bacterial protein synthesis (bacteriostatic or bactericidal, depending on the drug).

Chloramphenicol (CAP) Considerations

Resistance can be a problem, potentially involving cross-resistance with other antibiotics.
Synergistic with tetracycline.
Rapid absorption in all tissues.
Intravenous (IV), intramuscular (IM), or oral (PO) administration.
IV dosing is 4-5 times per day due to absorption.
Some CAP is excreted unchanged by the kidneys, useful for urinary tract infections.
- T1/2:
  - Horses: 1 hour or less.
  - Foals: 6+ hours.
  - Cats: 5-6 hours (much lower doses).
  - Dogs: 3-4 hours.
Common forms include: Azramycine®, Centracol®, Chlor Palm®, Chlor Tablets®, Karomycin Palmitate®, Rogar Mycine®, Zoommycetine® Palmitate.
Available as tablets, oral suspension, and injections.
Well-absorbed, especially orally, and widely distributed.

Florfenicol (Nuflor®)

Related to chloramphenicols, but modified.
Safely used in cattle for respiratory disease, pneumonia, and foot rot.
Dosage: 2 x IM injections (20mg/kg, 48 hours apart) or 1 x SQ high dose injection (40mg/kg).
Withdrawal time: 38 days.
IM injection may cause tissue reactions, potentially leading to trim loss.
Tissue reaction is more severe outside the neck region.

Zeleris®

Approved in 2020.
Medicinal ingredients: florfenicol, meloxicam.
Used for bovine respiratory disease with accompanying fever.
Associated pathogens: Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni.
Approved for beef and non-lactating dairy cattle.

Tetracycline

Bacteriostatic - binds to bacterial ribosomes, preventing transfer RNA from linking.
Inhibits bacterial cellular function and division.
Used for many years, significant resistance.
Bacteria actively take up tetracycline and concentrate it in the cell.
- Benefits from absorption are improved penetration of tissues.
Gram positives, gram negatives, rickettsial diseases.
Concerns: Variable absorption, older forms are hydrophilic, newer are lipophilic, they chelate.
- Avoid in animals 4-16 weeks old, because it binds to developing tooth enamel.

Aminoglycosides Considerations

Specific aminoglycosides like gentamycin is the most nephrotoxic, thus urine monitoring for casts is important.
Longer intervals between doses may reduce toxic blood levels.

Rifamycins Considerations

Resistant to rifamycin may develop rapidly in a one-step process, so it is often used in combinations.
- Gram-positive: mycobacteria
- Gram-negative: chlamydia
- Anaerobes
Several viruses (@high concentrations).
- Red-orange colored urine, tears and saliva (+ sweat) in horses.

Aminocyclitols Considerations

Lincosamides and Macrolides are bacteriostatic or bactericidal, depending on the substance.
Good for bacteria resistant to penicillins and cephalosporins, and works on anaerobes.

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Description

Test your knowledge on various antibiotics such as Chloramphenicol, Tetracyclines, and Aminoglycosides. This quiz covers their mechanisms, effects, and important considerations in usage. Perfect for veterinary or microbiology students.