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Questions and Answers
What is a common side effect associated with aminoglycosides such as streptomycin?
Which type of bacterial infections can tetracyclines treat effectively?
Why is neomycin not used systemically?
What major limitation is associated with the use of tetracyclines in pregnant women?
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Which antibiotic is associated with a risk of bone marrow suppression?
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What is the primary spectrum of activity of erythromycin?
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Which macrolide has an enhanced gram-negative spectrum and longer half-life?
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What is a significant side effect associated with clindamycin?
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Which antibiotic is specifically noted for its effectiveness against anaerobes?
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What type of infections is linezolid primarily used for?
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What is the main clinical use of telithromycin?
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What is a key feature of oxazolidinones like linezolid?
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Which of the following antibiotics is most widely used topically?
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What is a significant reason for limiting the use of tetracyclines in children?
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Which antibiotic is specifically noted for treating infections caused by multidrug resistant bacteria?
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Which of the following statements is true regarding chloramphenicol?
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Which of the following antibiotics is mainly used for preoperative bowel preparation?
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What is a clinical application for telithromycin?
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Which antibiotic is chemically unrelated to macrolides but has a similar mode of action?
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Which gram-positive bacterium is effectively treated with clindamycin?
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What type of resistance is NOT present with linezolid?
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Which of the following is a significant adverse effect associated with clindamycin?
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Which macrolide is known for having an enhanced spectrum against gram-negative bacteria?
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Which of the following infections are oxazolidinones mainly used to treat?
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Which antibiotic is effective against multi-drug resistant strains of pneumococci?
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Which statement is true regarding the use of clindamycin in dental infections?
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Study Notes
Aminoglycosides
- Streptomycin is used to treat tuberculosis and brucellosis.
- Gentamycin and tobramycin are widely used topically and in eye preparations.
- Neomycin is used orally, as it is not absorbed systemically.
Tetracyclines
- Tetracyclines are broad spectrum coverage including gram-positive and gram-negative rods and cocci, aerobics and anaerobics.
- Tetracyclines can be chelated by certain foods - reduce absorption.
- Tetracycline use in pregnancy and children is limited as it can cause calcium chelation, impairment of fetal long bone growth and dental discoloration.
- Tigecycline has a wide spectrum of activity against bacteria including those of multidrug resistant
- Tigecycline is a category D drug for pregnant women.
Chloramphenicol
- Chloramphenicol is broad spectrum, like tetracyclines.
- It is readily absorbed and diffused into most body compartments, including the cerebrospinal fluid (CSF).
- It is used to treat infections caused by Haemophilus influenzae, meningitis, typhoid fever, and Bacteroides fragilis.
- Side effects include bone marrow suppression and aplastic anemia.
Macrolides/Ketolides
- Erythromycin was the first macrolide antibiotic.
- Azithromycin and clarithromycin have enhanced gram-negative coverage compared to erythromycin.
- Azithromycin has a longer half-life.
- Telithromycin (ketolide) is used for community-acquired pneumonia, including those caused by multi-drug resistant pneumococci.
Lincosamide
- Clindamycin is chemically unrelated to macrolides, but has similar mechanisms of action and spectrum.
- A major side effect is pseudomembranous colitis.
- Clindamycin is used for oral acne treatment and dental infections.
- It penetrates bone better than most antibiotics, making it useful for osteomyelitis.
Oxazolidinones
- Linezolid is useful for pneumonia and infections caused by resistant strains of staphylococci, pneumococci, and enterococci.
- It has a high oral absorption, even when taken with food.
- It is relatively safe for short-term use.
- There is no cross-resistance with other antibiotics due to a unique site of action.
### Fluoroquinolones
- Ciprofloxacin:
- Similar activity to other fluoroquinolones.
- Used for acute exacerbation of chronic bronchitis (AECB), and community-acquired pneumonia (CAP).
- Levofloxacin:
- Same as Ciprofloxacin, with expanded gram-positive coverage, including penicillin-sensitive and resistant Streptococcus pneumoniae.
- Sparfloxacin:
- Same as Ciprofloxacin and Levofloxacin.
- Moxifloxacin:
- Same as previous generation fluoroquinolones, plus broad anaerobic coverage.
- Used for abdominal infections, nosocomial pneumonia, pelvic infections.
Rifamycins
- Rifampicin and rifabutin are bactericidal antibiotics from the rifamycin group.
- They inhibit RNA by inhibiting bacterial RNA polymerase, thereby preventing the production of mRNA, without affecting the RNA polymerase of human cells.
- Rifampicin is used primarily for the treatment of tuberculosis, in combination with other drugs.
- Rifampicin is also used for prophylaxis in close contacts of patients with meningitis caused by Neisseria meningitidis or Haemophilus influenzae.
- Rifampicin is given in combination with other drugs because resistant mutants appear at a high rate when it is used alone.
- Rifampicin causes orange discoloration of urine, saliva, and sweat.
- Rifampicin is excreted in high concentration in saliva, aiding in prophylaxis of bacterial meningitis.
### Antibacterial Drugs that Affect Metabolic Pathways
- Sulfonamides and trimethoprim are synthetic drugs that act by competing the normal substrate of an enzyme in a process called competitive inhibition.
- They interfere with folate metabolism by blocking enzymes required for the synthesis of tetrahydrofolate, which is needed by bacterial cells for the synthesis of folic acid and the eventual production of DNA and RNA and amino acids.
- Trimethoprim and sulfonamides are orally active and often given simultaneously to achieve a bactericidal synergistic effect.
Aminoglycosides
- Streptomycin treats Tuberculosis and Brucellosis, but can be ototoxic and nephrotoxic
- Gentamycin and Tobramycin are widely used topically in eye preparations
- Neomycin is orally used, but is used primarily for preoperative bowel preparation
Tetracyclines
- Tetracyclines are effective against gram-positive and negative rods and cocci, including aerobic and anaerobic bacteria
- They can be orally absorbed, but are chelated by some foods
- They should be limited in pregnant women and children due to calcium chelation, and problems with fetal long bone growth and dental discoloration
- Tigecycline is a wide spectrum tetracycline, and can treat multi-drug resistant infections.
Chloramphenicol
- Chloramphenicol has a broad spectrum similar to tetracyclines, including Haemophilus influenzae, meningitis, typhoid fever, and Bacteroides fragilis
- It is readily absorbed and diffused into many body compartments, including the CSF
- Though effective against serious infections, its use is limited due to its strong potential for bone marrow suppression and aplastic anemia
Macrolides/Ketolides
- Erythromycin was the first macrolide, with a higher activity against gram-positive bacteria
- Other macrolides include Azithromycin and Clarithromycin, which have an expanded gram-negative spectrum and longer half-lives, and are used to treat H pylori in combination with other agents
- Telithromycin (ketolide) treats community-acquired pneumonia, including multi-drug resistant pneumococci.
Lincosamide
- Clindamycin is chemically unrelated to macrolides, and is active against both gram-positive and negative anaerobes
- Pseudomembranous colitis is a serious side effect
- Clindamycin is effective against acne and is commonly used as a topical treatment
- Clindamycin penetrates bone better than most antibiotics, and is used in osteomyelitis
Oxazolidinones
- Linezolid is effective in pneumonia and soft tissue infections, especially against resistant bacteria
- It has high oral absorption, even with food
- High safety, unless taken for extended periods
- Unique site of action, leading to no cross-resistance
Fluoroquinolones
- Ciprofloxacin is used for Acute Exacerbation of Chronic Bronchitis (AECB), and community-acquired pneumonia, including penicillin-sensitive and resistant bacteria.
- Levofloxacin and Sparfloxacin are effective against an expanded gram-positive spectrum
- Moxifloxacin has a broad anaerobic spectrum in addition to its gram-positive spectrum, treating abdominal infections, nosocomial pneumonia, and pelvic infections.
Rifampicin and Rifabutin
- They are bactericidal antibiotics that inhibit bacterial RNA polymerase, preventing the production of mRNA
- They are used for the treatment of tuberculosis, in combination with other drugs
- Rifampicin is used as prophylaxis in close contacts of patients with meningitis caused by either N.meningitidis or H.influenzae.
- It is given in combination to avoid resistance
- It is excreted in saliva, which is why it works for the prophylaxis of bacterial meningitis.
Sulfonamides and Trimethoprim
- They are synthetic drugs that inhibit folate metabolism
- They block enzymes needed for the synthesis of tetrahydrofolate, which is required by bacterial cells for the synthesis of folic acid, DNA, RNA, and amino acids
- They are orally active and often given together for a synergistic bactericidal effect.
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Description
This quiz focuses on the uses, mechanisms, and precautions associated with aminoglycosides, tetracyclines, and chloramphenicol. Learn about the critical applications of these antibiotics, including their spectrum of activity and the impact on special populations such as pregnant women. Test your knowledge on how these drugs function and their clinical significance.
