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Questions and Answers
Which enzyme is inhibited by fluoroquinolones, leading to their antimicrobial activity?
Which enzyme is inhibited by fluoroquinolones, leading to their antimicrobial activity?
- DNA polymerase
- RNA helicase
- DNA gyrase (correct)
- RNA polymerase
In the context of antimetabolites, what reactive free radicals are formed by the prodrug Metronidazole that are directly toxic to DNA?
In the context of antimetabolites, what reactive free radicals are formed by the prodrug Metronidazole that are directly toxic to DNA?
- Nitrogen radicals
- Nitric oxide
- Oxygen ions
- Hydroxyl radicals (correct)
What is the first-line use of fluoroquinolones like levofloxacin and moxifloxacin?
What is the first-line use of fluoroquinolones like levofloxacin and moxifloxacin?
- Osteomyelitis (correct)
- MRSA infections
- Urinary tract infections
- Anaerobic infections
What condition poses a higher risk of anemia in patients taking Sulfamethoxazole + Trimethoprim (SMX/TMP)?
What condition poses a higher risk of anemia in patients taking Sulfamethoxazole + Trimethoprim (SMX/TMP)?
Which fluoroquinolone is the only active agent against anaerobic infections on its own?
Which fluoroquinolone is the only active agent against anaerobic infections on its own?
Which type of killing is associated with the statement 'the LONGER the antibiotic concentration stays above MIC, the greater the extent of killing'?
Which type of killing is associated with the statement 'the LONGER the antibiotic concentration stays above MIC, the greater the extent of killing'?
Which of the following antibiotics is an example of concentration dependent killing according to the text?
Which of the following antibiotics is an example of concentration dependent killing according to the text?
What is the mechanism of action of Sulfamethoxazole + Trimethoprim (SMX/TMP)?
What is the mechanism of action of Sulfamethoxazole + Trimethoprim (SMX/TMP)?
What distinguishes Empiric Therapy from Targeted Therapy?
What distinguishes Empiric Therapy from Targeted Therapy?
Which unique toxicity is associated with Sulfamethoxazole + Trimethoprim (SMX/TMP)?
Which unique toxicity is associated with Sulfamethoxazole + Trimethoprim (SMX/TMP)?
What is the advantage of using Empiric Therapy according to the text?
What is the advantage of using Empiric Therapy according to the text?
What is a common indication for Sulfamethoxazole + Trimethoprim (SMX/TMP)?
What is a common indication for Sulfamethoxazole + Trimethoprim (SMX/TMP)?
What does a Loading Dose (LD) refer to in antimicrobial pharmacokinetics?
What does a Loading Dose (LD) refer to in antimicrobial pharmacokinetics?
Which of the following is not a known toxicity associated with SMX/TMP?
Which of the following is not a known toxicity associated with SMX/TMP?
What is the mechanism of action of Sulfamethoxazole alone?
What is the mechanism of action of Sulfamethoxazole alone?
What is the significance of the Minimum Inhibitory Concentration (MIC) of an antibiotic?
What is the significance of the Minimum Inhibitory Concentration (MIC) of an antibiotic?
Which statement accurately describes the Minimum Bacteriostatic Concentration (MBC) of an antibiotic?
Which statement accurately describes the Minimum Bacteriostatic Concentration (MBC) of an antibiotic?
If the MBC:MIC ratio is 2, how is the antibiotic classified in terms of its effect on the bacteria?
If the MBC:MIC ratio is 2, how is the antibiotic classified in terms of its effect on the bacteria?
In terms of antibiotic action, what does it mean if an antibiotic is considered bacteriostatic?
In terms of antibiotic action, what does it mean if an antibiotic is considered bacteriostatic?
What does it mean when it is said that increasing the concentration of a bacteriostatic antibiotic high enough will turn it into bactericidal?
What does it mean when it is said that increasing the concentration of a bacteriostatic antibiotic high enough will turn it into bactericidal?
How do Sulfamethoxazole and Trimethoprim (SMX/TMP) work synergistically to prevent bacterial DNA synthesis?
How do Sulfamethoxazole and Trimethoprim (SMX/TMP) work synergistically to prevent bacterial DNA synthesis?
Which enzyme is targeted by Sulfamethoxazole in bacterial DNA synthesis?
Which enzyme is targeted by Sulfamethoxazole in bacterial DNA synthesis?
What type of infections are Sulfamethoxazole + Trimethoprim (SMX/TMP) NOT reliably active against?
What type of infections are Sulfamethoxazole + Trimethoprim (SMX/TMP) NOT reliably active against?
Which of the following is an indication for the use of Sulfamethoxazole + Trimethoprim (SMX/TMP)?
Which of the following is an indication for the use of Sulfamethoxazole + Trimethoprim (SMX/TMP)?
How does Trimethoprim work to inhibit bacterial DNA synthesis in combination with Sulfamethoxazole?
How does Trimethoprim work to inhibit bacterial DNA synthesis in combination with Sulfamethoxazole?
Which class of antibiotic inhibitors targets key steps in nucleic acid synthesis during the replication cycle?
Which class of antibiotic inhibitors targets key steps in nucleic acid synthesis during the replication cycle?
What is the mechanism of action of Sulfamethoxazole (SMX) in bacterial DNA synthesis?
What is the mechanism of action of Sulfamethoxazole (SMX) in bacterial DNA synthesis?
Which antibiotic combination has no reliable coverage against Pseudomonas infections?
Which antibiotic combination has no reliable coverage against Pseudomonas infections?
What is the primary target of Trimethoprim (TMP) in bacterial DNA synthesis when combined with Sulfamethoxazole?
What is the primary target of Trimethoprim (TMP) in bacterial DNA synthesis when combined with Sulfamethoxazole?
What distinguishes Minimum Inhibitory Concentration (MIC) from Minimum Bactericidal Concentration (MBC)?
What distinguishes Minimum Inhibitory Concentration (MIC) from Minimum Bactericidal Concentration (MBC)?
In the context of antibiotics, what does it mean if an antibiotic is considered bacteriostatic?
In the context of antibiotics, what does it mean if an antibiotic is considered bacteriostatic?
Which antibiotic is no longer used first line to treat uncomplicated C. diff infection?
Which antibiotic is no longer used first line to treat uncomplicated C. diff infection?
What is the unique toxicity associated with Nitrofurantoin use?
What is the unique toxicity associated with Nitrofurantoin use?
What unique toxicity is associated with Mycobacterial Inhibitors?
What unique toxicity is associated with Mycobacterial Inhibitors?
Which antibiotic is a DNA synthesis inhibitor and can cause discoloration of body fluids?
Which antibiotic is a DNA synthesis inhibitor and can cause discoloration of body fluids?
In terms of antibiotic action, what does it mean if an antibiotic is considered bacteriostatic?
In terms of antibiotic action, what does it mean if an antibiotic is considered bacteriostatic?
What is the specific combination drug for latent tuberculosis?
What is the specific combination drug for latent tuberculosis?
Which antibiotic should be coadministered with vitamin B6 (pyridoxine) to prevent neuropathy?
Which antibiotic should be coadministered with vitamin B6 (pyridoxine) to prevent neuropathy?
What is the role of Minimum Inhibitory Concentration (MIC) in determining antibiotic efficacy?
What is the role of Minimum Inhibitory Concentration (MIC) in determining antibiotic efficacy?
What distinguishes concentration dependent killing from time dependent killing of antibiotics?
What distinguishes concentration dependent killing from time dependent killing of antibiotics?
Which antibiotics are examples of concentration dependent killing according to the text?
Which antibiotics are examples of concentration dependent killing according to the text?
What is the primary advantage of using targeted therapy over empiric therapy?
What is the primary advantage of using targeted therapy over empiric therapy?
What is the significance of the Minimum Inhibitory Concentration (MIC) in determining antibiotic efficacy?
What is the significance of the Minimum Inhibitory Concentration (MIC) in determining antibiotic efficacy?
Which enzyme is targeted by fluoroquinolones to exert their antimicrobial activity?
Which enzyme is targeted by fluoroquinolones to exert their antimicrobial activity?
What is the primary difference between empiric therapy and targeted therapy?
What is the primary difference between empiric therapy and targeted therapy?
What does the term Loading Dose (LD) refer to in antimicrobial pharmacokinetics?
What does the term Loading Dose (LD) refer to in antimicrobial pharmacokinetics?
Which statement accurately describes the Minimum Bactericidal Concentration (MBC) of an antibiotic?
Which statement accurately describes the Minimum Bactericidal Concentration (MBC) of an antibiotic?
What is the significance of the Minimum Bactericidal Concentration (MBC) of an antibiotic?
What is the significance of the Minimum Bactericidal Concentration (MBC) of an antibiotic?
What distinguishes bacteriostatic antibiotics from bactericidal antibiotics?
What distinguishes bacteriostatic antibiotics from bactericidal antibiotics?
Which type of antibiotic action is associated with an MBC:MIC ratio greater than 4?
Which type of antibiotic action is associated with an MBC:MIC ratio greater than 4?
In terms of antibiotic classification based on MBC:MIC ratio, what does a ratio less than or equal to 4 indicate?
In terms of antibiotic classification based on MBC:MIC ratio, what does a ratio less than or equal to 4 indicate?
What happens theoretically when increasing the concentration of a bacteriostatic antibiotic high enough?
What happens theoretically when increasing the concentration of a bacteriostatic antibiotic high enough?
Which antibiotic action is associated with an MBC:MIC ratio greater than 4 in antimicrobial testing?
Which antibiotic action is associated with an MBC:MIC ratio greater than 4 in antimicrobial testing?
Which antibiotic is a prodrug that forms reactive free radicals directly toxic to bacterial DNA?
Which antibiotic is a prodrug that forms reactive free radicals directly toxic to bacterial DNA?
In the context of antibiotics, what does the Minimum Inhibitory Concentration (MIC) measure?
In the context of antibiotics, what does the Minimum Inhibitory Concentration (MIC) measure?
What is the unique toxicity associated with fluoroquinolones like ciprofloxacin and levofloxacin?
What is the unique toxicity associated with fluoroquinolones like ciprofloxacin and levofloxacin?
Which antibiotic is used first-line in osteomyelitis if the bacteria is sensitive to it?
Which antibiotic is used first-line in osteomyelitis if the bacteria is sensitive to it?
What does the Minimum Bactericidal Concentration (MBC) of an antibiotic represent?
What does the Minimum Bactericidal Concentration (MBC) of an antibiotic represent?
Which antibiotic is mainly active against Gram-negative infections and is used topically as ear drops for otic infections?
Which antibiotic is mainly active against Gram-negative infections and is used topically as ear drops for otic infections?
What is the mechanism of action for nitrofurantoin in inhibiting bacterial growth?
What is the mechanism of action for nitrofurantoin in inhibiting bacterial growth?
Which antibiotic forms reactive free radicals that are toxic to DNA, functioning as a mycobacterial inhibitor?
Which antibiotic forms reactive free radicals that are toxic to DNA, functioning as a mycobacterial inhibitor?
Study Notes
Bacterial DNA Synthesis Inhibitors
- Inhibit bacteria by targeting key steps in nucleic acid synthesis during the replication cycle
- Subdivided into two classes: Antimetabolites (pseudo-analogs) and Direct enzyme inhibitors blocking synthesis of DNA
Antimetabolites
- Sulfamethoxazole + Trimethoprim (SMX/TMP)
- Sulfamethoxazole is a structural analog of para-amino benzoic acid (PABA)
- Competes with PABA for dihydropteroate synthase (DHPS) to stop DNA synthesis
- Trimethoprim is a structural analog of folate
- Competes with folate for dihydrofolate reductase (DHFR) to stop DNA synthesis
- SMX+TMP work synergistically to prevent bacterial DNA synthesis
- Active against Gram positive and Gram negative infections, including MRSA infections
- No reliable pseudomonas coverage
- First line option for E.coli (e.g. urinary tract infections), pneumocystis pneumonia (PCP), and toxoplasmosis in immunocompromised patients (e.g. AIDS)
Direct Enzyme Inhibitors
- Fluoroquinolones (FQ)
- Inhibit bacterial topoisomerase II (aka DNA gyrase)
- Mainly active against Gram negative infections
- Used FIRST LINE in osteomyelitis (only if the bacteria is sensitive)
- "Respiratory FQ" are levofloxacin and moxifloxacin
- Ciprofloxacin is an option to treat urinary tract infections
- Ofloxacin is used topically as ear drops for otic infections
- Only agent active against MRSA is delafloxacin
- Only agent active against anaerobic infection on its own is moxifloxacin
- Metronidazole
- Prodrug, forms reactive free radicals that are directly toxic to DNA
- Mainly active against anaerobic infections (below the diaphragm)
- First line treatment for trichomonas vaginalis infection and bacterial vaginosis (BV)
- Used in combination with FQ to treat intra-abdominal infections (e.g. fistulas in patients with inflammatory bowel disease)
- Nitrofurantoin
- Broad spectrum, active against Gram positive and Gram negative organisms
- Used primarily in urinary tract infections
- Unique toxicity: Pulmonary fibrosis
Mycobacterial Inhibitors
- Rifapentine+isoniazid is for latent TB
- Dapsone is for leprosy (in combo with rifampin)
- All of them cause hepatotoxicity
- Unique toxicity: DNA synthesis inhibitor, Induction of hepatic enzymes, Discoloration of body fluids
Mechanisms of Action
- Isoniazid: Mycolic acid cell wall inhibitor
- Pyrazinamide: Unknown
- Ethambutol: Mycolic acid cell wall inhibitor
- Rifampin/Rifapentine: Rifampin, Isoniazid, Pyrazinamide, and Ethambutol (RIPE) are for active tuberculosis (TB)
Antibiotic Summary
- Concentration dependent killing: The HIGHER the antibiotic concentration is above the MIC, the greater the extent of killing
- Time dependent killing: The LONGER the antibiotic concentration stays above MIC, the greater the extent of killing
- Bacteriostatic: An antibiotic that slows down the growth of bacteria
- Bactericidal: An antibiotic that kills bacteria
- Empiric Tx: Broad spectrum antibiotic used until lab data comes back
- Targeted Tx: Narrow spectrum antibiotic selected based on known identity and sensitivity of the causative organism
Basics of Antimicrobial Pharmacokinetics
- Loading dose (LD): The amount of drug needed to achieve a therapeutic level in the body
- Minimum Inhibitory Concentration (MIC): The concentration of antibiotic that inhibits visible bacterial growth at 24 hours
- Minimum Bactericidal Concentration (MBC): The concentration of antibiotic that results in a 1,000-fold reduction in bacterial density at 24 hours
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Description
Test your knowledge on key information about Metronidazole and Nitrofurantoin, including their uses, indications, and toxicities. Explore their roles in treating different infections and understand their clinical significance.
