Antimicrobial Agents Practice Questions

Q: Drugs of choice for MRSA in skin and soft tissue infections are:

Vancomycin, Linezolid. ***Vancomycin, Linezolid*** - **Vancomycin** is a cornerstone for treating **MRSA** infections, particularly severe ones, due to its efficacy against resistant staphylococci. - **Linezolid** is an alternative for **MRSA** infections, especially in cases of vancomycin resistance or intolerance, and offers good oral bioavailability. *Clindamycin, Vancomycin* - While **vancomycin** is correct, **clindamycin** has varying efficacy against **MRSA** and high rates of inducible resistance, making it less reliable as a primary drug of choice. - Clindamycin's use for MRSA often requires initial susceptibility testing, including a **D-test**, to rule out inducible clindamycin resistance. *Vancomycin, Teicoplanin* - **Vancomycin** is a primary **MRSA** drug, but **teicoplanin** is largely used in Europe and is structurally similar to vancomycin, often reserved for cases where vancomycin is not tolerated or preferred. - While effective, **teicoplanin** is not as universally recognized as a first-line option alongside vancomycin in all regions. *Dicloxacillin, Vancomycin* - **Vancomycin** is appropriate, but **dicloxacillin** is an **anti-staphylococcal penicillin** and is not effective against **MRSA** (Methicillin-Resistant Staphylococcus aureus) because MRSA, by definition, is resistant to all beta-lactam antibiotics. - Dicloxacillin is mainly used for **MSSA** (Methicillin-Sensitive Staphylococcus aureus) infections.

Q: Not true about iodophores?

Inorganic compounds. ***Inorganic compounds*** ✓ **Correct Answer** - This statement is **NOT TRUE** - Iodophores are **organic complexes**, not inorganic compounds. - They are formed by combining iodine with a **solubilizing agent** or carrier molecule, typically a surfactant or polymer (e.g., povidone-iodine). - This organic formulation allows for **controlled release** of iodine and reduces irritation compared to free iodine solutions. *Surfactants* - Many iodophores are formulated with **surfactants** to enhance their solubility and wettability. - These surfactants help to release the **active iodine** gradually, providing sustained antimicrobial action. *Release iodine* - Iodophores function by **slowly releasing free iodine**, which is the active antimicrobial agent. - This gradual release mechanism provides a **prolonged antiseptic effect** while minimizing irritation. *Disinfectant* - Iodophores are widely used as **disinfectants** and antiseptics in healthcare settings and for skin preparation. - Their broad-spectrum antimicrobial activity makes them effective against **bacteria, viruses, fungi, and spores**.

Q: Treatment of Neurocysticercosis includes all of the following except -

Niclosamide. ***Niclosamide***- **Niclosamide** is an oral anthelmintic primarily used to treat **intestinal tapeworm infections** by inhibiting **oxidative phosphorylation** in the parasites.- It has **poor systemic absorption** and therefore is **not effective** against **neurocysticercosis**, which involves cysts in the brain parenchyma requiring drugs with good CNS penetration.*Praziquantel*- **Praziquantel** is an orally administered anthelmintic that increases the **calcium permeability** of the parasite's cell membrane, leading to paralysis and death.- It is used in the treatment of **neurocysticercosis**, particularly for **viable parenchymal cysts** and as an alternative to albendazole [2].*Albendazole*- **Albendazole** is a broad-spectrum anthelmintic that works by inhibiting **tubulin polymerization**, causing disruption of **parasite metabolism** and glucose uptake.- It is considered the **first-line treatment** for **parenchymal neurocysticercosis** due to its excellent penetration into the central nervous system and proven efficacy.*Corticosteroids*- **Corticosteroids** (such as **dexamethasone** or **prednisolone**) are used as **adjunct therapy** in neurocysticercosis management.- They help reduce **inflammation and edema** associated with parasite death, preventing complications like seizures and increased intracranial pressure during anthelmintic treatment [1].

Q: Penicillin should be given to a patient with group A beta haemolytic streptococci infection of the tonsils for a period of:

10-14 days. ***10-14 days*** - A **10-day course** of oral penicillin is the standard recommendation for treating **Group A beta-hemolytic streptococcal (GABHS) pharyngitis** to ensure complete eradication of the organism. - This duration helps prevent complications like **acute rheumatic fever** and **acute post-streptococcal glomerulonephritis**. - Some guidelines extend treatment up to 14 days to ensure compliance and complete bacterial eradication. *21 days* - A 21-day antibiotic course is generally **too long** for uncomplicated GABHS pharyngitis and can increase the risk of antibiotic resistance or side effects. - This duration might be considered for more severe or recurrent infections, but not as an initial standard treatment. *3-5 days* - A 3-5 day course of antibiotics is **insufficient** for eradicating GABHS and significantly increases the risk of developing future complications like **rheumatic fever**. - While some antibiotics for other conditions have shorter courses, penicillin for strep throat requires a longer duration to be effective. *1 month* - A 1-month course of penicillin is **excessively long** for uncomplicated GABHS pharyngitis and is not indicated for this condition. - Such prolonged antibiotic therapy is typically reserved for ongoing prophylaxis in patients with a history of **rheumatic fever** or specific deep-seated infections.

Q: What is the drug that can be used for rheumatic fever prophylaxis in a patient with a history of allergy to Penicillin?

Erythromycin. ***Erythromycin*** - **Erythromycin** is a macrolide antibiotic that is a suitable alternative for **rheumatic fever prophylaxis** in patients with a documented allergy to penicillin. - It effectively covers *Streptococcus pyogenes*, the causative agent of group A streptococcal (GAS) pharyngitis that precedes rheumatic fever. *Amoxicillin* - **Amoxicillin** is a penicillin-class antibiotic and would be contraindicated in a patient with a **penicillin allergy**, as it carries a high risk of cross-reactivity and allergic reaction. - Using amoxicillin in this scenario could lead to severe hypersensitivity reactions, compromising patient safety. *Streptomycin* - **Streptomycin** is an aminoglycoside antibiotic primarily used for infections like **tuberculosis** and severe bacterial endocarditis. - It is not indicated for the treatment of *Streptococcus pyogenes* infections or for **rheumatic fever prophylaxis**. *Sulfasalazine* - **Sulfasalazine** is an anti-inflammatory and immunomodulatory drug primarily used in the management of **inflammatory bowel disease** and **rheumatoid arthritis**. - It has no antimicrobial activity against *Streptococcus pyogenes* and is therefore not used for **rheumatic fever prophylaxis**.

Q: Red man syndrome is caused by

Vancomycin. ***Vancomycin*** - **Red man syndrome** is a well-known adverse reaction associated with **rapid intravenous infusion** of vancomycin. - It results from the **non-IgE mediated release of histamine** from mast cells and basophils. *Ciprofloxacin* - This antibiotic belongs to the **fluoroquinolone** class and is primarily associated with side effects such as **tendon rupture**, **QT prolongation**, and **GI disturbances**, not red man syndrome. - Ciprofloxacin has a different mechanism of action and adverse effect profile compared to vancomycin. *Teicoplanin* - While **teicoplanin** is a glycopeptide antibiotic similar to vancomycin, it is much **less likely** to cause red man syndrome due to its different molecular structure and slower histamine-releasing potential. - It generally has a more favorable safety profile regarding infusion-related reactions. *Amikacin* - **Amikacin** is an **aminoglycoside** antibiotic known for side effects like **ototoxicity** and **nephrotoxicity**. - It does not cause red man syndrome, as its mechanism of action and adverse effects are distinctly different from vancomycin.

Q: A patient was given chloroquine and doxycycline for 7 days. The patient's fever decreased in 4 days, but on day 6, parasitemia recurred with reappearance of asexual forms of Plasmodium falciparum on peripheral smear. This type of drug resistance is?

R1 type. ***R1 type*** - **R1 resistance (Resistance level I)** is characterized by **initial clearance or marked reduction of asexual parasitemia followed by recrudescence within 7 days** of treatment initiation. - In this case, the fever decreased (indicating initial parasite suppression), but asexual forms reappeared on day 6, fulfilling the criteria for R1 resistance. - This represents **partial drug sensitivity** where parasites are initially suppressed but not completely eliminated. *R2 type* - **R2 resistance (Resistance level II)** involves **marked reduction but not complete clearance** of asexual parasitemia during treatment. - Parasites remain detectable throughout treatment without an initial period of clearance. - This patient showed initial improvement with subsequent recrudescence, which is characteristic of R1, not R2. *R3 type* - **R3 resistance (Resistance level III)** signifies **complete failure of treatment with no reduction** in asexual parasite count. - This patient's fever decreased in 4 days, indicating at least partial response, ruling out R3 resistance. *R4 type* - **R4 is not a recognized category** in the WHO classification of antimalarial drug resistance. - The standard WHO classification includes only **R1, R2, and R3 resistance levels** based on asexual parasite response to treatment.

Q: Cidofovir is used for intralesional treatment of:

Respiratory papillomatosis. ***Respiratory papillomatosis*** - Cidofovir is an **antiviral medication** that has shown efficacy in the intralesional treatment of **recurrent respiratory papillomatosis**, reducing the frequency of surgical interventions required. - This condition is caused by the **human papillomavirus (HPV)**, and cidofovir works by inhibiting viral DNA synthesis. *EBV* - **Epstein-Barr virus (EBV)** is primarily associated with infectious mononucleosis, certain lymphomas, and nasopharyngeal carcinoma. - While cidofovir has some in vitro activity against EBV, it is **not the standard or primary treatment** for EBV-related conditions, especially not for intralesional treatment. *Herpes zoster* - **Herpes zoster (shingles)** is caused by the varicella-zoster virus (VZV) and is typically treated with oral antiviral agents like **acyclovir, valacyclovir, or famciclovir**. - Cidofovir is **not a first-line treatment** for herpes zoster, and intralesional treatment is not a common approach for this widespread viral rash. *Granuloma inguinale* - **Granuloma inguinale** (also known as donovanosis) is a **bacterial infection** caused by *Klebsiella granulomatis*. - It is treated with antibiotics like **azithromycin, doxycycline, or ciprofloxacin**, not antiviral medications like cidofovir.

Q: A patient develops an infection of methicillin resistant Staphylococcus aureus. All of the following can be used to treat this infection except

Cefaclor. ***Cefaclor*** - **Cefaclor** is a second-generation **cephalosporin**, which, like all beta-lactam antibiotics, is ineffective against **MRSA** because **MRSA** produces an altered penicillin-binding protein (PBP2a) encoded by the **mecA** gene. - This altered **PBP2a** has a low affinity for **beta-lactam antibiotics**, rendering them inactive. *Cotrimoxazole* - **Cotrimoxazole** (trimethoprim/sulfamethoxazole) is a commonly used and effective oral antibiotic for treating **MRSA** infections, particularly in outpatient settings. - It inhibits **folate synthesis** in bacteria, an essential pathway for their growth and replication. *Ciprofloxacin* - **Ciprofloxacin** is a **fluoroquinolone antibiotic** that can be used to treat certain **MRSA** infections, although resistance can be an issue. [2] - It works by inhibiting bacterial **DNA gyrase** and **topoisomerase IV**, crucial enzymes for DNA replication. [2] *Vancomycin* - **Vancomycin** is a **glycopeptide antibiotic** that is a first-line treatment for serious **MRSA** infections, especially in hospitalized patients. [1] - It works by inhibiting **bacterial cell wall synthesis** at a different site than beta-lactams, making it effective against **MRSA**. [1]

Q: Drug of choice for pertussis is?

Azithromycin. ***Azithromycin*** - **Macrolides** are the preferred antibiotics for treating pertussis, and **azithromycin** is favored due to its convenient dosing schedule and lower incidence of gastrointestinal side effects compared to erythromycin. - It works by **inhibiting bacterial protein synthesis**, effectively eradicating *Bordetella pertussis* from the nasopharynx, which reduces contagiousness and helps minimize disease transmission. *Ceftriaxone* - **Ceftriaxone** is a third-generation cephalosporin that is effective against a broad spectrum of bacteria but is **not the drug of choice for pertussis**. - Its mechanism of action involves inhibiting **bacterial cell wall synthesis**, but *Bordetella pertussis* is typically susceptible to macrolides, rather than cephalosporins. *Penicillin* - **Penicillin** is a narrow-spectrum antibiotic that primarily targets gram-positive bacteria and some gram-negative cocci; it is **largely ineffective against *Bordetella pertussis***. - *Bordetella pertussis* is a gram-negative coccobacillus that is not typically sensitive to penicillin, making it an inappropriate treatment choice. *Erythromycin* - While **erythromycin** is a macrolide and can be used for pertussis, it is **often associated with significant gastrointestinal side effects** such as nausea, vomiting, and abdominal cramping due to its motilin receptor agonist activity. - **Azithromycin** is generally preferred over erythromycin due to its better tolerability and once-daily dosing, improving patient adherence.

Question 1

Drugs of choice for MRSA in skin and soft tissue infections are:

Accepted Answer

Vancomycin, Linezolid

Answer

Clindamycin, Vancomycin

Answer

Vancomycin, Teicoplanin

Answer

Dicloxacillin, Vancomycin

Question 2

Not true about iodophores?

Accepted Answer

Inorganic compounds

Answer

Surfactants

Answer

Release iodine

Answer

Disinfectant

Question 3

Treatment of Neurocysticercosis includes all of the following except -

Accepted Answer

Niclosamide

Answer

Praziquantel

Answer

Albendazole

Answer

Corticosteroids

Question 4

Penicillin should be given to a patient with group A beta haemolytic streptococci infection of the tonsils for a period of:

Accepted Answer

10-14 days

Answer

21 days

Answer

3-5 days

Answer

1 month

Question 5

What is the drug that can be used for rheumatic fever prophylaxis in a patient with a history of allergy to Penicillin?

Accepted Answer

Erythromycin

Answer

Amoxicillin

Answer

Streptomycin

Answer

Sulfasalazine

Question 6

Red man syndrome is caused by

Accepted Answer

Vancomycin

Answer

Ciprofloxacin

Answer

Teicoplanin

Answer

Amikacin

Question 7

A patient was given chloroquine and doxycycline for 7 days. The patient's fever decreased in 4 days, but on day 6, parasitemia recurred with reappearance of asexual forms of Plasmodium falciparum on peripheral smear. This type of drug resistance is?

Accepted Answer

R1 type

Answer

R3 type

Answer

R4 type

Answer

R2 type

Question 8

Cidofovir is used for intralesional treatment of:

Accepted Answer

Respiratory papillomatosis

Answer

EBV

Answer

Herpes zoster

Answer

Granuloma inguinale

Question 9

A patient develops an infection of methicillin resistant Staphylococcus aureus. All of the following can be used to treat this infection except

Accepted Answer

Cefaclor

Answer

Cotrimoxazole

Answer

Ciprofloxacin

Answer

Vancomycin

Question 10

Drug of choice for pertussis is?

Accepted Answer

Azithromycin

Answer

Ceftriaxone

Answer

Penicillin

Answer

Erythromycin

Antimicrobial Agents — MCQs

Antimicrobial Agents — MCQs

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