Antibiotics

Antibiotics US Medical PG Question 1: An 8-year-old girl is brought to the emergency room for a 6-hour history of fever, sore throat, and difficulty swallowing. Physical examination shows pooling of oral secretions and inspiratory stridor. Lateral x-ray of the neck shows thickening of the epiglottis and aryepiglottic folds. Throat culture with chocolate agar shows small, gram-negative coccobacilli. The patient's brother is started on the recommended antibiotic for chemoprophylaxis. Which of the following is the primary mechanism of action of this drug?

• A. Inhibition of the 50S ribosomal subunit
• B. Inhibition of prokaryotic topoisomerase II
• C. Inhibition of DNA-dependent RNA-polymerase (Correct Answer)
• D. Inhibition of the 30S ribosomal subunit
• E. Inhibition of peptidoglycan crosslinking

Antibiotics Explanation: ***Inhibition of DNA-dependent RNA-polymerase*** - The clinical picture strongly suggests **epiglottitis** caused by *Haemophilus influenzae type b* (Hib), characterized by **fever, sore throat, difficulty swallowing, pooling of oral secretions, inspiratory stridor**, and **epiglottic thickening** on X-ray. - **Rifampin** is the recommended antibiotic for chemoprophylaxis in close contacts of Hib patients; its primary mechanism of action is to inhibit bacterial **DNA-dependent RNA polymerase**, thereby preventing **mRNA synthesis**. *Inhibition of the 50S ribosomal subunit* - This mechanism is characteristic of **macrolides** (e.g., azithromycin, erythromycin) and **clindamycin**, which are not the primary choice for Hib chemoprophylaxis. - These drugs prevent **protein synthesis** by interfering with translocation or peptide bond formation on the larger ribosomal subunit. *Inhibition of prokaryotic topoisomerase II* - This is the mechanism of action for **fluoroquinolones** (e.g., ciprofloxacin), which are typically reserved for specific infections due to potential side effects in children. - Fluoroquinolones interfere with **DNA replication** and **transcription** by preventing DNA unwinding and supercoiling. *Inhibition of the 30S ribosomal subunit* - This mechanism is associated with **tetracyclines** and **aminoglycosides** (e.g., doxycycline, gentamicin). - These antibiotics block **protein synthesis** by preventing tRNA attachment or causing misreading of mRNA. *Inhibition of peptidoglycan crosslinking* - This describes the mechanism of **beta-lactam antibiotics** (e.g., penicillin, amoxicillin, cephalosporins), which inhibit bacterial **cell wall synthesis**. - While some beta-lactams are used to treat Hib infections, they are not the primary drug for **chemoprophylaxis**.

Antibiotics US Medical PG Question 2: A 37-year-old woman with a history of anorectal abscesses complains of pain in the perianal region. Physical examination reveals mild swelling, tenderness, and erythema of the perianal skin. She is prescribed oral ampicillin and asked to return for follow-up. Two days later, the patient presents with a high-grade fever, syncope, and increased swelling. Which of the following would be the most common mechanism of resistance leading to the failure of antibiotic therapy in this patient?

• A. Intrinsic absence of a target site for the drug
• B. Use of an altered metabolic pathway
• C. Production of beta-lactamase enzyme (Correct Answer)
• D. Altered structural target for the drug
• E. Drug efflux pump

Antibiotics Explanation: ***Production of beta-lactamase enzyme*** - The patient's symptoms of a rapidly worsening infection despite ampicillin treatment suggest the presence of a **beta-lactamase producing organism**. Ampicillin is a **beta-lactam antibiotic** that is inactivated by these enzymes. - Anorectal abscesses and rapidly progressing soft tissue infections are often caused by **polymicrobial flora**, including staphylococci and enterococci, many of which can produce **beta-lactamase**. *Intrinsic absence of a target site for the drug* - While some bacteria inherently lack the target site for certain drugs (e.g., mycoplasma lacking a cell wall, thus being resistant to beta-lactams), this is less likely to be the **most common mechanism of acquired resistance** leading to treatment failure in a typical perianal infection. - The rapid progression and failed initial treatment point towards an **acquired mechanism of resistance** rather than an intrinsic one. *Use of an altered metabolic pathway* - This mechanism, such as altered **folate synthesis pathways** in resistance to trimethoprim-sulfamethoxazole, is less common as the primary mechanism for ampicillin resistance. - Ampicillin's mechanism of action primarily targets the **bacterial cell wall**, not a metabolic pathway in the same way. *Altered structural target for the drug* - This involves modifications to the **penicillin-binding proteins (PBPs)**, which are the targets of beta-lactam antibiotics like ampicillin. While a valid mechanism (e.g., in MRSA), the **production of beta-lactamase** is generally a more widespread and common cause of ampicillin failure, especially in infections involving mixed flora from the perianal region. - Given the abrupt failure of ampicillin, **beta-lactamase inactivation** is a more immediate and common cause than a rapid mutational change in PBPs. *Drug efflux pump* - **Efflux pumps** actively remove antibiotics from the bacterial cell, contributing to resistance against various drug classes. - While efflux pumps can play a role, the dominant mechanism for resistance to **ampicillin** in many common perianal pathogens is the **enzymatic degradation by beta-lactamases**.

Antibiotics US Medical PG Question 3: Three days after admission to the hospital following a motor vehicle accident, a 45-year-old woman develops a fever. A central venous catheter was placed on the day of admission for treatment of severe hypotension. Her temperature is 39.2°C (102.5°F). Examination shows erythema surrounding the catheter insertion site at the right internal jugular vein. Blood cultures show gram-positive, catalase-positive cocci that have a high minimum inhibitory concentration when exposed to novobiocin. Which of the following is the most appropriate pharmacotherapy?

• A. Clarithromycin
• B. Vancomycin (Correct Answer)
• C. Metronidazole
• D. Penicillin G
• E. Polymyxin B

Antibiotics Explanation: ***Vancomycin*** - The description of **gram-positive, catalase-positive cocci** that are **novobiocin-resistant** (high MIC) strongly points to **Staphylococcus epidermidis** or other coagulase-negative staphylococci. *S. epidermidis* is the most common cause of **catheter-related bloodstream infections** and is often **methicillin-resistant**, making **vancomycin** the drug of choice. - The presence of erythema at the catheter site and fever in a patient with a central venous catheter indicates a **central line-associated bloodstream infection (CLABSI)**, for which empiric coverage with vancomycin is standard until sensitivities are known. - The novobiocin resistance test helps differentiate *S. epidermidis* (resistant) from *S. saprophyticus* (sensitive). *Clarithromycin* - **Clarithromycin** is a macrolide antibiotic primarily used for respiratory tract infections and *Mycobacterium avium complex*. - It is **not effective** against methicillin-resistant staphylococci and would not be appropriate for a suspected CLABSI. *Metronidazole* - **Metronidazole** is an antibiotic mainly used for **anaerobic bacterial infections** and certain parasitic infections. - It has **no activity** against gram-positive cocci like staphylococci. *Penicillin G* - **Penicillin G** is a narrow-spectrum penicillin effective against some gram-positive cocci, like **Streptococcus pyogenes**. - However, virtually all staphylococci, especially those causing hospital-acquired infections, are **resistant to penicillin G** due to beta-lactamase (penicillinase) production. *Polymyxin B* - **Polymyxin B** is an antibiotic primarily effective against **gram-negative bacteria**, particularly those with multi-drug resistance such as **Pseudomonas aeruginosa** and **Acinetobacter baumannii**. - It has **no significant activity** against gram-positive cocci like staphylococci.

Antibiotics US Medical PG Question 4: You are a resident in the surgical ICU. One of the patients you are covering is a 35-year-old pregnant G1P0 in her first trimester admitted for complicated appendicitis and awaiting appendectomy. Your attending surgeon would like you to start the patient on moxifloxacin IV preoperatively. You remember from your obstetrics clerkship, however, that moxifloxacin is Pregnancy Category C, and animal studies have shown that immature animals exposed to fluoroquinolones like moxifloxacin may experience cartilage damage. You know that there are potentially safer antibiotics, such as piperacillin/tazobactam, which is in Pregnancy Category B. What should you do?

• A. Administer moxifloxacin since it is only Pregnancy Category C and, although studies may have revealed adverse effects in animals, there is no definite evidence that it causes risk in humans.
• B. Administer piperacillin/tazobactam instead of moxifloxacin without discussing with the attending since your obligation is to "first, do no harm" and both are acceptable antibiotics for complicated appendicitis.
• C. Discuss the adverse effects of each antibiotic with the patient, and then let the patient decide which antibiotic she would prefer.
• D. Wait to administer any antibiotics until you discuss your safety concerns with your attending. (Correct Answer)
• E. Administer moxifloxacin since the attending is the executive decision maker and had to know the patient was pregnant when deciding on an antibiotic.

Antibiotics Explanation: **Wait to administer any antibiotics until you discuss your safety concerns with your attending.** - As a resident, you have a **professional and ethical obligation** to voice concerns about patient safety, especially regarding medication choices in vulnerable populations like pregnant women. - Discussing your concerns with the attending physician allows for a **re-evaluation of the treatment plan** based on current evidence and patient-specific factors, ensuring the safest care. *Administer moxifloxacin since it is only Pregnancy Category C and, although studies may have revealed adverse effects in animals, there is no definite evidence that it causes risk in humans.* - While Category C means risk cannot be ruled out and benefits *may* outweigh risks, the presence of **known adverse effects in animal studies** and the availability of a safer alternative warrant reconsideration. - Administering a drug with known potential harm without discussing alternatives or concerns goes against the principle of **prudence and patient safety**. *Administer piperacillin/tazobactam instead of moxifloxacin without discussing with the attending since your obligation is to "first, do no harm" and both are acceptable antibiotics for complicated appendicitis.* - While "first, do no harm" is paramount, **unilaterally changing a treatment plan** ordered by an attending physician is inappropriate and breaches professional hierarchy and communication protocols. - The correct approach is to **communicate concerns** to the attending, allowing for a collaborative decision, rather than making independent substitutions. *Discuss the adverse effects of each antibiotic with the patient, and then let the patient decide which antibiotic she would prefer.* - While patient autonomy and informed consent are crucial, decisions about specific antibiotic choices, especially for a complicated condition like appendicitis, require **medical expertise**. - As a resident, it is your role to present information but not to delegate such complex medical decisions to a patient, particularly when you yourself have **unresolved concerns** with the attending's order. *Administer moxifloxacin since the attending is the executive decision maker and had to know the patient was pregnant when deciding on an antibiotic.* - While the attending is the senior decision-maker, it is possible for **oversights or errors to occur**, even with experienced physicians. - Assuming the attending "had to know" and therefore dismissing your own clinical judgment and knowledge of potential harm is **irresponsible** and compromises patient safety.

Antibiotics US Medical PG Question 5: You are treating a neonate with meningitis using ampicillin and a second antibiotic, X, that is known to cause ototoxicity. What is the mechanism of antibiotic X?

• A. It binds the 50S ribosomal subunit and inhibits formation of the initiation complex
• B. It binds the 30S ribosomal subunit and inhibits formation of the initiation complex (Correct Answer)
• C. It binds the 30S ribosomal subunit and reversibly inhibits translocation
• D. It binds the 50S ribosomal subunit and inhibits peptidyltransferase
• E. It binds the 50S ribosomal subunit and reversibly inhibits translocation

Antibiotics Explanation: ***It binds the 30s ribosomal subunit and inhibits formation of the initiation complex*** - The second antibiotic, X, is likely an **aminoglycoside**, such as **gentamicin** or **amikacin**, which are commonly used in combination with ampicillin for neonatal meningitis and are known to cause ototoxicity. - Aminoglycosides exert their bactericidal effect by **irreversibly binding to the 30S ribosomal subunit**, thereby **inhibiting the formation of the initiation complex** and leading to misreading of mRNA. *It binds the 50S ribosomal subunit and inhibits formation of the initiation complex* - This mechanism is characteristic of **linezolid**, which targets the 50S ribosomal subunit to prevent the formation of the initiation complex. - While linezolid can cause side effects, **ototoxicity** is less commonly associated with it compared to aminoglycosides, and it is not a primary drug for neonatal meningitis alongside ampicillin. *It binds the 50S ribosomal subunit and inhibits peptidyltransferase* - This is the mechanism of action for **chloramphenicol**, which inhibits **peptidyltransferase** activity on the 50S ribosomal subunit, preventing peptide bond formation. - Although chloramphenicol can cause **ototoxicity** and **aplastic anemia**, its use in neonates is limited due to the risk of **Gray Baby Syndrome**. *It binds the 30s ribosomal subunit and reversibly inhibits translocation* - This describes the mechanism of action of **tetracyclines**, which reversibly bind to the 30S ribosomal subunit and prevent the attachment of aminoacyl-tRNA, thereby inhibiting protein synthesis. - Tetracyclines are **contraindicated in neonates** due to their potential to cause **tooth discoloration** and **bone growth inhibition**, and ototoxicity is not their primary adverse effect. *It binds the 50s ribosomal subunit and reversibly inhibits translocation* - This mechanism of reversibly inhibiting translocation by binding to the 50S ribosomal subunit is characteristic of **macrolides** (e.g., erythromycin, azithromycin) and **clindamycin**. - While some macrolides can cause **transient ototoxicity**, they are not typically the second antibiotic of choice for neonatal meningitis in combination with ampicillin, and clindamycin's side effect profile is different.

Antibiotics US Medical PG Question 6: A 44-year-old woman presents to her primary care physician for worsening dysuria, hematuria, and lower abdominal pain. Her symptoms began approximately 2 days ago and have progressively worsened. She denies headache, nausea, vomiting, or diarrhea. She endorses feeling "feverish" and notes to having foul smelling urine. She has a past medical history of Romano-Ward syndrome and is not on any treatment. She experiences profuse diarrhea and nausea when taking carbapenems and develops a severe rash with cephalosporins. Her temperature is 100.4°F (38C), blood pressure is 138/93 mmHg, pulse is 100/min, and respirations are 18/min. On physical exam, the patient appears uncomfortable and there is tenderness to palpation around the bilateral flanks and costovertebral angle. A urinalysis and urine culture is obtained and appropriate antibiotics are administered. On her next clinical visit urine studies and a basic metabolic panel is obtained, which is shown below: Serum: Na+: 140 mEq/L Cl-: 101 mEq/L K+: 4.2 mEq/L HCO3-: 22 mEq/L BUN: 20 mg/dL Glucose: 94 mg/dL Creatinine: 2.4 mg/dL Urinalysis Color: Yellow Appearance: Clear Blood: Negative pH: 7 (Normal 5-8) Protein: Negative Nitrite: Negative Leukocyte esterase: Negative Cast: Epithelial casts FeNa: 3% Urine culture Preliminary report: 10,000 CFU/mL E. coli Which of the following antibiotics was most likely given to this patient?

• A. Aztreonam (Correct Answer)
• B. Vancomycin
• C. Clindamycin
• D. Levofloxacin
• E. Tobramycin

Antibiotics Explanation: ***Aztreonam*** - This patient presents with **pyelonephritis** (fever, flank pain, dysuria, hematuria, CVA tenderness) with confirmed *E. coli* urinary tract infection - She has **severe allergies to both carbapenems and cephalosporins**, eliminating most beta-lactam options - **Aztreonam** is a monobactam antibiotic with excellent activity against **gram-negative bacteria** including *E. coli* - Critically, aztreonam **does not cross-react** with other beta-lactams due to its unique monocyclic structure, making it safe in patients with penicillin/cephalosporin allergies - **No QT prolongation** - safe in Romano-Ward syndrome *Vancomycin* - Primarily effective against **gram-positive bacteria** (MRSA, enterococci) - **No activity against gram-negative organisms** like *E. coli* - Would not be appropriate for this urinary tract infection *Clindamycin* - Used primarily for **anaerobic infections** and some gram-positive bacteria - **Limited to no activity against *E. coli*** and other gram-negative organisms - Not an effective choice for gram-negative pyelonephritis *Levofloxacin* - Fluoroquinolone with excellent gram-negative coverage and urinary penetration - Generally a good choice for *E. coli* pyelonephritis - **CONTRAINDICATED in this patient**: Fluoroquinolones cause **QT interval prolongation**, which is dangerous in patients with **Romano-Ward syndrome (congenital long QT syndrome)** - This critical drug-disease interaction eliminates fluoroquinolones as an option *Tobramycin* - Aminoglycoside with good gram-negative coverage including *E. coli* - **Highly nephrotoxic** - contraindicated in this patient with **acute kidney injury** (elevated creatinine 2.4 mg/dL, epithelial casts, FENa 3%) - Risk of worsening renal function and ototoxicity makes it a poor choice

Antibiotics US Medical PG Question 7: A 62-year-old man is brought to the emergency department from a senior-care facility after he was found with a decreased level of consciousness and fever. His personal history is relevant for colorectal cancer that was managed with surgical excision of the tumor. Upon admission, he is found to have a blood pressure of 130/80 mm Hg, a pulse of 102/min, a respiratory rate of 20/min, and a body temperature 38.8°C (101.8°F). There is no rash on physical examination; he is found to have neck rigidity, confusion, and photophobia. There are no focal neurological deficits. A head CT is normal without mass or hydrocephalus. A lumbar puncture was performed and cerebrospinal fluid (CSF) is sent to analysis while ceftriaxone and vancomycin are started. Which of the following additional antimicrobials should be added in the management of this patient?

• A. Trimethoprim-sulfamethoxazole (TMP-SMX)
• B. Ampicillin (Correct Answer)
• C. Amphotericin
• D. Meropenem
• E. Clindamycin

Antibiotics Explanation: ***Ampicillin*** - This patient is a 62-year-old, indicating an increased risk for **Listeria monocytogenes** meningitis, which is typically susceptible to ampicillin. - Given his age and presentation with **meningeal signs** and fever, empirical coverage for Listeria with ampicillin is crucial, especially before CSF culture results are known. *Trimethoprim-sulfamethoxazole (TMP-SMX)* - While TMP-SMX can cover Listeria, it is generally considered a **second-line agent** for severe infections like meningitis due to slower bactericidal activity and potential for higher rates of treatment failure compared to ampicillin. - Ampicillin is the **preferred first-line treatment** for Listeria meningitis unless there is a specific contraindication. *Amphotericin* - Amphotericin is an **antifungal agent** used for fungal meningitis. - Although fungemia can occur in immunocompromised individuals or those with indwelling catheters, the initial presentation with bacterial meningitis symptoms and absence of specific risk factors for fungal infection do not support its empirical use. *Meropenem* - Meropenem is a **carbapenem** with a broad spectrum of activity, including many gram-negative and gram-positive bacteria, and some anaerobes. - While it has good CNS penetration and could cover some organisms like penicillin-resistant S. pneumoniae or gram-negative rods, it is not the primary empirical choice specifically for **Listeria monocytogenes**, and there's no indication for its broad-spectrum coverage over standard empirical therapy currently. *Clindamycin* - Clindamycin is primarily active against **gram-positive bacteria**, especially anaerobes and some staphylococci and streptococci. - It has **poor penetration into the CNS** and is therefore not effective for meningitis treatment, especially for common bacterial pathogens or Listeria.

Antibiotics US Medical PG Question 8: A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

• A. "Does the diarrhea typically precede the constipation, or vice-versa?"
• B. "Is the diarrhea foul-smelling?"
• C. "Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"
• D. "Are the symptoms worse in the morning or at night?"
• E. "Can you tell me more about the symptoms you have been experiencing?" (Correct Answer)

Antibiotics Explanation: ***Can you tell me more about the symptoms you have been experiencing?*** - This **open-ended question** encourages the patient to provide a **comprehensive narrative** of their symptoms, including details about onset, frequency, duration, alleviating/aggravating factors, and associated symptoms, which is crucial for diagnosis. - In a patient presenting with vague, intermittent symptoms like alternating constipation and diarrhea, allowing them to elaborate freely can reveal important clues that might not be captured by more targeted questions. *Does the diarrhea typically precede the constipation, or vice-versa?* - While knowing the sequence of symptoms can be helpful in understanding the **pattern of bowel dysfunction**, it is a very specific question that might overlook other important aspects of the patient's experience. - It prematurely narrows the focus without first obtaining a broad understanding of the patient's overall symptomatic picture. *Is the diarrhea foul-smelling?* - Foul-smelling diarrhea can indicate **malabsorption** or **bacterial overgrowth**, which are important to consider in some gastrointestinal conditions. - However, this is a **specific symptom inquiry** that should follow a more general exploration of the patient's symptoms, as it may not be relevant if other crucial details are missed. *Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life* - Quantifying pain intensity is useful for assessing the **severity of discomfort** and monitoring changes over time. - However, for a patient with intermittent rather than acute, severe pain, understanding the **character, location, and triggers** of the pain is often more diagnostically valuable than just a numerical rating initially. *Are the symptoms worse in the morning or at night?* - Diurnal variation can be relevant in certain conditions, such as inflammatory bowel diseases where nocturnal symptoms might be more concerning, or functional disorders whose symptoms might be stress-related. - This is another **specific question** that should come after gathering a more complete initial picture of the patient's symptoms to ensure no key information is overlooked.

Antibiotics US Medical PG Question 9: An investigator is studying a strain of bacteria that retains a blue color after crystal violet dye and acetone are applied. The bacteria are inoculated in a petri dish containing hypotonic saline. After the addition of an antibiotic, the bacteria swell and rupture. This antibiotic most likely belongs to which of the following classes?

• A. Macrolide
• B. Cephalosporin (Correct Answer)
• C. Sulfonamide
• D. Fluoroquinolone
• E. Tetracycline

Antibiotics Explanation: ***Cephalosporin*** - This scenario describes a **Gram-positive bacterium** (retains blue color) which, after antibiotic treatment, swells and lyses in a hypotonic solution. This indicates a defect in the **peptidoglycan cell wall**. - **Cephalosporins** are **β-lactam antibiotics** that inhibit bacterial cell wall synthesis by interfering with **peptidoglycan cross-linking**, leading to osmotic lysis in hypotonic environments. *Macrolide* - Macrolides like **azithromycin** and **erythromycin** inhibit bacterial **protein synthesis** by binding to the 50S ribosomal subunit. - They do not directly target the cell wall, so they would not cause immediate osmotic lysis in this manner. *Sulfonamide* - Sulfonamides inhibit bacterial **folic acid synthesis** by acting as a competitive inhibitor of dihydropteroate synthase, disrupting DNA and RNA production. - Their mechanism of action does not involve direct cell wall disruption or osmotic lysis. *Fluoroquinolone* - Fluoroquinolones interfere with bacterial **DNA replication and transcription** by inhibiting **DNA gyrase** and **topoisomerase IV**. - This class of antibiotics does not primarily target the cell wall, and therefore would not lead to prompt osmotic swelling and rupture. *Tetracycline* - Tetracyclines inhibit bacterial **protein synthesis** by binding to the 30S ribosomal subunit, preventing the attachment of aminoacyl-tRNA. - They do not affect the cell wall, so they would not cause the observed osmotic lysis.

Antibiotics US Medical PG Question 10: A 49-year-old man presents to the emergency department with acute onset of pain and redness of the skin of his lower leg for the past 3 days. He has had type 2 diabetes mellitus for the past 12 years, but he is not compliant with his medications. He has smoked 10–15 cigarettes per day for the past 20 years. His temperature is 38°C (100.4°F), pulse is 95/min, and blood pressure is 110/70 mm Hg. On physical examination, the pretibial area is erythematous, edematous, and tender. He is diagnosed with acute cellulitis, and intravenous ceftazidime sodium is started. On the 5th day of antibiotic therapy, the patient complains of severe watery diarrhea, fever, and abdominal tenderness without rigidity. Complete blood count is ordered for the patient and shows 14,000 white blood cells/mm3. Which of the following is the best initial therapy for this patient?

• A. Intravenous vancomycin
• B. Oral ciprofloxacin
• C. Fecal microbiota transplantation
• D. Oral vancomycin (Correct Answer)
• E. Oral metronidazole

Antibiotics Explanation: ***Oral vancomycin*** - The patient exhibits classic symptoms of **Clostridioides difficile infection (CDI)**: watery diarrhea, fever, abdominal tenderness, and leukocytosis following antibiotic use (ceftazidime). Oral vancomycin is the **first-line therapy** for severe CDI. - Oral vancomycin achieves high intraluminal concentrations, effectively targeting C. difficile in the colon with minimal systemic absorption. *Intravenous vancomycin* - Intravenous vancomycin has **poor penetration** into the gastrointestinal tract and is therefore ineffective for treating C. difficile infection. - It is primarily used for systemic infections caused by **methicillin-resistant Staphylococcus aureus (MRSA)**. *Oral ciprofloxacin* - **Fluoroquinolones** like ciprofloxacin are associated with an increased risk of developing C. difficile infection due to their broad-spectrum activity. - They are not effective treatments for C. difficile and can potentially worsen the condition or select for resistant strains. *Fecal microbiota transplantation* - **Fecal microbiota transplantation (FMT)** is a highly effective treatment for recurrent C. difficile infection, but it is typically reserved for patients who have failed multiple courses of standard antibiotic therapy. - It is not considered the initial therapy for acute, uncomplicated C. difficile infection. *Oral metronidazole* - **Oral metronidazole** was historically used for C. difficile infection but is **no longer recommended** as first-line therapy per current **2021 IDSA/SHEA guidelines** due to inferior clinical outcomes compared to vancomycin or fidaxomicin. - Given the patient's fever and leukocytosis indicating severe infection, vancomycin is the preferred initial treatment.

Antibiotics Flashcard 1 of 10

Question: What class of beta-lactam antibiotics are indicated in drug-resistant infections?_____

Answer: Carbapenems

Antibiotics Flashcard 2 of 10

Question: Carbapenems are what class of antibiotics?_____

Answer: -lactams

Antibiotics Flashcard 3 of 10

Question: Which antibiotic binds the 30S ribosomal subunit, irreversibly inhibiting formation of the initiation complex?_____

Answer: Aminoglycosides

Antibiotics Flashcard 4 of 10

Question: All -lactam antibiotics are _____, as cell walls of bacteria are essential for growth and development.

Answer: bactericidal

Antibiotics Flashcard 5 of 10

Question: Which antibiotic binds directly to the D-ala-D-ala sequence of bacterial cell walls?_____

Answer: Vancomycin

Antibiotics Flashcard 6 of 10

Question: β-lactam antibiotics inhibit what family of enzymes involved in cell wall synthesis? _____

Answer: Penicillin binding protein transpeptidases

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Antibiotics Flashcard 7 of 10

Question: _____-toxicity is associated with Isoniazid use

Answer: Hepato

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Antibiotics Flashcard 8 of 10

Question: Clavulanic acid (clavulanate) is a suicide β-lactamase inhibitor that is combined with the aminopenicillin _____ (Augmentin) or the antipseudomonal _____

Answer: amoxicillin

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Antibiotics Flashcard 9 of 10

Question: _____ Mycobacterium tuberculosis infection is treated with RIPE therapy

Answer: Active

Extra Information:    https://onlinemeded.org?ref=anki  

Antibiotics Flashcard 10 of 10

Question: Cephalosporins can cause a Vitamin _____ deficiency

Answer: K

Extra Information:   https://onlinemeded.org/spa/infectious-disease?ref=anki