Antimicrobials

Antimicrobials US Medical PG Question 1: A 64-year-old woman with a past medical history of poorly managed diabetes presents to the emergency department with nausea and vomiting. Her symptoms started yesterday and have been progressively worsening. She is unable to eat given her symptoms. Her temperature is 102°F (38.9°C), blood pressure is 115/68 mmHg, pulse is 120/min, respirations are 17/min, and oxygen saturation is 98% on room air. Physical exam is notable for left-sided costovertebral angle tenderness, and urinalysis demonstrates bacteriuria and pyuria. The patient is admitted to the hospital and started on IV ceftriaxone. On day 3 of her hospital stay she is afebrile, able to eat and drink, and feels better. Which of the following antibiotic regimens should be started or continued as an outpatient upon discharge?

• A. Amoxicillin
• B. Nitrofurantoin
• C. Ciprofloxacin
• D. Ceftriaxone
• E. Trimethoprim-sulfamethoxazole (Correct Answer)

Antimicrobials Explanation: ***Trimethoprim-sulfamethoxazole*** - This patient presents with **acute pyelonephritis**, indicated by fever, CVA tenderness, bacteriuria, and pyuria, requiring a 7-14 day course of treatment. - After 3 days of IV ceftriaxone with clinical improvement, **step-down to oral therapy** is appropriate. - **Trimethoprim-sulfamethoxazole** is a first-line oral agent for completing treatment of uncomplicated pyelonephritis and is preferred when **local resistance rates are <20%** and no specific resistance data is available. - It achieves adequate concentrations in renal tissue and is cost-effective for outpatient therapy. *Amoxicillin* - **Amoxicillin** is not recommended for pyelonephritis due to **high resistance rates** among common uropathogens like *E. coli* (often >30%). - It does not achieve adequate concentrations in the renal parenchyma to effectively treat **upper urinary tract infections**. *Nitrofurantoin* - **Nitrofurantoin** is concentrated in the bladder and is highly effective for **lower urinary tract infections (cystitis)**. - It is **contraindicated for pyelonephritis** because it does not reach therapeutic levels in the renal parenchyma or bloodstream. - Additionally, it should be avoided in patients with impaired renal function. *Ciprofloxacin* - **Ciprofloxacin** is also a first-line oral agent for pyelonephritis and would be an appropriate choice for step-down therapy. - However, when no culture or susceptibility data is available, **TMP-SMX is generally preferred** as an initial oral choice due to concerns about promoting fluoroquinolone resistance and potential adverse effects (tendonitis, QT prolongation, C. difficile). - Fluoroquinolones are particularly valuable when reserved for cases with known resistance to other agents or specific patient contraindications. *Ceftriaxone* - **Ceftriaxone** is an IV third-generation cephalosporin used for initial empiric treatment of acute pyelonephritis in hospitalized patients. - Once the patient is **clinically stable, afebrile, and tolerating oral intake**, transitioning to oral therapy is standard practice. - Continued IV therapy as an outpatient is unnecessarily invasive and costly when oral options are effective.

Antimicrobials US Medical PG Question 2: A 77-year-old woman is brought to the emergency department from her nursing home because she was found down overnight. On presentation she was found to be delirious and was unable to answer questions. Chart review shows that she is allergic to cephalosporins. Her temperature is 102.2°F (39°C), blood pressure is 105/52 mmHg, pulse is 94/min, and respirations are 23/min. Physical exam reveals a productive cough. A metabolic panel is obtained with the following results: Serum: Na+: 135 mEq/L Cl-: 95 mEq/L K+: 4 mEq/L HCO3-: 19 mEq/L BUN: 40 mg/dL Creatinine: 2.5 mg/dL Glucose: 150 mg/dL Based on these findings two different drugs are started empirically. Gram stain on a blood sample is performed showing the presence of gram-positive organisms on all samples. One of the drugs is subsequently stopped. The drug that was most likely stopped has which of the following characteristics?

• A. Resistance conveyed through acetylation
• B. Associated with red man syndrome
• C. Single-ringed ß-lactam structure (Correct Answer)
• D. Causes discolored teeth in children
• E. Accumulates inside bacteria via O2-dependent uptake

Antimicrobials Explanation: ***Single-ringed ß-lactam structure*** - The patient presents with **sepsis** due to **pneumonia** likely caused by **gram-positive organisms**. Given a cephalosporin allergy, **aztreonam** (a monobactam) would be an initial empirical antibiotic choice to cover gram-negative bacteria, alongside a drug for gram-positive coverage (like vancomycin). - Since the **blood cultures** confirmed **gram-positive organisms**, the drug covering gram-negative bacteria (aztreonam) would be stopped. Aztreonam is characterized by its **single-ringed β-lactam structure**. *Resistance conveyed through acetylation* - This mechanism of resistance is typical of **aminoglycosides** (e.g., gentamicin) and **chloramphenicol**. - Aminoglycosides were unlikely to be one of the empirically started drugs, as they are often used in combination with β-lactams, and this patient has a cephalosporin allergy. *Associated with red man syndrome* - **Red man syndrome** is a common adverse effect associated with **vancomycin** administration, especially with rapid infusion. - Vancomycin would likely be continued, as it effectively targets gram-positive organisms, including **MRSA**, and is a suitable alternative given the cephalosporin allergy. *Causes discolored teeth in children* - This is a characteristic side effect of **tetracyclines** (e.g., doxycycline), which are contraindicated in young children and pregnant women due to their effects on bone and teeth development. - Tetracyclines are not typically first-line empiric therapy for severe pneumonia or sepsis, especially in an elderly patient. *Accumulates inside bacteria via O2-dependent uptake* - This describes the mechanism of uptake for **aminoglycosides**. Their entry into bacteria is an **energy-dependent process** requiring oxygen. - As mentioned, aminoglycosides are less likely to be the initial drug stopped in this scenario, as they target gram-negative bacteria.

Antimicrobials US Medical PG Question 3: A 64-year-old female with type 2 diabetes mellitus comes to the physician because of a 1-week history of painful red swelling on her left thigh. Examination shows a 3- x 4-cm, tender, fluctuant mass. Incision and drainage of the abscess are performed. Culture of the abscess fluid grows gram-positive, coagulase-positive cocci that are resistant to oxacillin. Which of the following best describes the mechanism of resistance of the causal organism to oxacillin?

• A. Degradation of the antibiotic
• B. Decreased uptake of the antibiotic
• C. Decreased activation of the antibiotic
• D. Altered target of the antibiotic (Correct Answer)
• E. Acetylation of the antibiotic

Antimicrobials Explanation: ***Altered target of the antibiotic*** - The organism described (gram-positive, coagulase-positive cocci, oxacillin-resistant) is **methicillin-resistant *Staphylococcus aureus* (MRSA)**. - MRSA achieves oxacillin (and other beta-lactam) resistance by acquiring the ***mecA* gene**, which encodes for a **modified penicillin-binding protein (PBP2a)** with reduced affinity for beta-lactam antibiotics. *Degradation of the antibiotic* - This mechanism, primarily through the production of **beta-lactamase enzymes**, can degrade beta-lactam antibiotics. - While *Staphylococcus aureus* can produce beta-lactamases, oxacillin (a **penicillinase-resistant penicillin**) is specifically engineered to be stable against these enzymes. *Decreased uptake of the antibiotic* - Reduced permeability of the bacterial cell wall can lead to decreased uptake, a mechanism more commonly associated with **gram-negative bacteria** due to their outer membrane. - This is not the primary mechanism of resistance for MRSA to oxacillin. *Decreased activation of the antibiotic* - Some antibiotics are prodrugs that require activation by bacterial enzymes, and resistance can arise from mutations affecting this activation. - Oxacillin is active in its administered form and does not require bacterial activation. *Acetylation of the antibiotic* - **Enzymatic modification**, such as acetylation, adenylylation, or phosphorylation, is a common mechanism of resistance, particularly against **aminoglycoside antibiotics**. - This specific mechanism is not responsible for oxacillin resistance in MRSA.

Antimicrobials US Medical PG Question 4: 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

Antimicrobials 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.

Antimicrobials US Medical PG Question 5: A scientist is studying the mechanisms by which bacteria become resistant to antibiotics. She begins by obtaining a culture of vancomycin-resistant Enterococcus faecalis and conducts replicate plating experiments. In these experiments, colonies are inoculated onto a membrane and smeared on 2 separate plates, 1 containing vancomycin and the other with no antibiotics. She finds that all of the bacterial colonies are vancomycin resistant because they grow on both plates. She then maintains the bacteria in liquid culture without vancomycin while she performs her other studies. Fifteen generations of bacteria later, she conducts replicate plating experiments again and finds that 20% of the colonies are now sensitive to vancomycin. Which of the following mechanisms is the most likely explanation for why these colonies have become vancomycin sensitive?

• A. Point mutation
• B. Gain of function mutation
• C. Viral infection
• D. Plasmid loss (Correct Answer)
• E. Loss of function mutation

Antimicrobials Explanation: ***Plasmid loss*** - The initial **vancomycin resistance** in *Enterococcus faecalis* is often mediated by genes located on **plasmids**, which are extrachromosomal DNA. - In the absence of selective pressure (vancomycin), bacteria that lose the plasmid (and thus the resistance genes) have a **growth advantage** over those that retain the energetically costly plasmid, leading to an increase in sensitive colonies over generations. *Point mutation* - A **point mutation** typically involves a change in a single nucleotide and could lead to loss of resistance if it occurred in a gene conferring resistance. - However, since there was no selective pressure for loss of resistance, it is less likely that 20% of the population would acquire such a specific point mutation to revert resistance. *Gain of function mutation* - A **gain of function mutation** would imply that the bacteria acquired a *new* advantageous trait, not the *loss* of resistance. - This type of mutation would not explain why some colonies became sensitive to vancomycin after the drug was removed. *Viral infection* - **Viral infection** (bacteriophages) can transfer genes through transduction or cause bacterial lysis, but it's not the primary mechanism for a widespread reversion of resistance in the absence of antibiotic pressure. - It would not explain the observed increase in vancomycin-sensitive colonies due to evolutionary pressure. *Loss of function mutation* - While a **loss of function mutation** in a gene conferring resistance could lead to sensitivity, it's generally less likely to explain a 20% shift without selective pressure than **plasmid loss**. - Plasmids are often unstable and are easily lost in the absence of selection, whereas a specific gene mutation causing loss of function would need to arise and become prevalent in the population.

Antimicrobials US Medical PG Question 6: 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

Antimicrobials 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.

Antimicrobials US Medical PG Question 7: A drug that inhibits mRNA synthesis has the well-documented side effect of red-orange body fluids. For which of the following is this drug used as monotherapy?

• A. Brucellosis
• B. Tuberculosis
• C. Methicillin-resistant staphylococcus aureus infection
• D. Mycobacterium avium intracellulare infection
• E. Neisseria meningitidis prophylaxis (Correct Answer)

Antimicrobials Explanation: ***Neisseria meningitidis prophylaxis*** - The drug described is **rifampin**, which inhibits bacterial **DNA-dependent RNA polymerase**, thereby blocking **mRNA synthesis** and causes characteristic **red-orange discoloration of body fluids** (tears, urine, sweat). - Rifampin is used as **monotherapy** for **prophylaxis** against **Neisseria meningitidis** infection in close contacts of infected patients. - This is the **only indication** where rifampin monotherapy is appropriate, as prophylaxis requires short-term use where resistance development is not a concern. *Tuberculosis* - Rifampin is a **first-line agent** for tuberculosis treatment and a cornerstone of all TB regimens. - However, it is **never used as monotherapy** for TB due to rapid development of resistance. - Standard TB treatment requires **multidrug therapy** with rifampin, isoniazid, pyrazinamide, and ethambutol (RIPE) for initial phase. *Methicillin-resistant Staphylococcus aureus infection* - Rifampin is sometimes used in **combination** with other antibiotics (e.g., vancomycin, daptomycin) to treat **MRSA infections**, especially those involving **prosthetic devices** or **biofilms**. - It is **not used as monotherapy** for active MRSA infections due to extremely high rates of spontaneous resistance. *Mycobacterium avium intracellulare infection* - **Mycobacterium avium complex (MAC)** infections require a multidrug regimen, typically including **macrolides (azithromycin or clarithromycin)**, **ethambutol**, and sometimes **rifabutin** (a rifamycin derivative preferred over rifampin). - **Monotherapy is never appropriate** for MAC infections due to resistance concerns and treatment failure. *Brucellosis* - **Brucellosis** treatment requires **combination therapy**, typically **doxycycline plus rifampin** for 6 weeks or longer. - **Rifampin monotherapy** is inadequate for eradicating Brucella infection and leads to treatment failure and resistance development.

Antimicrobials US Medical PG Question 8: A 15-year-old boy presents with his father to the urgent care with 5 days of frequent diarrhea, occasionally with streaks of blood mixed in. Stool cultures are pending, but preliminary stool samples demonstrate fecal leukocytes and erythrocytes. His vital signs are as follows: blood pressure is 126/83 mm Hg, heart rate is 97/min, and respiratory rate is 15/min. He is started on outpatient therapy for presumed Shigella infection. Which of the following is the most appropriate therapy?

• A. Oral doxycycline
• B. Oral vancomycin
• C. Oral TMP-SMX
• D. Oral azithromycin (Correct Answer)
• E. Oral ciprofloxacin

Antimicrobials Explanation: ***Oral azithromycin*** - **Azithromycin** is the **first-line empiric treatment** for suspected **Shigella infection** based on current CDC and WHO guidelines, particularly in pediatric and adolescent patients. - The presence of **fecal leukocytes and erythrocytes** indicates an invasive bacterial infection, which warrants antibiotic therapy to shorten the course of illness and reduce transmission risks. - Azithromycin has excellent efficacy against Shigella with relatively low resistance rates compared to older agents, and it is well-tolerated in adolescents. *Oral TMP-SMX* - **TMP-SMX (trimethoprim-sulfamethoxazole)** was historically first-line for Shigella, but **widespread resistance** (often >50% globally) has made it no longer recommended for empiric therapy. - It may still be used if culture and susceptibility testing confirm sensitivity, but should not be chosen empirically. *Oral ciprofloxacin* - **Ciprofloxacin**, a fluoroquinolone, is highly effective against **Shigella** and is first-line in adults. - However, its use in **pediatric patients under 18 years** is generally limited due to potential adverse effects on **cartilage development** and risk of tendinopathy. - In a 15-year-old, while approaching adult age, azithromycin remains preferred unless there are specific contraindications. *Oral doxycycline* - **Doxycycline** has limited activity against **Shigella** and is not considered appropriate empiric therapy for this infection. - It is more commonly used for atypical pathogens, certain sexually transmitted infections, or specific tick-borne diseases. *Oral vancomycin* - **Oral vancomycin** is primarily used to treat **Clostridioides difficile infection** (CDI) and is completely ineffective against **Shigella**. - Vancomycin acts only on gram-positive bacteria and does not penetrate the systemic circulation when given orally, making it unsuitable for gram-negative enteric infections.

Antimicrobials US Medical PG Question 9: An 82-year-old man is brought to the emergency department because of severe pain and joint stiffness in his right knee. The pain started 3 days ago and has worsened despite acetaminophen intake. He has benign prostatic hyperplasia and hypertension. One week ago, he had a urinary tract infection and was treated with nitrofurantoin. He does not smoke or drink alcohol. His current medications include enalapril, hydrochlorothiazide, and tamsulosin. He appears to be in severe pain and has trouble moving his right knee. His temperature is 38.7°C (101.5°F), pulse is 92/min, and blood pressure is 135/90 mm Hg. Physical examination shows a swollen, erythematous, warm right knee; range of motion is limited by pain. Synovial fluid aspiration shows a yellow-green turbid fluid. Gram stain of the synovial aspirate shows numerous leukocytes and multiple gram-negative rods. An x-ray of the right knee shows no abnormalities. Which of the following is the most appropriate pharmacotherapy?

• A. IV ceftazidime and gentamicin
• B. IV cefepime (Correct Answer)
• C. IV vancomycin and ceftazidime
• D. IV vancomycin
• E. IV nafcillin

Antimicrobials Explanation: ***IV cefepime*** - This patient presents with **septic arthritis** due to **gram-negative rods**, likely originating from a recent **urinary tract infection** given his history of BPH. **Cefepime** is a **fourth-generation cephalosporin** with broad-spectrum activity against many gram-negative bacteria, including *Pseudomonas aeruginosa*, and provides excellent coverage for this suspected etiology. - The patient's presentation with **fever**, a **hot, swollen, painful joint**, and **turbid synovial fluid** with **numerous leukocytes** and **gram-negative rods** on Gram stain points to severe bacterial infection requiring empiric broad-spectrum intravenous antibiotic coverage targeting gram-negative organisms. *IV ceftazidime and gentamicin* - **Ceftazidime** is a **third-generation cephalosporin** with good activity against gram-negative bacteria, including *Pseudomonas*. However, adding **gentamicin**, an **aminoglycoside**, could increase the risk of **nephrotoxicity** in an elderly patient with potential underlying renal impairment due to hypertension and multiple medications, especially when a single agent like cefepime might suffice initially. - While this combination offers broad gram-negative coverage, **monotherapy with cefepime** is often preferred for empiric treatment of suspected gram-negative sepsis or osteomyelitis to minimize potential adverse effects and simplify treatment, especially in an elderly patient. *IV vancomycin and ceftazidime* - **Vancomycin** is primarily used for **gram-positive organisms**, particularly **MRSA**. While it addresses potential *Staphylococcus* infection if gram stain was equivocal or negative, the presence of **gram-negative rods** makes it less critical as an initial empiric therapy for this specific presentation. - The combination would provide very broad coverage, but the primary pathology involves gram-negative rods, making the inclusion of vancomycin less targeted than alternatives, and risking unnecessary antibiotic exposure while not optimally covering common UTI-related gram-negative pathogens as effectively as cefepime. *IV vancomycin* - **Vancomycin** provides excellent coverage for **methicillin-resistant *Staphylococcus aureus* (MRSA)** and other gram-positive organisms, but it has **no activity against gram-negative rods**. - Since the Gram stain specifically shows **gram-negative rods**, vancomycin monotherapy would be ineffective against the identified pathogen and is therefore an inappropriate choice. *IV nafcillin* - **Nafcillin** is a **penicillinase-resistant penicillin** primarily used for **methicillin-sensitive *Staphylococcus aureus* (MSSA)** and other gram-positive infections. - It has **no significant activity against gram-negative rods**, making it an ineffective treatment option for an infection caused by gram-negative organisms.

Antimicrobials 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

Antimicrobials 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.

Antimicrobials Flashcard 1 of 10

Question: In addition to increased risk for C. difficile infection, patients on proton pump inhibitors are also at increased risk for _____

Answer: pneumonia

Antimicrobials Flashcard 2 of 10

Question: Fluoroquinolones are _____ due to them causing cartilage damage to the fetus

Answer: teratogenic

Antimicrobials Flashcard 3 of 10

Question: Isoniazid works to treat tuberculosis by inhibiting mycobacterial _____ production

Answer: cell wall

Antimicrobials Flashcard 4 of 10

Question: Which antimicrobials displace unconjugated bilirubin from serum albumin in the blood?_____

Answer: Sulfonamides

Antimicrobials Flashcard 5 of 10

Question: What antimicrobial is similar to sulfonamides, inhibiting dihydropteroate synthase?_____

Answer: Dapsone

Antimicrobials Flashcard 6 of 10

Question: Doxorubicin has a _____ range of chemotherapeutic uses and is commonly used in clinical practice

Answer: broad

Antimicrobials Flashcard 7 of 10

Question: What is the common treatment for all rickettsial diseases?

Answer: doxycycline

Antimicrobials Flashcard 8 of 10

Question: aminoglycosides

Answer: CN 8 toxicity

Antimicrobials Flashcard 9 of 10

Question: tetracyclines

Answer: discolored teeth

Antimicrobials Flashcard 10 of 10

Question: antimycin A

Answer:

Extra Information: inhibits the electron transport chaininhibits oxidative phosphorylation