Cephalosporins US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Cephalosporins. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Cephalosporins US Medical PG Question 1: A neonate born at 33 weeks is transferred to the NICU after a complicated pregnancy and C-section. A week after being admitted, he developed a fever and became lethargic and minimally responsive to stimuli. A lumbar puncture is performed that reveals the following:
Appearance Cloudy
Protein 64 mg/dL
Glucose 22 mg/dL
Pressure 330 mm H20
Cells 295 cells/mm³ (> 90% PMN)
A specimen is sent to microbiology and reveals gram-negative rods. Which of the following is the next appropriate step in management?
- A. MRI scan of the head
- B. Start the patient on IV ceftriaxone
- C. Provide supportive measures only
- D. Start the patient on IV cefotaxime (Correct Answer)
- E. Start the patient on oral rifampin
Cephalosporins Explanation: ***Start the patient on IV cefotaxime***
- The cerebrospinal fluid (CSF) analysis with **cloudy appearance, elevated protein, low glucose, high pressure, and predominant PMNs**, coupled with **gram-negative rods** on microscopy, is highly suggestive of **bacterial meningitis** in a neonate.
- **Cefotaxime** is a third-generation cephalosporin commonly used for neonatal meningitis caused by gram-negative organisms due to its excellent CSF penetration and broad-spectrum activity, particularly against common neonatal pathogens like *E. coli* which can present as gram-negative rods.
*MRI scan of the head*
- An MRI would be considered **after initiating appropriate antibiotic treatment** to assess for complications like abscess formation or ventriculitis, not as the immediate next step in an acute, life-threatening infection.
- Delaying antibiotic treatment for imaging in acute bacterial meningitis can lead to increased morbidity and mortality.
*Start the patient on IV ceftriaxone*
- While ceftriaxone is a third-generation cephalosporin, it is **generally avoided in neonates** due to the risk of **biliary sludging** and **kernicterus**.
- Ceftriaxone competes with bilirubin for albumin binding sites, which is particularly risky in neonates who are already prone to hyperbilirubinemia.
*Provide supportive measures only*
- Given the strong evidence of **bacterial meningitis**, providing only supportive measures without specific antibiotic treatment would be inadequate and would lead to rapid deterioration and potentially fatal outcomes.
- Bacterial meningitis requires prompt and aggressive antimicrobial therapy.
*Start the patient on oral rifampin*
- **Rifampin is never used as monotherapy for bacterial meningitis** due to rapid resistance development and its primary role is in specific infections like tuberculosis or as part of combination therapy for certain resistant bacteria.
- Oral administration is also not ideal for acutely ill neonates with meningitis needing rapid, high-concentration antibiotics in the CSF.
Cephalosporins US Medical PG Question 2: A 70-year-old man presents with fever, headache, and vomiting. He says that symptoms onset acutely 2 days ago and have not improved. He also reports associated weakness and chills. Past medical history is significant for occasional heartburn. His temperature is 39.4°C (103.0°F), the pulse rate is 124/min, the blood pressure is 130/84 mm Hg, and the respiratory rate is 22/min. On physical examination, there is significant nuchal rigidity. No signs of raised intracranial pressure are present. A lumbar puncture is performed and cerebrospinal fluid (CSF) analysis shows lymphocyte-dominant pleocytosis with increased CSF protein levels. Bacteriological culture of the CSF reveals the growth of Listeria monocytogenes. Which of the following antibiotics is the best choice for the treatment of this patient?
- A. Ampicillin (Correct Answer)
- B. Ceftriaxone
- C. Ciprofloxacin
- D. Chloramphenicol
- E. Vancomycin
Cephalosporins Explanation: ***Ampicillin***
- **Ampicillin** is the drug of choice for treating **Listeria monocytogenes** infections due to its excellent activity against this bacterium.
- Given the patient's age (70 years old) and the serious nature of **bacterial meningitis**, prompt and appropriate antibiotic therapy with ampicillin is crucial.
*Ceftriaxone*
- While a broad-spectrum antibiotic often used for meningitis, **ceftriaxone lacks reliable coverage** against **Listeria monocytogenes**.
- Using ceftriaxone alone in this case would lead to **treatment failure** and potentially severe outcomes.
*Ciprofloxacin*
- **Ciprofloxacin** is a fluoroquinolone antibiotic that has **limited efficacy** against **Listeria monocytogenes**.
- It is not recommended as a primary treatment for listerial meningitis.
*Chloramphenicol*
- **Chloramphenicol** has activity against Listeria but is **not a first-line agent** due to potential side effects like **bone marrow suppression** (aplastic anemia).
- Its use is generally reserved for cases where other, safer options are contraindicated or ineffective.
*Vancomycin*
- **Vancomycin** is primarily effective against **Gram-positive bacteria**, particularly MRSA and drug-resistant pneumococci.
- While Listeria is Gram-positive, **vancomycin has poor penetration into the CSF** and **limited efficacy** against Listeria monocytogenes, making it unsuitable as a primary treatment for listerial meningitis.
Cephalosporins US Medical PG Question 3: A 72-year-old man is admitted to the hospital with productive cough and fever. A chest radiograph is obtained and shows lobar consolidation. The patient is diagnosed with pneumonia. He has a history of penicillin allergy. The attending physician orders IV levofloxacin as empiric therapy. On morning rounds the next day, the team discovers that the patient was administered ceftriaxone instead of levofloxacin. The patient has already received a full dose of ceftriaxone and had no signs of allergic reaction, and his pneumonia appears to be improving clinically. What is the most appropriate next step?
- A. Administer diphenhydramine as prophylaxis against allergic reaction
- B. Continue with ceftriaxone as empiric therapy
- C. Switch the patient to oral azithromycin in preparation for discharge and home therapy
- D. Switch the patient back to levofloxacin and discuss the error with the patient
- E. Continue with ceftriaxone and add azithromycin as inpatient empiric pneumonia therapy (Correct Answer)
Cephalosporins Explanation: ***Continue with ceftriaxone and add azithromycin as inpatient empiric pneumonia therapy***
- This is the **guideline-recommended approach** for hospitalized community-acquired pneumonia (CAP) according to ATS/IDSA guidelines.
- Ceftriaxone (beta-lactam) plus azithromycin (macrolide) provides **dual coverage** for typical bacteria (Streptococcus pneumoniae) and atypical organisms (Mycoplasma, Chlamydophila, Legionella).
- Since the patient has already tolerated ceftriaxone without allergic reaction despite penicillin allergy history, continuing it is safe, and **adding azithromycin completes appropriate empiric therapy** for a 72-year-old hospitalized patient.
- The cross-reactivity between penicillins and cephalosporins is low (1-3%), and the patient's tolerance of ceftriaxone confirms safety.
*Continue with ceftriaxone as empiric therapy*
- While the patient is improving on ceftriaxone and tolerated it without allergic reaction, **monotherapy with a beta-lactam alone is suboptimal** for hospitalized CAP.
- Guidelines recommend dual therapy (beta-lactam + macrolide) or fluoroquinolone monotherapy for hospitalized non-ICU patients to ensure adequate atypical coverage.
- Continuing ceftriaxone alone misses potential atypical pathogens that may be contributing to the pneumonia.
*Switch the patient to oral azithromycin in preparation for discharge and home therapy*
- It is **premature to switch to oral therapy** or consider discharge after only one day of treatment for a 72-year-old with pneumonia requiring hospitalization.
- The patient should remain on IV therapy until clinically stable (afebrile, hemodynamically stable, improving oxygenation) for an appropriate duration.
*Administer diphenhydramine as prophylaxis against allergic reaction*
- Since the patient has already tolerated a full dose of ceftriaxone without any allergic reaction, **prophylactic antihistamines are unnecessary**.
- The low cross-reactivity between penicillins and third-generation cephalosporins, combined with the successful first dose, indicates minimal risk.
*Switch the patient back to levofloxacin and discuss the error with the patient*
- Switching back to levofloxacin is **unnecessary and potentially disruptive** given that the patient is clinically improving on ceftriaxone and has demonstrated tolerance to it.
- While the original plan was levofloxacin (appropriate fluoroquinolone monotherapy), the inadvertent use of ceftriaxone has proven safe and provides an opportunity to implement the preferred dual-therapy regimen.
- While discussing medication errors is important for transparency, the immediate medical priority is optimizing pneumonia treatment.
Cephalosporins US Medical PG Question 4: Blood cultures are sent to the laboratory and empiric treatment with intravenous vancomycin is started. Blood cultures grow gram-negative bacilli identified as Cardiobacterium hominis. Which of the following is the most appropriate next step in management?
- A. Switch to intravenous gentamicin
- B. Switch to intravenous ampicillin
- C. Switch to intravenous ceftriaxone (Correct Answer)
- D. Switch to intravenous cefazolin
- E. Add intravenous rifampin
Cephalosporins Explanation: ***Switch to intravenous ceftriaxone***
- **Cardiobacterium hominis** is part of the **HACEK group** of bacteria, which are known for causing **endocarditis**.
- These organisms are typically susceptible to **beta-lactam antibiotics**, with **third-generation cephalosporins** like ceftriaxone being the drug of choice due to their excellent activity and good penetration.
*Switch to intravenous gentamicin*
- While **aminoglycosides** like gentamicin can be used in combination regimens for serious infections, they are generally **not monotherapy** for HACEK endocarditis and are associated with **nephrotoxicity** and **ototoxicity**.
- The primary treatment for HACEK endocarditis is a **beta-lactam antibiotic**, not an aminoglycoside alone.
*Switch to intravenous ampicillin*
- **Ampicillin** is a beta-lactam, but it may not consistently provide optimal coverage for all HACEK organisms, and some strains may have reduced susceptibility.
- **Third-generation cephalosporins** are preferred due to their broader and more consistent activity against this group.
*Switch to intravenous cefazolin*
- **Cefazolin** is a first-generation cephalosporin and typically has **limited activity** against gram-negative bacilli, especially those like Cardiobacterium hominis which require broader-spectrum beta-lactams.
- Its spectrum of activity is primarily against **gram-positive bacteria** and some **gram-negative cocci**.
*Add intravenous rifampin*
- **Rifampin** is primarily used for **mycobacterial infections** and in combination regimens for specific bacterial infections (e.g., bone and joint infections, prosthetic device infections) often due to resistant staphylococci.
- It is **not a first-line agent** for Cardiobacterium hominis infections and there's no indication for its use here with an organism susceptible to ceftriaxone.
Cephalosporins 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
Cephalosporins 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.
Cephalosporins US Medical PG Question 6: A 21-year-old woman comes to the physician because of a 4-day history of abdominal cramps and bloody diarrhea 5 times per day. Her symptoms began after she ate an egg sandwich from a restaurant. Her vital signs are within normal limits. Physical examination shows diffuse abdominal tenderness. Stool culture shows gram-negative rods that produce hydrogen sulfide and do not ferment lactose. Which of the following effects is most likely to occur if she receives antibiotic therapy?
- A. Orange discoloration of bodily fluids
- B. Pruritic maculopapular rash on the extensor surface
- C. Self-limiting systemic inflammatory response
- D. Prolonged fecal excretion of the pathogen (Correct Answer)
- E. Thrombocytopenia and hemolytic anemia
Cephalosporins Explanation: ***Prolonged fecal excretion of the pathogen***
- The patient's symptoms (abdominal cramps, bloody diarrhea after eating an egg sandwich) and stool culture results (gram-negative rods, hydrogen sulfide producers, non-lactose fermenting) are highly suggestive of **Salmonella enterica** infection.
- Antibiotic treatment for non-typhoidal Salmonella gastroenteritis typically **prolongs fecal excretion** and does not shorten the illness, reserving antibiotics for severe cases or immunocompromised individuals.
*Orange discoloration of bodily fluids*
- **Orange discoloration of bodily fluids** (urine, sweat, tears) is a known side effect of **rifampin**, an antibiotic primarily used for tuberculosis and some bacterial meningitides.
- Rifampin is not indicated nor commonly used for Salmonella gastroenteritis.
*Pruritic maculopapular rash on the extensor surface*
- A **pruritic maculopapular rash on the extensor surfaces** is a common presentation of drug reactions, often associated with **penicillins** or **cephalosporins**, especially in viral infections (e.g., amoxicillin rash in mononucleosis).
- This is a general antibiotic side effect and not specifically linked to the outcome of treating Salmonella.
*Self-limiting systemic inflammatory response*
- A self-limiting systemic inflammatory response could be a general reaction to an active infection or a drug, but it's not the most likely or specific outcome of **antibiotic therapy in Salmonella gastroenteritis**.
- Worsening of symptoms can occur in some cases due to toxemia from bacterial lysis (e.g., Jarisch-Herxheimer reaction), but "self-limiting systemic inflammatory response" is too generic for this specific scenario.
*Thrombocytopenia and hemolytic anemia*
- **Thrombocytopenia and hemolytic anemia** in the setting of diarrheal illness strongly suggest **hemolytic uremic syndrome (HUS)**, which is typically associated with **Shiga toxin-producing E. coli** (STEC), particularly E. coli O157:H7.
- While Salmonella can cause severe disease, HUS is not a typical complication of its treatment, and antibiotics are often avoided in STEC infections due to increased risk of HUS.
Cephalosporins US Medical PG Question 7: 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
Cephalosporins 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.
Cephalosporins US Medical PG Question 8: A 37-year-old man with a history of IV drug use presents to the ED with complaints of fevers, chills, and malaise for one week. He admits to recently using IV and intramuscular heroin. Vital signs are as follows: T 40.0 C, HR 120 bpm, BP 110/68 mmHg, RR 14, O2Sat 98%. Examination reveals a new systolic murmur that is loudest at the lower left sternal border. Initial management includes administration of which of the following regimens?
- A. IV Vancomycin, IV ceftriaxone, IV fluconazole
- B. IV Vancomycin, IV ceftriaxone (Correct Answer)
- C. IV Vancomycin, IV levofloxacin
- D. IV Vancomycin
- E. IV Vancomycin, IV gentamicin, PO rifampin
Cephalosporins Explanation: ***IV Vancomycin, IV ceftriaxone***
- The patient's history of **IV drug use**, fevers, chills, new systolic murmur, and likely **tricuspid valve involvement** (murmur loudest at the lower left sternal border) strongly suggest **infective endocarditis**.
- The empiric regimen for suspected endocarditis in an IV drug user should cover **methicillin-resistant _Staphylococcus aureus_ (MRSA)** with **vancomycin** and gram-negative organisms with a **third-generation cephalosporin** like **ceftriaxone**.
- This combination provides broad coverage for the most common pathogens in native valve endocarditis among IV drug users, including MRSA, streptococci, and many gram-negative organisms.
*IV Vancomycin, IV ceftriaxone, IV fluconazole*
- While vancomycin and ceftriaxone are appropriate, **fluconazole** is an antifungal and is generally not indicated for empiric treatment of bacterial endocarditis unless there's a strong suspicion of **fungal infection**.
- Fungal endocarditis is less common and usually requires prolonged treatment with specific antifungals, often alongside surgical intervention.
*IV Vancomycin, IV levofloxacin*
- **Levofloxacin** is a fluoroquinolone that covers a broad spectrum of bacteria but is not the preferred empiric agent for gram-negative coverage in suspected endocarditis in IV drug users due to concerns about resistance and lack of superior coverage compared to third-generation cephalosporins.
- **Ceftriaxone** provides better coverage for common gram-negative pathogens associated with endocarditis among IV drug users in this context.
*IV Vancomycin, IV gentamicin, PO rifampin*
- **Gentamicin** is an aminoglycoside that provides effective gram-negative coverage and is often used in combination therapy for endocarditis, but **rifampin** is typically reserved for prosthetic valve endocarditis or refractory cases due to its risk of drug interactions and resistance development.
- **Oral rifampin** may not be appropriate for initial aggressive treatment in an acutely ill patient with suspected acute endocarditis, where IV therapy is preferred.
*IV Vancomycin*
- While **vancomycin** is crucial for covering **MRSA** which is common in IV drug users, it alone does not provide adequate coverage for potential **gram-negative pathogens** that can also cause endocarditis in this population.
- **Multidrug empiric therapy** is essential to cover a broad range of likely pathogens causing endocarditis in IV drug users, especially with severe symptoms.
Cephalosporins US Medical PG Question 9: A 32-year-old woman is admitted to the hospital after undergoing an open cholecystectomy under general anesthesia. Preoperatively, the patient was administered a single dose of intravenous ceftriaxone. Now, the anesthetic effects have worn off, and her pain is well managed. The patient has a prior medical history of hypertension which has been well-controlled by captopril for 2 years. Her vitals currently show: blood pressure 134/82 mm Hg, heart rate 84/min, and respiratory rate 16/min. Postoperative laboratory findings are significant for the following:
Serum glucose (random) 174 mg/dL
Serum electrolytes
Sodium 142 mEq/L
Potassium 3.9 mEq/L
Chloride 101 mEq/L
Serum creatinine 0.9 mg/dL
Blood urea nitrogen 10 mg/dL
Alanine aminotransferase (ALT) 150 U/L
Aspartate aminotransferase (AST) 172 U/L
Serum bilirubin (total) 0.9 mg/dL
Preoperative labs were all within normal limits. Which of the following drugs is most likely responsible for this patient’s abnormal laboratory findings?
- A. Captopril
- B. Propofol
- C. Nitrous oxide
- D. Sevoflurane (Correct Answer)
- E. Ceftriaxone
Cephalosporins Explanation: ***Sevoflurane***
- **Sevoflurane** is a volatile halogenated anesthetic that can rarely cause **postoperative hepatotoxicity** (halogenated anesthetic hepatitis)
- This presents with **elevated transaminases** (ALT and AST) within 2-14 days post-surgery
- Sevoflurane can also cause **transient hyperglycemia** through stress response and insulin resistance during and after anesthesia
- While less hepatotoxic than halothane, sevoflurane metabolism produces trifluoroacetic acid derivatives that can trigger immune-mediated liver injury in susceptible individuals
- Renal function remains normal, distinguishing this from fluoride-induced nephrotoxicity
*Captopril*
- **Captopril** is an ACE inhibitor that can rarely cause **cholestatic hepatitis** with chronic use
- However, the patient has been on captopril for 2 years with normal preoperative labs, making it an unlikely cause of acute postoperative transaminase elevation
- Does not explain the hyperglycemia observed
*Propofol*
- **Propofol** is an intravenous anesthetic that can cause **propofol infusion syndrome** with prolonged high-dose infusions (typically >48 hours)
- While propofol can cause metabolic derangements, acute transaminase elevation is not a typical feature of short-term use for routine surgery
- The degree of liver enzyme elevation seen here is more consistent with volatile anesthetic hepatotoxicity
*Nitrous oxide*
- **Nitrous oxide** inactivates **vitamin B12** (methionine synthase inhibition), leading to megaloblastic anemia and neurological complications with prolonged or repeated exposure
- Does not cause acute hepatotoxicity or explain the elevated transaminases and glucose seen in this case
*Ceftriaxone*
- **Ceftriaxone** can cause **cholestatic hepatitis** and hyperbilirubinemia, particularly with prolonged use
- However, this patient received only a **single preoperative dose**, making ceftriaxone an unlikely cause
- The patient's bilirubin is normal (0.9 mg/dL), which would be elevated in ceftriaxone-induced cholestasis
- Does not explain the hyperglycemia
Cephalosporins US Medical PG Question 10: A 22-year-old female with no past medical history presents to her primary care physician with a 3-day history of knee pain. She denies any recent injury or trauma. On physical examination her knee is warm, erythematous, and has diminished range of movement. The patient reports having multiple sexual partners over the last year and does not use protection regularly. Her blood pressure is 124/85 mmHg, heart rate is 76/min, and temperature is 38.3℃ (101.0℉). A joint aspiration is performed and a growth of gram-negative diplococci is noted on bacterial culture. What is the treatment of choice for this patient's condition?
- A. Vancomycin monotherapy
- B. Fluoroquinolones
- C. Nafcillin monotherapy and joint aspiration
- D. Oxacillin and ceftriaxone
- E. Ceftriaxone monotherapy and joint aspiration (Correct Answer)
Cephalosporins Explanation: ***Ceftriaxone monotherapy and joint aspiration***
- The patient's presentation with **acute monoarthritis**, fever, and **gram-negative diplococci** on joint culture is highly suggestive of **gonococcal arthritis**. Intravenous ceftriaxone is the treatment of choice for disseminated gonococcal infection.
- While joint aspiration confirms the diagnosis and can relieve pressure, definitive treatment requires systemic antibiotics to clear the infection.
*Vancomycin monotherapy*
- **Vancomycin** is primarily effective against **gram-positive bacteria**, particularly MRSA, and would not adequately cover the gram-negative diplococci found in this case.
- Using vancomycin alone would leave the patient's gonococcal infection untreated, potentially leading to worsening of symptoms or complications.
*Fluoroquinolones*
- While some fluoroquinolones have activity against *Neisseria gonorrhoeae*, **widespread resistance** to this class of antibiotics has emerged, making them an unreliable choice for empiric or first-line treatment of gonococcal infections.
- The CDC no longer recommends fluoroquinolones for gonococcal infections due to high rates of resistance.
*Nafcillin monotherapy and joint aspiration*
- **Nafcillin** is a narrow-spectrum penicillin effective primarily against **methicillin-sensitive *Staphylococcus aureus*** and other gram-positive organisms.
- It would not provide appropriate coverage for the **gram-negative diplococci** identified in this patient's joint fluid.
*Oxacillin and ceftriaxone*
- While **ceftriaxone** is appropriate, the addition of **oxacillin** (another anti-staphylococcal penicillin) would be unnecessary.
- Oxacillin is primarily used for gram-positive infections and would not add benefit against **gonococcal arthritis**, increasing the risk of adverse effects without improving efficacy.
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