Central line-associated bloodstream infections US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Central line-associated bloodstream infections. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Central line-associated bloodstream infections US Medical PG Question 1: Two hours after admission to the intensive care unit, a 56-year-old man with necrotizing pancreatitis develops profound hypotension. His blood pressure is 80/50 mm Hg and he is started on vasopressors. A central venous access line is placed. Which of the following is most likely to decrease the risk of complications from this procedure?
- A. Placement of the central venous line in the femoral vein
- B. Replacement of the central venous line every 7-10 days
- C. Initiation of anticoagulation after placement
- D. Preparation of the skin with chlorhexidine and alcohol (Correct Answer)
- E. Initiation of periprocedural systemic antibiotic prophylaxis
Central line-associated bloodstream infections Explanation: ***Preparation of the skin with chlorhexidine and alcohol***
- **Chlorhexidine** with alcohol is the most effective skin antiseptic for preventing **catheter-related bloodstream infections (CRBSIs)** by significantly reducing skin microbial counts.
- Proper skin preparation is a cornerstone of preventing **infectious complications** associated with central venous catheter insertion.
*Placement of the central venous line in the femoral vein*
- The femoral site is generally associated with a **higher risk of infection** and **deep venous thrombosis** compared to subclavian or internal jugular sites in adult patients.
- Femoral access is often reserved for situations where other sites are inaccessible or contraindicated, due to its **less favorable complication profile**.
*Replacement of the central venous line every 7-10 days*
- Routine replacement of central venous lines at fixed intervals, without clinical indication, has **not been shown to reduce infection rates**.
- This practice can actually **increase the risk** of mechanical complications and introduce new opportunities for infection with each procedure.
*Initiation of anticoagulation after placement*
- Routine systemic **anticoagulation** after central venous line placement is generally **not recommended** due to an increased risk of **bleeding complications**.
- Anticoagulation is typically reserved for specific indications such as documented **catheter-related thrombosis**.
*Initiation of periprocedural systemic antibiotic prophylaxis*
- Routine **systemic antibiotic prophylaxis** is **not recommended** for central venous catheter insertion as it promotes **antibiotic resistance** without significantly reducing CRBSIs.
- Strict adherence to **aseptic technique** and proper skin antisepsis are more effective for preventing infections.
Central line-associated bloodstream infections US Medical PG Question 2: A 25-year-old woman comes to the physician because of a 2-week history of episodic bleeding from the nose and gums and one episode of blood in her urine. She was treated with chloramphenicol 1 month ago for Rickettsia rickettsii infection. Her pulse is 130/min, respirations are 22/min, and blood pressure is 105/70 mm Hg. Examination shows mucosal pallor, scattered petechiae, and ecchymoses on the extremities. Laboratory studies show:
Hemoglobin 6.3 g/dL
Hematocrit 26%
Leukocyte count 900/mm3 (30% neutrophils)
Platelet count 50,000/mm3
The physician recommends a blood transfusion and informs her of the risks and benefits. Which of the following red blood cell preparations will most significantly reduce the risk of transfusion-related cytomegalovirus infection?
- A. Warming
- B. Irradiation
- C. Centrifugation
- D. Washing
- E. Leukoreduction (Correct Answer)
Central line-associated bloodstream infections Explanation: ***Leukoreduction***
- **Cytomegalovirus (CMV)** is primarily transmitted via **leukocytes** in blood products, as it is a latent infection within these cells.
- **Leukoreduction** removes most white blood cells, thereby significantly reducing the risk of CMV transmission, especially in immunocompromised patients or those at high risk.
*Warming*
- **Warming blood** to body temperature before transfusion helps prevent hypothermia in the recipient and reduces the risk of cardiac arrhythmias.
- It does not, however, have any significant effect on reducing the transmission of infectious agents like CMV.
*Irradiation*
- **Irradiation** of blood products inactivates donor T lymphocytes, preventing **transfusion-associated graft-versus-host disease (TA-GVHD)**, predominantly in immunocompromised recipients.
- It does not effectively remove or inactivate viruses like CMV that reside within cells.
*Centrifugation*
- **Centrifugation** is used to separate blood components based on their different densities (e.g., plasma, platelets, red blood cells).
- While it separates components, it does not specifically remove or inactivate CMV-infected white blood cells from the remaining red blood cell product in a manner that significantly reduces infection risk.
*Washing*
- **Washing red blood cells** with saline removes plasma proteins, antibodies, and some white blood cells, which can prevent allergic reactions to plasma proteins or hyperkalemia.
- While it may remove some leukocytes, it is generally less effective than leukoreduction for preventing CMV transmission and is primarily indicated for other specific transfusion reactions.
Central line-associated bloodstream infections US Medical PG Question 3: A 24-year-old woman presents to the ED with symptoms of pelvic inflammatory disease despite being previously treated with azithromycin for chlamydial infection. Based on your clinical understanding about the epidemiology of PID, you decide to obtain a gram stain which shows a gram-negative diplococci. What is the next step in order to confirm the identity of the organism described?
- A. Perform an RT-PCR
- B. Culture in TCBS agar
- C. Culture in Thayer-Martin media (Correct Answer)
- D. Obtain an acid fast stain
- E. Culture in Bordet-Gengou agar
Central line-associated bloodstream infections Explanation: ***Culture in Thayer-Martin media***
- The presence of **gram-negative diplococci** in a patient with PID symptoms strongly suggests *Neisseria gonorrhoeae*.
- **Thayer-Martin media** is a selective **agar** specifically designed for the isolation and identification of *Neisseria* species, including *N. gonorrhoeae*, by inhibiting the growth of most commensal bacteria and fungi.
*Perform an RT-PCR*
- While **RT-PCR** can detect *Neisseria gonorrhoeae* nucleic acids, it is primarily used for **molecular diagnosis** and not directly for confirming the identity of a cultured organism visualized on gram stain.
- **RT-PCR** is generally used for direct detection from clinical samples and is particularly useful in situations where culture is difficult or unavailable.
*Culture in TCBS agar*
- **TCBS (Thiosulfate Citrate Bile Salts Sucrose) agar** is a selective medium primarily used for the isolation of *Vibrio* species, which are not typically associated with pelvic inflammatory disease or characterized as gram-negative diplococci.
- This medium is designed to differentiate between different *Vibrio* species based on sucrose fermentation.
*Obtain an acid fast stain*
- An **acid-fast stain** (e.g., Ziehl-Neelsen stain) is used to identify bacteria with a **waxy cell wall**, such as *Mycobacterium* species (e.g., *Mycobacterium tuberculosis*).
- *Neisseria gonorrhoeae* is not acid-fast, and this stain would not be appropriate for its identification.
*Culture in Bordet-Gengou agar*
- **Bordet-Gengou agar** is a specialized culture medium used for the isolation of *Bordetella pertussis*, the causative agent of whooping cough.
- This medium is not suitable for the isolation of *Neisseria gonorrhoeae*.
Central line-associated bloodstream infections 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
Central line-associated bloodstream infections 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.
Central line-associated bloodstream infections US Medical PG Question 5: A 38-year-old female presents to the emergency room with fevers, fatigue, and anorexia for over a month. Past medical history includes mild mitral valve prolapse. She underwent an uncomplicated tooth extraction approximately 6 weeks ago. Her vital signs include a temperature of 100.8 F, pulse of 83, blood pressure of 110/77, and SpO2 of 97% on room air. On exam, you note a grade III/VI holosystolic murmur at the apex radiating to the axilla as well as several red, painful nodules on her fingers. Which of the following is the next best course of action?
- A. Blood cultures are not needed. Start empiric antibiotics
- B. Start anticoagulation with heparin
- C. Consult cardiothoracic surgery for mitral valve replacement
- D. Obtain blood cultures x3 sites over 24 hours and start antibiotics after culture results are available
- E. Obtain blood cultures x3 sites over 1 hour and start empiric antibiotics (Correct Answer)
Central line-associated bloodstream infections Explanation: ***Obtain blood cultures x3 sites over 1 hour and start empiric antibiotics***
- The patient's presentation with **fever, fatigue, anorexia, new murmur, and painful finger nodules (Osler's nodes)** after a recent dental procedure strongly suggests **infective endocarditis**. Prompt initiation of **empiric antibiotics** after obtaining adequate blood cultures is crucial to improve outcomes and prevent further complications like septic emboli or valvular damage.
- Obtaining **multiple blood cultures rapidly (e.g., three sets over 1 hour)** from different sites maximizes the chance of isolating the causative organism before antibiotics are given, enabling targeted therapy later, while minimizing delay to treatment.
*Blood cultures are not needed. Start empiric antibiotics*
- **Blood cultures are essential** for diagnosing infective endocarditis, identifying the causative organism, and guiding appropriate antibiotic therapy. Skipping blood cultures could lead to inappropriate antibiotic selection and treatment failure.
- While empiric antibiotics are warranted, they should always be initiated **after blood cultures** have been drawn to avoid sterilizing the blood and making microbial identification difficult.
*Start anticoagulation with heparin*
- **Anticoagulation is generally contraindicated** in infective endocarditis due to the increased risk of hemorrhagic complications, especially in cases of septic emboli to the brain.
- While patients with endocarditis can form vegetations that may embolize, the risks of **bleeding outweigh the benefits** of routine anticoagulation.
*Consult cardiothoracic surgery for mitral valve replacement*
- While **mitral valve prolapse** is a risk factor for endocarditis and severe valvular damage may eventually require surgery, primary management involves **antibiotic therapy**.
- Surgical intervention is typically reserved for cases with **severe valvular regurgitation/stenosis leading to heart failure**, uncontrolled infection despite antibiotics, or recurrent emboli, and is not the immediate next step.
*Obtain blood cultures x3 sites over 24 hours and start antibiotics after culture results are available*
- Waiting for **24 hours to collect blood cultures** would significantly delay the initiation of antibiotics, which is dangerous in a potentially life-threatening infection like endocarditis.
- Delaying antibiotics until **culture results are available** could take several days, leading to worsening infection, organ damage, and increased mortality. **Empiric antibiotics** must be started promptly after initial blood collection.
Central line-associated bloodstream infections US Medical PG Question 6: A 63-year-old female recovering from a total shoulder arthroplasty completed 6 days ago presents complaining of joint pain in her repaired shoulder. Temperature is 39 degrees Celsius. Physical examination demonstrates erythema and significant tenderness around the incision site. Wound cultures reveal Gram-positive cocci that are resistant to nafcillin. Which of the following organisms is the most likely cause of this patient's condition?
- A. Streptococcus pyogenes
- B. Escherichia coli
- C. Streptococcus viridans
- D. Staphylococcus epidermidis
- E. Staphylococcus aureus (Correct Answer)
Central line-associated bloodstream infections Explanation: ***Staphylococcus aureus***
- The combination of **post-surgical infection**, **erythema**, and fever with **Gram-positive cocci** that are **nafcillin-resistant** is highly indicative of **Methicillin-Resistant Staphylococcus aureus (MRSA)**.
- *S. aureus* is a common cause of **surgical site infections**, and its resistance to nafcillin implies it is MRSA, a significant clinical concern for its difficulty in treatment.
*Streptococcus pyogenes*
- While *S. pyogenes* is a Gram-positive coccus that can cause skin and soft tissue infections, it is typically **susceptible to penicillin** and related antibiotics like nafcillin, unlike the organism described.
- It is more commonly associated with **streptococcal pharyngitis** or **cellulitis**, and while it can cause severe disease, its resistance profile doesn't match the clinical picture.
*Escherichia coli*
- *E. coli* is a **Gram-negative rod**, not a Gram-positive coccus.
- It is a common cause of **urinary tract infections** and **gastrointestinal infections**, making it an unlikely pathogen for a post-surgical joint infection unless contaminated from a visceral source.
*Streptococcus viridans*
- **Viridans streptococci** are Gram-positive cocci but are typically associated with **endocarditis** or dental infections, especially after poor dental hygiene or procedures.
- They are usually **susceptible to penicillin** and do not typically exhibit nafcillin resistance as the primary feature in a post-arthroplasty infection.
*Staphylococcus epidermidis*
- *S. epidermidis* is a **coagulase-negative Staphylococcus** known for forming **biofilms on prosthetic devices**, leading to chronic, low-grade infections.
- While it can be nafcillin-resistant, the **acute presentation** with fever and significant inflammation suggests a more virulent pathogen like *S. aureus*, as *S. epidermidis* infections are typically indolent.
Central line-associated bloodstream infections US Medical PG Question 7: A 27-year-old man presents to the emergency department with weakness and a fever for the past week. The patient is homeless and has a past medical history of alcohol and IV drug abuse. His temperature is 102°F (38.9°C), blood pressure is 107/68 mmHg, pulse is 120/min, respirations are 17/min, and oxygen saturation is 98% on room air. Physical exam is notable for a tremulous patient with antecubital scars and a murmur over the left lower sternal border. Blood cultures are drawn and the patient is started on vancomycin and ceftriaxone and is admitted to the ICU. The patient's fever and symptoms do not improve despite antibiotic therapy for which the initial identified organism is susceptible. Cultures currently reveal MRSA as one of the infective organisms. Which of the following is the best next step in management?
- A. Transesophageal echocardiography (Correct Answer)
- B. Obtain new blood cultures
- C. CT scan of the chest
- D. Nafcillin and piperacillin-tazobactam
- E. Vancomycin and gentamicin
Central line-associated bloodstream infections Explanation: ***Transesophageal echocardiography***
- The patient's history of **IV drug abuse**, **fever**, **new murmur**, and identification of **MRSA** strongly suggest **infective endocarditis**.
- A Transesophageal echocardiography (TEE) is the **most sensitive and specific imaging modality** to detect vegetations, abscesses, or valvular damage, which is crucial for guiding further management.
*Obtain new blood cultures*
- While repeating blood cultures can be useful to confirm eradication or identify new pathogens, the initial blood cultures already revealed MRSA, which is a common cause of **endocarditis in IV drug users**.
- The immediate priority given the lack of improvement and high suspicion of endocarditis is to visualize the heart valves for vegetations.
*CT scan of the chest*
- A CT scan of the chest would be useful to look for complications such as **septic emboli in the lungs** or other pulmonary pathologies.
- However, it would not provide the detailed visualization of heart valves necessary to diagnose or rule out valvular vegetations characteristic of endocarditis.
*Nafcillin and piperacillin-tazobactam*
- **Nafcillin** is active against **methicillin-susceptible Staphylococcus aureus (MSSA)**, but the patient's cultures already identified **MRSA**.
- **Piperacillin-tazobactam** is a broad-spectrum antibiotic but not a first-line treatment for MRSA infections and would not be appropriate given the identified pathogen.
*Vancomycin and gentamicin*
- The patient is already on **Vancomycin**, which is appropriate for MRSA, but adding **gentamicin** without clear indication would not be the best next step.
- While gentamicin is sometimes used as an adjunct in specific endocarditis regimens (e.g., enterococcal), the primary concern here is the lack of clinical improvement despite appropriate MRSA coverage, pointing towards a structural cardiac issue.
Central line-associated bloodstream infections US Medical PG Question 8: A 54-year-old man presents with fever, abdominal pain, nausea, and bloody diarrhea. He says that his symptoms started 36 hours ago and have not improved. Past medical history is significant for a left-leg abscess secondary to an injury he sustained from a fall 4 days ago while walking his dog. He has been taking clindamycin for this infection. In addition, he has long-standing gastroesophageal reflux disease, managed with omeprazole. His vital signs include: temperature 38.5°C (101.3°F), respiratory rate 19/min, heart rate 90/min, and blood pressure 110/70 mm Hg. Which of the following is the best course of treatment for this patient’s most likely diagnosis?
- A. Tetracycline
- B. Ciprofloxacin
- C. Trimethoprim-sulfamethoxazole
- D. Erythromycin
- E. Vancomycin (Correct Answer)
Central line-associated bloodstream infections Explanation: ***Vancomycin***
- The patient's history of recent **clindamycin** use for an abscess, development of **fever, abdominal pain, nausea, and bloody diarrhea**, and use of **omeprazole** (a risk factor), strongly suggests **_Clostridioides difficile_ infection (CDI)**.
- **Oral vancomycin** is a first-line treatment for **severe non-fulminant CDI**, which this patient's symptoms (fever, bloody diarrhea) are consistent with.
*Tetracycline*
- **Tetracycline** is typically used for bacterial infections like **chlamydia, Lyme disease, and rickettsial infections**; it is not effective against _C. difficile_.
- It works by **inhibiting bacterial protein synthesis** but does not target the cell wall of _C. difficile_.
*Ciprofloxacin*
- **Ciprofloxacin**, a fluoroquinolone, is generally **contraindicated in CDI** as it can be a risk factor for developing the infection or exacerbate it due to disruption of gut flora.
- While effective against many gram-negative bacteria, it has **no significant activity against _C. difficile_**.
*Trimethoprim-sulfamethoxazole*
- **Trimethoprim-sulfamethoxazole** is a combination antibiotic used for various bacterial infections, including **UTIs and some respiratory infections**.
- It is **not effective against _C. difficile_** and is not recommended for its treatment.
*Erythromycin*
- **Erythromycin**, a macrolide, is effective against a range of bacterial infections including **atypical pneumonia and skin infections**.
- It has **no role in the treatment of _C. difficile_ infection** and its use could potentially further disrupt the gut microbiome.
Central line-associated bloodstream infections US Medical PG Question 9: A 20-year-old man presents with a painless neck mass that has gradually increased in size. The mass is anteromedial to the right sternocleidomastoid muscle and has been present for 3 years. The mass increased in size and became more tender following an upper respiratory infection. An ultrasound of the neck identifies a single, round cystic mass with uniform, low echogenicity, and no internal septations. A contrast-enhanced CT scan of the neck shows a homogeneous mass with low attenuation centrally and with smooth rim enhancement. Which of the following is the most likely diagnosis?
- A. First branchial cleft cyst
- B. Sternomastoid tumor
- C. Second branchial cleft cyst (Correct Answer)
- D. Ectopic thyroid tissue
- E. Cervical lymphadenopathy
Central line-associated bloodstream infections Explanation: **Second branchial cleft cyst**
- The **location** (anteromedial to the sternocleidomastoid muscle), **painless** nature, and history of **gradual enlargement** becoming tender after an URI are classic presentations.
- **Imaging findings** (single, round cystic mass with uniform low echogenicity on ultrasound; homogeneous mass with low attenuation centrally and smooth rim enhancement on CT) are highly characteristic of an infected branchial cleft cyst.
*First branchial cleft cyst*
- Typically presents with a mass located near the **external auditory canal** or **angle of the mandible**, often causing otorrhea or recurrent infections.
- The presented mass is in a different anatomical location, **anteromedial** to the sternocleidomastoid.
*Sternomastoid tumor*
- This condition usually presents as a **fibrotic mass** within the sternocleidomastoid muscle in **neonates or infants**, associated with **congenital muscular torticollis**.
- The patient's age (20 years old) and the **cystic nature** of the mass make this diagnosis unlikely.
*Ectopic thyroid tissue*
- While possible in the neck, ectopic thyroid tissue would typically present as a **solid mass** and would show **iodine uptake** on nuclear imaging, not a cystic appearance on ultrasound and CT.
- It is more commonly located in the **midline** of the neck (e.g., lingual thyroid) rather than anteromedial to the sternocleidomastoid.
*Cervical lymphadenopathy*
- Enlarged lymph nodes typically present with **multiple, often tender, solid masses** or a single mass with typical lymph node morphology (e.g., hilar fat, oval shape), especially after an infection.
- The **cystic nature** described by imaging, with uniform low echogenicity and rim enhancement, is not typical for uncomplicated lymphadenopathy.
Central line-associated bloodstream infections US Medical PG Question 10: A 7-year-old girl is brought to the physician by her mother because of a 4-week history of irritability, diarrhea, and a 2.2-kg (5-lb) weight loss that was preceded by a dry cough. The family returned from a vacation to Indonesia 2 months ago. Her vital signs are within normal limits. Abdominal examination shows mild tenderness with no guarding or rebound and increased bowel sounds. Her leukocyte count is 9,200/mm3 with 20% eosinophils. A photomicrograph of a wet stool mount is shown. Which of the following is the most appropriate pharmacotherapy?
- A. Diethylcarbamazine
- B. Metronidazole
- C. Albendazole (Correct Answer)
- D. Praziquantel
- E. Doxycycline
Central line-associated bloodstream infections Explanation: ***Albendazole***
- The image shows a **hookworm egg**, characterized by its thin shell and developing larva inside; clinical features like **eosinophilia**, diarrhea, weight loss, and travel to an endemic area (Indonesia) are consistent with hookworm infection.
- **Albendazole** is the drug of choice for treating hookworm infections and other intestinal nematode infections.
*Diethylcarbamazine*
- This drug is primarily used for treating **lymphatic filariasis** (e.g., Wuchereria bancrofti, Brugia malayi) and **Loiasis** (African eye worm).
- It is not effective against hookworm infections.
*Metronidazole*
- **Metronidazole** is an antimicrobial agent effective against certain parasitic infections like **Giardia**, **Entamoeba histolytica**, and bacterial vaginosis.
- It is not indicated for the treatment of hookworm infections.
*Praziquantel*
- **Praziquantel** is an anthelminthic drug primarily used to treat infections caused by **flukes** (e.g., Schistosoma species) and **tapeworms** (e.g., Taenia species).
- It is not effective against hookworm infections.
*Doxycycline*
- **Doxycycline** is a tetracycline antibiotic with broad-spectrum activity against various bacterial infections and is also used in the treatment of some parasitic infections like **malaria prophylaxis** and **filariasis** (due to activity against Wolbachia endosymbionts).
- It is not a primary treatment for hookworm infections.
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