A 3-month old male infant with HIV infection is brought to the physician for evaluation. The physician recommends monthly intramuscular injections of a monoclonal antibody to protect against a particular infection. The causal pathogen for this infection is most likely transmitted by which of the following routes?
Q2
The surgical equipment used during a craniectomy is sterilized using pressurized steam at 121°C for 15 minutes. Reuse of these instruments can cause transmission of which of the following pathogens?
Q3
An 18-year-old female college student is brought to the emergency department by ambulance for a headache and altered mental status. The patient lives with her boyfriend who is with her currently. He states she had not been feeling well for the past day and has vomited several times in the past 12 hours. Lumbar puncture is performed in the emergency room and demonstrates an increased cell count with a neutrophil predominance and gram-negative diplococci on Gram stain. The patient is started on vancomycin and ceftriaxone. Which of the following is the best next step in management?
Q4
An unconscious 22-year-old woman is brought to the emergency department by police after being found in a park. Physical examination reveals torn clothing and evidence of sexual assault. Which of the following is the most appropriate first step in collecting forensic evidence?
Q5
The occupational health department at a hospital implements new safety precautions to prevent laboratory-acquired infections. One of the new precautions includes disinfecting the microbiology laboratory benches with 70% ethanol before and after use. This measure is most likely to be effective in preventing the transmission of which of the following viruses?
Q6
A 54-year-old male carpenter accidentally amputated his right thumb while working in his workshop 30 minutes ago. He reports that he was cutting a piece of wood, and his hand became caught up in the machinery. He is calling the emergency physician for advice on how to transport his thumb and if it is necessary. Which of the following is the best information for this patient?
Q7
A 78-year-old woman is brought to the emergency ward by her son for lethargy and generalized weakness. The patient speaks in short utterances and does not make eye contact with the provider or her son throughout the interview and examination. You elicit that the patient lives with her son and daughter-in-law, and she reports vague weakness for the last couple days. The emergency room provider notices 3-4 healing bruises on the patient's upper extremities; otherwise, examination is not revealing. Routine chemistries and blood counts are unremarkable; non-contrast head CT demonstrates normal age-related changes. Which of the following is the most appropriate next step in management?
Q8
A 36-year-old man comes to the physician because of a 2-week history of productive cough, weight loss, and intermittent fever. He recently returned from a 6-month medical deployment to Indonesia. He appears tired. Physical examination shows nontender, enlarged, palpable cervical lymph nodes. An x-ray of the chest shows right-sided hilar lymphadenopathy. A sputum smear shows acid-fast bacilli. A diagnosis of pulmonary tuberculosis is made from PCR testing of the sputum. The patient requests that the physician does not inform anyone of this diagnosis because he is worried about losing his job. Which of the following is the most appropriate initial action by the physician?
Q9
A surgical ICU has implemented multiple interventions over 18 months: chlorhexidine bathing, antibiotic stewardship, contact precautions for MRSA, and environmental cleaning protocols. Despite these efforts, MRSA surgical site infection rates remain unchanged at 8 per 1000 surgical procedures. Universal MRSA screening shows 15% of admitted patients are colonized. Evaluate the most effective evidence-based strategy to reduce MRSA SSI rates further.
Q10
A 70-year-old man with prosthetic aortic valve develops fever and bacteremia 3 weeks after valve replacement. Blood cultures grow Enterococcus faecium resistant to ampicillin and vancomycin (VRE). Susceptibilities show sensitivity to linezolid and daptomycin. TEE shows a small vegetation on the prosthetic valve. Creatinine is 1.8 mg/dL (baseline 1.0). Evaluate the optimal treatment strategy considering the infection location and drug characteristics.
Isolation precautions US Medical PG Practice Questions and MCQs
Question 1: A 3-month old male infant with HIV infection is brought to the physician for evaluation. The physician recommends monthly intramuscular injections of a monoclonal antibody to protect against a particular infection. The causal pathogen for this infection is most likely transmitted by which of the following routes?
A. Fecal-oral route
B. Skin inoculation
C. Aerosol inhalation (Correct Answer)
D. Blood transfusion
E. Breast feeding
Explanation: ***Aerosol inhalation***
- This scenario describes prophylaxis for **Respiratory Syncytial Virus (RSV)** with palivizumab, a monoclonal antibody typically given to high-risk infants (like those with HIV). **RSV** is primarily transmitted via **aerosol inhalation** of respiratory droplets.
- RSV infection can lead to severe **bronchiolitis** and **pneumonia** in immunocompromised infants, making prophylaxis crucial.
*Fecal-oral route*
- Pathogens transmitted via the **fecal-oral route** (e.g., rotavirus, poliovirus) typically cause gastrointestinal or systemic infections but are not primarily targeted by monthly monoclonal antibody injections in this context.
- While immune-compromised infants are susceptible to various infections, **RSV** is specifically associated with aerosol transmission and prophylaxis with palivizumab.
*Skin inoculation*
- **Skin inoculation** is the route for infections like tetanus, human papillomavirus (HPV), or some arboviruses, which are less likely to be the target of monthly monoclonal antibody prophylaxis in a 3-month-old HIV-positive infant.
- This route is not characteristic of the common severe respiratory infections that disproportionately affect immunocompromised neonates.
*Blood transfusion*
- Infections transmitted via **blood transfusion** (e.g., HIV, hepatitis B, hepatitis C) are typically not prevented with monthly intramuscular monoclonal antibody injections in infants.
- The risk of acquiring new infections via transfusion is usually addressed through proper screening of blood products.
*Breast feeding*
- While **breastfeeding** can transmit certain infections, including HIV itself, it is not the primary transmission route for respiratory viruses like RSV, which is targeted by the described prophylaxis.
- Recommendations for breastfeeding in mothers with HIV vary based on resource availability and local guidelines.
Question 2: The surgical equipment used during a craniectomy is sterilized using pressurized steam at 121°C for 15 minutes. Reuse of these instruments can cause transmission of which of the following pathogens?
A. Non-enveloped viruses
B. Sporulating bacteria
C. Prions (Correct Answer)
D. Enveloped viruses
E. Yeasts
Explanation: ***Prions***
- Prions are **abnormally folded proteins** that are highly resistant to standard sterilization methods like steam autoclaving at 121°C, making them a risk for transmission through reused surgical instruments.
- They cause transmissible spongiform encephalopathies (TSEs) like **Creutzfeldt-Jakob disease**, where even trace amounts can be highly infectious.
*Non-enveloped viruses*
- Non-enveloped viruses are generally **more resistant to heat and disinfectants** than enveloped viruses but are typically inactivated by recommended steam sterilization protocols.
- Standard autoclaving conditions are effective in destroying most non-enveloped viruses.
*Sporulating bacteria*
- **Bacterial spores**, such as those from *Clostridium* or *Bacillus*, are known for their high resistance to heat and chemicals, but are usually **inactivated by steam sterilization at 121°C** for 15 minutes.
- This method is specifically designed to kill bacterial spores effectively.
*Enveloped viruses*
- Enveloped viruses are the **least resistant to heat and chemical disinfectants** due to their lipid envelope.
- They are readily **inactivated by standard steam sterilization** at 121°C.
*Yeasts*
- **Yeasts** are eukaryotic microorganisms that are typically **susceptible to heat sterilization**.
- They are effectively killed by typical steam autoclaving conditions used for surgical instruments.
Question 3: An 18-year-old female college student is brought to the emergency department by ambulance for a headache and altered mental status. The patient lives with her boyfriend who is with her currently. He states she had not been feeling well for the past day and has vomited several times in the past 12 hours. Lumbar puncture is performed in the emergency room and demonstrates an increased cell count with a neutrophil predominance and gram-negative diplococci on Gram stain. The patient is started on vancomycin and ceftriaxone. Which of the following is the best next step in management?
A. Treat boyfriend with rifampin (Correct Answer)
B. Add ampicillin to treatment regimen
C. Add ampicillin, dexamethasone, and rifampin to treatment regimen
D. Add dexamethasone to treatment regimen
E. Treat boyfriend with ceftriaxone and vancomycin
Explanation: ***Treat boyfriend with rifampin***
- The patient's presentation with headache, altered mental status, neutrophilic pleocytosis, and **Gram-negative diplococci** on CSF Gram stain is highly suggestive of **Neisseria meningitidis** meningitis.
- The patient is already on appropriate empiric antibiotic therapy (vancomycin and ceftriaxone), so the **immediate priority** is to prevent secondary cases through **post-exposure prophylaxis** for close contacts.
- Close contacts, including household members like the boyfriend, are at high risk of contracting the infection and should receive prophylaxis within **24 hours** of case identification, with **rifampin**, **ciprofloxacin**, or **IM ceftriaxone** being standard options.
*Add ampicillin to treatment regimen*
- Ampicillin provides coverage for **Listeria monocytogenes**, but the Gram stain demonstrating **Gram-negative diplococci** makes Listeria (Gram-positive rod) unlikely in this otherwise healthy young adult without specific risk factors for Listeria.
- The current regimen of vancomycin and ceftriaxone provides adequate empiric coverage for acute bacterial meningitis, targeting common pathogens like **S. pneumoniae** and **N. meningitidis**.
*Add ampicillin, dexamethasone, and rifampin to treatment regimen*
- While providing rifampin prophylaxis to the boyfriend is appropriate, adding it to the **patient's** treatment regimen is not indicated for her active infection.
- **Dexamethasone** is often added to reduce inflammation and neurological sequelae but should be given **prior to or concurrently** with the first dose of antibiotics; adding it later in the course may not be as beneficial.
- This option conflates treatment of the patient with prophylaxis of contacts.
*Add dexamethasone to treatment regimen*
- Dexamethasone is recommended in adults with suspected pneumococcal meningitis to reduce mortality and neurological sequelae, but ideal administration is **prior to or with the first dose of antibiotics**.
- While it might still be considered, the priority given the **Gram-negative diplococci** (suggesting N. meningitidis rather than S. pneumoniae) is **contact prophylaxis** to prevent further spread, and the timing for optimal dexamethasone benefit has likely passed.
*Treat boyfriend with ceftriaxone and vancomycin*
- Ceftriaxone and vancomycin are appropriate for treating the patient's active meningitis, but they are not the standard or preferred agents for **post-exposure prophylaxis** in contacts.
- Post-exposure prophylaxis typically involves a short course of agents like **rifampin**, **ciprofloxacin**, or a single dose of **intramuscular ceftriaxone**, primarily to eradicate nasopharyngeal carriage and prevent transmission.
Question 4: An unconscious 22-year-old woman is brought to the emergency department by police after being found in a park. Physical examination reveals torn clothing and evidence of sexual assault. Which of the following is the most appropriate first step in collecting forensic evidence?
A. Contact law enforcement
B. Begin prophylactic antibiotics
C. Order toxicology screening
D. Document injuries photographically (Correct Answer)
E. Obtain written consent from family
Explanation: ***Document injuries photographically***
- **Photographing injuries** is a crucial first step in forensic evidence collection, as it provides objective visual documentation before any changes occur due to medical intervention or passage of time.
- This method helps preserve the appearance and nature of injuries, which can be critical for **legal proceedings** and understanding the mechanism of injury.
*Contact law enforcement*
- While law enforcement must be contacted for sexual assault cases, the **immediate priority** is to secure and document forensic evidence **on the patient's person** before it is compromised.
- Contacting law enforcement does not directly contribute to the **physical collection or preservation** of evidence from the victim.
*Begin prophylactic antibiotics*
- Prophylactic antibiotics are part of the **post-rape care protocol** but should be administered **after** forensic samples have been collected to avoid contamination or alteration of potential evidence.
- Administering antibiotics early could potentially impact the ability to culture certain pathogens for evidence.
*Order toxicology screening*
- Toxicology screening is an important component of the overall assessment, especially given the patient's unconscious state and potential drug-facilitated assault.
- However, **physical evidence of injury** on the body that could change or be lost is a more immediate priority for initial forensic documentation.
*Obtain written consent from family*
- For an unconscious adult, obtaining consent from family for medical treatment is generally required, but **forensic evidence collection** in cases of sexual assault can proceed without immediate family consent, especially when suspicion of a crime is high.
- The immediate priority is the **preservation of time-sensitive evidence**, and delaying for family consent could compromise the collection process.
Question 5: The occupational health department at a hospital implements new safety precautions to prevent laboratory-acquired infections. One of the new precautions includes disinfecting the microbiology laboratory benches with 70% ethanol before and after use. This measure is most likely to be effective in preventing the transmission of which of the following viruses?
A. Hepatitis A virus
B. Herpes simplex virus (Correct Answer)
C. Poliovirus
D. Parvovirus
E. Polyomavirus
Explanation: ***Herpes simplex virus***
- Herpes simplex virus is an **enveloped virus**, meaning it has a lipid outer layer that is easily disrupted by disinfectants like **70% ethanol**.
- The disruption of its envelope renders the virus inactive and unable to infect host cells, making this a highly effective prevention strategy.
*Hepatitis A virus*
- Hepatitis A virus is a **non-enveloped virus**, making it relatively **resistant to many common disinfectants**, including alcohol-based ones.
- Its robust protein capsid protects its genetic material, requiring stronger disinfection methods than 70% ethanol for inactivation.
*Poliovirus*
- Poliovirus is another **non-enveloped virus** that exhibits significant **resistance to alcohol-based disinfectants** due to its stable protein capsid.
- Effective inactivation typically requires disinfectants with greater germicidal activity, such as chlorine-based solutions.
*Parvovirus*
- Parvovirus is one of the **most resistant non-enveloped viruses** to disinfection, including inactivation by 70% ethanol.
- Its small size and extremely stable capsid make it challenging to eliminate from surfaces, often necessitating harsh chemical treatments.
*Polyomavirus*
- Polyomaviruses are **non-enveloped DNA viruses** that are generally more **resistant to alcohol-based disinfectants** than enveloped viruses.
- Their lack of a lipid envelope provides protection against agents like ethanol that target lipid bilayers.
Question 6: A 54-year-old male carpenter accidentally amputated his right thumb while working in his workshop 30 minutes ago. He reports that he was cutting a piece of wood, and his hand became caught up in the machinery. He is calling the emergency physician for advice on how to transport his thumb and if it is necessary. Which of the following is the best information for this patient?
A. Place thumb in cup of cold milk
B. Wrap thumb in saline-moistened, sterile gauze and place in sterile bag (Correct Answer)
C. Wrap thumb in sterile gauze and submerge in a cup of saline
D. There is no need to save the thumb
E. Place thumb directly into cooler of ice
Explanation: ***Wrap thumb in saline-moistened, sterile gauze and place in sterile bag***
- This method provides a **moist, sterile environment** for the amputated part, which is crucial for preserving tissue viability.
- The use of a sterile bag helps prevent contamination and allows the part to be placed inside a cooler without direct ice contact, preventing **frostbite**.
*Place thumb in cup of cold milk*
- While cold milk might offer some cooling, it is **not sterile** and could introduce bacteria, increasing the risk of infection.
- Milk's composition is **not ideal for cell preservation** compared to saline, which is more isotonic.
*Wrap thumb in sterile gauze and submerge in a cup of saline*
- Submerging the amputated part directly in saline, even with sterile gauze, can lead to **tissue maceration** due to overhydration.
- This method also makes it more difficult to prevent contamination during transportation if the cup is not sealed.
*There is no need to save the thumb*
- **Replantation surgery** is often possible and highly desirable for thumb amputations due to its critical functional role.
- Dismissing the amputated part would deprive the patient of a chance to restore function, especially given the short time since amputation.
*Place thumb directly into cooler of ice*
- Direct contact with ice can cause **frostbite** and **tissue damage**, compromising the viability of the amputated part.
- The preferred method is to keep the amputated part cool, but not frozen, usually by placing it in a sealed bag within an ice-filled container.
Question 7: A 78-year-old woman is brought to the emergency ward by her son for lethargy and generalized weakness. The patient speaks in short utterances and does not make eye contact with the provider or her son throughout the interview and examination. You elicit that the patient lives with her son and daughter-in-law, and she reports vague weakness for the last couple days. The emergency room provider notices 3-4 healing bruises on the patient's upper extremities; otherwise, examination is not revealing. Routine chemistries and blood counts are unremarkable; non-contrast head CT demonstrates normal age-related changes. Which of the following is the most appropriate next step in management?
A. Ask the patient's son to leave the room (Correct Answer)
B. Question the patient's son regarding the home situation
C. Call Adult Protective Services to report the patient's son
D. Perform lumbar puncture
E. Question the patient regarding abuse or neglect
Explanation: ***Ask the patient's son to leave the room***
- The patient's **lethargy**, **non-engagement**, and **healing bruises** raise strong suspicions for elder abuse or neglect. Removing the son allows for a private interview, which is crucial for her to feel safe enough to disclose information.
- In situations of suspected abuse, it is paramount to prioritize the **patient's safety and ability to speak freely** without the presence of the suspected abuser.
*Question the patient's son regarding the home situation*
- Questioning the son directly at this point may escalate the situation or make the patient even less likely to disclose abuse, as she is likely **frightened or coerced**.
- This step is premature and should only occur after a private interview with the patient, and potentially with the involvement of Protective Services.
*Call Adult Protective Services to report the patient's son*
- While reporting to **Adult Protective Services** is a critical step if abuse is confirmed, it is not the immediate first action until a private interview with the patient has been conducted to gather more information.
- Making a report without attempting to speak with the patient alone first can hinder the investigation and potentially jeopardize her safety if the abuser is alerted prematurely.
*Perform lumbar puncture*
- A lumbar puncture is an invasive procedure generally performed to diagnose **central nervous system infections** or **inflammatory conditions**.
- There are no clinical indications (e.g., fever, meningeal signs, focal neurological deficits) to suggest a need for a lumbar puncture, especially given the history and physical findings that point towards abuse.
*Question the patient regarding abuse or neglect*
- While it's important to question the patient about abuse, it must be done in a **safe and private environment** where she feels comfortable speaking freely.
- Questioning her while the suspected abuser (her son) is present would likely yield unhelpful responses due to fear or intimidation, as seen by her lack of eye contact and short utterances.
Question 8: A 36-year-old man comes to the physician because of a 2-week history of productive cough, weight loss, and intermittent fever. He recently returned from a 6-month medical deployment to Indonesia. He appears tired. Physical examination shows nontender, enlarged, palpable cervical lymph nodes. An x-ray of the chest shows right-sided hilar lymphadenopathy. A sputum smear shows acid-fast bacilli. A diagnosis of pulmonary tuberculosis is made from PCR testing of the sputum. The patient requests that the physician does not inform anyone of this diagnosis because he is worried about losing his job. Which of the following is the most appropriate initial action by the physician?
A. Request the patient's permission to discuss the diagnosis with an infectious disease specialist
B. Assure the patient that his diagnosis will remain confidential
C. Confirm the diagnosis with a sputum culture
D. Notify all of the patient's household contacts of the diagnosis
E. Inform the local public health department of the diagnosis (Correct Answer)
Explanation: ***Inform the local public health department of the diagnosis***
- **Tuberculosis** is a **reportable disease** to public health authorities due to its significant public health implications, including the risk of transmission.
- Physicians have a **legal and ethical obligation** to report such diagnoses to protect the community, even against a patient's wishes for secrecy.
*Request the patient's permission to discuss the diagnosis with an infectious disease specialist*
- While consulting an infectious disease specialist is often beneficial for managing TB, the immediate and most appropriate initial action is related to **public health notification**.
- Delaying notification to seek patient permission first would **compromise public health safety** regarding a reportable disease.
*Assure the patient that his diagnosis will remain confidential*
- This assurance would be **misleading and unethical** because TB is a reportable condition, meaning its confidentiality is necessarily breached for public health purposes.
- Physicians are bound by law to report communicable diseases, which supersedes general confidentiality in this specific context.
*Confirm the diagnosis with a sputum culture*
- The diagnosis of pulmonary tuberculosis has already been established by a **sputum smear showing acid-fast bacilli** and **PCR testing**, which are highly reliable.
- While a sputum culture provides drug susceptibility information, it is not the *initial* most appropriate action regarding the patient's stated concerns about confidentiality in the context of a reportable disease.
*Notify all of the patient's household contacts of the diagnosis*
- While contact tracing is an important part of TB control, it is typically initiated and managed by the **public health department** after notification.
- The physician's primary responsibility is to notify the health department, who then assumes the role of **contact investigation** and management.
Question 9: A surgical ICU has implemented multiple interventions over 18 months: chlorhexidine bathing, antibiotic stewardship, contact precautions for MRSA, and environmental cleaning protocols. Despite these efforts, MRSA surgical site infection rates remain unchanged at 8 per 1000 surgical procedures. Universal MRSA screening shows 15% of admitted patients are colonized. Evaluate the most effective evidence-based strategy to reduce MRSA SSI rates further.
A. Targeted decolonization only for MRSA-positive patients with mupirocin and chlorhexidine
B. Isolation of all surgical patients in private rooms until discharge
C. Routine screening and decolonization of all healthcare workers
D. Extended vancomycin prophylaxis for all surgical patients for 48 hours postoperatively
E. Universal MRSA decolonization for all surgical patients regardless of screening results (Correct Answer)
Explanation: ***Universal MRSA decolonization for all surgical patients regardless of screening results***
- **Universal decolonization** has been proven more effective than screening-based strategies in high-risk settings like the ICU, significantly reducing **MRSA surgical site infections** and bloodstream infections.
- This approach is superior because it addresses **undetected carriers**, eliminates delays associated with waiting for lab cultures, and is often more **cost-effective** and easier to implement.
*Targeted decolonization only for MRSA-positive patients with mupirocin and chlorhexidine*
- While logical, **targeted decolonization** is less effective than the universal approach because it misses patients who may be **falsely negative** or colonized at levels below detection thresholds.
- Evidence from recent large-scale trials shows that **targeted strategies** do not reduce MRSA infection rates as drastically as treating the entire cohort at risk.
*Isolation of all surgical patients in private rooms until discharge*
- This strategy is **logistically impractical** and extremely expensive, focusing on **containment** rather than the active reduction of the patient's own bacterial load (colonization).
- Research indicates that **contact precautions** and isolation alone are less effective than decolonization protocols in preventing **autoinoculation** during surgery.
*Routine screening and decolonization of all healthcare workers*
- Screening of **healthcare workers (HCWs)** is not recommended as a routine practice; it is typically reserved for **outbreak investigations** where an epidemiological link is suspected.
- Constant recolonization from patients and the environment makes **HCW decolonization** an unsustainable and transient solution for reducing overall SSI rates.
*Extended vancomycin prophylaxis for all surgical patients for 48 hours postoperatively*
- **Extended antibiotic prophylaxis** beyond 24 hours provides no additional protection against SSIs and significantly increases the risk of **C. difficile** and antibiotic resistance.
- Proper surgical prophylaxis involves **timely administration** before the incision, not prolonged courses which violate **antibiotic stewardship** principles.
Question 10: A 70-year-old man with prosthetic aortic valve develops fever and bacteremia 3 weeks after valve replacement. Blood cultures grow Enterococcus faecium resistant to ampicillin and vancomycin (VRE). Susceptibilities show sensitivity to linezolid and daptomycin. TEE shows a small vegetation on the prosthetic valve. Creatinine is 1.8 mg/dL (baseline 1.0). Evaluate the optimal treatment strategy considering the infection location and drug characteristics.
A. Combination daptomycin and linezolid (Correct Answer)
B. Linezolid plus gentamicin for synergy
C. Daptomycin plus ampicillin despite resistance
D. Daptomycin monotherapy with high dose (10-12 mg/kg)
E. Linezolid monotherapy for 6 weeks
Explanation: ***Combination daptomycin and linezolid***
- For **VRE prosthetic valve endocarditis (PVE)**, monotherapy often fails due to high bacterial inoculum and **biofilm formation**, necessitating synergistic combinations.
- **Daptomycin** provides bactericidal activity, while **linezolid** enhances biofilm penetration; this combination is a salvage strategy to prevent the emergence of **daptomycin resistance** during prolonged therapy.
*Linezolid plus gentamicin for synergy*
- **Gentamicin** synergy is typically reserved for **ampicillin-susceptible** enterococci and requires a cell-wall active agent to facilitate entry, which linezolid (protein synthesis inhibitor) does not provide.
- The patient has an elevated **creatinine (1.8 mg/dL)**, making the use of **nephrotoxic aminoglycosides** like gentamicin highly risky and suboptimal.
*Daptomycin plus ampicillin despite resistance*
- While **ampicillin** can sometimes enhance daptomycin binding by reducing the net negative surface charge of the bacteria, it is generally less effective when high-level **ampicillin resistance** is already confirmed in *E. faecium*.
- This strategy is typically considered when other secondary agents are unavailable or contraindicated, but it is not superior to linezolid-based combinations in VRE endocarditis.
*Daptomycin monotherapy with high dose (10-12 mg/kg)*
- High-dose **daptomycin (10-12 mg/kg)** is recommended for endocarditis, but monotherapy for **prosthetic valve** infections carries a high risk of treatment failure.
- *Enterococcus faecium* can rapidly develop **resistance** (via the LiaFSR system) during daptomycin monotherapy, making a second agent necessary for such a high-burden infection.
*Linezolid monotherapy for 6 weeks*
- **Linezolid** is primarily **bacteriostatic** against enterococci, which is generally insufficient for the definitive treatment of **infective endocarditis** where bactericidal activity is required.
- Long-term use (over 2 weeks) carries significant risks of **bone marrow suppression** (thrombocytopenia) and **mitochondrial toxicity**, making it unsafe as a sole agent for a 6-week course.
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