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?

Add ampicillin to treatment regimen

Add ampicillin, dexamethasone, and rifampin to treatment regimen

Add dexamethasone to treatment regimen

Treat boyfriend with ceftriaxone and vancomycin

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?

Document injuries photographically

Obtain written consent from family

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?

Wrap thumb in saline-moistened, sterile gauze and place in sterile bag

Place thumb in cup of cold milk

Wrap thumb in sterile gauze and submerge in a cup of saline

There is no need to save the thumb

Place thumb directly into cooler of ice

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?

Ask the patient's son to leave the room

Question the patient's son regarding the home situation

Call Adult Protective Services to report the patient's son

Question the patient regarding abuse or neglect

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?

Inform the local public health department of the diagnosis

Request the patient's permission to discuss the diagnosis with an infectious disease specialist

Assure the patient that his diagnosis will remain confidential

Confirm the diagnosis with a sputum culture

Notify all of the patient's household contacts of the diagnosis

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.

Universal MRSA decolonization for all surgical patients regardless of screening results

Targeted decolonization only for MRSA-positive patients with mupirocin and chlorhexidine

Isolation of all surgical patients in private rooms until discharge

Routine screening and decolonization of all healthcare workers

Extended vancomycin prophylaxis for all surgical patients for 48 hours postoperatively

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.

Combination daptomycin and linezolid

Linezolid plus gentamicin for synergy

Daptomycin plus ampicillin despite resistance

Daptomycin monotherapy with high dose (10-12 mg/kg)

Linezolid monotherapy for 6 weeks

Isolation precautions for USMLE Step 2 CK: High-Yield Microbiology Lessons

Standard Precautions - Every Patient, Every Time

Core Principle: The minimum infection prevention practices applied to ALL patient care, regardless of suspected or confirmed infection status. Treat all blood, body fluids (except sweat), nonintact skin, and mucous membranes as potentially infectious.
Key Practices:
- Hand Hygiene: The single most critical measure. Perform before and after every patient contact.
- Personal Protective Equipment (PPE): Use gloves, gowns, and face protection (masks, goggles, face shields) based on anticipated exposure risk.
- Respiratory Hygiene & Cough Etiquette.
- Safe Injection Practices.

⭐ Assumes that every patient is potentially infectious, which is why these precautions are universal.

Standard Precautions in Healthcare Settings

Transmission-Based Precautions - The Specifics

Applied for patients with known/suspected infections, these are used in addition to Standard Precautions. The specific tier is dictated by the pathogen's mode of transmission.

Precaution	Required PPE	Room Type	Key Pathogens & Conditions
Contact	Gown & Gloves	Private or cohort	MRSA, VRE, C. difficile, Scabies, Lice, RSV (can be contact/droplet)
Droplet	Surgical Mask	Private or cohort	N. meningitidis, Influenza, Pertussis, Mumps, Rubella, Diphtheria
Airborne	N95 Respirator	Negative Pressure (AIIR)	M. tuberculosis, Varicella (Chickenpox), Rubeola (Measles) (📌 MTV)

PPE Protocol - Gearing Up & Down

Donning (Gearing Up): Order is generally gown, mask/respirator, goggles/face shield, and finally gloves. Think ground-up.
Doffing (Gearing Down): More critical due to self-contamination risk. Remove most contaminated items first.

⭐ The sequence of doffing is the highest-yield step for exams. Incorrect removal is a primary vector for self-contamination.

📌 Mnemonic for Doffing: Gloves → Goggles → Gown → Mask (alphabetical order).

High‑Yield Points - ⚡ Biggest Takeaways

Standard Precautions are universal for all patients; hand hygiene is paramount.

Contact Precautions (gown, gloves) are for MRSA, VRE, and C. difficile. Use soap and water for C. diff spores, as alcohol sanitizers are ineffective.

Droplet Precautions (surgical mask) are for pathogens like N. meningitidis, Influenza, and H. influenzae.

Airborne Precautions (N95 respirator, negative pressure room) are for M. tuberculosis, measles, and varicella.

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