About This Page
This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- Common HAIs: CAUTI, CLABSI, VAP/HAP, surgical site infection, C difficile, and device-associated bloodstream infection
- Prevention is device-focused: avoid unnecessary catheters/lines/ventilation and remove as early as possible
- Standard precautions apply to all patients; transmission-based precautions are contact, droplet, and airborne
- C difficile and norovirus require contact precautions and soap-and-water emphasis; TB/measles/varicella require airborne isolation
- Needlestick exposure: wash area, assess source, baseline labs, start HIV PEP as soon as possible if indicated, and address HBV/HCV risk
- Antimicrobial stewardship reduces resistance, C difficile, toxicity, and unnecessary broad-spectrum exposure
Overview
Healthcare-associated infections arise during medical care and are often linked to invasive devices, procedures, antibiotic exposure, and vulnerable hosts. Infection control combines standard precautions, transmission-based isolation, hand hygiene, personal protective equipment, environmental cleaning, sterilization/disinfection, vaccination, occupational exposure management, and antimicrobial stewardship. Step 2 CK frequently tests which isolation room or PPE is needed and when to remove a catheter or line.
Epidemiology
HAIs contribute substantially to morbidity, mortality, length of stay, and cost. Device-associated infections are central targets because central lines, urinary catheters, and ventilators bypass normal host defenses and allow biofilm formation. Multidrug-resistant organisms include MRSA, VRE, ESBL-producing Enterobacterales, CRE, multidrug-resistant Pseudomonas/Acinetobacter, and Candida auris.
Clinical Features
Symptoms
CAUTI: fever, suprapubic/flank pain, rigors, delirium without alternative source in catheterized patient
CLABSI: fever, chills, hypotension, or sepsis with central line and no other source
VAP/HAP: new infiltrate plus fever, purulent secretions, leukocytosis, worsening oxygenation
SSI: erythema, warmth, pain, purulence, dehiscence, fever after surgery
C difficile: watery diarrhea after antibiotics or hospitalization
Occupational exposure: needlestick, mucous membrane splash, or nonintact skin exposure to blood/body fluids
Signs
Device site erythema, purulence, tenderness, or tunnel infection
Fever or sepsis in hospitalized patient with line, catheter, ventilator, or recent surgery
New oxygen requirement or ventilator changes with purulent sputum
Diarrhea with abdominal tenderness and leukocytosis after antibiotics
Rash/respiratory syndrome in facility outbreak may signal measles, varicella, influenza, COVID, or TB
Investigations
First-line
Culture before antibiotics when feasibleBlood cultures from peripheral and catheter sites if CLABSI suspected; urine culture after catheter replacement for CAUTI
Device assessmentDaily necessity review of urinary catheter, central line, ventilator, drains, and implanted devices
Syndrome-specific testingC difficile stool test for diarrhea; respiratory viral tests; wound cultures for purulence; chest imaging for pneumonia
Second-line
NHSN/epidemiologic reviewCluster detection, line days, catheter days, ventilator days, and standardized infection ratios in prevention programs
Antimicrobial susceptibility testingGuides de-escalation and infection-control response for resistant organisms
Post-exposure labsSource HIV Ag/Ab, HBsAg, HCV Ab/RNA as appropriate; exposed worker baseline HIV, HBV immunity, HCV testing
Specialist
Infection prevention consultationOutbreaks, MDRO transmission, construction-related risks, C auris, TB exposure, or complex isolation questions
Public health notificationReportable diseases and outbreaks per jurisdiction
1
Standard and transmission-based precautions
- Standard precautions: hand hygiene, gloves when body fluid contact expected, respiratory hygiene, sharps safety, safe injection practices
- Contact precautions: C difficile, norovirus, draining wounds, uncontrolled secretions, many MDROs
- Droplet precautions: influenza, meningococcal disease, pertussis, many respiratory viruses depending setting
- Airborne precautions: TB, measles, varicella; use negative-pressure room and N95 or higher respirator
2
Device-associated infection prevention
- CAUTI: avoid unnecessary urinary catheters, aseptic insertion, closed drainage, unobstructed flow, early removal
- CLABSI: hand hygiene, maximal sterile barrier, chlorhexidine skin prep, optimal site selection, scrub the hub, daily line necessity review
- VAP: elevate head of bed, oral care, minimize sedation, spontaneous awakening/breathing trials, early mobility
- SSI: appropriate perioperative antibiotics, normothermia, glycemic control, sterile technique, hair clipping rather than shaving
3
Occupational exposure
- Needlestick: wash immediately, report, assess exposure and source risk
- HIV PEP: start as soon as possible, ideally within hours and no later than 72 hours, for significant exposure
- HBV: management depends on vaccination and anti-HBs status plus source HBsAg
- HCV: no recommended PEP; baseline and follow-up testing for early detection and treatment
4
Antimicrobial stewardship
- Use the narrowest effective therapy, right dose, right duration, and source control
- Review antibiotics at 48-72 hours for de-escalation or discontinuation
- Avoid treating colonization, viral infections, and asymptomatic bacteriuria except specific indications
Complications
- MDRO transmission: Resistant organisms can spread through hands, devices, environment, and antibiotic pressure
- Outbreaks: Norovirus, C difficile, influenza, measles, TB, C auris, and device-related clusters
- Occupational infection: HIV, HBV, HCV, TB, and respiratory viruses
- Antibiotic harm: C difficile, allergy, nephrotoxicity, resistance selection
- Preventable mortality: CLABSI, VAP, SSI, and sepsis can be fatal
USMLE Step 2 CK Exam Tips
- 1TB, measles, varicella = airborne isolation with negative pressure
- 2Meningococcemia and pertussis = droplet precautions
- 3C difficile = contact precautions and soap-and-water hand hygiene emphasis
- 4CAUTI prevention = remove unnecessary catheter; do not treat asymptomatic bacteriuria in most catheterized patients
- 5Needlestick HIV PEP should start immediately if indicated, not after source viral load returns
- 6HCV needlestick has no PEP; test and treat early infection if it occurs
- 7Antibiotic time-out at 48-72 hours is stewardship: narrow, stop, or set duration
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