4.11 Infection Prevention, Nosocomial Infection & Postexposure Prophylaxis
Key Takeaways
- Prevention of infectious disease, nosocomial infections and procedure- and device-associated infections are three separate blueprint subsections.
- Hand hygiene remains the single most effective measure for preventing healthcare-associated infection, and alcohol-based rub is ineffective against Clostridioides difficile spores.
- After a percutaneous HIV exposure, three-drug postexposure prophylaxis should begin within hours and continue for 28 days.
- An unvaccinated worker exposed to hepatitis B surface antigen-positive blood receives both hepatitis B immune globulin and vaccination.
- Airborne precautions with a negative-pressure room are required for tuberculosis, measles and varicella, whereas influenza requires droplet precautions.
1. Isolation Precautions
Standard precautions apply to every patient, every time, and assume that all blood and body fluids are potentially infectious. Transmission-based precautions are layered on top.
| Category | Requirements | Key organisms |
|---|---|---|
| Contact | Gown and gloves; dedicated equipment | MRSA, VRE, Clostridioides difficile, resistant gram-negatives, scabies, norovirus |
| Droplet | Surgical mask within about 6 feet; private room preferred | Influenza, Neisseria meningitidis, Bordetella pertussis, group A Streptococcus, mumps, rubella |
| Airborne | N95 respirator or higher; negative-pressure room | Tuberculosis, measles, varicella, disseminated zoster |
The two most commonly missed points:
- Clostridioides difficile requires soap-and-water handwashing. Alcohol-based hand rub does not kill spores. It also requires a sporicidal agent such as bleach for environmental cleaning.
- Varicella and disseminated zoster require airborne and contact precautions, not contact alone. Localized zoster in an immunocompetent host with coverable lesions needs only standard precautions.
2. Preventing Device-Associated Infection
The blueprint lists procedure- and device-associated infections separately, reflecting how much of modern nosocomial infection is iatrogenic.
Central line-associated bloodstream infection (CLABSI) is prevented by a bundle: hand hygiene, maximal sterile barrier precautions at insertion, chlorhexidine skin antisepsis, avoiding the femoral site in adults, and — most important and most often the answer — daily review of line necessity with prompt removal.
Catheter-associated urinary tract infection (CAUTI): the single most effective intervention is avoiding unnecessary catheterization and removing catheters early. Two rules that generate exam points:
- Do not screen for or treat asymptomatic bacteriuria in catheterized patients. The exceptions are pregnancy and before urologic procedures with anticipated mucosal bleeding.
- Pyuria alone does not establish infection in a catheterized patient.
Ventilator-associated pneumonia: elevate the head of the bed, use daily sedation interruption with spontaneous breathing trials, and provide oral care.
Surgical site infection: appropriately timed preoperative antibiotics (within 60 minutes of incision), clipping rather than shaving, glycemic control, and normothermia.
3. Antimicrobial Stewardship
Stewardship reduces resistance, C. difficile infection and cost. The core interventions are de-escalation from empiric broad-spectrum therapy once cultures return, converting intravenous to oral therapy when the patient is tolerating oral intake, and defining a stop date at the time of prescribing. Shorter courses are now standard for most common infections, and the exam consistently rewards the shorter, narrower, oral option in a stable, improving patient.
4. Needlestick and Postexposure Prophylaxis
Enumerated explicitly in the blueprint under both nosocomial infections and prevention of infectious disease.
Approximate transmission risk per percutaneous exposure to an infected source:
| Pathogen | Risk |
|---|---|
| Hepatitis B (surface antigen and e-antigen positive) | Highest — up to roughly 30% |
| Hepatitis C | Roughly 2% |
| HIV | Roughly 0.3% |
Immediate steps: wash the site with soap and water (do not squeeze or apply caustic agents), flush mucous membranes with water, report immediately, and test the source patient for HIV, hepatitis B surface antigen and hepatitis C, plus baseline testing of the exposed worker.
HIV
Start prophylaxis within hours — ideally within two hours, and it is not recommended beyond 72 hours. The regimen is three drugs for 28 days, typically an integrase inhibitor with two nucleoside analogues. Do not wait for source testing if results will be delayed; start and stop later if the source proves negative. Follow-up testing occurs at intervals through 4 to 6 months.
Hepatitis B
Management depends on the exposed worker vaccination and antibody status:
| Worker status | Source HBsAg positive or unknown |
|---|---|
| Unvaccinated | Hepatitis B immune globulin plus initiate vaccine series |
| Vaccinated, known responder (anti-HBs ≥ 10 mIU/mL) | No treatment needed |
| Vaccinated, known non-responder | Hepatitis B immune globulin, and repeat the vaccine series or give a second dose of immune globulin |
| Vaccinated, response unknown | Test anti-HBs and manage per result |
Hepatitis C
There is no postexposure prophylaxis and no vaccine. Management is serial monitoring with HCV RNA at 3 to 6 weeks and antibody testing at 4 to 6 months, with prompt direct-acting antiviral treatment if infection is established. Immunoglobulin and antivirals given prophylactically are not recommended, and this is a frequently tested distinction from hepatitis B.
5. Immunization as Infection Prevention
The blueprint lists immunization as a prevention topic under Infectious Disease, and the details of the adult schedule are covered in the preventive medicine chapter. Two principles govern nearly every exam item:
- Live vaccines are contraindicated in significant immunosuppression and pregnancy. Live vaccines include measles-mumps-rubella, varicella, live attenuated influenza, yellow fever, and oral typhoid. Recombinant zoster vaccine is not live and is safe in immunocompromised adults.
- Asplenic and complement-deficient patients require pneumococcal, meningococcal (including serogroup B) and Haemophilus influenzae type b vaccination. When splenectomy is elective, vaccinate at least two weeks before surgery; after emergency splenectomy, vaccinate about two weeks after, once the transient post-splenectomy immune dysregulation has settled.
Healthcare personnel should be immune to measles, mumps, rubella, varicella and hepatitis B, receive annual influenza vaccination, and have documented tuberculosis screening per facility policy.
A medical resident sustains a deep needlestick from a hollow-bore needle used on a patient with untreated chronic hepatitis C and a high viral load. The resident completed the hepatitis B vaccine series with a documented protective antibody titer and is HIV-negative. What is the most appropriate management for the hepatitis C exposure?
A patient with severe Clostridioides difficile colitis is placed on contact precautions. Which additional measure is specifically required for this organism?