Health Care-Associated Infections - Nosocomial Infections

Diagnosis

Indications for Testing

  • Clinical deterioration and/or new onset fever in hospitalized patient

Laboratory Testing

  • Initial testing – CBC, urine and blood culture
    • Urine – significant bacteruria for indwelling catheter
      • ≥102 CFU/mL in indwelling catheter or in catheter specimen from patient with intermittent catheterizing
      • ≥103 CFU/mL of ≥1 bacterial species in catheter-free patients
  • Specific site cultures to identify pathogen and antimicrobial resistance profile
    • Pneumonia – new infiltrates plus ≥2 of the following symptoms
      • Body temperature >38°C or <35.5°C
      • WBC >12 K/μL or <4 K/μL
      • Purulent respiratory secretions
        • Bronchoalveolar lavage specimen >104 CFU/mL
        • Sputum >105 CFU/mL
  • Bacterial strain characterization – identify causative organism and source to aid in infection control and in the investigation of outbreaks

Imaging Studies

  • Chest x-ray – rule out pneumonia
  • May need further imaging based on clinical evaluation

Clinical Background

Health care-associated (nosocomial) infections (HCAI) develop as a result of treatment in a hospital or health care facility and are often caused by organisms resistant to standard antibiotic/antifungal therapies. Outbreaks in hospitals and extended-care facilities may spread to the general community and can cause substantial morbidity and mortality. For more on specific types of health care-associated infections, refer to the CDC website.

Epidemiology

  • Prevalence – 5-10% of patients admitted to U.S. hospitals will develop HCAI
  • Transmission – acquisition of HCAI may occur from poor hand hygiene, prosthetic devices, inadequate decontamination of fomites (eg, doorknobs, handrails)

Organisms

  • Resistance to HCAI is specific to the infected population
  • Organism resistance to first-line therapies is not uncommon for any of the following pathogens
    • Staphylococcus aureus – most common HCAI
      • Methicillin-resistant (MRSA) organisms are becoming more common in community-associated infections
    • Enterococcus
      • May be vancomycin resistant
    • Enterobacteriaceae (predominantly Escherichia coli)
      • May possess multiple drug resistance mechanisms including ESBL, AmpC, or KPC, giving rise to third-generation cephalosporin or carbapenem resistance
    • Pseudomonas aeruginosa
      • May possess multiple drug resistance mechanisms against beta lactams, aminoglycosides and fluoroquinolones
    • Candida albicans
      • May be resistant to first-generation triazoles
    • Clostridium difficile
    • Acinetobacter spp
      • May be extensively drug resistant (eg, susceptible to only 1-2 antibiotics)

Risk Factors

  • Presence of an indwelling catheter
    • Majority are associated with a central venous catheter
  • Prolonged hospitalization
  • Prior exposure to antibiotics
  • Prolonged ventilation

Anatomic Distribution of Infections (CDC 2007)

  • Adults
    • Urinary tract – 32%
    • Surgical site – 22%
    • Lung – 15%
    • Blood stream – 14%
    • Other – 17%
  • Children
    • Higher rates of bloodstream, viral, and lower respiratory tract infections than adults
    • Lower rates of catheter-related urinary tract infections, ventilator-associated pneumonia, and surgical-site infections

Clinical Presentation

  • Nonspecific – worsening clinical condition with no distinct symptoms
  • Fever or hypothermia
  • Pneumonia – new infiltrates on chest x-ray
  • Meningitis – altered consciousness, irritability, seizures

Prevention

  • Hand washing
  • Appropriate insertion and maintenance of catheters
  • Avoiding unnecessary antibiotics

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
CBC with Platelet Count 0040002
Method: Automated Cell Count

Assess for presence of leukocytosis, leukopenia or differential shift

Findings are not specific for a particular organism

 
Urine Culture 0060131
Method: Culture/Identification

Determine source of infection and causative organism(s)

Gram stain is performed by request only

   
Blood Culture 0060102
Method: Continuous Monitoring Blood Culture/Identification

Determine source of infection and causative organism(s)

Testing is limited to the University of Utah Health Sciences Center only

 
Bronchoscopy Culture and Gram Stain 0060700
Method: Quantitative Culture/Identification

Identify causative organism in presumed pneumonia

Includes gram stain testing

   
Wound Culture and Gram Stain 0060132
Method: Stain/Culture/Identification

Determine source of infection and causative organism(s)

Includes gram stain testing

   
Bacterial Strain Characterization by Pulsed-Field Gel Electrophoresis 0060182
Method: Pulsed-Field Gel Electrophoresis

Determine organism causing outbreak

Distinguish reinfection from relapse