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