What is invasive candidiasis?

Invasive Candidiasis: Definition and Clinical Significance

Invasive candidiasis is a serious fungal infection characterized by the presence of Candida species in normally sterile sites of the body, including bloodstream (candidemia) and deep tissues or organs, with significant associated morbidity and mortality rates of 15-47%.1

Types of Invasive Candidiasis

Invasive candidiasis encompasses three distinct clinical entities:

1. Candidemia without deep-seated infection - Candida in bloodstream only
2. Candidemia with deep-seated infection - Bloodstream infection with organ involvement
3. Deep-seated candidiasis without candidemia - Organ infection without positive blood cultures1

These three entities are approximately equal in distribution among affected patients.1

Diagnostic Challenges

The diagnosis of invasive candidiasis presents several challenges:

• Blood culture limitations: Only about 50% sensitivity for detecting invasive candidiasis1, 2
• Slow detection: Blood cultures typically require 2-3 days for positivity (range 1-7+ days)1
• Deep tissue sampling: Often requires invasive procedures with poor sensitivity (<50%)1
• Distinguishing colonization from infection: Particularly challenging in intra-abdominal candidiasis1

Non-Culture Diagnostic Methods

Several non-culture methods can aid in diagnosis:

• β-D-glucan detection: High sensitivity but limited by false positives; useful for excluding invasive candidiasis due to high negative predictive value1, 2
• Mannan/anti-mannan antibody assays: Variable sensitivity and specificity1
• PCR testing: Similar sensitivity to β-D-glucan for candidemia but potentially more sensitive for other forms of invasive candidiasis1
• T2Candida assay: Promising rapid detection technology from whole blood samples1, 2
• Corrected Candida colonization index: Using semiquantitative culture techniques to assess colonization intensity1

Risk Factors

Major risk factors for invasive candidiasis include:

• Healthcare-related factors:

  • Broad-spectrum antibiotic use
  • Central venous catheters
  • Parenteral nutrition
  • ICU admission
  • Recent major surgery (particularly abdominal)
  • Renal replacement therapy1, 3

• Patient factors:

  • Immunosuppression (including glucocorticoids, chemotherapy)
  • Neutropenia
  • Implantable prosthetic devices
  • Multiple sites of Candida colonization (≥2 sites)1, 3

Clinical Impact and Outcomes

Invasive candidiasis has substantial clinical and economic impacts:

• Mortality: Attributable mortality ranges from 15-47%, with higher rates in critically ill patients1
• Economic burden: Each episode costs approximately $40,000 in additional healthcare expenses1
• ICU impact: Increases ICU and hospital length of stay1
• Delayed therapy consequences: Mortality approaches 100% in patients with Candida septic shock who do not receive appropriate therapy within 24 hours1

Causative Species

While Candida albicans remains the most common cause of invasive candidiasis, non-albicans species are increasingly important:

• Common species: C. albicans, C. glabrata, C. tropicalis, C. parapsilosis, and C. krusei account for >90% of cases2
• Emerging concern: Increasing resistance to azoles among C. glabrata isolates1
• Emerging threats: C. auris has been designated as a critical pathogen by WHO due to multidrug resistance1

Prevention and Treatment Considerations

For high-risk patients, preventive strategies may include:

• Antifungal prophylaxis: For selected high-risk populations (transplant recipients, neutropenic patients)1
• Catheter management: Prompt removal of central venous catheters when candidemia is diagnosed1
• Early empiric therapy: Consideration of empiric antifungal therapy in high-risk ICU patients with suspected infection1

The management of invasive candidiasis requires prompt recognition of risk factors, appropriate diagnostic testing, and early initiation of effective antifungal therapy to improve outcomes in this serious infection.