What are the primary organisms to worry about in patients with Invasive Candidiasis (ICC)?

Primary Organisms in Invasive Candidiasis (ICC)

Five Candida species account for 92% of invasive candidiasis cases: Candida albicans, Candida glabrata, Candida tropicalis, Candida parapsilosis, and Candida krusei. 1

Major Pathogens and Epidemiology

• Candida albicans remains the predominant cause of invasive candidiasis in most settings, though there is an increasing shift toward non-albicans species 1
• The emergence of non-albicans Candida species is particularly important in specific patient populations:
  • C. tropicalis is more commonly isolated from neutropenic patients receiving chemotherapy on hemato-oncology services 1
  • C. glabrata and C. parapsilosis are increasingly important in critically ill non-neutropenic patients 1
• Recent epidemiological data shows a progressive transition from C. albicans to non-albicans Candida species as etiological agents 1

Emerging Threat: Candida auris

• C. auris is the most concerning emerging pathogen, classified by the CDC as an urgent public threat due to:
  • Association with increased mortality
  • Potential for developing pan-drug resistance
  • Ability to become entrenched in hospital environments 1
• There has been a significant increase in C. auris cases in the USA in recent years, with outbreaks reported across various European countries 1
• A tripling of echinocandin-resistant isolates has been observed, further complicating treatment options 1

Antifungal Resistance Patterns

• C. krusei is intrinsically resistant to fluconazole but is relatively rare in most hospital settings 1
• Non-susceptibility to fluconazole (including susceptible-dose dependent and resistant strains) is becoming a major concern, particularly in:
  • C. glabrata (with cross-resistance to other triazoles)
  • C. tropicalis (with cross-resistance to other triazoles) 1
• Prior azole exposure is associated with higher probability of infection by azole-resistant or non-albicans strains 2
• The emergence of pan-drug-resistant C. auris strains indicates an insufficient range of available medications 3

Clinical Considerations

• Candida peritonitis is the predominant form of invasive candidiasis after candidemia in ICU patients 1
• Intra-abdominal candidiasis (IAC) has mortality rates exceeding 50%, even with modern antifungal treatments 1
• Mixed infections with bacteria are common in intra-abdominal candidiasis, complicating diagnosis and treatment 1
• Only 6.9% of patients with intra-abdominal candidiasis have concomitant positive blood cultures for Candida species, making diagnosis challenging 1

Risk Factors and Prevention

• Intensive care unit patients are at highest risk for invasive candidiasis 1
• Rapid colonization of mucocutaneous surfaces after ICU admission is an important risk factor for candidemia 1
• Alterations in the gastrointestinal microbiome typically precede intra-abdominal candidiasis 1
• Risk factors include use of antibiotics, central venous catheters, surgical procedures, parenteral nutrition, sepsis, neutropenia, renal failure, mechanical ventilation, immunosuppressive agents, and Candida colonization 1
• Standard precautions including hand hygiene are essential as most Candida blood isolates are similar or identical to prior colonization in the patient's urinary and gastrointestinal tracts 1

Diagnostic Challenges

• Differentiation between contamination, colonization, and infection is difficult when Candida is present in intra-abdominal samples 1
• Up to 80% of patients with peritonitis are colonized with Candida species, further complicating diagnosis 1
• Non-culture-based diagnostic methods are increasingly important due to the limitations of conventional culture techniques 4