What is the significance of Candida growth in endotracheal (ET) tube secretion culture?

From the Guidelines

Candida growth in endotracheal tube secretion cultures typically represents colonization rather than infection and does not require antifungal treatment in most cases. This is supported by the 2016 update by the Infectious Diseases Society of America, which states that the isolation of Candida species from the respiratory tract is commonly encountered among patients who are in the ICU and are intubated or have a chronic tracheostomy, and this almost always reflects colonization of the airways and not infection 1.

Key Considerations

• The diagnosis of Candida pneumonia is supported by isolation of the organism from a bronchoalveolar lavage (BAL) specimen, but a firm diagnosis requires histopathological evidence of invasive disease 1.
• Multiple prospective and retrospective autopsy studies consistently demonstrate the poor predictive value of the growth of Candida from respiratory secretions, including BAL fluid 1.
• A decision to initiate antifungal therapy should not be made on the basis of respiratory tract culture results alone, due to the rarity of Candida pneumonia and the lack of specificity of this finding 1.

Treatment Approach

• No specific antifungal therapy is recommended for Candida isolated from respiratory secretions alone.
• Treatment should only be considered if there are signs of invasive fungal infection, such as positive blood cultures for Candida, deteriorating clinical condition despite appropriate antibacterial therapy, or histopathological evidence of tissue invasion.
• If treatment becomes necessary due to confirmed invasive candidiasis, options include fluconazole or an echinocandin like caspofungin, as suggested by the clinical practice guideline for the management of candidiasis 1.

Important Implications

• The distinction between colonization and infection is crucial because unnecessary antifungal therapy can lead to increased resistance, drug toxicity, and healthcare costs without clinical benefit.
• Recent observations suggest that colonization of the airway with Candida species is associated with the development of bacterial colonization and pneumonia, and worse clinical outcomes and higher mortality, but it is not clear if Candida airway colonization has a causal relationship to poorer outcomes or is simply a marker of disease severity 1.

From the Research

Candida Growth in Endotracheal Tube Secretion Culture

• Candida spp. are responsible for most of the fungal infections in humans, and their growth in endotracheal tube secretion culture is a significant concern in critically ill patients 2.
• A study found that 45% of intubated patients showed respiratory tract colonization by yeasts of the Candida genus, with C. albicans being the most frequently isolated species (66.7%) 3.
• The same study also found that blastoconidia of the same yeast were found in the infra-cuff portion of the endotracheal tube in almost 90% of these patients, as evidenced by scanning electron microscopy (SEM) 3.
• The presence of Candida in the lung may be associated with persistent inflammation and immunosuppression, as evidenced by higher plasma TNF-α levels and lower innate immune function in patients with VAP and Candida compared to those without Candida 4.

Risk Factors for Invasive Candida Infection

• Several risk factors have been identified for invasive Candida infection in critically ill patients, including broad-spectrum antibiotics, blood transfusion, Candida colonization, central venous catheter, and total parenteral nutrition 5.
• Candida colonization is a significant risk factor for invasive Candida infection, with an odds ratio of 4.7 (95% CI, 1.6-14.3) 5.
• The use of antifungal therapy in patients with Candida in their endotracheal secretions is still unclear, and a pilot study found no evidence to support a larger trial examining the efficacy of empiric antifungal treatment in these patients 4.

Treatment and Prophylaxis of Invasive Candidiasis

• Echinocandins, such as caspofungin, micafungin, and anidulafungin, are a relatively new class of antifungal drugs that are available for the treatment of candidemia and invasive candidiasis 6.
• These drugs are comparatively expensive, but their use has been shown to be cost-effective in certain settings, such as treatment of invasive candidiasis and prophylaxis in patients with hematopoietic stem cell transplantation (HSCT) 6.
• Switch strategies involving early initiation of broadly active therapy with switch to cheaper alternatives according to microbiology results and clinical status have been proven to be cost-efficient independent of the antifungal agent 6.