How do I interpret Candida in respiratory tract cultures?

Dr Tan Ban Hock
Senior Consultant 
Department of Infectious Diseases
Singapore General Hospital
Singapore

Candida in the human microbiota

Candida is part of the human microbiota of the respiratory tract. As such, Candida can be cultured from the mouth of people with and without pneumonia, and appears rapidly in the lower respiratory tract (LRT) in patients admitted to the ICU.¹ Unfortunately, there is still no culture-based or molecular test of respiratory specimens that can distinguish between Candida contamination, colonization and invasive disease.²

Significance of Candida in the lower respiratory tract

An observational study found no relationship between Candida spp. in the LRT and invasive candidiasis. Moreover, there was also no link between Candida-dominated LRT microbiota and intra-hospital or 30-day overall mortality.¹

A prospective study that assessed cultures of immediate postmortem lung biopsies showed extensive Candida colonization throughout the lungs in patients with and without pneumonia.³ Candida pneumonia is extremely rare in ICU patients, as shown by a prospective study of autopsies performed on patients who died in the ICU: there was no histopathologically proven case of Candida pneumonia found in patients with pneumonia on autopsy and a Candida-positive airway culture prior to death. ⁴

Treating patients with Candida in the respiratory tract

There is no benefit to treating patients with Candida in the airways. Results from a retrospective study showed that in critically ill patients with pulmonary Candida spp. colonization, antifungal therapy did not affect the incidence of new pneumonia or mortality.⁵ A randomized placebo-controlled trial similarly demonstrated that antifungal therapy did not have a significant impact on hospital/ICU length of stay and mortality in critically ill patients with Candida-positive airway secretions.⁶

References

1. Krause R, et al. PLoS One 2016;11:e0155033.
2. Pendleton KM, et al. Pathog Dis 2017;75(3).
3. el-Ebiary M, et al. Am J Respir Crit Care Med 1997;156:583-590.
4. Meersseman W, et al. Intensive Care Med 2009;35:1526-1531.
5. Lindau S, et al. J Intensive Care 2015;3:31.
6. Albert M, et al. Intensive Care Med 2014;40:1313-1322.