Higher Prevalence of Oral Candida Fungus Found in CF Patients

Steve Bryson, PhD avatar

by Steve Bryson, PhD |

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Oral bacteria in CF

People with cystic fibrosis (CF) are more frequently infected with oral Candida fungus and carry a higher number of fungi than healthy individuals, a study has found.

All fungal species identified in the study’s CF patients were susceptible to currently available anti-fungal medications.

The study, “Oral prevalence and anti-fungal susceptibility of Candida species in cystic fibrosis patients,” was published in the journal Archives of Oral Biology.

CF is characterized by the buildup of mucus in the airways, which can lead to lung infections primarily caused by bacteria. Fungal infections, either alone or in combination with bacteria, have been linked to decreased lung function. In particular, mixed infections with the bacteria Pseudomonas aeruginosa and the fungus Candida albicans have been correlated with the progression of CF lung disease.

The mouth (oral cavity) is considered a potential reservoir for opportunistic microorganisms, which can eventually lead to systemic infection.

While P. aeruginosa bacteria have been found in saliva and sputum samples isolated from CF patients, little is known about the prevalence of fungal infections such as Candida in the oral cavities of this patient population.

Thus, a team led by researchers at São Paulo State University in Brazil investigated the oral prevalence of Candida species in CF patients with different levels of disease severity.

“To our knowledge, this is the first comprehensive analysis of the oral prevalence of Candida [species] in a cohort of cystic fibrosis patients with different disease severities,” the team wrote.

A total of 100 CF patients were enrolled, which included 50 males and 50 females from 3 to 20 years old. As a comparison group, 50 healthy age- and gender-matched individuals were included as controls.

As part of routine examinations, disease severity was measured using the Shwachman-Kulczycki (SK) score, which is based on general activity, physical examination, nutrition, and radiological findings. Lower scores represent more severe disease.

Patients were divided into two group: 25 patients with SK scores between 100 and 70 were considered to have low severity disease, and 25 patients with SK scores under 40 were defined as having severe disease.

Saliva samples were collected after patients had been fasting for a minimum of two hours. Samples were cultured for fungal growth, and the species of fungus were identified.

Initial clinical examinations did not find any oral lesions consistent with fungal disease.

The results revealed that 80% of CF patients with severe disease tested positive for Candida, whereas 68% of those with low disease severity tested positive, compared with 44% of control subjects.

Quantitative analysis showed that CF patients had significantly higher concentrations of oral fungus than controls. However, severe CF patients had similar oral fungal levels compared with those who had low disease severity.

Two Candida species — Candida dubliniensis and Candida tropicalis — were detected only in the CF groups, whereas Trichosporon asahii was found exclusively in patients with severe CF, and Saccharomyces cerevisiae (baker’s yeast) was found exclusively in the control group.

C. dubliniensis has been found as a prevalent and persistent microorganism colonizing the respiratory tract of cystic patients and has been correlated to severe cases of pulmonary infection,” the researchers wrote.

“Future longitudinal (over time) studies are important to evaluate the persistence of C. dubliniensis oral colonization and possible correlation with the clinical evolution of cystic fibrosis,” they added.

An assessment of resistance to fungicide medications — namely flucytosine and fluconazole — found that most of the isolated Candida species were susceptible to treatment.

Overall, the “results suggest that cystic fibrosis patients may be more prone to Candida infections when compared to controls and that the medical staff should monitor the occurrence of oral fungal infections that can serve as reservoirs to systemic disease,” the researchers wrote.

“Although no resistant isolate was detected in this study, the increasing occurrence of resistance in other fungal species points out to the importance of continuous monitoring,” the team added. “Further longitudinal studies are required to assess the long-term colonization by Candida species and the impacts on pulmonary disease.”