Prevalence of Candida species in the oral cavity of patients undergoing head and neck radiotherapy

Oral Candida in post-radiotherapy patients with xerostomia/hyposalivation: A narrative review

OBJECTIVE

Head and Neck Cancer (HNC) patients receiving radiotherapy (RT) often suffer from xerostomia and/or hyposalivation. As saliva plays an important antimicrobial and cleansing roles, these patients are at higher risks of opportunistic infections. This narrative review aims to provide an overview of current evidence on oral Candida colonisation and infection in these patients.

METHODS

A literature review of clinical studies on oral Candida colonisation and candidiasis in HNC patients receiving radiotherapy/chemoradiotherapy was conducted.

RESULTS

Many clinical studies found high levels of Candida colonisation and a substantial proportion of post-RT HNC patients suffering from oropharyngeal candidiasis (OPC). Importantly, oral Candida could be a reservoir for life-threatening systemic infection in immunocompromised patients. The rising prevalence of non-albicans Candida species and drug-resistant infections has made identification of Candida species and antifungal susceptibility more important. Recent advances in oral microbiome and its interactions with Candida are discussed. This review also offers perspectives on limitations of current evidence and suggestions for future research.

CONCLUSION

Further research to better understand Candida carriage, microbiome, OPC, and xerostomia/hyposalivation post-RT would aid in devising a more comprehensive long-term management plan and novel therapeutic approaches for HNC patients to achieve the full benefits of RT while minimising side effects.

Evaluation of the Effects of Photodynamic Therapy With Methylene Blue on Different Candida Species In Vitro

Introduction: Oral candidiasis is the most prevalent opportunistic infection of the oral cavity. The most common cause of this infection is Candida albicans. Considering the side effects of conventional antifungal therapies, this study aimed to evaluate the efficacy of photodynamic therapy with new methylene blue (a photosensitizer) in inhibiting the growth of C. albicans, C. tropicalis, C. glabrata, and C. krusei in vitro. Methods: In this experimental study, 200 samples of standard suspension (0.5 McFarland) were prepared from C. albicans, C. tropicalis, C. glabrata, and C. krusei (50 samples from each species). The samples of each species were divided into five groups (n=10), including photodynamic therapy with a photosensitizer, with or without laser irradiation, nystatin treatment, laser therapy, and control. Next, cultivation of samples was performed on Sabouraud dextrose agar, and the colony-forming units were determined after 24 hours of incubation at 37 °C. Data were analyzed in SPSS version 22 by means of the Kruskal-Wallis test (P<0.05). Results: The most sensitive and resistant species to nystatin therapy were C. glabrata and C. krusei, respectively. On the other hand, C. krusei was the most sensitive species to photodynamic therapy, and C. glabrata was the most resistant type to this treatment. The highest therapeutic effectiveness was attributed to nystatin therapy, although photodynamic therapy was also effective. Laser therapy was recognized as the least effective method. Conclusion: Photodynamic therapy with new methylene blue, as a suitable adjunct therapy, can be effective in the management of candidiasis. It may also be a potential novel treatment for immunocompromised patients with oral candidiasis.

Efficacy of gel-based artificial saliva on Candida colonization and saliva properties in xerostomic post-radiotherapy head and neck cancer patients: a randomized controlled trial

Objective

To evaluate the efficacy of an edible artificial saliva gel, oral moisturizing jelly (OMJ), and a topical commercial gel (GC dry mouth gel) on Candida colonization and saliva properties.

Materials and methods

This study was a secondary analysis of a single-blinded randomized controlled trial conducted in xerostomic post-radiotherapy head and neck cancer patients. Candida colonization, stimulated salivary flow rate (SSFR), saliva pH, and buffering capacity (BC) were measured at 0, 1, and 2 months after each intervention. Candida colonization was quantified by colony counts and species identified by Candida Chromagar, polymerase chain reaction, and API 20C AUX system. Statistical significance level was 0.05.

Results

A total of 56 participants in OMJ (N = 30) and GC (N = 26) groups completed the study. OMJ significantly increased saliva pH (p = 0.042) and BC (p = 0.013) after 1-month use, while GC only improved saliva pH (p = 0.027). Both interventions tended to increase SSFR but only GC had a significant increase at 2 months (p = 0.015). GC and OMJ significantly decreased the number of Candida species at 1 and 2 months, respectively. Both groups tended to reduce Candida counts but not significant.

Conclusions

Both OMJ and GC saliva gels could improve saliva pH and decrease the number of Candida species. OMJ is superior to GC in its buffering capacity, while GC may better improve salivary flow rate. Long-term and large-scale study is warranted to test the efficacy of artificial saliva in oral health improvement.

Clinical relevance

OMJ and GC gel could decrease the number of Candida species and improve saliva properties in post-radiation xerostomic patients.

Trial registration number

Clinicaltrials.gov NCT03035825. Date of registration: 25th January 2017.

Late Oral Complications Caused by Head and Neck Radiotherapy: Clinical and Laboratory Study

Objectives

The aim of presented cross-sectional and observational study was to determine the prevalence of late oral complications of patients with head and neck cancer who underwent radiotherapy, by clinical and laboratory analyses.

Material and Methods

Fifty-five patients, 43 (78.2%) men and 12 (21.8%) women, mean age 60; range 38 to 87 years, who have completed radiotherapy for head and neck cancer for at least 6 months were enrolled. The presence of xerostomia, hyposalivation, oral candidiasis, and type of oral yeasts were correlated with post-radiotherapy period. A control group, age and gender matched, was used for comparisons. The Pearson’s Chi-square or Fischer’s exact test was used at a significance level of 5%.

Results

The mean post-radiotherapy period was 32 months. The oral complications found were xerostomia (45/55, [81.8%]), hyposalivation (44/55 [80%]) and oral candidiasis (15/55 [27.2%]). Xerostomia and hyposalivation was statistically higher in the study group when compared to the control group (P < 0.05). The presence of yeast occurred in 39 (70.9%) of the patients in the study group, and Candida albicans was the most prevalent etiological agent in 25 (64.1%) of those patients (P < 0.05).

Conclusions

Xerostomia and hyposalivation were the more prevalent late oral complications related to radiotherapy. Oral candidiasis was also observed, although its prevalence was lower. The need for long-term dental follow-up of patients who underwent radiotherapy of the head and neck cancer is mandatory.

Incidence and spectrum of yeast species isolated from the oral cavity of Iranian patients suffering from hematological malignancies

Background: Oral candidiasis (OC) has a profound effect on the life quality of immunocompromised patients, such as those undergoing chemotherapy. Objective: Systematic investigation of clinical outcome and microbiological features of yeast isolates recovered from the oral cavity of 150 Iranian patients with hematological malignancies. Design: MALDI-TOF MS, 21-plex PCR, and rDNA sequencing were used for identification. Antifungal susceptibility testing (broth microdilution, CLSI M27-A3/S4) and genotypic diversity of yeast isolates (amplified fragment length polymorphism) were assessed. Results: Nystatin treatment resulted in 70% therapeutic failure and administration of 150 mg fluconazole (FLZ) + nystatin for patients with OC relapse showed 70% clinical failure. Previous history of OC was significantly correlated with FLZ treatment requirement and nystatin failure (P = 0.005, α < 0.05). Candida albicans (80.3%) and Kluyveromyces marxianus (C. kefyr) (12.7%) were the two most prevalent yeast species isolated. FLZ and AMB exhibited the highest geometric mean values. 21-PCR showed 98.9% agreement with MALDI-TOF MS. K. marxianus isolates had the same genotype, while C. albicans isolates grouped in 15 genotypes. Conclusions: Marked rate of therapeutic failure of nystatin necessitated OC treatment with systemic antifungals. K. marxianus was the second most prevalent yeast and 21-plex PCR could be considered as an inexpensive identification tool.

Salivary gland stem cells: A review of development, regeneration and cancer

Salivary glands are responsible for maintaining the health of the oral cavity and are routinely damaged by therapeutic radiation for head and neck cancer as well as by autoimmune diseases such as Sjögren's syndrome. Regenerative approaches based on the reactivation of endogenous stem cells or the transplant of exogenous stem cells hold substantial promise in restoring the structure and function of these organs to improve patient quality of life. However, these approaches have been hampered by a lack of knowledge on the identity of salivary stem cell populations and their regulators. In this review we discuss our current knowledge on salivary stem cells and their regulators during organ development, homeostasis and regeneration. As increasing evidence in other systems suggests that progenitor cells may be a source of cancer, we also review whether these same salivary stem cells may also be cancer initiating cells.

An in vitro study of isolation of candidal strains in oral squamous cell carcinoma patients undergoing radiation therapy and quantitative analysis of the various strains using CHROMagar

Background:

Patients undergoing radiation therapy for oral squamous cell carcinoma (OSCC) have an increased risk of developing oral candidiasis. Radiation-induced hyposalivation is thought to be a major predisposing factor for it. Radiation therapy for 2–3 weeks leads to increase in the number of candidal species in the oral cavity, eventually leading to oral candidiasis.

Objective:

To evaluate and correlate the prevalence of candidal species in the oral cavity of OSCC patients and to compare with radiation dosage at 3^rd and 6^th week following radiotherapy.

Materials and Methods:

This study includes fifty patients undergoing radiation therapy for OSCC. Patients were examined at 3^rd and 6^th week following radiation therapy, and smear samples were obtained from lesional sites and the radiation dose was recorded. Smear samples were cultured on CHROMagar, and identification of various candidal species was done on the basis of colony color and their morphology.

Results:

The present study isolated four types of candidal species, namely, Candida albicans, Candida glabrata, Candida tropicalis and Candida krusei. All the organisms, except C. krusei, showed a significant increase from 3^rd to 6^th week of radiotherapy whereas C. glabrata and C. tropicalis showed a sudden exponential increase. Total radiation dosage did not show any correlation to candidal colonization at 3^rd and 6^th week following radiotherapy.

Conclusion:

OSCC patients undergoing radiotherapy show an increase in candidal colonization which is independent of radiation dosage and may be related to other factors. However, such findings should be further evaluated using a larger sample size.

Oropharyngeal candidiasis in children with lymphohematopoietic malignancies in Mashhad, Iran

Background and Purpose:

Over the past years, the role of fungi as a cause of nosocomial infections in hospitalized patients has been accentuated. Candida species constitute an important group of fungi causing diseases in immunocompromised patients. Oropharyngeal candidiasis continues to be a prevalent infection in immunodeficient patients. In this study, we aimed to determine the incidence of oropharyngeal candidiasis in children with lymphohematopoietic malignancies.

Materials and Methods:

In total, 102 patients with lymphohematopoietic malignancies and 50 healthy controls were examined in terms of Candida infections via direct sampling of the oropharyngeal cavity. Fresh smears were prepared with 10% potassium hydroxide and Gram staining was carried out. Subsequently, the obtained specimens were cultured on Sabouraud dextrose agar for further analysis.

Results:

The most common Candida species were Candida albicans (31%), other non-C. albicans species (14.7%), C. glabrata (6.8%), and C. krusei (0.98%) in the case group, while in the control group, other non-C. albicans species (10%) and C. albicans (8%) were the most common species.

Conclusion:

In the present study, Candida species were the most common fungal pathogens in pediatric cancer patients; therefore, efforts should be made to prevent fungemia and fungal pneumonia. Also, non-C. albicans species must be considered as a new risk factor for pediatric cancer patients.