Oropharyngeal Candidiasis in Palliative Care Patients in Denmark

Abstract

Background:

Oropharyngeal candidiasis (OPC) is a significant cause of morbidity, especially among patients with advanced cancer. The incidence and significance of yeast carriage and OPC in the palliative care setting in Denmark is unknown. The best diagnostic strategy and treatment regimen has to be defined.

Objective:

This study evaluated the clinical and microbiological incidence of yeast carriage/OPC and assessed available diagnostic procedures—culture and microscopy. The distribution of Candida species and fluconazole susceptibility was determined.

Methods:

Terminal care patients admitted to Hospice Sjaelland (Denmark) March to June 2012 were included. Patients were evaluated for clinical OPC and a questionnaire including previous antifungal treatment was obtained. Paired samples from the buccal mucosa and the tongue were sent to microscopy and culture. In total, 105 microscopy slides and 105 cultures from 54 patients were included, yielding 71 Candida isolates. At admission, 22% were in fluconazole treatment and 56% had received an antifungal treatment within the last month.

Results:

The yeast carriage rate was 83%, whereas 48% of the patients had clinical signs of OPC. Microscopy had low positive and negative predictive value (∼50%). Candida albicans accounted for half of the isolates cultured. No C. albicans isolate displayed acquired fluconazole resistance; however, 3 out of 12 isolates of normally fluconazole-susceptible species were fluconazole resistant. These were all from patients recently treated with azoles.

Conclusions:

In total, 52% of culture-positive patients harbored at least one isolate with innately or acquired decreased fluconazole susceptibility. Therefore, susceptibility testing appears recommendable for patients with clinical signs of OPC.

Introduction

Oropharyngeal candidiasis (OPC) is an opportunistic condition accounting for significant morbidity in patients with advanced cancer. Yeast carriage rates of 66% to 86% with OPC rates of 10% to 40% have ben reported.^1–6

Candida albicans is the main yeast of the digestive tract and genital area followed by C. glabrata, C. parapsilosis, and C. tropicalis.^7–9 OPC has primarily been associated with C. albicans, but recent studies have documented the shift to non-albicans species such as C. dubliniensis and C. glabrata.^10–12 Furthermore, national surveillance programs are reporting both an increasing number of non-albicans species causing candidemia^13,14 and an increasing incidence of fluconazole resistance. Selection of fluconazole resistance in C. albicans during treatment of OPC in HIV patients has been documented.¹⁸

The aim of this study was to evaluate the prevalence of symptoms, the diagnostic sampling procedures, and the burden of OPC in a cohort of terminally ill Danish patients. The clinical need for species identification and susceptibility testing also was assessed.

Methods

From March 1 to June 15, 2012, 54 patients admitted to Hospice Sjaelland (Roskilde, Denmark) were enrolled in the study. The inclusion criteria were no psychiatric disturbances, a Performance Status (PS)¹⁵ enabling informed consent, and a terminal illness necessitating palliative treatment. One patient was admitted twice (101 days apart) and included twice. A questionnaire with diagnosis, previous antifungal treatment, PS, and symptoms of OPC were obtained at admission. No ethical restraints applied (The Committees on Health Research Ethics [Capital Region] H-4-2015-FSP).

Paired samples from the buccal mucosa and the surface of the tongue were taken. The sampling included one sterile cotton swab smeared on a glass slide, fixated with methanol, followed by a sterile charcoal swab in Stuart Transport Medium (SSI Diagnostica, Denmark). In one patient, samples were only obtained from the tongue. Samples from three patients were excluded due to leakage. In total, 105 microscopy slides and 105 cultures from 54 included patients were examined. All isolates except five (three C. albicans, one C. glabrata, and one C. tropicalis from three patients) were stored (at −80°C) and subsequently referred to the reference laboratory for mycology at Statens Serum Institute for species confirmation and susceptibility testing.

At admission, patients were evaluated for clinical signs of OPC (angular cheilitis, pseudomembranous, and/or erythromatous mucosa) and subjective symptoms. The receiving physicians treated patients suspected of OPC with azoles. Microscopy slides were gram-stained and evaluated for the presence of fungal elements. The swabs were plated on chromogenic agar (BBL CHROMagar Candida, Becton Dickinson) and incubated at 35° C for 48 hours. Candida species identification was done as previously described.¹⁴

Each unique Candida isolate per patient was tested against a panel of antifungals: fluconazole, miconazole, voriconazole, and itraconazole according to the EUCAST EDef 7.2.¹⁶ Susceptibility testing for amphotericin B was performed as previously described.¹⁴ The minimal inhibitory concentration (MIC) was defined as the lowest drug dilution giving 100% growth inhibition for amphotericin B and 50% growth inhibition for the azoles.

Results

Included in the study were 30 women and 24 men; the median age was 69 years (range 40 to 87 years). One patient (admitted twice) had terminal chronic obstructive pulmonary disease. The remaining patients all had a diagnosis of terminal cancer. The performance status was 3–4 for 90% of the patients (capable of only limited self-care and confined to bed/chair more than 50% of waking hours). The median duration of hospice admission was 11 days (range 2–108 days). Forty-seven patients died at the hospice, while the remaining were discharged after stabilizing treatment. More than half (56%) of the patients were either in systemic antifungal treatment at the time of admission or had concluded a treatment within the preceding month. Twelve (22%) of the patients were in fluconazole treatment when admitted (50–200 mg/day, mean 125 mg/day), nine of whom remained on treatment after being evaluated by the receiving physician. Overall, 26 of the 54 patients had symptoms or clinical signs of OPC at admission.

Culture and microscopy

Culture yielded 71 distinct isolates from 45 patients (0–4 different isolates per patient; mean 1.6 isolate/patient). In 35 out of 43 patients with two swabs submitted for culture, we found identical results; the remaining eight patients had more isolates from one location (more often the tongue: 75%). Completely different isolates from the two swabs were not detected.

More samples were culture positive than microscopy positive. Almost all microscopy-positive samples grew yeast. There was no correlation between a positive culture or microscopy and the presence of symptoms and clinical signs prompting antifungal treatment at admission. The positive predictive value (PPV) and the negative predictive value (NPV) were both around 50% for microscopy and culture (see Table 1).

Table 1.

Test Performance Based on Symptoms ^a (Present/Not Present) or Culture Results (Positive/Negative) as the Golden Standard

Test (golden standard)	Swab	SENS (%)	SPEC (%)	PPV (%)	NPV (%)
Microscopy (symptoms)	Buccal	35	67	50	51
	Tongue	27	58	39	44
Culture (symptoms)	Buccal	76	21	46	50
	Tongue	84	15	48	50
Microscopy (culture)	Buccal	43	92	94	32
	Tongue	40	100	NA	24

Clinical signs and patient symptoms resulting in treatment for OPC.

NPV, negative predictive value; OPC, oropharyngeal candidiasis; PPV, positive predictive value; SENS, sensitivity; SPEC, specificity.

Isolates

C. albicans accounted for 49%, followed by C. glabrata (17%) and C. tropicalis (11%) (see Table 2). Nearly half (47%) of the patients had growth of several Candida species, and of these, 48% had symptoms of OPC. Half of the patients growing one species had symptoms, the majority (83%) caused by C. albicans. Whether alone or in combination, C. albicans, C. glabrata, and C. tropicalis were the species most likely to cause symptoms (see Table 2).

Table 2.

Species Identification and Distribution in Culture-Positive Patients, Single or Multiple Species, and Symptomatic Patients

				In % of
Species	No. of isolates	Patients with a single species identified	Symptomatic patients with a single species	Isolates (71=100%)	Patients (45=100%)	Found in % of symptomatic patients^a
C. albicans	35	17	10	49.3	77.8	66
C. glabrata	12	1	1	16.9	26.7	67
C. tropicalis	8	1	1	11.3	17.8	63
S. cerevisiae	5	2	0	7.0	11.1	20
C. krusei ^b	5	1	0	7.0	8.9	25
C. dubliniensis	4	1	0	5.6	8.9	25
C. parapsilosis	1	0	0	1.4	2.2	0
C. norvegiensis	1	1	0	1.4	2.2	0
Total	71	24	12	99.9	ND	ND

Regardless of single or multiple species identified.

One patient yielded two morphologically different isolates.

ND, not determined.

Susceptibility

MICs were determined in 66 isolates. No fluconazole resistance was detected among C. albicans isolates. However, one out of seven C. tropicalis and two out of four C. dubliniensis isolates had MICs of ≥16 mg/L (see Table 3) and were panazole resistant.

Table 3.

Fluconazole MIC Values for the Individual Isolates

	Fluconazole MIC (mg/L) values
Species	≤0.125	0.25	0.5	1	2	4	8	16	>16	Total
C. albicans	8	16	5	3						32
C. glabrata			1		3	5	1		1	11
C. tropicalis			5		1			1		7
C. krusei							1		4	5
S. cerevisiae					1		2	2		5
C. dubliniensis	1			1					2	4
C. parapsilosis			1							1
C. norvegensis								1		1
Total	9	16	12	4	5	5	4	4	7	66

The gray area demonstrates MIC values above the nonspecies-specific EUCAST breakpoint for fluconazole.²⁵

MIC, minimal inhibitory concentration.

C. krusei, C. glabrata, C. norvegensis, and Saccharomyces cerevisiae are innately less susceptible to fluconazole. Therefore, one-third of the isolates were inappropriate targets for azole therapy. Eighteen of the 42 patients (43%) with determined MICs had at least one isolate with a fluconazole MIC ≥4 mg/L. Twenty-two (52%) culture-positive patients harbored either an isolate with an MIC ≥4 mg/L and/or an isolate innately less susceptible to fluconazole. The amphotericin B MIC was above 1 mg/L for three (one C. glabrata of 1.5 mg/L and two C. tropicalis of 1.5 and 2.0 mg/L, respectively).

Discussion

The incidence of OPC among terminally ill patients in Denmark equals numbers from other countries,^1–5 with a carrier rate of 83% based on culture. More than half of the patients had received antifungal treatment within the last month before admission to hospice. Clinically, 48% of the patients were insufficiently treated when admitted. The presence of hyphae at microscopy has been perceived as indicating infection rather than colonization; however, C. glabrata does not form pseudo-hyphae. Microscopy is dependent on the amount of material and the method of staining and has been associated with inferior sensitivity.^17,18 On the other hand, culture positivity may reflect clinical disease or merely colonization. Neither microscopy nor culture was useful in guiding the diagnosis of OPC in our study, as both positive and negative predictive values were around 50%. Swabs from the tongue seem to yield a higher proportion of growth positive samples and to represent the species distribution correctly. Due to clinical symptoms, four out of nine culture-negative patients were started on treatment. Half of these were or had recently been in fluconazole treatment, possibly rendering the cultures negative. In contrast, 63% of culture-positive patients were started on treatment. However, culture gave additional information about species and susceptibility patterns. Especially C. albicans, C. tropicalis, and C. glabrata were positively associated with symptoms.

We found no acquired azole resistance in C. albicans. Three out of twelve (25%) non-albicans isolates (C. dubliniensis, C. tropicalis, and C. parapsilosis) displayed acquired panazole resistance. These three patients had all been treated with azoles within a month of admission, thereby possibly inducing resistance.

Almost half (43%) of culture-positive patients harbored at least one fluconazole-resistant isolate (MIC of ≥4 mg/L). These patients may not respond to fluconazole in normal dosages. International treatment guidelines for OPC are not uniform nor target palliative care patients.^19–22 Treatment options include nystatin solution, miconazol oral gel, and systemic fluconazole in dosages from 50–200 mg/day. Triazoles and echinocandins are reserved for refractory OPC.

Even though the infection by definition is superficial, the immunocompromised group of palliative care patients normally requires systemic treatment as a supplement to general hygienic measures to suppress the growth of Candida biofilm, e.g., on dental prosthesis.²³ Due to the static nature of the azoles, and to encompass the highest “susceptible” fluconazole MIC of 2 mg/L, a dosage of 200 mg/day will be needed, whereas 100 mg will be sufficient when more susceptible isolates are involved.²⁴ Three isolates (one C. glabrata and two C. tropicalis) from normally amphotericin B susceptible species displayed a slightly elevated MIC value (>1 mg/L). Whether this reflects true resistance because of prior nystatin treatment is unknown.

We found that more than 80% of all patients referred to hospice had growth of yeast from their oropharynx. Many of these patients had previously received antifungals, possibly explaining the significant proportion of Candida isolates displaying intrinsic or acquired resistance. We therefore recommend species identification and susceptibility testing on swabs from palliative care patients with symptoms of OPC.

Footnotes

Acknowledgments

We are most grateful to Professor Maiken Cavling Arendrup (at the Unit of Mycology, Statens Serum Institut, Copenhagen) for valuable comments to the manuscript and for assistance performing the EUCAST susceptibility testing.

Author Disclosure Statement

We have no conflicts of interest related to this paper. The Novo Nordisk Foundation supported HKJ with a clinical research stipend and KA has received travel grants from Pfizer and Gilead.

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