Onychomycosis Unresponsive to Antifungals: Etiology and Treatment with a New Direct Technique

Abstract

Aims and Objectives:

The aim of this study was to identify the fungal agents causing onychomycosis that were unresponsive to antifungal treatment and to treat these cases by placing under-nail cushions with a mild keratolytic to clear the fungus-invaded tissue.

Materials and Methods:

Fungal agents were identified by the matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) technique.

Results:

Nine patients had Aspergillus spp. (7 Aspergillus niger, 2 Aspergillus flavus); four had Candida species and one had Trichophyton rubrum. All patients were free of infection at the end of treatment.

Conclusion:

As per the results, we may state that onychomycosis that is unresponsive to treatment in immunocompetent patients seems to be mostly associated with molds. Direct application of a mild keratolytic to the fungus-invaded part, e.g., the nail plate and/or nail bed and removal of fungal elements may provide a successful treatment outcome.

Introduction

The incidence of onychomycosis has increased, but successful treatment outcome is yet to be achieved.[1,2,3,4,5] Two major reasons for treatment failure believed to be are increasing resistance to systemic antifungals and inability of topical antifungals to pass through the nail plate to reach the nail bed.[6,7,8,9] Recently, resistant strains of dermatophytes have been discovered.[10] Onychomycosis due to nondermatophytes is also increasing.[11,12,13]

One of the aims of this study was to identify the fungi causing onychomycosis that were unresponsive to standard antifungal treatment. The second aim was to develop a technique for clearing fungal elements directly from the site where they were located without the use of antifungals.

Materials and Methods

We obtained clearance from the ethics committee prior to the study. Our inclusion criteria were as follows:

1. Adult immunocompetent patients with onychomycosis having failed at least 2 months of either topical and/or systemic antifungals (systemic terbinafine, systemic daily or pulse itraconazole and/or topical ciclopirox olamine citrate, tioconazole or amorolfine)

2. Observation of fungal elements in a 20% potassium hydroxide (KOH) preparation

3. Growth of the same fungal agent in all three consecutive cultures of the specimen taken from the same patient at one week intervals

4. Growth of the same nondermatophytic agent in all three cultures was mandatory to accept the agent as causative.

The pretreatment onychomycosis severity index (OSI) scores were calculated as described by Carney et al.[14]

All specimens were cultured on Sabouraud dextrose agar supplemented with chloramphenicol, for identifying the causative fungal agents. The matrix-assisted laser desorption/ionization - time of flight (MALDI-TOF) technique was used as it was reported to be as efficient as molecular methods.[15,16] An antifungal susceptibility test was not performed, as a standardized, cost-effective method was unavailable.[17,18,19] To clear fungal elements from the nail plate and nail bed, polyvinyl alcohol (PVA) under-nail cushions wet with 5% w/v citric acid solution in tap water were used. Triangular cushions were placed where fungal colonization was prominent. However, we never placed cushions forcefully. The method of application differed by the type of onychomycosis.

In patients with distal lateral subungual onychomycosis, infected keratin was first softened by a citric acid-based solution applied twice daily [Figure 1]. After 1 week, subungual softened keratin debris was removed manually using the blunt edge of a lancet and a room was prepared for the triangular PVA cushion that was gently placed from the tip [Figure 2]. Then, the cushion was soaked with the same citric acid solution twice daily [Figure 3]. This process enabled us to clear the fungi from under the surface of the nail plate and from nail bed [Figure 4]. Meanwhile, we made scratches on the nail plate that enabled citric acid to reach inner layers of the nail unit inhabited by fungal elements. We aimed to place the cushion at the most proximal point of color change to clean the nail bed [Figures 5-7].

Figure 1.

Aspergillus flavus onychomycosis - present for 10 years at the beginning of treatment

Figure 2.

One week after treatment with citric acid. A room for the cushion is prepared using the blunt edge of a lancet

Figure 3.

Cushion is placed under the nail

Figure 4.

One year after the cessation of treatment

Figure 5.

Subungual Alternaria onychomycosis present for 12 months

Figure 7.

After 10 months of treatment, the whole nail is cleared

Figure 6.

Under-nail cushion is placed at the proximal part of the nail bed

In patients with superficial white onychomycosis, the cushion was placed between the layers of nail where it stayed only for 1 day, which was sufficient for clearance of infected keratin parts.

In patients with proximal subungual onychomycosis, we softened the nail covering the infected part followed by drilling a small hole with a lancet to place the under-nail cushion.

The end point of the study was the emergence of a healthy nail plate from the matrix progressing to a healthy nail bed. Patients cleaned both nail plate and nail bed mechanically by removing debris with a file every week after showering. Clinical clearance, negative KOH, and negative culture results after the treatment were the final end points of this study [Figures 8 and 9]. All patients were checked once again 1 year after cessation of the treatment to search for any recurrence.

Figure 8.

Paecilomyces variotii onychomycosis

Figure 9.

After 8 months of treatment, the nail is cleared

Statistical methods

Data analysis was performed with SPSS (Statistical Packages for Social Analysis) 25.0. We have tested the difference between pretreatment and posttreatment OSI scores of patients with the Wilcoxon Sign test. P < 0.05 was considered as statistically significant.

Results

We had 20 patients, 5 males and 15 females, who fulfilled the inclusion criteria over a period of 18 months (June 2015 to December 2016). None of the patients had diabetes, HIV, or malignancy or had received chemotherapy. Overall 6 had total dystrophic, 11 had distal lateral subungual, 2 proximal subungual, and 1 superficial white onychomycoses. Among the 20 patients, 18 had infected toe-nails, and 2 had infected finger-nails.

The mean pretreatment OSI score was 22.40 ± 9.92 and the posttreatment OSI score was 0.5 ± 1.05. The difference in OSI scores was statistically significant (P < 0.001).

Fungal elements were seen in KOH preparation in all patients. The culture showed four patients had Candida species, one had Trichophyton rubrum, and the remaining 15 had molds (9 Aspergillus, 2 Paecilomyces variotii, 2 Alternaria alternata, 1 Cladophialophora, and 1 Penicillium) as the causative agents. The most common mold identified was the Aspergillus species [Table 1]. The average age of the group was 50.25 ± 16.48. The average duration of their complaints was 33 ± 28.57 months (12–120 months). All had received antifungal treatment previously; half received systemic antifungals and half received topical antifungals without benefit [Table 1]. The average duration of citric acid plus cushion treatment was 5.80 ± 2.74 months (2–11 month). All the patients had total clearance and were followed for at least one more year after cessation of therapy and none had recurrence.

Table 1.

List of clinical, demographic characteristics, and causative agents

Result of MaldiTof	Number of patients	Age (mean±SD)	Complaint duration (month) (mean±SD)	Type of onychomycosis	Type of previous treatment	Pretreatment OSI (mean±SD)	Posttreatment OSI (mean±SD)	Duration of Citric acid therapy (month) (mean±SD)
Aspergillus spp.	9	54.56±20,44	24.0±10,39	6 DLS 3 total dystrophic	3 topical cicloproxolamine citrate 2 systemic itraconazole 2 topical cicloproxolamine citrate+systemic terbinafine	21.56±9.07	2.78±3.34	5.44±2.87
Candida spp.	4	41.50±15.86	54.00±48.49	1 DLS 2 total dystrophic 1 superficial white	3 topical cicloproxolamine citrate 1 systemic terbinafine	24.75±14.61	0.50±1.00	6.50±3.10
Paecilomyces variotii	2	51,50±19.09	24,00±16.97	1 proximal subungual 1 DLS	1 topical tioconazole 1 topical cicloproxolamine citrate	25.50±13.43	0.50±0.70	7.50±0.70
Alternaria alternata	2	52.50±7.77	18.00±8.48	1 DLS 1 proximal subungual	Topical amorolfine Systemic itraconazole	21.00±1.41	1.00±1.41	5.00±1.41
Trichophyton rubrum	1	54	24	DLS	Topical ciclopirox olamine citrate	26	0	2
Cladophialophora sp.	1	39	96	Total dystrophic	Systemic itraconazole, Topical ciclopirox olamine citrate	30	1	10
Penicillium sp.	1	47	24	DLS	Systemic terbinafine	6	0	4

OSI: Onychomycosis severity index; DLSO: Distal lateral subungual; SD: Standard deviation

Discussion

Our first aim was to discover the causative agent of onychomycosis that was unresponsive to antifungals. First, we expected to isolate mostly dermatophytes because until recently, they were considered the major etiologic agent for onychomycosis in immunocompetent persons. However, once considered saphrophytes; recently, nondermatophyte onychomycosis is becoming more prevalent in otherwise healthy persons, which is in accordance with our findings.[11,12,20,21]

We preferred the MALDI-TOF technique for fungal isolation which had been found to be as efficient as molecular methods while being cost effective and requiring less time.[15,16,22]

Another belief was that keratin was the house mainly of dermatophytes, but it had been shown to be shared by molds as well.[23,24] Invasion of keratin shown as subungual thickening or as a color stain on the nail plate is shared by molds, which are clinically similar to dermatophytes.

Our second aim was to develop a treatment technique reaching directly to the fungus invaded keratin, namely, the nail plate, nail bed, and/or nail matrix, to achieve fungal clearance without nail avulsion or without the use of antifungal agents. We aimed at the treatment to be carried out mostly by the patients themselves, after one or two physician visits which would be cost effective for the patients and reduced time required by the physicians. Although treatment outcome of onychomycosis was once believed to be better in avulsed nails, there was controversy about this finding. Therefore, we avoided removal of the nail plate and instead applied PVA under-nail cushions to distribute citric acid over the nail bed.[2,25,26] Our goal was to reach and clean the nail plate and nail bed of fungal elements by periodic application of a mild keratolytic.

Although our technique may mimic mechanical and/or chemical debridement, mechanical debridement for onychomycosis is widely performed by podiatrists, which is different from our method:

1. It is usually performed on the dorsal surface of the nail and mainly for cosmetic purposes and/or to decrease fungal load

2. It is performed weeks or months apart

3. It generally does not include the nail bed or ventral surface of the nail, which we mostly targeted.

Microporation may also be similar to our technique, which is performed on the nail plate mainly to enhance antifungal drug absorption. However, we performed daily washing off infected material until a normal nail grew completely. Antifungal use was outside the scope of our study, as our patients had previously failed to antifungal treatment.

We followed patients comparing OSI scores which was considered a valid and reliable scoring system to evaluate treatment outcome for onychomycosis.[14] Comparison of OSI scores pre and post treatment revealed that we had achieved our goal (P < 0.001).

There is increasing evidence that penetration of topical agents into the nail plate increases in hydrophilic formulations.[27,28] This increase was the reason why we preferred hydrophilic citric acid solution as a clearing agent. The reason why we chose citric acid as a keratolytic agent is that it is not irritating to the skin, is well tolerated by most patients, and has been shown to have antifungal properties when >2.5% concentration in a water-based solution is used.[29,30,31,32,33]

In this study, we had the following observations:-

1. Most cases of treatment unresponsive onychomycosis in immunocompetent adults were due to molds

2. Keratin might be invaded by molds

3. About 5% citric acid caused no irritation to the nail bed or adjacent skin

4. Removing fungus-invaded tissue from the nail plate and nail bed by application of a mild keratolytic might lead to a successful treatment outcome, and

5. Clearing fungus-invaded parts was sufficient; therefore, removing the whole nail plate might be unnecessary to reach higher cure rate.

Conclusion

Although the number of cases with dermatophyte and candida infections is limited in our study, citric acid plus mechanical cleaning of the nail bed seemed to be successful in treating onychomycosis independent of the causative agent.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.