Prevalence of Onychomycosis by Non Dermatophyte Molds in a Tertiary Care Hospital in Kolkata , West Bengal, India

INTRODUCTION

Onychomycosis is a major cause of nail dystrophy caused by dermatophytes, Candida and Non Dermatophyte Molds (NDM). Different species of molds have been diagnosed from nails [1]. Though Dermatophytes are the major causative agents of Onychomycosis, Non Dermatophyte Molds (NDM) are also gaining importance as emerging causes of Onychomycosis in recent days.

NDM Onychomycosis is often difficult to diagnose as they have been considered nail contaminants. Though various diagnostic methods are there to diagnose NDMs however,  repeated isolation by culture in laboratory is  recommended  to  confirm NDMs as pathogens of Onychomycosis. Increased incidence of Onychomycosis by NDM and mixed infection (both Dermatophytes  with Non Dermatophyte Molds) onychomycosis have been observed in recent days recommends towards more  accurate clinical diagnosis along with mycological tests [2].

Opportunistic NDMs are seen in nature as plant pathogens and soil saprophytes. They are fast growing with universal presence and are often un-noticed laboratory contaminants. Different literature revealed that the most commonly isolated species of NDM are Scopulariopsis brevicaulis, Fusarium sp., Acremonium sp., Aspergillus sp., Scytalidium sp., and Onychocola canadienses [3].

A wide group of NDM species and some saprophyte yeasts may also affect the nail plate directly. These include some species of the genera Alternaria, Curvularia, Trichosporon and Hendersonula [4].

It is difficult to establish the pathogenicity of opportunistic, NDMs on nails as in all opportunistic infection. There are always a number of criteria that need to be fulfilled. The culture must be free from dermatophytes and the NDMs should be observed in the microscopic examination using 10-40% potassium hydroxide (KOH) [5].

Onychomycosis is the most difficult to treat superficial mycosis. It is chronic infection that is prone to relapse. Therefore, it is important to identify the causative agent to ensure that the appropriate treatment is employed for each case [6].

PATIENTS AND METHODS

All samples from onychomycosis cases sent by different Clinical departments of our hospital for Fungal culture in our Mycology laboratory of Department of Microbiology, NRS Medical College, were studied over a period of one year from January 2023 to December 2023 after meeting all ethical Consideration as per declaration of Helsinki .

After informed consent, history-taking and patients’ examination, , samples were collected from both nail plates & subungual debris as per clinical presentation;  the collected samples were evaluated by KOH wet mount and Fungal culture in Sabouraud’s Dextrose Agar (SDA) and Sabouraud’s Dextrose Chloramphenicol  Agar (SDCA) at 37°C and 25°C followed by study of Culture growth by their colony morphology, presentation, pigmentation of reverse & obverse surfaces followed by LPCB teased mount and Slide culture where ever necessary. Inoculation into Blood Agar plates done in some cases to demonstrate Schizogenous yeast conversion.  Comparison of findings of KOH wet mount with culture  and Repeat culture from samples were also done to establish that the isolates were pathogenic fungi not laboratory contaminants [7].

The received data was summarized using counts and percentages and other statistical methods in Microsoft Excel software as appropriate.

RESULTS

Among the 114 samples of culture positive Onychomycosis, 32 cases (28.07%) of Non Dermatophyte Molds (NDMs)  were detected to cause Onychomycosis [Chart: 1].

Gender-wise distribution of NDM Onychomycosis  revealed females were more commonly affected (22 cases, 68.75 %) than males ( 10 cases , 31.25%) [Chart: 2].

 The most common age group of NDM Onychomycosis were among 25 years to 60 years (22 patients, 68.75%) followed by 16-24 years ( 5 patients , 15.62% ) followed by more than 60 years group ( 3 patients , 9.37%) and lastly 6-15 years age group ( 2 patients , 6.25%) [Table :1].

Among these NDM onychomycosis, the finger nails were found to be more affected with 40.63% (13 cases) followed by toe nails of 34.37% (11 cases)  and both Toe & Finger nail involvement was 25.00% (8 cases) [Table: 2]. Clinical type-wise distribution of the 32 NDM Onychomycosis revealed 20 patients (62.50%) were of Total Dystrophic Onychomycosis (TDO), 11 (34.37%) were White Superficial Onychomycosis (WSO), 2 (6.25%) were Distal & Lateral Subungual Onychomycosis (DLSO) and we did not get any NDM isolate from Proximal Subungual Onychomycosis (PSO). In almost all clinical types of Onychomycosis females were found to be more affected than males [Table : 3].

The demographic data of the study population revealed that the patients were mostly from poor socio-economic background; Some adult females were house-wives and some were working as domestic help and some were working in brick manufacturing units. Males were mostly farmers, Some were gardeners and few were garage workers.

Among the 32 unusual NDM isolates causing onychomycosis 8 cases (25%) were Talaromyces spp. [Figure: 1], 6 cases (18.75%) were Fusarium spp. [Figure: 2], 4 cases (12.5%) were Mucor spp. [Figure: 3], 4 cases (12.5%) were Rhizopus spp. [Figure: 4], and 2 cases (6.25%) each of Medicopsis romeroi [Figure: 5], Hortaea werneckii [Figure: 6], Trichosporon sp [Figure: 7], Paecilomyces spp.[Figure: 8] and Bipolaris spp.[Figure: 9A &9B].

DISCUSSION

In our study of Onychomycosis we found 28.07% of NDM isolates among culture positive onychomycosis which is nearly corroborated with a study by Pukhrambam PD et. al. [8]  in RIMS, Imphal of India revealing 31.3% of NDM onychomycosis isolates and also closely in accordance with a study by Raghabendra KR. et. al. [9]  in South East Rajasthan of India showing 35.33% of the same.

Among the NDM Onychomycosis of our study the females were more affected with 68.75% which is in tandem with  studies by Marinez-Herrera EO. et. al. [10] in Guatemala and a study by S Hilmioglu Polat et. al. [11] in Turkey revealing  65.6% and 76% of female preponderance of NDM onychomycosis respectively The most affected age group of NDM Onychomycosis in our study was 68.75% from (25-60) years followed by 15.62% from (16-24).

years age group,   9.37% from more than 60 years age group and 6.25% from ( 6-15) years age group; All these findings are in close accordance with a study by Raghabendra KR et. al. [9]  in South East Rajasthan showing their mean affected age group of (34.6+ 18) years. Similar demographic features are also seen in a study by Marinez-Herrera EO. et. al. [10]  in Guatemala  which revealed (41-65) year age group to be mostly affected group of NDM Onychomycosis and closely corroborates with the observation of our present study. Site of involvement-wise, the finger nails alone were found to be more affected with 41% followed by toe nails of 35% which are very closely corroborated with the study by Raghabendra KR et.al. [9] showing involvement of 38% finger nails & 33.33% of toe nails. both Toe & Finger nail involvement was 25% (8 cases) in our study which is in tandem with a study by Raghabendra KR et.al. [9]   with 15% cases.

The higher  incidence of finger nail onychomycosis may be due to occupation of domestic help or farming  which needs active involvement of hands in moist conditions and slight lower incidence of toe nail involvement may be due to open footwear habit and lesser concern of feet & toenails in those occupation in our present study [9] .

Clinical type wise NDM Onychomycosis showed 62.50% were of Total Dystrophic Onychomycosis (TDO) which is highest in our present study and closely corroborates with a study by Raghabendra KR et.al.[9] showing TDO to be the major contributor with 46% in their study. The second major contributor of NDM Onychomycosis was 34.37% of White Superficial Onychomycosis (WSO) followed by 6.25% of Distal & Lateral Subungual Onychomycosis (DLSO) in our study;  this observation was not in tandem with other studies by Raghabendra KR et.al. [9] , revealing WSO of 7.33% & DLSO of 34.6% and another study by Marinez-Herrera EO. et. al. [10] revealing DSLO of 62.5% & TDO of 37.5%. The different geographical location and variety of occupation may be responsible for these variations in occurrence .

In our study Talaromyces spp. was the major NDM isolate with 25% contribution among the 32 unusual NDM isolates causing onychomycosis followed by 18.75% of Fusarium spp., 12.5% were Mucor spp., 12.5% were Rhizopus spp., 6.25% each of Medicopsis romeroi , Hortaea werneckii, Trichosporon spp, Paecilomyces spp., & Bipolaris spp.; A study by Pukhrambam PD. et.al. [8] revealed that Aspergillus spp. was commonest NDM causing Onychomycosis  followed by Penicillium spp. 14% , Acremonium spp. 4.8%, Fusarium spp. 1.8%, Curvularia spp. 1.6%,  Alternaria spp. 1.4%, Scopulariopsis spp. 1%,  Cladosporium spp. & Nigrospora spp. 0.8% each , Mucor spp. 0.4%,  and Paecilomyces spp.,  Pseudo-allescheria spp., Rhizopus spp., Verticillium spp. & Exophiala jeanselmei with 0.2% each. These observation though not much in agreement as per their incidence with our study but many NDM Mold species  were in common to be the cause of Onychomycosis.

Another study by Sarkar M. et. al. [12] in 2014-15 in Kolkata revealed Fusarium as the major NDM isolate to cause onychomycosis followed by Aspergillous spp. is partially in tandem with our study findings as Fusarium was the second most common isolate after Talaromyces spp.in our present study. All these observations prompt to the fact that NDM isolates causing Onychomycosis vary with geographical location and passage of time.

Occurrence of NDM Onychomycosis by unusual pathogen is a rising trend and in India relatively less work has been done on the onychomycosis as compared to western countries[13,14]. The evolving role of non-dermatophytic molds has added a new dimension to the clinical patterns of onychomycosis as they are relatively resistant to conventional antifungals [14].

CONCLUSION

The study showed that non-dermatophytic molds were responsible for nearly 28% of onychomycoses cases attending in different clinical out patient departments of our hospital. Dystrophic Onychomycosis was present in 62.5% cases. The two most common NDM isolates were Talaromyces spp  & Fusarium spp. As molds are common laboratory contaminants, repeat culture isolation of the same species and matching the findings with KOH wet mount  from successively taken nail samples are ideal and should be carefully evaluated to diagnose a "NDM Onychomycosis". Changing trends of causative agents by unusual Non Dermatophyte Molds causing Onychomycosis  needs continuous study and evaluation to manage these patients with empirical therapy based on available data.

Author contribution: We declare that all listed authors have made substantial contributions to all of the following three parts of the manuscript:

- research design, or acquisition, analysis or interpretation of data;

- drafting the paper or revising it critically;

- approving the submitted version.

We also declare that no-one who qualifies for authorship has been excluded from the list of authors.

Funding : None. Author funded

Conflict of interest : None

Acknowledgment : The authors would thank all colleagues who helped to conduct this study. We are also grateful to all other faculties and Medical Technologists of Microbiology department of NRS Medical College, Kolkata, West Bengal, India.

Ethical Considerations :The study was conducted after meeting all ethical Consideration as per declaration of Helsinki .