Chronic Dermatophytosis: Clinico-Mycological Determinants and Antifungal Susceptibility Pattern.

BACKGROUND: Recent years have witnessed a dramatic increase in chronic unresponsive dermatophytosis. A study was conducted to quantify the proportion of patients with chronic dermatophytosis and to determine the clinico-mycological predictors of chronicity including antifungal susceptibility.
METHODS: Hospital-based cross-sectional study design was adopted. Four hundred and twenty-five patients were studied. The outcome variable was chronic dermatophytosis and the determinants were clinico-mycological characteristics. Chi-square and odds ratio (OR) with 95% confidence interval (CI) were calculated.
RESULTS: Chronic dermatophytosis was seen in 29.4%. Past history of dermatophytosis, OR 0.44 (95% CI 0.28-0.68); family history of dermatophytosis, OR 1.66 (95% CI 1.06-2.56); HIV infection, OR 9.88 (95% CI 1.09-89.33); treatment with topical antifungals, OR 2.4 (95% CI 1.5-3.9); systemic antifungals, OR 3.9 (95% CI 2.5-6.1); topical steroids, OR 2.02 (95% CI 1.25-3.25); multiple-site infection, OR 1.97 (95% CI 1.24-3.13); and tinea unguium, OR 6.52 (95% CI 2.89-14.7) were the significant determinants. Trichophyton mentagrophytes (73.6%) was the most common isolate followed by Trichophyton rubrum and Microsporum gypseum (13.2%) each. A percentage of 77.4 of the isolates were resistant-73.6% isolates to terbinafine and 3.8% isolates to fluconazole. None of the isolates were resistant to itraconazole.
CONCLUSION: Significant determinants were host-related factors. Thorough history taking, patient examination, and education can improve the present scenario. Microbiological resistance was not a significant predictor. High proportion of resistant strains should be an eye opener. Developing and adopting a standard uniform treatment protocol throughout the country should be the need of the hour. Copyright:

Introduction

Dermatophytosis is a common condition encountered by dermatologists and general practitioners alike in India. Over the last 5–6 years, an alarming change has occurred in the clinical profile of dermatophytosis. The prevalence has increased many folds. Chronicity, relapse, recurrence, reinfection, and treatment unresponsiveness became the norm.[123] Our center has also been witnessing this changing trend in the clinical profile of dermatophytosis. Many postulates related to agent, host, and environment like the emergence of Trichophyton mentagrophytes, resistance to antifungal drugs, irrational treatment, noncompliance, etc., have been suggested.[4] But there is a dearth of published studies investigating and quantifying the risk factors for the current scenario, especially chronic dermatophytosis.[5] In this background, we undertook this study on dermatophytosis to estimate the proportion of patients with chronic dermatophytosis and to determine a significant difference, if any, in the clinico-mycological characteristics and antifungal susceptibility of patients with and without chronic dermatophytosis.

Methods

The study setting was the Department of Dermatology of a tertiary care center in Kerala, South India. The cross-sectional study design was adopted. A sample size of 87 cases of chronic dermatophytosis was calculated based on the formula 4 pq/d2 (proportion of patients with chronic dermatophytosis, 'p'[6] as 68%, the proportion of patients without chronic dermatophytosis, 'q' as 32% and precision, 'd' as 10). Institutional ethics committee clearance was obtained. All clinically diagnosed patients with dermatophytosis, confirmed by a faculty member, were included after getting informed written consent. The outcome variable chronic dermatophytosis was defined as disease continuing for more than 6 months to 1 year with or without recurrence despite being treated.[1] The dependent variable was chronic dermatophytosis and the independent variables were sociodemographic characteristics: age, sex, occupation, family history of dermatophytosis, sharing of clothes among family members; disease characteristics: duration of disease, past history of dermatophytosis, comorbid conditions like atopy, diabetes mellitus, and HIV infection; drug therapy: topical antifungals, systemic antifungals, topical steroids, systemic steroids, immunosuppressants, site of infection; and mycological characteristics: species isolated and antifungal susceptibility. Scraping from the skin and/or nail and/or hair was subjected for direct microscopy with 10% KOH. The specimen was sent to the Department of Microbiology for culture, species identification, and antifungal susceptibility testing. The culture media used were Sabouraud's dextrose agar with chloramphenicol and cycloheximide, and dermatophyte test medium. The species of dermatophytes were identified by colony morphology, pigment production, and microscopic examination by slide-culture technique in lactophenol cotton blue. T. mentagrophytes and Trichophyton rubrum were distinguished by urease test and in-vitro hair perforation test. The cultured isolates were subjected to antifungal susceptibility testing to fluconazole, itraconazole, and terbinafine according to the Clinical and Laboratory Standard Institute M38-A standards.[7] Data were entered in Microsoft Excel and analyzed using Excel and Epi Info 7. Chi-square test was used for testing of proportion and Student's t-test for testing of means. Odds ratio (OR) with 95% confidence interval (CI) was calculated for the independent variables.

Results

Clinico-mycological characteristics of 425 patients with dermatophytosis were studied. Chronic dermatophytosis was present in 125 (29.4%) patients. There were 22.4% patients each in the 2nd and 5th decade (mean age 37.9 years). Females constituted 78 (62.4%) with a female-to-male ratio of 1.7:1. Homemakers constituted the majority of patients (46,36.8%) followed by students (40,32%). Past history of dermatophytosis was present in 41 (32.8%), family history of dermatophytosis in 49 (39.2%), and sharing clothes among family members in 50 (40%). The comorbidities observed were atopy in 31 (24.8%), diabetes mellitus in 20 (16%), and HIV infection in 4 (3.2%). Ninety-seven (77.6%) patients gave a history of applying topical antifungals before the hospital visit. Eighty-three (66.4%) patients gave a history of taking systemic antifungals before the hospital visit. Forty (32%) patients gave a history of applying topical steroids and two (1.6%) took systemic steroids before the hospital visit. Three (2.4%) were on immunosuppressants. Infection in multiple sites was seen in 43 patients (34.4%) and the most common combination was tinea corporis and cruris 23 (18.4%). The most common single-site infection was tinea corporis (44, 35.2%) followed by tinea unguium (21, 16.8%).

Table 1 shows the univariate analysis of the risk factors for chronic dermatophytosis. The P value was <0.05 for the following variables—past history of dermatophytosis, family history of dermatophytosis, HIV infection, treatment with topical antifungals, systemic antifungals and topical steroids, multiple-site infection, and tinea unguium. P value was >0.05 for the variables like age, gender, occupation, comorbidity like atopy, diabetes mellitus, and treatment with systemic steroids.

Table 1

Univariate analysis of predictors of dermatophytosis

Independent variables		Chronic dermatophytosis		Chi-square/t	P, odds ratio (95% CI)
		Yes (125)	No (300)
Age	Range (mean)	10-80 (37.99±17.69)	3-83 (33.28±16.83)	0.454	0.501
Gender	Male	47 (37.6%)	132 (44%)	1.482	0.133
	Female	78 (62.4%)	168 (56%)
Occupation	Unemployed	18 (14.4%)	23 (7.6%)
	Professional	6 (6.1%)	11 ((3.6%)	0.36	0.54
	Skilled	5 (4%)	21 (7%)	4.2	0.039, 0.3 (0.09-0.96)
	Manual laborer	10 (8%)	28 (9.3%)	2.6	0.1
	Student	40 (32%)	120 (40%)	5.65	0.017, 0.42 (0.2-0.9)
	Home maker	46 (36.8%)	97 (32.3%)	1.9	0.165
Past history	Yes	41 (32.8%)	157 (52.3%)	12.75	<0.0001, 0.44 (0.28-0.68)
	No	84 (67.2%)	143 (47.7%)
Family history	Yes	49 (39.2%)	84 (28%)	4.64	0.031, 1.66 (1.06-2.56)
	No	76 (60.8%)	216 (72%)
Share clothes	Yes	50 (40%)	100 (33.4%)	1.72	0.22
	No	75 (60%)	200 (66.6%)
Atopy	Yes	31 (24.8%)	65 (21.7%)	0.495	0.53
	No	94 (75.2%)	235 (78.3%)
Diabetes	Yes	20 (16%)	33 (11%)	2.02	0.197
	No	105 (84%)	267 (89%)
HIV	Yes	4 (3.2%)	1 (0.3%)	4.01	0.027, 9.88 (1.09-89.33)
	No	121 (96.8%)	299 (99.7%)
Topical antifungals	Yes	97 (77.6%)	177 (59%)	13	0.00023, 2.4 (1.5-3.9)
	No	28 (22.4%)	123 (41%)
Systemic	Yes	83 (66.4%)	100 (33.3%)	38.01	0.0000, 3.9 (2.5-6.1)
antifungals	No	42 (33.6%)	200 (66.7%)
Topical steroids	Yes	40 (32%)	55 (18.3%)	7.74	0.0053, 2.02 (1.25-3.25)
	No	85 (68%)	245 (81.7%)
Systemic steroids	Yes	2 (1.6%)	12 (4%)	1.59	0.25
	No	123 (98.4%)	288 (96%)
Multiple site	Yes	43 (34.4%)	63 (21%)	8.46	0.0036,1.97 (1.24-3.13)
	No	82 (65.6%)	237 (79%)
Tinea unguium	Yes	21 (16.8%)	9 (3%)	25.55	<0.0001, 6.52 (2.89-14.7)
	No	104 (83.2%)	291 (97%)

Among 425 patients, fungal hyphae on direct microscopy were observed in 104 (83.2%) patients with chronic dermatophytosis and 232 (77.3%) without chronic dermatophytosis. Fungal growth was observed in 53 (12.5%). The proportion of patients with culture positivity in those with and without chronic dermatophytosis was almost the same, 16 (12.8%) and 37 (12.3%), respectively. T. mentagrophytes (39, 73.6%) was the most common isolate followed by T. rubrum and Microsporum gypseum (7, 13.2%) each.

Table 2 shows antifungal susceptibility testing pattern. The Minimum inhibitory concentration (MIC) value of fluconazole ranged from 2 to 8 μg/mL, itraconazole ranged from 0.031 to 0.25 μg/mL, and terbinafine ranged from 0.031 to 0.5 μg/mL for T. mentagrophytes. The MIC value of fluconazole ranged from 2 to 8 μg/mL, itraconazole ranged from 0.031 to 0.125 μg/mL, and terbinafine ranged from 0.031 to 0.25 μg/mL for T. rubrum isolates. The MIC value of fluconazole ranged from 0.25 to 4 μg/mL, itraconazole ranged from 0.0312 to 0.125 μg/mL, and terbinafine ranged from 0.031 to 0.25 μg/mL for M. gypseum.

Table 2

MIC values of drugs for different species of dermatophytes

Drug	MIC (μg/mL)	T. mentagrophytes* (39 isolates)	T. rubrum† (7 isolates)	M. gypseum‡ (7 isolates)
Fluconazole	0.25	0	0	1
	0.5	0	0	1
	2	5	4	3
	4	19	1	2
	8	15	2	0
Itraconazole	0.031	4	1	0
	0.0312	3	1	1
	0.06	13	2	4
	0.125	10	3	2
	0.25	9	0	0
Terbinafine	0.031	6	1	2
	0.0312	1	0	0
	0.06	14	4	2
	0.125	8	1	2
	0.25	6	1	1
	0.5	4	0	0

Fluconazole sensitive: *MIC≤64 μg/mL, †MIC≤4 μg/mL, ‡MIC≤64 μg/mL. Itraconazole sensitive: *MIC≤0.25 μg/mL, †MIC≤8 μg/mL, ‡MIC≤8 μg/mL. Terbinafine sensitive: *MIC≤0.008 μg/mL, †MIC≤1 μg/mL, ‡MIC≤1 μg/mL

Table 3 shows the mycological characteristics and antifungal susceptibility of patients with chronic dermatophytosis. Microbiological resistance was observed in 41 (77.4%) out of 53 isolates.

Table 3

Chronic dermatophytosis and mycological characteristics

Mycological characteristics		Chronic dermatophytosis
		Yes (16)	No (37)
Species (53 isolates)
T. mentagrophytes (39)		11 (68.7%)	28 (75.7%)
T. rubrum (7)		3 (18.8%)	4 (10.8%)
M. gypseum (7)		2 (12.5%)	5 (13.5%)
Antifungal susceptibility
Resistance to any antifungal	Yes	11 (68.8%)	30 (88.1%)
	No	5 (31.3%)	7 (18.9%)

Chi square: 0.95, P: 0.32

Discussion

Chronic dermatophytosis constituted 29.4% of the dermatophytosis cases and has almost doubled in our center compared to the preexisting unpublished data. The prevalence of chronic dermatophytosis varied in the reported literature from 5% to 68% based on the definition used for chronic dermatophytosis and the study setting.[1268]

The fact that almost one-third of the dermatophytosis cases are chronic is a matter of grave concern and the risk factors that lead to chronicity need to be looked into to address this issue. Hence, the patients with and without chronic dermatophytosis were compared concerning their sociodemographic characteristics, disease characteristics, drug therapy, and mycological characteristics to analyze their role as determinants of chronicity, and the determinants were quantified in terms of the OR. The significant determinants in the present study were the absence of a history of dermatophytosis in the past (OR: 2.2, P < 0.0001), dermatophytosis in a family member (OR: 1.66, P: 0.031), coinfection with HIV (OR: 9.88, P: 0.027), treatment with topical antifungals (OR: 2.4, P: 0.0002), systemic antifungals (OR: 3.9, P < 0.0001), and topical steroids (OR: 2.02, P: 0.0053), dermatophytic infection in multiple sites (OR: 1.9, P: 0.003), and tinea unguium (OR: 6.52, P < 0.001). Age, gender, occupation, comorbidities like atopy and diabetes, species, and microbiological resistance were not significant determinants.

Among patients with chronic dermatophytosis, there were only 32.8% with a past history of dermatophytosis compared to 52.3% among those without chronic dermatophytosis. In the absence of a history of dermatophytosis in the past, there was a 2.2-fold increase in chronic dermatophytosis. Patients, who had experience with dermatophytosis in the past and suffered the morbidity associated with dermatophytosis, may have resorted to treatment at the earliest, preventing chronicity. This shows that awareness and knowledge about the disease can to some extent prevent chronicity.

At least one family member was affected in 39.2% of patients with chronic dermatophytosis compared to 28% without chronic dermatophytosis. The chronicity increased by 1.7 times when a family member was affected. Studies have shown that an important cause of treatment failure is an affected family member who can act as a constant source of reinfection.[16]

Coinfection with HIV was present in 3.2% with chronic dermatophytosis and 0.3% without chronic dermatophytosis. Patients with HIV infection had 9.9 times higher risk of developing chronic dermatophytosis. As the clearance of dermatophytes from the skin is secondary to the activation of cell-mediated immunity (CMI), HIV patients, in whom the CMI is compromised, can present with atypical lesions leading to delayed diagnosis and chronicity.

Prior antifungal treatment, both topical (77.6% vs. 59%) and systemic (66.4% vs. 33.3%), was more in patients with chronic dermatophytosis than in patients without chronic dermatophytosis. The odds of chronic dermatophytosis in those who have applied topical antifungals were 2.4 times and in those who have taken systemic antifungal were 3.9 times higher compared to those without prior treatment. The morbidity associated with the longer duration of disease might have forced the patients to adopt antifungal treatment and this may be the reason for the significant association between antifungal usage and chronicity. Moreover, relapse and resistance consequent to poor adherence to antifungals can also explain the association between antifungal usage and chronicity.

Topical steroid was applied by 32% of patients with chronic dermatophytosis compared to 18.3% of patients without chronic dermatophytosis. Patients who have applied topical steroids were 2.2 times more likely to develop chronic dermatophytosis relative to those who did not apply. Steroids by suppressing T-cell-mediated immune response to the dermatophyte and by stimulating fungal growth and metabolism in low concentrations can facilitate the spread of infection.[9]

Multiple sites were affected in 34.4% of our patients with chronic dermatophytosis compared to 21% without chronic dermatophytosis. When the association between sites of infection and chronic dermatophytosis was analyzed, it was observed that the risk of chronic dermatophytosis was 1.9 times more in patients with multiple-site involvement relative to patients with single-site involvement. When multiple sites are affected, it may be difficult to eradicate the fungus and may lead to chronicity. Similarly, chronicity due to other causes can lead to persistence and spread of infection to multiple sites. Whether chronicity predisposes to infection in multiple sites or vice versa is difficult to predict. When data were analyzed to assess whether infection in any particular site can lead to chronicity, no site other than nail was significant for the persistence of infection leading to chronic dermatophytosis. Tinea unguium was observed in 16.8% of patients with chronic dermatophytosis compared to 3% in those without chronic dermatophytosis and it increased the risk of chronic dermatophytosis by 6.5 times. Nail infections are often overlooked and can remain as a source of infection leading to chronicity.

Our culture positivity rate was only 12.5%. There was no significant difference in the culture positivity rate among those with and without chronic dermatophytosis. The culture positivity rates varied across different centers based on whether the sample was taken from either new cases or already treated/current treatment cases. In most of the studies with high culture positivity, the samples were taken from new cases. The majority of our patients were already on antifungals at the time of hospital visit and this could well explain our low culture positivity rate.

Among the isolates, 73.6% were T. mentagrophytes followed by T. rubrum and M. gypseum in equal proportions. These findings reflect the gradual transition of the most common species from T. rubrum to T. mentagrophytes as reported from other parts of India.[8101112] Though this change has been suggested as one of the reasons for the current change in the clinical profile of dermatophytosis,[131415161718] our observation of P > 0.05 in the difference in proportion of T. mentagrophytes in those with (68.7%) and without chronic dermatophytosis (75.7%) rules out the possibility of this species as a cause for chronicity.

In-vitro antifungal susceptibility testing was performed against three commonly used antifungals, fluconazole, itraconazole, and terbinafine, to analyze the role of antifungal resistance as a cause for clinical nonresponsiveness and chronicity. Antifungal resistance was observed in 77.4% of isolates—73.6% resistant to terbinafine and 3.8% resistant to fluconazole. Since the systemic and topical antifungal use was significantly more in chronic dermatophytosis patients, we expected more of drug-resistant isolates among them. Surprisingly, the proportion of drug-resistant isolates was more in those without chronic dermatophytosis (88.1% vs. 68.8%), though not statistically significant. The prior treatment with antifungals may account for the low culture positivity and low proportion of resistant isolates among patients with chronic dermatophytosis.

All the terbinafine-resistant isolates in this study were T. mentagrophytes. There are similar reports in the literature of a gradual shift in the species to T. mentagrophytes and parallel increase in the microbiological resistance to terbinafine.[192021222324] Irrational prescription practices, topical usage of terbinafine primarily intended for systemic use, poor adherence due to cost factor, or a survival mechanism of the fungus may be the reason for terbinafine resistance. All the fluconazole-resistant isolates were T. rubrum. The observed fluconazole resistance was low compared to other reports where the proportion of fluconazole-resistant isolates ranged from 5.6% to 97.5%.[1920252627] The low proportion of fluconazole-resistant isolates came as a big surprise amid popular belief that fluconazole is no longer useful in dermatophytosis. The availability of fluconazole free of cost from all the government hospitals in Kerala, right from Primary Health Centers (PHCs) to tertiary care centers, and the convenient weekly dosing schedule might have resulted in good patient compliance and may account for the observed low proportion of fluconazole resistance.

Though clinically unresponsive dermatophytosis to itraconazole is a hot topic in scientific forums, none of our isolates were resistant to itraconazole. We may have to wait for a few years to observe itraconazole-resistant isolates since itraconazole is only a recent introduction into the market and not widely prescribed in government hospitals in our state due to the cost factor and availability of fluconazole free of cost. Low quality of the drug, poor compliance, high cost, and irrational dosage schedule are some of the suggested postulates for resistance.[2324252829]

Strengths

There are many studies discussing predisposing factors related to dermatophytosis and the resulting data are only an assumption that those are risk factors. By comparing those with and without chronic dermatophytosis, we were able to determine the significance and quantify the predisposing factors in terms of OR.

Limitations

The sample size was adequate for the estimation of the proportion of chronic dermatophytosis but was inadequate when the patients were grouped into those with and without chronic dermatophytosis. The findings lack generalizability due to the tertiary care nature of the study setting. Low culture positivity and antifungal susceptibility testing done with the low numbers might have influenced the lack of association between chronicity and the observed microbiological resistance. Financial constraints restricted us from conducting antifungal susceptibility to topical antifungals and griseofulvin.

Conclusion

Clinically unresponsive dermatophytic infections have doubled in our center. The significant determinants were host-related factors, stressing upon the importance of patient education. Eliciting detailed family history, personal hygiene-related practices, comorbidities, and detailed examination of the commonly overlooked site like the nails and examination of all family members and their simultaneous treatment can work wonders. Though microbiological resistance was not a significant predictor of chronicity, the high proportion of resistant isolates should be an eye opener. Education of general physicians and pharmacists regarding the avoidance of steroids and combination creams, avoidance of topical preparation of systemic antifungals, and irrational use of systemic antifungals reserved for invasive fungal infections should be the need of the hour. Developing and adopting a standard uniform treatment protocol throughout the country and ensuring adherence to the protocol may prevent the development of resistant strains and arrest the burden of the present great Indian epidemic of dermatophytosis.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.