In vitro antifungal resistance and molecular analysis of the SQLE gene in dermatophytosis: a laboratory-based study
,
Abstract
Background and Objectives: Dermatophytosis is a common superficial fungal infection that affects the keratinised tissues. This study examines the antifungal resistance mechanisms and molecular detection of squalene epoxidase gene alterations in clinical isolates from patients.
Materials and Methods: A cross-sectional study conducted from January 2019 to December 2020 included 110 clinically suspected dermatophytosis specimens. Microscopy, culture, CLSI M38-A2 broth microdilution testing, and PCR-based ITS and SQLE (520 bp) amplification were performed. MIC50, MIC90, geometric mean, and ranges were analysed using SPSS version 19 with P < 0.05.
Results: A total of 110 suspected cases were evaluated, with 78 (70.9%) males. KOH positivity reached 100%, while culture positivity was 47.3% (52/110). Trichophyton rubrum accounted for 38.5% isolates. Fluconazole MICs were ≥64 µg/mL. 39/52 isolates showed terbinafine resistance, with 23 expressing the 520 bp SQLE gene.
Conclusion: Terbinafine and caspofungin showed consistent in vitro activity, while fluconazole showed limited activity. Routine susceptibility testing guides drug selection, improves treatment outcomes, and supports rational management of resistant dermatophytosis cases.
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4. Begum J, Mir NA, Lingaraju MC, Buyamayum B, Dev K. Recent advances in the diagnosis of dermatophytosis. J Basic Microbiol 2020; 60: 293-303.
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6. Bouchara JP, Mignon B, Chaturvedi V. Dermatophytes and dermatophytoses: a thematic overview of the state of the art and directions for future research and developments. Mycopathologia 2017; 182: 1-4.
7. Osman M, Kasir D, Rafei R, Kassem II, Ismail MB, El Omari K, et al. Trends in the epidemiology of dermatophytosis in the Middle East and North Africa region. Int J Dermatol 2022; 61: 935-968.
8. Narayanasetty NK, Pai VV, Athanikar SB. Annular lesions in dermatology. Indian J Dermatol 2013; 58: 157.
9. Mendonça MB, Cabral AKLF, Arantes BBA, Dos Santos RC, Medina-Alarcón KP, Dos Santos KS, et al. Biofilm development in three-dimensional models infected with Trichophyton rubrum. Microbiol Spectr 2025; 13(10): e0108725.
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11. Faway É, Lambert de Rouvroit C, Poumay Y. In vitro models of dermatophyte infection to investigate epidermal barrier alterations. Exp Dermatol 2018; 27: 915-922.
12. Bitencourt TA, Macedo C, Franco ME, Assis AF, Komoto TT, Stehling EG, et al. Transcription profile of Trichophyton rubrum conidia grown on keratin reveals the induction of an adhesin-like protein gene with a tandem repeat pattern. BMC Genomics 2016; 17: 249.
13. De Peres NTA, Maranhão FCA, Rossi A, Martinez-Rossi NM. Dermatophytes: host-pathogen interaction and antifungal resistance. An Bras Dermatol 2010; 85: 657-667.
14. Martinez-Rossi NM, Peres NTA, Bitencourt TA, Martins MP, Rossi A. State-of-the-art dermatophyte infections: epidemiology aspects, pathophysiology, and resistance mechanisms. J Fungi 2021; 7: 629.
15. Khurana A, Sardana K, Chowdhary A. Antifungal resistance in dermatophytes: recent trends and therapeutic implications. Fungal Genet Biol 2019; 132: 103255.
16. Badali H, Mohammadi R, Mashedi O, de Hoog GS, Meis JF. In vitro susceptibility patterns of clinically important Trichophyton and Epidermophyton species against nine antifungal drugs. Mycoses 2015; 58: 303-307.
17. Martins MP, Rossi A, Sanches PR, Martinez-Rossi NM. Differential expression of multidrug-resistance genes in Trichophyton rubrum. J Integr OMICS 2019; 9:65-69.
18. Osborne CS, Hofbauer B, Favre B, Ryder NS. In vitro analysis of the ability of Trichophyton rubrum to become resistant to terbinafine. Antimicrob Agents Chemother 2003; 47: 3634-3636.
19. Santos HL, Lang EAS, Segato F, Rossi A, Martinez-Rossi NM. Terbinafine resistance conferred by multiple copies of the salicylate 1-monooxygenase gene in Trichophyton rubrum. Med Mycol 2018; 56: 378-381.
20. Chen X, Jiang X, Yang M, Bennett C, González U, Lin X, et al. Systemic antifungal therapy for tinea capitis in children: an abridged Cochrane review. J Am Acad Dermatol 2017; 76: 368-374.
21. Monod M, Feuermann M, Salamin K, Fratti M, Makino M, Alshahni MM, et al. Trichophyton rubrum azole resistance mediated by a new ABC transporter, TruMDR3. Antimicrob Agents Chemother 2019; 63: e00863–19.
22. Chander J (2018). Textbook of Medical Mycology. 4th ed. Jaypee Brothers Medical Publishers. New Delhi.
23. Clinical and Laboratory Standards Institute (CLSI) (2008). Reference method for broth dilution antifungal susceptibility testing of filamentous fungi; approved standard M38-A2. 2nd ed. CLSI. Wayne, PA.
24. Smith WL, Edlind TD. Histone deacetylase inhibitors enhance Candida albicans sensitivity to azoles and related antifungals. Antimicrob Agents Chemother 2002; 46: 3532-3539.
25. Salehi Z, Shams-Ghahfarokhi M, Razzaghi-Abyaneh M. Antifungal drug susceptibility profile of clinically important dermatophytes and determination of point mutations in terbinafine-resistant isolates. Eur J Clin Microbiol Infect Dis 2018; 37: 1841-1846.
26. Grover S, Roy P. Clinico-mycological profile of superficial mycosis in a hospital in North-East India. Med J Armed Forces India 2003; 59: 114-116.
27. Havlickova B, Czaika VA, Friedrich M. Epidemiological trends in skin mycoses worldwide. Mycoses 2008; 51: 2-15.
28. Patnaik M, Guru R, Pujari RR. Clinico-Mycological Study of Dermatophytosis in Western Odisha: Prevalence, Causative Agents, and Diagnostic Implications. Eur J Cardiovasc Med 2023; 13: 834-840.
29. Adesiji YO, Omolade FB, Aderibigbe IA, Ogungbe O, Adefioye OA, Adedokun SA, et al. Prevalence of tinea capitis among children in Osogbo, Nigeria, and the associated risk factors. Diseases 2019; 7: 13.
30. Araujo CR, Miranda KC, Fernandes OF, Soares AJ, Silva Mdo R. In vitro susceptibility testing of dermatophytes isolated in Goiania, Brazil, against five antifungal agents by broth microdilution method. Rev Inst Med Trop Sao Paulo 2009; 51: 9-12.
31. Nweze EI, Ogbonna CC, Okafor JI. In vitro susceptibility testing of dermatophytes isolated from paediatric cases in Nigeria against five antifungals. Rev Inst Med Trop Sao Paulo 2007; 49: 293-295.
32. Fernandez-Torres B, Cabanes FJ, Carrillo-Munoz AJ, Esteban A, Inza I, Abraca L, et al. Collaborative evaluation of optimal antifungal susceptibility testing conditions for dermatophytes. J Clin Microbiol 2002; 40: 3999-4003.
33. Adimi P, Hashemi SJ, Mahmoudi M, Mirhendi H. In vitro activity of ten antifungal agents against 320 dermatophyte strains using a microdilution method in Tehran. Iran J Pharm Res 2013; 12: 537-545.
34. Maurya VK, Kachhwaha D, Bora A, Khatri PK, Rathore L. Determination of antifungal minimum inhibitory concentration and its clinical correlation among treatment failure cases of dermatophytosis. J Fam Med Prim Care 2019; 8: 2577-2581.
35. Dogra S, Shaw D, Rudramurthy SM. Antifungal Drug Susceptibility Testing of Dermatophytes: Laboratory Findings to Clinical Implications. Indian Dermatol Online J 2019; 10: 225-233.
36. Sharma S, Maheshwari M, Thakur R, Sah SP, Chauhan S. Antifungal susceptibility testing of five antifungal agents against clinically isolated dermatophyte species from a tertiary care hospital in Northern India. J Clin Diagn Res 2022; 16(3): DC36-DC42.
37. Yamada T, Maeda M, Alshahni MM, Tanaka R, Yaguchi T, Bontems O, et al. Terbinafine resistance of Trichophyton clinical isolates caused by specific point mutations in the squalene epoxidase gene. Antimicrob Agents Chemother 2017; 61: 115-117.
38. Singh A, Masih A, Khurana A, Singh PK, Gupta M, Hagen F, et al. High terbinafine resistance in Trichophyton interdigitale isolates in Delhi, India harbouring mutations in the squalene epoxidase (SQLE) gene. Mycoses 2018; 61: 477-484.
39. Martinez-Rossi NM, Peres NT, Rossi A. Antifungal resistance mechanisms in dermatophytes. Mycopathologia 2008; 166: 369-383.
2. Mushtaq S, Faizi N, Amin SS, Adil M, Mohtashim M. Impact on quality of life in patients with dermatophytosis. Australas J Dermatol 2020; 61: e184-e188.
3. Gnat S, Nowakiewicz A, Łagowski D, Zięba P. Host- and pathogen-dependent susceptibility and predisposition to dermatophytosis. J Med Microbiol 2019; 68: 823-836.
4. Begum J, Mir NA, Lingaraju MC, Buyamayum B, Dev K. Recent advances in the diagnosis of dermatophytosis. J Basic Microbiol 2020; 60: 293-303.
5. De Hoog GS, Dukik K, Monod M, Packeu A, Stubbe D, Hendrickx M, et al. Toward a novel multilocus phylogenetic taxonomy for the dermatophytes. Mycopathologia 2017; 182: 5-31.
6. Bouchara JP, Mignon B, Chaturvedi V. Dermatophytes and dermatophytoses: a thematic overview of the state of the art and directions for future research and developments. Mycopathologia 2017; 182: 1-4.
7. Osman M, Kasir D, Rafei R, Kassem II, Ismail MB, El Omari K, et al. Trends in the epidemiology of dermatophytosis in the Middle East and North Africa region. Int J Dermatol 2022; 61: 935-968.
8. Narayanasetty NK, Pai VV, Athanikar SB. Annular lesions in dermatology. Indian J Dermatol 2013; 58: 157.
9. Mendonça MB, Cabral AKLF, Arantes BBA, Dos Santos RC, Medina-Alarcón KP, Dos Santos KS, et al. Biofilm development in three-dimensional models infected with Trichophyton rubrum. Microbiol Spectr 2025; 13(10): e0108725.
10. Tainwala R, Sharma Y. Pathogenesis of dermatophytoses. Indian J Dermatol 2011; 56: 259-261.
11. Faway É, Lambert de Rouvroit C, Poumay Y. In vitro models of dermatophyte infection to investigate epidermal barrier alterations. Exp Dermatol 2018; 27: 915-922.
12. Bitencourt TA, Macedo C, Franco ME, Assis AF, Komoto TT, Stehling EG, et al. Transcription profile of Trichophyton rubrum conidia grown on keratin reveals the induction of an adhesin-like protein gene with a tandem repeat pattern. BMC Genomics 2016; 17: 249.
13. De Peres NTA, Maranhão FCA, Rossi A, Martinez-Rossi NM. Dermatophytes: host-pathogen interaction and antifungal resistance. An Bras Dermatol 2010; 85: 657-667.
14. Martinez-Rossi NM, Peres NTA, Bitencourt TA, Martins MP, Rossi A. State-of-the-art dermatophyte infections: epidemiology aspects, pathophysiology, and resistance mechanisms. J Fungi 2021; 7: 629.
15. Khurana A, Sardana K, Chowdhary A. Antifungal resistance in dermatophytes: recent trends and therapeutic implications. Fungal Genet Biol 2019; 132: 103255.
16. Badali H, Mohammadi R, Mashedi O, de Hoog GS, Meis JF. In vitro susceptibility patterns of clinically important Trichophyton and Epidermophyton species against nine antifungal drugs. Mycoses 2015; 58: 303-307.
17. Martins MP, Rossi A, Sanches PR, Martinez-Rossi NM. Differential expression of multidrug-resistance genes in Trichophyton rubrum. J Integr OMICS 2019; 9:65-69.
18. Osborne CS, Hofbauer B, Favre B, Ryder NS. In vitro analysis of the ability of Trichophyton rubrum to become resistant to terbinafine. Antimicrob Agents Chemother 2003; 47: 3634-3636.
19. Santos HL, Lang EAS, Segato F, Rossi A, Martinez-Rossi NM. Terbinafine resistance conferred by multiple copies of the salicylate 1-monooxygenase gene in Trichophyton rubrum. Med Mycol 2018; 56: 378-381.
20. Chen X, Jiang X, Yang M, Bennett C, González U, Lin X, et al. Systemic antifungal therapy for tinea capitis in children: an abridged Cochrane review. J Am Acad Dermatol 2017; 76: 368-374.
21. Monod M, Feuermann M, Salamin K, Fratti M, Makino M, Alshahni MM, et al. Trichophyton rubrum azole resistance mediated by a new ABC transporter, TruMDR3. Antimicrob Agents Chemother 2019; 63: e00863–19.
22. Chander J (2018). Textbook of Medical Mycology. 4th ed. Jaypee Brothers Medical Publishers. New Delhi.
23. Clinical and Laboratory Standards Institute (CLSI) (2008). Reference method for broth dilution antifungal susceptibility testing of filamentous fungi; approved standard M38-A2. 2nd ed. CLSI. Wayne, PA.
24. Smith WL, Edlind TD. Histone deacetylase inhibitors enhance Candida albicans sensitivity to azoles and related antifungals. Antimicrob Agents Chemother 2002; 46: 3532-3539.
25. Salehi Z, Shams-Ghahfarokhi M, Razzaghi-Abyaneh M. Antifungal drug susceptibility profile of clinically important dermatophytes and determination of point mutations in terbinafine-resistant isolates. Eur J Clin Microbiol Infect Dis 2018; 37: 1841-1846.
26. Grover S, Roy P. Clinico-mycological profile of superficial mycosis in a hospital in North-East India. Med J Armed Forces India 2003; 59: 114-116.
27. Havlickova B, Czaika VA, Friedrich M. Epidemiological trends in skin mycoses worldwide. Mycoses 2008; 51: 2-15.
28. Patnaik M, Guru R, Pujari RR. Clinico-Mycological Study of Dermatophytosis in Western Odisha: Prevalence, Causative Agents, and Diagnostic Implications. Eur J Cardiovasc Med 2023; 13: 834-840.
29. Adesiji YO, Omolade FB, Aderibigbe IA, Ogungbe O, Adefioye OA, Adedokun SA, et al. Prevalence of tinea capitis among children in Osogbo, Nigeria, and the associated risk factors. Diseases 2019; 7: 13.
30. Araujo CR, Miranda KC, Fernandes OF, Soares AJ, Silva Mdo R. In vitro susceptibility testing of dermatophytes isolated in Goiania, Brazil, against five antifungal agents by broth microdilution method. Rev Inst Med Trop Sao Paulo 2009; 51: 9-12.
31. Nweze EI, Ogbonna CC, Okafor JI. In vitro susceptibility testing of dermatophytes isolated from paediatric cases in Nigeria against five antifungals. Rev Inst Med Trop Sao Paulo 2007; 49: 293-295.
32. Fernandez-Torres B, Cabanes FJ, Carrillo-Munoz AJ, Esteban A, Inza I, Abraca L, et al. Collaborative evaluation of optimal antifungal susceptibility testing conditions for dermatophytes. J Clin Microbiol 2002; 40: 3999-4003.
33. Adimi P, Hashemi SJ, Mahmoudi M, Mirhendi H. In vitro activity of ten antifungal agents against 320 dermatophyte strains using a microdilution method in Tehran. Iran J Pharm Res 2013; 12: 537-545.
34. Maurya VK, Kachhwaha D, Bora A, Khatri PK, Rathore L. Determination of antifungal minimum inhibitory concentration and its clinical correlation among treatment failure cases of dermatophytosis. J Fam Med Prim Care 2019; 8: 2577-2581.
35. Dogra S, Shaw D, Rudramurthy SM. Antifungal Drug Susceptibility Testing of Dermatophytes: Laboratory Findings to Clinical Implications. Indian Dermatol Online J 2019; 10: 225-233.
36. Sharma S, Maheshwari M, Thakur R, Sah SP, Chauhan S. Antifungal susceptibility testing of five antifungal agents against clinically isolated dermatophyte species from a tertiary care hospital in Northern India. J Clin Diagn Res 2022; 16(3): DC36-DC42.
37. Yamada T, Maeda M, Alshahni MM, Tanaka R, Yaguchi T, Bontems O, et al. Terbinafine resistance of Trichophyton clinical isolates caused by specific point mutations in the squalene epoxidase gene. Antimicrob Agents Chemother 2017; 61: 115-117.
38. Singh A, Masih A, Khurana A, Singh PK, Gupta M, Hagen F, et al. High terbinafine resistance in Trichophyton interdigitale isolates in Delhi, India harbouring mutations in the squalene epoxidase (SQLE) gene. Mycoses 2018; 61: 477-484.
39. Martinez-Rossi NM, Peres NT, Rossi A. Antifungal resistance mechanisms in dermatophytes. Mycopathologia 2008; 166: 369-383.
| Files | ||
| Issue | Vol 18 No 3 (2026) | |
| Section | Original Article(s) | |
| DOI | https://doi.org/10.18502/ijm.v18i3.21667 | |
| Keywords | ||
| Antifungal resistance Gene expression Minimum inhibitory concentration Polymerase chain reaction Squalene epoxidase | ||
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How to Cite
1.
Charlies J, Ragunathan L, Kanniyan K, Duraipandian J. In vitro antifungal resistance and molecular analysis of the SQLE gene in dermatophytosis: a laboratory-based study. Iran J Microbiol. 2026;18(3):403-412.
