Send that fungus to the lab, clinicians urged

Treatment-resistant tinea cases are increasing, and they need to be identified.

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That persistent case of tinea could be caused by a drug-resistant species, T. indotineae, which is showing up more frequently around the world, including here. 

“Clinicians should be aware of this new infection and collect skin scrapings for fungal microscopy and culture in patients with widespread tinea of the body, groin and face, or in patients where the infection has not responded to topical antifungal therapy, and should avoid prescribing topical corticosteroid treatment,” the authors of a recently published case study in the MJA warn. 

The subject of their paper was a young man who’d suffered from an itchy rash on his thigh and groin for 15 months, with no systemic symptoms. He had arrived in the country 12 months previously as a refugee, travelling from Afghanistan via Pakistan.  

He’d been on oral fluconazole 150 mg weekly for two months, but the rash persisted. Before that, he’d self medicated with topical clotrimazole and 0.05% betamethasone dipropionate and had been prescribed terbinafine 1% cream.  

The lab results came back showing a dermatophyte, a fungus that requires keratin for growth and infects skin, hair and nails –Trichophyton indotineae, with a minimum of 0.06 mg/L of itraconazole concentration required to effectively treat it.  

Relief was finally found with an eight-week prescription for oral itraconazole. 

“We have since isolated T. indotineae from another patient … from Sri Lanka at our refugee health clinic who has yet to commence treatment,” the authors write. 

“These data indicate the potential for further importation of this infection into Australia.” 

First noted in India, which is a top 10 travel destination for Australians, in the 2010s, these infections are now seen globally. Just this month, US clinicians noted two cases in JAMA that showed up in New York City.  

“There were not just a few lesions, but many, covering the patient’s thighs and buttocks: maddeningly itchy disks that were striated as though the infection had pulsed as it expanded on the skin,” they write. 

Four weeks of oral terbinafine “made no difference”, they reported. A subsequent month on griseofulvin reduced but did not eliminate the rash. 

A second case had “the same crusty, ring-shaped patches not just on the thighs and buttocks but extending up the abdomen and neck”. Terbinafine did not work for them either and it took four weeks of itraconazole to clear it. 

The first case had travelled to Bangladesh, but the second had not recently left the United States. Both were identified by the lab as being caused by T. indotineae, the first reported in the country. 

While dermatophyte infections are common, the T. indotineae species has only recently been designated a separate species (in 2020) and it is responsible for a growing number of difficult to treat cases of tinea corporis (body), faciei (face), and cruris (pubic region and groin).  

Terbinafine is the recommended first-line treatment for tinea in Australia and is available over the counter.  

Globally, up to 76% of T. indotineae cases are terbinafine-resistant, the authors note, due partly to the availability of topical antifungal medications containing terbinafine and corticosteroids such as clobetasol. 

In Australia, “multiple surveys in aged care have shown inappropriate and increased use of topical antifungal agents with prolonged duration and as-required prescriptions,” the authors write. 

Tinea cases need to be sent to the lab for identification, the authors say, especially when they’re not responding to treatment. It’s a slow process, they acknowledge, and not all labs have the capacity to distinguish this particular species from others.  

“Overall, because of these limitations in laboratory diagnosis and the absence of local guidelines, there is likely to be an underdiagnosis of T. indotineae infection, and surveillance studies are required to document the frequency of the infection and its treatment outcomes in the Australian setting,” they write.  

“Clinicians and laboratories should be aware of T. indotineae infection and be alert to its possibility in the event of poor clinical response to terbinafine to ensure accurate mycological investigation.” 

MJA, 16 July 2024 

JAMA, 23 August 2024