The growing threat of antifungal resistance

Candidozyma auris

Candidozyma auris is a yeast which is related to the more common Candida species we have previously discussed. Since its first discovery as a pathogen in 2009, it has rapidly become a global concern with infections detected in >60 countries and 6 continents. A lot like Candida albicans, it can cause mucosal infections as well as more serious bloodstream infections.

It is believed to be an environmental yeast that became tolerant of higher temperatures, as in the human body. Due to its environmental nature, it can contaminate hospital environments, unlike most other yeasts. Due to its thermotolerance, it is especially effective at colonising when it is transmitted from person to person. However, not all patients who are colonised will develop an invasive fungal infection, but those vulnerable patients who do can have a mortality rate of 30-60%. This is, in part, due to its resistance to many antifungals.

Azole antifungal resistance is common in this species. However, the concern is of resistance to the other drugs we have introduced – amphotericin B and echinocandins. When resistance to all available drugs is found, this is called pan-resistance. For those exposed to such pan-resistant strains, treatment options can be very limited.

In a globalised world, these pan-resistant organisms can spread from one country and healthcare system to another. This reinforces the need not just for antifungal stewardship at home but also international collaboration, surveillance and appropriate screening for these organisms.

Trichophyton indotineae and mentagrophytes genotype VII (TMVII)

Trichophyton species cause itchy rashes on the skin, commonly called ringworm and athlete’s foot. They can also cause painful lumps or pustules, which can lead to scarring. They are very contagious either via direct human-to-human contact or via contaminated environments such as public gyms and swimming pools.

Trichophyton indotineae is a relatively new species closely related to the other main Trichophyton species. It is typically resistant to terbinafine, while most remained susceptible to alternatives such as itraconazole. Therefore, it has become the predominant species in countries like India, where antimicrobials are easily available in non-professional settings.

Trichophyton mentagrophytes genotype VII (TMVII) strain has emerged as a sexually transmissible cause of skin infections, particularly among men who have sex with men. It typically infects the groin area but can spread all over the body. Though normally responsive to terbinafine, successful treatment often requires longer courses (months) of systemic antifungals from the outset, even in cases with localised disease, as initial topical treatment has been associated with worsening of the lesions.

When new infections emerge, it is important to identify them quickly. When diagnosis and identification are rapid, then the right treatment can be given at the right time to prevent the emergence of new resistant strains in the future.

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