WIDELY USED FUNGICIDE FOUND TO BE DRIVING C. TROPICALIS INFECTIONS

'Candida tropicalis', an important fungal pathogen in India and in many other parts of the world, has been found using chromosome alterations to resist common anti-fungal drugs such as fluconazole and voriconazole

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Candida tropicalis is an important fungal pathogen in India and many parts of the world. Its infections are associated with a mortality rate of 55-60%. Anti-fungal drugs called azoles, such as fluconazole and voriconazole, are used to treat its infections. But there is a growing concern in medical circles that clinics are seeing an increasing number of infections by strains of C. tropicalis that exhibit high resistance to these drugs. What is driving this alarming increase in drug resistance?

A paper published recently in PLoS Biology by researchers from Fudan University in Shanghai has provided the answer. They found that an azole-related fungicide called tebuconazole widely used by farmers and gardeners, and which can accumulate and persist in the environment has driven the increase in azole-resistant C. tropicalis infections seen in clinics.

The team also found that tebuconazole-resistant strains exhibited aneuploidy — meaning their chromosome number showed differences from the normal chromosome count for the organism. Such deviation from the normal chromosome complement is known as ploidy plasticity.

Deviating from normal ploidy

In the human body, most cells have two sets of the genome: thus they are diploid. One set of 23 chromosomes comes via the father’s sperm and the other set of 23 from the mother’s egg. When we, in turn, make eggs or sperm, a process called meiosis ensures only one set of chromosomes each of the 23 pairs is transmitted to them. Eggs or sperm are the only haploid cells in us — meaning they each have one copy of the genome. When a sperm fertilises an egg to make the zygote, diploidy is restored. The zygote then develops into the baby.