Researchers question use of fungicides on imported flowers, bulbs that induce antifungal drug resistance

Scientists question the use of certain fungicides used on imported flowers and bulbs following evidence that they induce resistance to some anti-fungal drugs.

Researchers in Manchester are questioning the legal use of certain fungicides used on imported flowers and bulbs following evidence that they induce resistance to the drugs used to treat patients with Aspergillus fumigatus, a virulent of fungal disease.

One of the first countries of the world where researchers suggested the generation of triazole antifungal drug resistance originates in the environment was the Netherlands which is a world leader for the production of plant bulbs, with almost nine billion bulbs, mostly tulips, exported every year. These bulbs are sold throughout the world with major markets in the US, Japan, China, EU and Russia.

Professor Malcolm Richardson, Director of the NHS Mycology Reference Centre and a European Confederation of Medical Mycology Centre of Excellence at the University Hospital of South Manchester, Wythenshawe Hospital, Manchester, UK says the transfer of azole resistance on bulbs from the world’s resistance hotspot in the Netherlands has an “Armageddon feel to it” for the many millions of patients on or requiring anti-Aspergillus therapy.

He explains:

Five azole fungicides induce resistance in A. fumigatus and can still be legally used on bulbs – is this sensible from a public health perspective? With no backup agents available orally, and the massive proliferation potential of Aspergillus, this problem needs urgent attention from public health authorities, who have been silent to date.

In March, a team of researchers from Trinity University, in Dublin examined samples of plant bulbs imported into Ireland from the Netherlands. Samples taken from 2014, 2015 and 2016 all bore isolates of A.fumigatus that had resistance to one or more triazole antifungal drugs. Quite apart from the risk to people handling these bulbs this is a clear example of how resistant strains can be spread from country to country.

This is not a problem restricted to Europe. Colombia is the second most prolific exporter of cut flowers in the world. It is also a heavy user of triazole fungicides and a team of researchers from Columbia, France and Holland also detected triazole resistant strains of A. fumigatus in 9 per cent of samples taken from soil collected from places where flowers are grown.

Professor Richardson and his team believe these reports provide clues as to how resistant strains are being generated and spread. and why they are now present on all six continents of the world, but there are likely to be many more examples when we consider the amount of trade in materials likely to be contaminated with A. fumigatus that is exchanged internationally every day, and the amount of use of triazole fungicides for agricultural purposes throughout the world.