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Azole-resistant A. fumigatus yet to emerge in US
Azole-resistant Aspergillus fumigatus is common in Europe; however, the rates are extremely low in the United States, according to CDC surveillance data.
“Mutation-mediated azole-resistant A. fumigatus is uncommon in the United States, and environmentally mediated resistance does not seem to exist yet in the United States,” Cau D. Pham, PhD, associate research fellow at the CDC’s Mycotic Diseases Branch, told Infectious Disease News. “However, we should be vigilant in monitoring for azole-resistant A. fumigatus strains. Surveillance studies like ours will help prepare public health to detect such azole-resistant A. fumigatus if and when they appear in the United States.”
Cau D. Pham
That awareness is critical because US physicians have limited options when treating serious Aspergillus infections, according to Pham. Azole antifungal drugs, especially voriconazole and itraconazole, are the first-line treatment. Resistance to these medications can lead to treatment failure and death in patients.
Azole-resistant strains have been found in Europe, Asia, Africa and the Middle East, where they pose a serious public health threat. Given the number of aspergillosis cases in the United States, azole-resistant A. fumigatus could pose an equally significant threat in that country.
There are two causes for this resistance: a mutation in the lanosterol 14-alpha demethylase gene that encodes the CYP51A protein, and more recently, a mutation known as TR34/L98H.
Pham and colleagues obtained more than 1,000 clinical A. fumigatus isolates from 22 states from the American Society for Microbiology and the Association of Public Health Laboratories. The researchers screened all isolates using antifungal plate culture assay and the itraconazole Etest.
Their results demonstrated that in these samples, TR34/L98H does not seem to exist yet in the United States. About 5% of the isolates required a higher minimum inhibitory concentration for itraconazole, although most isolates did not have a detectable genetic mutation, the researchers wrote. Because of increasing reports of azole resistance in Europe and Asia, further surveillance is required.
Disclosure: The researchers report no relevant financial disclosures.