Widespread amphotericin B-resistant strains of Aspergillus fumigatus in Hamilton, Canada
Received 12 April 2018
Accepted for publication 14 July 2018
Published 20 September 2018 Volume 2018:11 Pages 1549—1555
Checked for plagiarism Yes
Review by Single-blind
Peer reviewer comments 4
Editor who approved publication: Professor Suresh Antony
Eta E Ashu,1 Gregory A Korfanty,1 Himeshi Samarasinghe,1 Nicole Pum,1 Man You,1 Deborah Yamamura,2 Jianping Xu1
1Department of Biology, McMaster University, Hamilton, ON, Canada; 2Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada
Purpose: Amphotericin B (AMB) is one of the major antifungal drugs used in the management of aspergillosis and is especially recommended for treating triazole-resistant strains of Aspergillus fumigatus. However, relatively little is known about the AMB susceptibility patterns of A. fumigatus in many parts of the world. This study aims to describe the AMB susceptibility patterns in Hamilton, Ontario, Canada.
Methods: The in vitro susceptibilities of 195 environmental and clinical A. fumigatus isolates to AMB were tested by the broth microdilution method as per the Clinical and Laboratory Standards Institute’s guidelines. Catalase-generated oxygen bubbles trapped by Triton X-100 were used to quantify catalase activity in a representative group of isolates.
Results: Of the 195 isolates, 188 (96.4%) had the minimum inhibitory concentration (MIC) of AMB ≥2 mg/L, with approximately 80% and 20% of all clinical and environmental isolates having MICs of ≥ 4 mg/L. Overall, the clinical isolates were less susceptible to AMB than environmental isolates (P-value <0.001). The strain with the highest AMB MIC (16 mg/L) had one of the highest catalase activities. However, there was no correlation between AMB MIC and catalase activity in our sample.
Conclusion: The widespread AMB resistance suggests that using AMB in the management of A. fumigatus infections in Hamilton would likely result in treatment failure. Although high catalase activity may have contributed to AMB resistance in some isolates, the mechanism(s) for the observed AMB resistance in Hamilton is unknown and likely complex.
Keywords: Aspergillus fumigatus, resistance, amphotericin B, catalase activity, Hamilton, Canada
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