title: In Vitro Activity of Isavuconazole and Comparators against Clinical Isolates of the Mucorales Order.
abstract: The in vitro activity of isavuconazole against Mucorales isolates measured by EUCAST E.Def 9.2 and CLSI M38-A2 methodologies was investigated in comparison with those of amphotericin B, posaconazole, and voriconazole. Seventy-two isolates were included: 12 of Lichtheimia corymbifera, 5 of Lichtheimia ramosa, 5 of group I and 9 of group II of Mucor circinelloides, 9 of Rhizomucor pusillus, 26 of Rhizopus microsporus, and 6 of Rhizopus oryzae. Species identification was confirmed by internal transcribed spacer (ITS) sequencing. EUCAST MICs were read on day 1 (EUCAST-d1) and day 2 (EUCAST-d2), and CLSI MICs were read on day 2 (CLSI-d2). Isavuconazole MIC50s (range) (mg/liter) by EUCAST-d1, CLSI-d2, and EUCAST-d2 were 1 (0.125 to 16), 1 (0.125 to 2), and 4 (0.5 to >16), respectively, across all isolates. The similar values for comparator drugs were as follows: posaconazole, 0.25 (≤ 0.03 to >16), 0.25 (0.06 to >16), and 1 (0.06 to >16); amphotericin, 0.06 (≤ 0.03 to 0.5), 0.06 (≤ 0.03 to 0.25), and 0.125 (≤ 0.03 to 1); voriconazole, 16 (2 to >16), 8 (1 to >16), and >16 (8 to >16), respectively. Isavuconazole activity varied by species: Lichtheimia corymbifera, 1 (0.5 to 2), 1 (1 to 2), and 2 (1 to 4); Lichtheimia ramosa, 0.25 (0.125 to 0.5), 1 (0.5 to 2), and 2 (0.5 to 4); Rhizomucor pusillus, 0.5 (0.5 to 1), 1 (0.125 to 1), and 2 (1 to 2); Rhizopus microsporus, 1 (0.5 to 4), 0.5 (0.125 to 1), and 4 (1 to 8); and Rhizopus oryzae, 1 (0.5 to 4), 1 (0.125 to 2), and 4 (0.5 to 8), respectively, were more susceptible than Mucor circinelloides: group I, 8 (4 to 8), 4 (2 to 4), and 16 (2 to 16), respectively, and group II, 8 (1 to 16), 8 (1 to 8), and 16 (4 to >16), respectively. This was also observed for posaconazole. The essential agreement was best between EUCAST-d1 and CLSI-d2 (75% to 83%). Isavuconazole displayed in vitro activity against Mucorales isolates with the exception of Mucor circinelloides. The MICs were in general 1 to 3 steps higher than those for posaconazole. However, in the clinical setting this may be compensated for by the higher exposure at standard dosing.
authors.affiliation: Unit of Mycology, Statens Serum Institut, Copenhagen, Denmark maca@ssi.dk.
authors.forename: Maiken Cavling
authors.initials: MC
authors.lastname: Arendrup
authors.affiliation: Unit of Mycology, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Rasmus Hare
authors.identifier: 0000-0002-9796-023X
authors.initials: RH
authors.lastname: Jensen
authors.affiliation: Clinical Microbiology Laboratory, Attikon University Hospital, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Joseph
authors.initials: J
authors.lastname: Meletiadis
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology*; D005658:Fungi / Q000187:drug effects; D006801:Humans; D008826:Microbial Sensitivity Tests; D009090:Mucorales / Q000187:drug effects*; D009091:Mucormycosis / Q000382:microbiology*; D009570:Nitriles / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology*; D013045:Species Specificity; D014230:Triazoles / Q000494:pharmacology*
chemical_list: D000935:Antifungal Agents; D009570:Nitriles; D011725:Pyridines; D014230:Triazoles; C508735:isavuconazole