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Mucor and Mucormycosis
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
The family Rhizopodaceae includes (1) a thermotolerant Rhizopus microsporus clade (R. microsporus, R. caespitosus, R. homothallicus, and R. schipperae, growing at up to 45°C); (2) a sub-thermotolerant R. arrhizus group (growing at 37°C–40°C); and (3) a mesophilic group (R. stolonifer, Sporodiniella, and Syzygites). Although several members of the genus Rhizopus are infective to humans (e.g., Rhizopus oryzae [synonyms: Rhizopus arrhizus, Rhizopus arrhizus var. arrhizus], Rhizopus microsporus var. rhizopodiformis), R. oryzae predominates human mucormycosis cases. Occurring in soil, on decaying fruits, on dung, and on moist fresh organic matter in contact with soil, Rhizopus may be occasionally involved in spoilage of bread and other food, and thus is called “black bread mold” or “pin-head mold” (a name shared with Mucor) [4].
Isavuconazole
Published in M. Lindsay Grayson, Sara E. Cosgrove, Suzanne M. Crowe, M. Lindsay Grayson, William Hope, James S. McCarthy, John Mills, Johan W. Mouton, David L. Paterson, Kucers’ The Use of Antibiotics, 2017
Michelle R. Ananda-Rajah, Christina C. Chang, Monica A. Slavin
Isavuconazole is less potent in vitro against the Mucorales compared with Aspergillus spp. Using either European Committee on Antimicrobial Susceptibility Testing (EUCAST) or Clinical and Laboratory Standards Institute (CLSI) methodology, five genera of 345 clinical isolates of Mucorales had MIC90 values to isavuconazole of 4–16 mg/l (Verweij et al., 2009), corroborating findings from a smaller study of 36 isolates which had MIC90 values of > 8 mg/l (Perkhofer et al., 2009). Posaconazole retains the greatest in vitro activity against the Mucorales, with isavuconazole and ravuconazole having similar activity (Gonzalez, 2009). Other global surveys have corroborated these findings, one showing that for three Mucorales isolates (Rhizomucor pusillus and Rhizopus microsporus group) isavuconazole was less active than posaconazole with MIC results of 4, 1, and 2 mg/l, respectively, to isavuconazole compared to 1 mg/l for posaconazole (Pfaller et al., 2013). While Arendrup et al. (2015) corroborated these findings, they also found that Mucor circinelloides was less susceptible to both isavuconazole and posaconazole compared to other Mucorales, with MIC50s for isavuconazole ≥ 4 mg/l by both EUCAST and CLSI methods.
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Published in Baylor University Medical Center Proceedings, 2022
Valliappan Muthu, Ritesh Agarwal
Existing knowledge and current recommendations suggest surgery as the primary treatment for all forms of mucormycosis, including rhino-orbital and pulmonary mucormycosis.2,3 The evidence for the combination of caspofungin with liposomal amphotericin is based on a retrospective study conducted over 12 years, comparing six patients receiving the combination therapy with 34 patients on monotherapy.4 Further, the effect of caspofungin on the murine model of mucormycosis was demonstrated for Rhizopus orzyae (also known as R. arrhizus). Mucorales are intrinsically resistant to echinocandins, except for Rhizopus oryzae, which has the FKS gene encoding for 1,3-β-glucan synthase (the target for echinocandins).5 Whether Rhizopus microsporus (current case) would respond to a combination of caspofungin and liposomal amphotericin remains unknown.
Subtle relationships between Pseudomonas aeruginosa and fungi in patients with cystic fibrosis
Published in Acta Clinica Belgica, 2022
Kaicheng Yan, Hong Yin, Jin Wang, Yun Cai
Accordingly, PA produces low-molecular-weight molecules known as siderophores, specifically chelate iron [16]. Pyoverdine and pyochelin are the two predominant siderophores produced by PA, and pyoverdine exhibits the highest affinity for iron [17]. There are three classes of pyoverdine, which are capable of chelating iron. Among the PA strains isolated from CF patients, type II pyoverdine is the most common one [18]. Sass et al. and Anand et al. have suggested that pyoverdine is the principal PA inhibitor to AF [19], because PA mutants which lose or are lack of pyoverdine production are found to have impaired anti-fungal activities. Pyoverdine is also necessary for the formation of PA biofilm. PA cells in the biofilm can produce more pyoverdine. The competition between PA and AF seems to depend on the relative content of iron carriers, the speed at which they are produced, and their relative affinity for iron. A study has compared the antifungal activity of 10 PA isolates from the lungs of CF patients. Strains producing a small amount of pyoverdine show lower antifungal activity than those with higher pyoverdine content [20]. Kousser et al. have found that PA inhibits the germination of Rhizopus microsporus, a common cause of mucormycosis. Moreover, the growth and germination of Rhizopus microsporus can be inhibited by pyoverdine alone [21].
Successful long-term therapy of mucormycosis with isavuconazole
Published in Baylor University Medical Center Proceedings, 2021
Matthew Marcus Brigmon, Brennan Ochoa, Karen Brust
A 55-year-old Hispanic man with a history of diabetes mellitus presented with a 10-day history of worsening left-sided facial pain, swelling, numbness, odontalgia, and diplopia. Initial laboratory evaluation was significant for diabetic ketoacidosis and an elevated hemoglobin A1c (11.4%). By hospital day 2, his acidosis had resolved, but he developed a left-sided cranial nerve VI palsy. Magnetic resonance imaging (MRI) showed extensive inflammation involving the left nasopharyngeal and suprazygomatic masticator space with an asymmetric prominence of the left cavernous sinus suspicious for thrombosis. On day 3, nasal endoscopy with debridement and exploration revealed necrotic mucosa and debris. Mucormycosis was suspected, and he was empirically started on intravenous liposomal amphotericin B (L-AmB) (7 mg/kg). Histopathology revealed broad fungal nonseptate hyphae, and molecular testing was positive for Rhizopus microsporus.