Antifungal Resistance and Virulence Among Candida spp. from Captive Amazonian manatees and West Indian Manatees: Potential Impacts on Animal and Environmental Health

CHARACTERIZATION OF THE FUNGAL MICROBIOTA IN THE NOSTRILS AND RECTUM OF AMAZONIAN MANATEES (TRICHECHUS INUNGUIS) FROM A REHABILITATION PROGRAM IN BRAZIL

The present study characterized the filamentous and yeast-like fungal microbiota of the nasal cavity and rectum of Amazonian manatees (Trichechus inunguis) undergoing rehabilitation at the Laboratory of Aquatic Mammals, National Institute of Amazonian Research, Manaus, Amazonas, and determined the antifungal susceptibility of these organisms. Nasal and rectal swabs were collected from 22 calves and three juveniles. The samples were seeded in Sabouraud agar supplemented with chloramphenicol 10%, incubated at 26°C, and observed daily for up to 7 d. The growth of different filamentous and yeast-like fungi was observed among the two anatomical sites. Filamentous fungi were categorized by macro- and microscopic characteristics of the colonies. Representatives of each group were selected for molecular identification based on the internal transcribed spacer region. Yeast identification was performed using MALDI-TOF MS and molecular analyses. Thirteen genera of filamentous fungi and six genera of yeasts were isolated and identified. The dominant filamentous species were Fusarium spp., Aspergillus spp., and Cochliobolus lunatus in the nostril samples and Aspergillus melleus in the rectal samples. Candida was the dominant genus among the identified yeasts at both anatomical sites. In the antifungal susceptibility test, 28 isolates showed resistance to fluconazole (78%), itraconazole (39%), and nystatin (42%). The knowledge of fungal microbiota composition of Amazonian manatees provides information that assists in monitoring the health status of individuals maintained in captivity, as these organisms can behave either as opportunists or as primary pathogens. Moreover, the composition and resistance of these organisms may vary among different rehabilitation institutions or different time frames of search, reinforcing the importance of constant in loco surveillance of these microorganisms. This study provides new perspectives on the fungal diversity in the microbiota of manatees and supports future studies concerning the clinical and epidemiological aspects and the impacts of these agents on the health of Amazonian manatees undergoing rehabilitation.

Analysis of the culturable gut yeast microbiota of dogs with digestive disorders

Despite the increasing interest in studying the gut mycobiota of dogs, the association between fungal colonization and the development of digestive disorders in this species remains largely understudied. On the other hand, the high prevalence of antifungal-resistant yeasts detected in previous studies in samples from animals represents a major threat to public health. We analyzed the presence of culturable yeasts in 112 rectal swab samples obtained from dogs with digestive disorders attended in a veterinary teaching hospital. Our results revealed that Malassezia pachydermatis was frequently isolated from the studied dog population (33.9% of samples), and that the isolation of this yeast was significantly associated to the age of animals, but not to their sex, disease group, or the presence of vomits and/or diarrhea. In contrast, other yeast species were less prevalent (17.9% of samples in total), and their isolation was not significantly associated to any variable included in the analysis. Additionally, we observed that 97.5% of the studied M. pachydermatis isolates (n = 158, 1-6 per positive episode) displayed a minimum inhibitory concentration (MIC) value >4 μg/ml to nystatin, 31.6% had a MIC ≥32 μg/ml to fluconazole, and 27.2% had a MIC >4 μg/ml to amphotericin B. The antifungal susceptibility profiles of non-Malassezia (n = 43, 1-7 per episode) were more variable and included elevated MIC values for some antifungal-species combinations. These results confirm that the intestine of dogs is a reservoir of opportunistic pathogenic yeasts and suggest that the prevalence of M. pachydermatis colonization depends more on the age of animals than on any specific digestive disorder.

Collateral consequences of agricultural fungicides on pathogenic yeasts: A One Health perspective to tackle azole resistance

Candida and Cryptococcus affect millions of people yearly, being responsible for a wide array of clinical presentations, including life-threatening diseases. Interestingly, most human pathogenic yeasts are not restricted to the clinical setting, as they are also ubiquitous in the environment. Recent studies raise concern regarding the potential impact of agricultural use of azoles on resistance to medical antifungals in yeasts, as previously outlined with Aspergillus fumigatus. Thus, we undertook a narrative review of the literature and provide lines of evidence suggesting that an alternative, environmental route of azole resistance, may develop in pathogenic yeasts, in addition to patient route. However, it warrants sound evidence to support that pathogenic yeasts cross border between plants, animals and humans and that environmental reservoirs may contribute to azole resistance in Candida or other yeasts for humans. As these possibilities could concern public health, we propose a road map for future studies under the One Health perspective.

Isolation of antifungal-resistant yeasts from bulk milk in Japan

We isolated ascomycetous yeasts including Candida species, that originally belonged to the genus Candida, from bulk milk in the Aichi area of Japan, and determined the minimum inhibitory concentrations (MICs) of antifungal drugs on these isolates by conducting E-tests. We isolated 7 human pathogenic species (14 isolates) from 14 bulk milk samples: 5 Candida species of yeasts, and 2 Candida-related species. Two isolates of C. albicans and C. inconspicua were resistant to fluconazole (MIC >32 mg/l). One isolate of C. krusei was resistant to both azoles (fluconazole: >256 mg/ml and itraconazole: 4 mg/l). One isolate of C. catenulata might be resistant to amphotericin B (>32 mg/l).

Azole resistance in Candida from animals calls for the One Health approach to tackle the emergence of antimicrobial resistance

This study initially aimed at investigating the occurrence of azole resistance among Candida spp. from animals and analyzing the involvement of efflux pumps in the resistance phenomenon. Then, the dynamics of antifungal resistance was assessed, by comparing the antifungal epidemiological cutoff values (ECVs) against C. albicans and C. tropicalis from humans and animals. Fifty azole-resistant isolates (24 C. albicans, 24 C. tropicalis; 2 C. parapsilosis sensu lato) were submitted to the efflux pump inhibition assay with promethazine and significant MIC reductions were observed for fluconazole (2 to 250-fold) and itraconazole (16 to 4000-fold). Then, the antifungal ECVs against C. albicans and C. tropicalis from human and animal isolates were compared. Fluconazole, itraconazole and voriconazole ECVs against human isolates were lower than those against animal isolates. Based on the antifungal ECVs against human isolates, only 33.73%, 50.39% and 63.53% of C. albicans and 52.23%, 61.85% and 55.17% of C. tropicalis from animals were classified as wild-type for fluconazole, itraconazole and voriconazole, respectively. Therefore, efflux-mediated mechanisms are involved in azole resistance among Candida spp. from animals and this phenomenon seems to emerge in animal-associated niches, pointing to the existence of environmental drivers of resistance and highlighting the importance of the One Health approach to control it.

First isolation of voriconazole-resistant Candida albicans, C. tropicalis, and Aspergillus niger from the blowholes of bottlenose dolphins (Tursiops truncatus)

Pulmonary mycosis is a fungal disease that commonly affects bottlenose dolphins (Tursiops truncatus) and is generally treated by the oral administration of azoles, such as itraconazole (ITZ) and voriconazole (VRZ). However, antifungal susceptibility testing of clinical isolates has not been well performed as a routine clinical examination in aquaria. In this study, we collected fungal species from the blowholes of 14 bottlenose dolphins, of which 12 were treated with ITZ or VRZ. All dolphins were housed in the Port of Nagoya Public Aquarium. The fungal species Candida albicans, C. tropicalis, C. glabrata, Aspergillus fumigatus, and A. niger were isolated. E-tests were performed to determine the minimum inhibitory concentrations (MICs) of ITZ and VRZ on these isolates. VRZ-resistant C. tropicalis (MIC: >32 µg/ml) and A. niger (MIC: >32 µg/ml) were isolated from three dolphins treated with ITZ or VRZ. Additionally, azole-resistant isolates of C. albicans and C. glabrata were collected from two dolphins that had never received azole therapy. To the best of our knowledge, our study is the first to report the isolation of VRZ-resistant C. albicans, C. tropicalis, and A. niger from the blowholes of bottlenose dolphins. Thus, antifungal susceptibility testing is a crucial strategy for selecting antifungal agents to treat respiratory fungal infections in bottlenose dolphins in aquaria.

Antifungal Susceptibility Testing of Ascomycetous Yeasts Isolated from Animals

Recent studies suggest that antifungal resistance in yeast isolates of veterinary origin may be an underdiagnosed threat. We tested a collection of 92 ascomycetous yeast isolates that were obtained in Spain from birds, mammals and insects for antifungal susceptibility. MICs to amphotericin B and azoles were low, and no resistant isolates were detected. Despite these results, and given the potential role of animals as reservoirs of resistant strains, continuous monitoring of antifungal susceptibility in the veterinary setting is recommended.