UFS Researchers Discover Drug-Resistant Yeast in South African Brown Locusts

Unveiling the Discovery: UFS Researchers Isolate Pathogenic Yeast from Locust Guts

In a pioneering study conducted by scientists at the University of the Free State (UFS) in South Africa, researchers have identified fluconazole-resistant strains of Candidozyma (Candida) auris, commonly known as Candida auris, within the digestive tracts of South African brown locusts (Locustana pardalina). This finding marks the first documented evidence of this emerging fungal pathogen in these agricultural pests, raising critical questions about environmental reservoirs and potential transmission pathways.

The research, initiated amid a major locust outbreak from September 2021 to May 2022, involved dissecting the alimentary canals of 20 gregarious adult locusts collected in the semi-arid Eastern Karoo region of the Eastern Cape. Three C. auris strains were isolated from the foreguts and hindguts of three different locusts, representing a 15% prevalence rate using non-selective media at 30°C. Two of these locusts also carried another potentially pathogenic yeast, Candida orthopsilosis.

Prof Carlien Pohl-Albertyn, NRF SARChI Research Chair in Pathogenic Yeasts at UFS, emphasized the significance: "The isolation from the foregut suggests acquisition through feeding, while hindgut presence indicates survival through digestion, enabling release into the environment via feces." This process underscores how locusts could serve as vectors in the One Health framework, linking agriculture, wildlife, and human health.

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Decoding Candida auris: The Multidrug-Resistant Fungal Threat

Candida auris is an ascomycetous yeast first identified in 2009 in Japan, though retrospective analysis traces its emergence to India, South Africa, and South Korea around the same time. Classified by the World Health Organization as a critical priority fungal pathogen, it causes invasive infections like candidemia and otitis with mortality rates of 30-60%, particularly in immunocompromised patients.

In South Africa, Clade III dominates, accounting for approximately 1 in 10 candidemia cases. High fluconazole resistance is prevalent, with 91.3% of isolates resistant in some studies, alongside variable resistance to amphotericin B (20.5%) and echinocandins (1.7%). Its ability to persist on surfaces, tolerate high temperatures (up to 42°C), and resist common disinfectants complicates hospital outbreaks.

The UFS-isolated strain, UOFS Y-4024 (deposited as CBS 19369), exhibited an MIC ≥32 µg/ml for fluconazole, confirming resistance, but remained susceptible to voriconazole, echinocandins, amphotericin B, and flucytosine. It harbored an ERG11 substitution (V125A/F126L) linked to azole resistance, aligning with Clade III clinical profiles.

Genomic sequencing placed it closely related to South African hospital strains from 2012-2014, suggesting shared evolutionary pressures. Aspiring microbiologists can find inspiration in UFS's work; check research jobs and academic CV tips on AcademicJobs.

Brown Locusts: South Africa's Persistent Agricultural Menace

The brown locust (Locustana pardalina) is one of four plague locust species in southern Africa, endemic to the Karoo and Nama-Karoo biomes. These solitarious grasshoppers phase into gregarious swarming forms under favorable conditions like good rainfall, forming hopper bands and adult swarms that devastate rangelands and crops.

Historical outbreaks, such as those in the 1930s and recent ones in 2021-2022, have threatened sheep grazing and irrigated crops in the Karoo. While quantitative economic impact data is sparse, swarms can strip vegetation, exacerbating desertification and food insecurity. Climate variability, including erratic rainfall, fuels these plagues.

• Preferred habitat: Semi-arid Karoo regions with short grasses.
• Outbreak triggers: Above-average rainfall promoting nymph survival.
• Economic threat: Damage to rangeland (primary) and emerging crops.
• Control challenges: Reliance on chemical sprays, pushing for biopesticides.

UFS's dual expertise in entomology and microbiology positions it as a leader. Faculty positions in lecturer jobs at such institutions offer platforms for interdisciplinary impact.

For deeper insights into locust management, visit the University of the Free State.

Step-by-Step: How UFS Conducted the Groundbreaking Analysis

The methodology was rigorous, blending classical microbiology with modern genomics. Here's the process:

1. Sample Collection: Surface-sterilized 20 adult locusts dissected; alimentary canals (fore-, mid-, hindgut) rinsed and plated on YM agar at 30°C.
2. Isolation and ID: ITS/D1D2 sequencing confirmed C. auris; strains preserved at -80°C.
3. Susceptibility Testing: VITEK 2 AST-YS08 for antifungals; spot assays for salt/temperature tolerance; disinfectant exposure tests.
4. Genomics: Illumina/Element sequencing, mycoSNP pipeline, phylogeny with 566 Clade III genomes.

This table illustrates the targeted resistance profile, emphasizing the need for diversified antifungal strategies.

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Photo by Jolame Chirwa on Unsplash

Key Findings: Resistance, Tolerance, and Genomic Ties

The characterized strain thrived at 50°C (max growth rate 0.009 h⁻¹) and 15% NaCl, mirroring locust physiology (body temp 39-41°C). Disinfectant MICs were low (e.g., ethanol 29.5%, hypochlorite 0.24%), suggesting hospital hygiene can contain it. Phylogeny confirmed Clade III proximity to clinical isolates, hinting at locusts as overlooked reservoirs.

• 15% carriage rate indicates abundance.
• Foregut isolation: Dietary uptake.
• Hindgut: Survival and excretion.
• 63 resistance markers, but only fluconazole confirmed.

Such discoveries fuel postdoc opportunities in fungal genomics.

Read the full study: PMC Article.

Public Health Implications: From Locust Swarms to Hospital Wards?

While healthy individuals face low risk from direct contact or ingestion, vulnerable groups (HIV patients, elderly, ICU) are threatened. Locusts as bird feed could bioaccumulate the yeast up the food chain. In regions consuming locusts, direct zoonotic risk exists. SA's high HIV prevalence amplifies concerns.

This aligns with global hypotheses: insects, wastewater, plastics as reservoirs. UFS research informs surveillance.

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Agricultural and Ecological Ramifications in the Karoo

Locust control using azoles? Unlikely direct cause, but environmental fungi interact. Outbreaks strain farmers; this adds pathogen vector role. Sustainable biocontrol needed.

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UFS's Leadership in Pathogenic Yeast Research

UFS's Department of Microbial, Biochemical and Food Biotechnology leads, funded by NRF. Collaborations with NHLS, Univ Venda exemplify SA higher ed synergy. Prof Pohl-Albertyn's chair drives innovation.

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Paper details: bioRxiv Preprint.

Photo by Steward Masweneng on Unsplash

Challenges, Solutions, and Future Directions

Challenges: MDR evolution, surveillance gaps. Solutions: New antifungals, insect monitoring, One Health policies. Future: Larger surveys, animal models, climate links.

• Develop clade-specific diagnostics.
• Monitor locust outbreaks for yeasts.
• Explore insect microbiomes.

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Conclusion: Pioneering Research for a Safer Future

UFS's discovery illuminates hidden pathogen dynamics, urging vigilance. Engage with experts via Rate My Professor, seek higher ed jobs, or explore career advice. For opportunities, visit university jobs and post a job.

UFS news: UFS Article.