UFS Microbiology Research: Drug-Resistant Yeast Discovered in South African Brown Locusts

In a significant advancement in microbiology research, scientists at the University of the Free State (UFS) in South Africa have uncovered a startling connection between common agricultural pests and a dangerous human pathogen. Researchers discovered fluconazole-resistant strains of the emerging yeast Candidozyma auris (formerly known as Candida auris), specifically Clade III, within the digestive tracts of South African brown locusts (Locustana pardalina). This finding not only sheds light on the environmental reservoirs of this multidrug-resistant fungus but also raises critical questions about how insects might contribute to its spread.

The study, conducted amid a major locust outbreak, highlights the intersection of entomology, microbiology, and public health. As brown locusts swarm across South Africa's semi-arid regions, devastating crops, they appear to harbor yeasts capable of causing severe bloodstream infections, particularly in immunocompromised patients. This UFS-led research underscores the university's pivotal role in addressing One Health challenges—where human, animal, and environmental health converge—in South African higher education.

UFS Researchers Pioneer the Investigation

The breakthrough originated from collaborative efforts at UFS's Department of Microbiology and Biochemistry, involving experts from the National Health Laboratory Service (NHLS) and the University of Venda. Led by Prof Carlien Pohl-Albertyn, an NRF SARChI Research Chair in Pathogenic Yeasts, the team isolated three C. auris strains from the guts of just 15% of sampled locusts—a prevalence suggesting the yeast's abundance without needing specialized isolation techniques.

Collection occurred in April 2022 during an extensive brown locust outbreak spanning September 2021 to May 2022 in South Africa's Eastern Karoo region. Twenty gregarious adult locusts were surface-sterilized, their alimentary canals dissected into foregut, midgut, and hindgut sections, and cultured on non-selective Yeast Malt Extract agar at 30°C. Identification relied on sequencing the Internal Transcribed Spacer (ITS) and D1/D2 Large Subunit (LSU) rRNA genes, confirming C. auris and co-occurring Candida orthopsilosis in two locusts.

One strain, UOFS Y-4024, underwent detailed phenotypic and genomic analysis. Its genome, sequenced via Illumina on an Element Biosciences Aviti platform, assembled to over 12 million base pairs and placed it firmly in Clade III—the dominant subtype in South African clinical cases, comprising 85% of isolates from 2009–2018. Prof Pohl-Albertyn noted, "Isolation from the foregut indicates acquisition through feeding, while hindgut presence confirms survival through digestion, enabling release via feces."

This rigorous methodology exemplifies UFS's commitment to cutting-edge higher education research. For aspiring scientists, opportunities in such interdisciplinary fields abound; explore research jobs or research assistant positions to contribute to similar breakthroughs.

Decoding the Pathogen: What is Candidozyma auris?

Candidozyma auris, reclassified from Candida auris, is a multidrug-resistant ascomycetous yeast first identified in 2009 in Japan. It poses a global threat due to high mortality rates (30–60%) in invasive infections like candidemia, often affecting ears, wounds, or bloodstreams in healthcare settings. Six clades exist, with Clade III prevalent in Africa, particularly South Africa, where it drives hospital outbreaks.

In South Africa, Clade III accounts for most cases, linked to early introductions around 2012–2014. The UFS isolate's fluconazole resistance stems from ERG11 gene mutations (V125A/F126L), yielding MIC ≥32 µg/ml, though it remains susceptible to voriconazole, echinocandins, amphotericin B, and flucytosine. Notably, its thermotolerance—optimal growth at 40°C, viability at 50°C—and halotolerance up to 15% NaCl mirror locust physiology (39–41°C preference), suggesting evolutionary adaptation.

• Thermotolerance: µ_max 0.061 h⁻¹ at 40°C vs. 0.044 h⁻¹ at 30°C.
• Disinfectant susceptibility: Inhibited by ethanol (29.5%), sodium hypochlorite (0.24%), below clinical thresholds.
• Genome: 93.1% BUSCO complete, Matα mating type.

Such traits enable persistence in harsh environments, amplifying dissemination risks. UFS's work positions South African universities at the forefront of combating antifungal resistance, a pressing global issue.

Brown Locusts: South Africa's Persistent Agricultural Threat

The brown locust (Locustana pardalina) is endemic to South Africa's Nama Karoo and Succulent Karoo biomes, with outbreak regions in the Northern Cape, Western Cape, and Eastern Cape. Gregarious phases trigger plagues every 7–11 years, exacerbated by climate variability. The 2021–2022 outbreak affected vast semi-arid areas, prompting government interventions like aerial spraying.

Locusts devastate crops—karoo veld, wheat, citrus—costing millions annually. Their alimentary canal processes vegetation rapidly: foregut for intake/storage, midgut for enzymatic digestion, hindgut for absorption/water reclamation. Hosting yeasts like C. auris implicates them in pathogen cycling: ingestion from contaminated plants, survival, and excretion in nutrient-rich frass.

Historical plagues date to the 1800s; modern management by the Directorate: Plant Health involves monitoring hopper bands and hopper/ adult control. UFS entomologists contributed to outbreak mapping, linking pest control to health surveillance.

For agriculture professionals eyeing academia, career advice on research roles can guide transitions into locust microbiology.

Key Scientific Insights and Phenotypic Profiles

The UFS team's phenotypic assays revealed the isolate's resilience: growth on 15% NaCl surpasses clinical strains, aiding survival in saline Karoo soils. Antifungal testing via VITEK 2 confirmed fluconazole resistance but broad susceptibility otherwise, contrasting full multidrug resistance in some hospital isolates.

• Foregut isolation (2A2): Acquired via foraging on yeast-contaminated vegetation.
• Hindgut isolations (15C2, 17C2): Transit through midgut without lysis.
• Co-isolation of C. orthopsilosis: Suggests broader yeast microbiome.

Whole-genome sequencing (100x coverage) via mycoSNP pipeline clustered it with SA Clade III clinical strains, implying shared ecology. No novel resistance genes in FKS1, but ERG11 polymorphisms explain azole tolerance.

This data, deposited in Biodiversity Biobanks SA, enables global comparisons. Read the full Medical Mycology publication for methodologies.

Photo by National Cancer Institute on Unsplash

Public Health Implications and One Health Perspective

While healthy individuals face low risk—C. auris rarely colonizes intact immunity—vulnerable groups (HIV/AIDS patients, chemotherapy recipients) are endangered. South Africa's high HIV prevalence amplifies threats; indirect transmission via birds feeding on locusts or frass-contaminated water is plausible.

In nations consuming locusts (e.g., parts of Asia/Africa), direct risks loom. Prof Pohl-Albertyn warns: "Locusts as food for wildlife could distribute yeast to humans." Disinfectant sensitivity offers control levers during outbreaks.

This aligns with One Health, urging integrated surveillance. UFS advocates environmental monitoring alongside hospital screening. For public health careers in higher ed, check clinical research jobs.

Insects as Reservoirs: Broader Ecological Role

Prior studies linked Candidozyma relatives to insects (mosquitoes, beetles). Thermophilic traits suit insect guts (high temp, peristalsis). Locusts, migrating hundreds of km, vector yeasts across ecosystems, seeding soils/plants.

South Africa's Clade III dominance suggests local evolution, possibly insect-driven. Future studies: qPCR prevalence in swarms, transmission experiments. UFS's yeast culture collection bolsters this.

UFS's Excellence in Higher Education Research

UFS, a leading South African university, excels in pathogenic yeasts via NRF chairs. Prof Pohl-Albertyn's lab advances antifungal discovery amid resistance crises. Collaborations with NHLS/Univen exemplify inter-institutional synergy.

This positions UFS for grants, publications (e.g., Medical Mycology). Students benefit from hands-on training; see postdoc opportunities or lecturer jobs in microbiology.

Challenges, Solutions, and Future Directions

Challenges: Locust control (pesticides) may aerosolize yeasts; climate change intensifies outbreaks. Solutions: Integrated Pest Management (IPM) with yeast surveillance; novel antifungals targeting ERG11.

• Monitor swarms for pathogens via metagenomics.
• Develop locust-safe biopesticides.
• Enhance hospital decontamination.

Future: Longitudinal studies on transmission. UFS calls for funding; explore academic CV tips for grants.

Stakeholder Perspectives and Global Context

Farmers view locusts as foes; health officials, vectors. Globally, C. auris outbreaks span 50+ countries; Africa's Clade III unique. UFS contributes to WHO priorities.

Balanced view: Risks contained, but vigilance key. For South Africa-focused roles, visit South African university jobs.

Photo by Michael Schiffer on Unsplash

Path Forward: Actionable Insights for Researchers and Policymakers

Leverage UFS findings for policy: Mandate One Health in locust response. Researchers: Sequence more isolates. Students: Pursue professor ratings, higher ed jobs, career advice.

This UFS discovery illuminates unseen threats, reinforcing higher education's role in safeguarding South Africa.