Dairy microbiology — “cheese cancer” defect in Swiss-type cheeses In Swiss and related hard cheeses, the defect historically termed “cheese cancer” (a surface, cratered, casein-digesting growth) is caused by which microorganism?

Introduction / Context:
In dairy technology, precise identification of microbial spoilage agents helps processors diagnose and prevent characteristic defects. One classical defect in Swiss-type cheeses is called “cheese cancer,” a historical term for a pitted, eroded, foul-smelling surface growth caused by proteolytic molds capable of digesting casein.

Given Data / Assumptions:

• The question specifically references Swiss and similar cheeses.
• “Cheese cancer” refers to a surface defect with proteolysis and crater formation.
• Oospora species names reflect older dairy literature terminology.

Concept / Approach:
“Cheese cancer” is associated with Oospora caseovorans, a strongly proteolytic mold historically cited in cheesemaking texts. It attacks casein, causing erosion, pits, and malodors on rinds—particularly under warm, moist storage that favors mold growth. Accurate naming helps differentiate from common dairy surface yeasts and benign rind flora.

Step-by-Step Solution:
Match the defect (“cheese cancer”) to its canonical causative mold in classical references: Oospora caseovorans.Eliminate other Oospora species not tied to this specific pathognomonic defect.Confirm that the context (Swiss-type cheese rinds) aligns with the historical reports.

Verification / Alternative check:
Traditional dairy microbiology manuals catalog Oospora caseovorans among the organisms producing erosive, crater-like rind lesions on Alpine-style cheeses under unhygienic or poorly controlled ripening conditions.

Why Other Options Are Wrong:
Oospora crustacea and Oospora aurianticum are not classically linked to “cheese cancer”; “none of these” conflicts with documented attributions; Geotrichum candidum (added as a plausible distractor) is a common rind yeast/mold that can cause defects but is not the historic “cheese cancer” agent.

Common Pitfalls:
Confusing general rind molds with the specific proteolytic Oospora associated with cratered lesions; overlooking environmental controls (humidity, temperature, airflow) that enable such molds.

Final Answer:
Oospora caseovorans.