Coccidioides: Spherule and Arthroconidia
Original bench-card visual for recognizing Coccidioides: tissue spherules packed with endospores and mold-phase barrel-shaped arthroconidia.
Coccidioides: spherules in tissue, arthroconidia in mold phase
Tissue diagnosis centers on spherules with endospores. Mold-phase arthroconidia are highly infectious; suspected cultures require strict safety handling.
Large round spherules contain many endospores. Free endospores can mimic budding yeast if the spherule wall is not seen.
Barrel-shaped arthroconidia are the culture hazard. Do not manipulate suspected Coccidioides culture outside approved containment.
Large round spherules contain many endospores. Free endospores can mimic budding yeast if the spherule wall is not seen.
Barrel-shaped arthroconidia are the culture hazard. Do not manipulate suspected Coccidioides culture outside approved containment.
Coccidioides visual anchors
| Visual clue | Meaning | Student shorthand |
|---|---|---|
| Spherule with endospores | Tissue-phase clue | Large round structure packed with internal endospores |
| Free endospores | Possible rupture | Can be mistaken for yeast if context is ignored |
| Barrel arthroconidia | Mold-phase clue | Alternating arthroconidia and empty cells in hyphae |
| Culture safety concern | High-risk mold handling | Follow lab containment and referral policy |
Coccidioides interpretation guide
| Pattern | What to call it | How to think about it |
|---|---|---|
| Spherules with endospores | Coccidioides-compatible tissue morphology | Escalate and confirm per SOP |
| Barrel arthroconidia in culture | Coccidioides mold-phase concern | Apply safety workflow immediately |
| Small oval intracellular yeasts | Histoplasma pattern | Not a spherule/endospore pattern |
- Coccidioides tissue form is a spherule, not a budding yeast.
- Mold-phase arthroconidia are the safety-critical feature.
- The safest next step is escalation, containment, and SOP-guided confirmation.
Cocci = spherule in tissue, barrel arthroconidia in culture, safety first.