CS CRCST Exam Prep


FREE STUDY TOOL

Welcome to the Germ Ward

Six germ patients are waiting for treatment. Tap a patient on the left, then tap the sterilization machine that cures it. Every cure comes with a memory anchor so the pairing sticks for exam day.

Patients cured0 of 6
Healing streak0 in a row

How to play: tap a germ patient, then tap the treatment machine that wipes it out. Watch out, the ward shuffles every round.

Germ Patients

Poor little guys. Pick one to treat.

Treatment Machines

Choose the right cure for each bug.

Doctor's orders: the two organisms are the whole game. Steam, IUSS, gas plasma, and ozone all share Geobacillus stearothermophilus. EtO and dry heat share Bacillus atrophaeus. Learn that split and you cannot miss these questions.
Doctor's notes: BI organism reference
Sterilization methodBI organismMemory anchor
Steam sterilization (gravity displacement)Geobacillus stearothermophilusGeobacillus lives near hot springs. Heat-loving bug for the heat-based process.
Steam sterilization (dynamic air removal / prevacuum)Geobacillus stearothermophilusSame cycle family, same bug. Both steam cycles use G. stearothermophilus.
Immediate-use steam sterilization (IUSS)Geobacillus stearothermophilusIUSS is still steam, so the BI organism does not change.
Ethylene oxide (EtO)Bacillus atrophaeusA for atrophaeus, A for EtO gas. The gas process gets the gas-resistant spore.
Hydrogen peroxide gas plasmaGeobacillus stearothermophilusPlasma systems group with steam: tough bug, low-temperature cycle.
Dry heatBacillus atrophaeusDry conditions, dry-heat spore. B. atrophaeus survives the long hot drought.

BI organism questions, answered

Which biological indicator organism is used to monitor steam sterilization on the CRCST exam?

Geobacillus stearothermophilus. It is the BI organism for steam sterilization (gravity and dynamic air removal cycles), immediate-use steam sterilization, hydrogen peroxide gas plasma, and ozone sterilization on the CRCST exam.

Which biological indicator organism is used for ethylene oxide sterilization?

Bacillus atrophaeus (formerly called Bacillus subtilis var. niger). It is also the BI organism for dry heat sterilization.

Why does the CRCST exam test BI organism pairings?

Biological indicators prove a sterilization cycle worked. The CRCST exam asks which organism belongs to which process, so matching each method to its BI organism is a fast, high-yield study drill.

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