(a) The laboratory must check the following for positive and negative reactivity using control organisms:

1. (1) Each day of use for beta-lactamase methods other than Cefinase ^TM.
2. (2) Each week of use for Gram stains.
3. (3) When each batch (prepared in-house), lot number (commercially prepared), and shipment of antisera is prepared or opened, and once every 6 months thereafter.

(b) For antimicrobial susceptibility tests, the laboratory must check each batch of media and each lot number and shipment of antimicrobial agent(s) before, or concurrent with, initial use, using approved control organisms.

1. (1) Each day tests are performed, the laboratory must use the appropriate control organism(s) to check the procedure.
2. (2) The laboratory's zone sizes or minimum inhibitory concentration for control organisms must be within established limits before reporting patient results.