I notice that whilst Timentin 85 is calibrated against Pseudomonas species in the CDS manual (fourth Edition), there are no reference ranges for Timentin against Pseudomonas species. How can we QC the discs if there are no reported reference ranges?
A. Quality Control testing is performed to ensure the antibiotic discs have retained their potency. It is the discs that are being tested, not the organism. It is not necessary to test the discs against organisms of same species as the isolate under investigation. In the CDS manual (Section 3.4 of the fourth edition, Section 3.1.3 of the online edition) it states that there is no need to perform duplicate controls on an antibiotic cartridge. In other words, where more than one reference organism is available for a particular antibiotic, the discs from any one cartridge need only be tested against one of these organisms. In the example you give, Timentin is a combination of Ticarcillin and clavulanic acid. QC testing needs to ensure that both components have retained their potency. Pseudomonas ACM 5189 does not possess a Bush group 2 β‑lactamase (those inhibited by clavulanic acid) and therefore cannot be used to quality control Timentin discs. The reference organism Escherichia coli AC
Related Questions
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