If the cost of phenotyping an individual isolate is CP, then the total cost from the phenotyping effort required to detect a novel resistance variant isCPtotal=fItCPIf the cost of a treatment failure is CTF, a composite of the costs from the individual clinical failure and secondary cases, the variant occurs in the mean number of expected cases, and assuming that every attempted treatment of infection caused by a pathogen with the variant results in failure, then the expected total cost of treatment failure due to a novel resistance variant isCTFtotal=CTFf. The gene discussed is CP; the disease is infection.