Antibiotic production can be assayed by the cross-streak
method (Figure 15.4b). Those isolates that show evidence of
antibiotic production are then studied further to determine if the compounds they produce are new. Most of the isolates obtained
produce known antibiotics, but when a new antibiotic is discovered,
it is produced in sufficient amounts for structural analyses
and then tested for toxicity and therapeutic activity in animals.
Unfortunately, most new antibiotics fail these tests. However, a
few prove to be medically useful and go on to be produced commercially.
The time and costs in developing a new antibiotic,
from discovery to clinical usage, average 15 years and 1 billion
($US). This includes many phases of clinical trials, which alone
can take several years to complete, analyze, and submit for
United States Food and Drug Administration (FDA) approval.