Medicine: PAB

When a sulfa drug comes along, some ordinarily susceptible bacteria do not just lie down and take it. Some of them develop such resistance that they can even multiply in the presence of the enemy. Up to now, laboratory workers have been unable to prove how a resistant strain differs from a susceptible one of the same species. They look alike, grow alike, form the same kind of colonies.

One theory holds that the resistance consists of increased production of PAB (para-aminobenzoic acid). But for a long time researchers were balked because there was no good test for the presence of PAB....

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