Sugust 10, 1955

Dr. J. C. Gould
Bacteriology Departmant
University New Building
Teviot Place Fdinburgh 1

Dear Dr. Gould:

Your note in Nature for July 23 has just come to my notice. Might I
ask the favor of reprints of your work on drug resistance, BRREATAKTY
XKR which I would particularly like to have for my reference file for a
monograph pn the subject.

I hope you are planning to investigate the mechan&sm of this effect
more fully. I would doubt! that an "ordinary" mutation to penicillin
resistance would alter the phage type, and wonder if exposure to the
drug is not the essential precondition. There is a strong suggestion
of such an ef fect in Voureka' s paper (J. Gen Microb.6:352). If so,
one might get changes in wat phage type after exposure without neces-—
sarily developing resistance. Alternatively, the new phage type might
directly confer resistance per se. Are there type IIT strains that are
penicillin-senshtive?

Another approach to this hypothetical mechanism would be replica plating
and indirect selection; if the phage type change depended on exposure to
the drug, then resistant mitants selected indirectly might smack
retain their dx original lysotype (and might be espectally suitable materia
do demonstrate direct effects of penicillin on the lysotype).

We had another suggestion of this effect some time ago: a lysogenic
Salmonella strain would (sometimes sporadically, but especially under the
*pehicillin)influence of*kiwograagm) release a more virulent phage which, in turn
re-infec ted the parent bacterium. The reinfected strain had a different

lysis pattern to various phages, but was not tested by the standard typing
reagents.

Yours sincerely,

Sow eh OF O™

 

Foyt et

ae

- Joshua Lederberg’ /

é

Professor of Genetics