Sensitivity of Serratia to tetracycline.

S. marcescens had two levels of resistance to tetracycline, bacteriostatic end-points 32 and 180 microgram/ml; the latter group consisted of strains resistant to carbenicillin and to streptomycinl S. plymouthica, S.l liquefaciens, and S. marinorubra were sensitive to tetracycline with the last-named as the least sensitive species. Less difference was found between the bactericidal end-points of the four species, but there was still 1-2 two-fold steps between S. marcescens and the remaining three species.