Resistance of the group A streptococcal L form to sonic oscillation

The mechanical fragility of the L form of two group A streptococcal strains was assessed by subjecting L-form suspensions to sonic oscillation (60 W, 20 kc/sec). To evaluate the effect of the sonic energy applied, the original streptococcal strains and aSerratia marcescens strain were subjected to the same treatment. The killing of the organisms by sonic oscillation followed the expression log N_o/N_t=–K·t^1/2. The mortality rate constants K of the streptococcus,S. marcescens and the L form of the AED and GL-8 streptococcal strains were –0.19,–0.98,–1.14 and–1.52 min^–1/2. respectively. The mortality rates of the L form of the two streptococcal strains differed significantly (P=0.01). From a comparison of these data, and taking into account the difference in cell envelope between the bacterial and the L form, it is concluded that the limiting envelopes of the group A streptococcal L-form elements probably possess a relatively marked stability. The factors which might be responsible for the difference in mortality rates between the L form of the streptococcal strains are discussed.The author wishes to thank Dr. W. Hijmans (Institute for Rheumatism Research, Leiden) for his contribution to and constant interest in the work and Mr. J. C. Houwelingen (Department of Mathematical Statistics, Utrecht) for the statistical analysis. This study could not have been accomplished without the able and conscientious technical assistance of Miss H. L. Ensering (Institute for Rheumatism Research, Leiden), which is gratefully acknowledged.