Inhibition of L-Forms of Staphylococci by Coccal Forms of Staphylococci 1

Abstract

It was observed that coccal colonies of one strain of staphylococcus growing in the presence of a confluent growth of the L-forms of another strain of staphylococcus were surrounded by circular areas devoid of L-form growth. The purpose of this study was to determine to what extent coccal forms of one strain of staphylococcus inhibit L-forms or coccal forms of other strains of staphylococcus. The data indicate that coccal strains of Staphylococcus aureus and of Staphylococcus albus show varying degrees of inhibition of growth of staphylococcal L-forms. This phenomenon appears to be related either to some toxic substance or to loss from the media of some unidentified nutritional factor. Alpha-hemolysin was shown not to be responsible for this effect.

Materials and Methods. The term L-form has been defined in detail in previous reports from this department (1–3).

Nine strains of staphylococcus (six S. aureus and three S. albus) and their derived L-forms were studied. The L-forms were induced with methicillin except No. 316, which was isolated directly from sputum of a patient with cystic fibrosis of the pancreas. Eight of the strains were from patients and one from the American Type Culture Collection (6538P).

The coccal forms were maintained on brain heart infusion (BHI) agar slants (Difco). The L-colonies were induced and maintained on the same medium, to which 10% inactivated horse serum, 0.1% MgSO₄.7H₂O, 3.5% NaCl, and 250 μg/ml of sodium methicillin were added (SSM, salt serum methicillin). Streaks of L-form colonies were transferred from the SSM plates to an L-form maintenance medium without methicillin (SS) (1). Streaks of parent colony growth were made at right angles across streaks of L-forms. On other plates L-forms of one strain were streaked across streaks of L-forms of other strains.