Pathogenicity of Stable L-Phase Variants of Staphylococcus aureus : Failure to Colonize Experimental Endocarditis in Rabbits

Abstract

Endocarditis was induced in the rabbit by the placement of a polyethylene catheter in the right heart. The catheter was filled with stable L-phase variants of Staphylococcus aureus to determine if the variant form would colonize the damaged endocardium and produce further tissue injury similar to that produced by the vegetative bacterial phase. No L-phase variants were recovered from cultures of blood or vegetations, although pure cultures of L-phase variants were obtained from all catheters, including one in place for 70 days. The vegetations were grossly similar in control animals with sterile media in the catheters and animals with catheters containing L-phase variants, although polymorphonuclear leukocytes and eosinophils were more frequently found in vegetations from animals inoculated with L-phase variants. Endocarditis was also induced in animals with vegetative S. aureus and then treated with penicillin G. Blood cultures in hypertonic media often grew vegetative S. aureus when there was no growth in routine media, but no L-phase variants were detected. Vegetative S. aureus, but not wall-defective variants, were isolated from vegetations of all treated animals. on August 1, 2020 by guest http://iai.asm.org/ Downloaded from 726 INFECT. IMMUNITY on August 1, 2020 by guest http://iai.asm.org/ Downloaded from

Controlled evaluation of hypertonic sucrose medium for detection of bacteremia and fungemia in supplemented peptone broth

“…The commonest explanation is that sucrose protects cell wall-defective bacteria from osmotic lysis in blood containing antimicrobial agents or enzymes that act on the cell wall (14,28). Although evidence is lacking that wall-defective bacteria themselves are pathogenic (10,18), hypertonic media have been helpful in a small number of carefully selected cases in isolating conventional forms of bacteria from the blood of patients who have received cell wall-active antimicrobial agents (11). Such appeared to be the case in our patient with relapsing S. epidermidis endocarditis.…”

In Vivo Behavior of Revertants from Staphylococcus aureus L-Phase Variants Compared with the Parent Strain

“…The role of wall-defective microbial variants in the initiation and persistence of infection continues to be debated. We have demonstrated in animal experiments that the stable L-phase variants of Staphylococcus aureus were unable to initiate infection under the most favorable experimental conditions (5,12). Other investigators have reported the reversion of walldefective microbial variants to the vegetative bacterial phase in experimental animals (4,6,13) and it has been postulated that these revertants might be responsible for the perpetuation or persistence of infection.…”

Controlled evaluation of hypertonic sucrose medium at a 1:5 ratio of blood to broth for detection of bacteremia and fungemia in supplemented peptone broth

“…Why sucrose should be beneficial in some media or some ratios of blood to broth is unclear. One explanation is that sucrose protects cell wall-defective bacteria from osmotic lysis (14,15,30), but evidence for a pathogenic role of these bacteria is lacking (11,19). Hypertonic media have been helpful in a small number of cases in recovering bacteria from patients receiving cell wall-active antimicrobial agents (12).…”