title: Klebsiella L-forms: effect of growth as L-form on virulence of reverted Klebsiella pneumoniae.
abstract: A strain of Klebsiella pneumoniae virulent for mice was serially passaged in vitro as a penicillin-induced L-form. Periodically, the L-form was reverted to the bacterial form by removal of penicillin, and the revertant was tested for virulence. Virulence was gradually reduced, and after 109 passages the revertant was totally avirulent. Virulence was not restored by 40 passages of the revertant through mouse peritoneum. The revertant grew less vigorously and did not infect mice when inoculated subcutaneously; in contrast, the parental form was found in all tissues examined. After phagocytosis in vitro or in vivo, the revertant survived but did not increase in numbers, whereas the parental form did increase in numbers. The revertant had a much smaller capsule than did the parental form. Immunization with the live revertant resulted in type-specific protection against infection with the parental form.
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001770:Blood Bactericidal Activity; D007114:Immunization; D007710:Klebsiella Infections / Q000097:blood / Q000276:immunology; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000254:growth & development / Q000472:pathogenicity*; D007740:L Forms / Q000472:pathogenicity*; D007928:Lethal Dose 50; D051379:Mice; D010406:Penicillins; D010529:Peritoneal Cavity; D010587:Phagocytosis; D014774:Virulence
chemical_list: D000900:Anti-Bacterial Agents; D010406:Penicillins