Fever of unknown origin: attempts to isolate L-forms and other aberrant bacterial forms.

An investigation was conducted with 65 selected febrile patients, 33 of whom fulfilled in all respects the classic criteria of "fever of unknown origin." Clinical evaluation included extensive radiological and immunological testing. Multiple blood cultures were examined by conventional methods in control studies. In addition, venous blood was cultured in a variety of hyperosmolar media using the special techniques used to detect L-forms and other cell wall-defective bacterial forms. By the extensive methods used, no bacterial forms were isolated. The use of media containing osmotic stabilizers did not detect L-forms or other aberrant bacterial forms, nor did it contribute to the determination of the etiology of fever of unknown origin in these patients.