Corynebacterium equi infection complicating neoplastic disease.

Corynebacterium equi, a soil-residing diphtheroid pathogenic in horses, swine and cows, caused pulmonary infection with bacteremia in two patients with lymphomas. Both patients were being treated with immunosuppressive therapy, as were the patients in three previously reported human cases. Unless certain characteristics of these organisms are recognized, they may be regarded as normal flora or contaminating diphtheroids. They could also be mistaken for other gram-positive rods, such as Bacillus species, Listeria monocytogenes, or Erysipelothrix insidiosa. C. equi isolates have usually been sensitive to erythromycin, tetracycline, gentamicin, and carbenicillin. One of the patients reported here was successfully treated with erythromycin, tetracycline, and surgery.