Antibiotic-sensitive Serratia marcescens infections complicating cardiopulmonary operations: contaminated disinfectant as a reservoir.

A cluster of Serratia marcescens infections complicating cardiopulmonary bypass operations was traced to contaminated quaternary ammonium disinfectant. Failure of hospital personnel to clean the disinfectant spray bottles before refilling them had enabled the organisms to survive and contaminate the environment, including the extracorporeal circulator. The organisms grew in two of four formulations of quaternary ammonium disinfectant. Serratia sensitivity to ampicillin and tetracycline was an epidemiological marker of a common-source outbreak.