Bacterial fouling of a hospital closed-loop cooling system by Pseudomonas sp

During the summer of 1979 the air-conditioning system at a hospital in Boston deteriorated, and this led to total failure of some chilling units. Patient care and operating-room areas were affected. Investigation of the problem ruled out mechanical and electrical causes, but revealed a strain of Pseudomonas sp. biofouling heat transfer tubes of the closed chilled water system. The pseudomonads apparently were stimulated to grow by low concentrations of ethylene glycol antifreeze. The proximate source of these organisms was an expansion tank located in a 33 degrees C environment. The organisms probably originated from the potable water supply of the hospital. Fouling was eventually cleaned by prolonged and expensive treatments of the closed chilled water system. Pseudomonas sp. is frequently isolated from hospital-acquired infections at our institution (Beth Israel Hospital, Boston, Mass.); however, our studies with fluorescent dye tracers indicated that organisms were prohibited from entering patient areas via contaminated water from the chillers. Microbiologists must become cognizant of seemingly unimportant microbial environments within hospitals that may indirectly contribute to hospital-acquired infections.