“Through a drinking glass and what was found there”: Pseudocontamination of a hospital's drinking water

OEJECTIVE: Examination of suspended macroscopic debris that was noted in hospital cafeteria drinking water over a prolonged period of time. SETTING: A tertiary care hospital. DESIGN: A retrospective description of events. METHODS: Conventional medical microbiology techniques were employed to determine if contamination of drinking water had occurred. RESULTS: Microscopic examinations of the debris showed live nematodes similar to Strongyloides stercoralis rhabditiform larvae and amoebic trophozoites. A culture of an ice container in the cafeteria yielded coliform bacteria. Hospital employees lost work because of a diarrheal illness thought to be contracted from drinking cafeteria water. Further investigation revealed that the debris contained numerous ciliated organisms, nematodes, fresh water amoebae, bacterial mats, flagellated fungi, and unidentified cysts suggesting that the debris was of a freshwater origin rather than fecal contamination. Another hospital served by a collateral city water line experienced a similar problem. The debris was observed in November when lake water in the reservoir undergoes inversion. CONCLUSIONS: Nonpathogenic freshwater microbiota probably originating from the city reservoir were the cause of pseudocontamination of hospital drinking water. (Infect Control Hosp Epidemiol. 1992;13:477-481.).