Epidemiological Complexity of Hospital Aeromonas Infections Revealed by Electrophoretic Typing of Esterases

An epidemiology analysis of a series of 12 Aeromonas hydrophila infections, including six of septicaemia, which occurred on several wards of one hospital during the summer of 1982 is presented. The hypothesis that the hospital water could be the source of these infections was supported by the isolation of 1-10 motile aeromonads per ml in most of the water samples collected from various points on the hospital water system. Electrophoretic esterase typing was used as an epidemiological screening method to determine the relationship between bacterial strains isolated from the patients and those from water samples. The epidemiology of A. hydrophila infection in the hospital was found to be complex. Amongst the 15 strains of A. hydrophila isolated from patients were 8 zymotypes, while amongst the 126 strains from the water samples there were 37. In some cases, several zymotypes were isolated simultaneously from the same tap water. On one ward, the same zymotype was found in 2 patients and in 2 water samples. The prophylactic measures taken in 1982-5 to avoid oral contamination of immuno-compromised patients with infected hospital water have significantly reduced the number of cases of septicaemia. This success has constituted additional retrospective evidence for the water-borne origin of these infections.