The use of a biotyping system to investigate an unusual clustering bacteraemias caused by Aeromonas species.

Aeromonas spp. were isolated from blood cultures taken from four clinically bacteraemic patients over an 18 day period on four separate wards. A common source was suspected and extensive environmental sampling revealed two more ward isolates of Aeromonas spp. A biotyping system was employed which distinguished the strains from each other and indicated that a common source was unlikely. This coincidental clustering occurred in the autumn, a period when isolates from water and faeces are normally at a peak. All patients were debilitated and it is postulated that their own gastrointestinal tracts acted as the most likely route for their bacteraemias.