OCCURRENCE, DIVERSITY AND PATHOGENICITY OF MESOPHILIC AEROMONAS IN ESTUARINE WATERS OF THE ITALIAN COAST OF THE ADRIATIC SEA

A total of 208 strains of Aeromonas were isolated by monthly sampling from two estuaries (one provided with, and the other devoid of a waste -water treatment system) on the Italian coast of the Adriatic sea betw een September 1994 and August 1995. Biotyping at the species level all owed the identification of 96 strains (46%) as Aer. caviae, 46 (22%) a s Aer. sobria, 33 (16%) as Aer. hydrophila and 25 (12%) as Aer. veroni i. Eight strains (4%) were regarded as unnamed aeromonads. Aeromonas c aviae was the most prevalent species in water with a high degree of po llution, while Aer. hydrophila strains were more commonly isolated fro m cleaner water. Aeromonas sobria and Aer. veronii were equally distri buted in both estuaries. There was no correlation between temperature and numbers of aeromonads in either estuary. Using a biochemical finge rprinting method, strains were divided into similarity groups (PhP-typ es) based on their biochemical phenotypes. Several different PhP-types were found in each estuary, yielding a high diversity for these strai ns. However, some identical PhP-types were also found in both estuarie s and at different times of the year, indicating that certain Aeromona s strains can survive more widely varying physico-chemical conditions. The production of toxins capable of causing cytoskeletal-dependent ch anges in the morphology of Chinese hamster ovary (CHO) cells was detec ted in 14 strains and appeared to be dependent on the season.