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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 between September 1994 and August 1995. Biotyping at the species level allowed the identification of 96 strains (46%) as Aer. caviae, 46 (22%) as Aer. sobria, 33 (16%) as Aer. hydrophila and 25 (12%) as Aer. veronii. Eight strains (4%) were regarded as unnamed aeromonads. Aeromonas caviae was the most prevalent species in water with a high degree of pollution, while Aer. hydrophila strains were more commonly isolated from cleaner water. Aeromonas sobria and Aer. veronii were equally distributed in both estuaries. There was no correlation between temperature and numbers of aeromonads in either estuary. Using a biochemical fingerprinting method, strains were divided into similarity groups (PhP-types) based on their biochemical phenotypes. Several different PhP-types were found in each estuary, yielding a high diversity for these strains. However, some identical PhP-types were also found in both estuaries and at different times of the year, indicating that certain Aeromonas strains can survive more widely varying physico-chemical conditions. The production of toxins capable of causing cytoskeletal-dependent changes in the morphology of Chinese hamster ovary (CHO) cells was detected in 14 strains and appeared to be dependent on the season.

The occurrence, diversity, and pathogenicity of Vibriospp. were investigated in two estuaries along the Italian Adriatic coast. Vibrio alginolyticus was the predominant species, followed by Vibrio parahaemolyticus, non-O1 Vibrio cholerae, and Vibrio vulnificus. By using a biochemical fingerprinting method, all isolates were grouped into nine phenotypes with similarity levels of 75 to 97.5%. The production of toxins capable of causing cytoskeleton-dependent changes was detected in a large number of Vibrio strains. These findings indicate a significant presence of potentially pathogenicVibrio strains along the Adriatic coast.

No abstract

The presence of Aeromonas spp. in water can represent a risk for human health. Therefore, it is important to know the physiological status of these bacteria and their survival in the environment. We studied the behavior of a strain of Aeromonas hydrophila in river water, spring water, brackish water, mineral water, and chlorinated drinking water, which had different physical and chemical characteristics. The bacterial content was evaluated by spectrophotometric and plate count techniques. Flow cytometric determination of viability was carried out using a dual-staining technique that enabled us to distinguish viable bacteria from damaged and membrane-compromised bacteria. The traditional methods showed that the bacterial content was variable and dependent on the type of water. The results obtained from the plate count analysis correlated with the absorbance data. In contrast, the flow cytometric analysis results did not correlate with the results obtained by traditional methods; in fact, this technique showed that there were viable cells even when the optical density was low or no longer detectable and there was no plate count value. According to our results, flow cytometry is a suitable method for assessing the viability of bacteria in water samples. Furthermore, it permits fast detection of bacteria that are in a viable but nonculturable state, which are not detectable by conventional methods.During the last decade scientific interest has turned to members of the genus Aeromonas as human and animal pathogens. Many Aeromonas species have been associated with human diseases, including gastroenteritis, hemolytic-uremic syndrome, septicemia, etc. (21, 30, 48).Aeromonas spp. are common aquatic microorganisms that occur in seawater, irrigation water, river water, brackish water, freshwater, groundwater, spring water, sewage-contaminated water, and activated sludge (4,7,9,14,15,23,24,37,43).The wide distribution of aeromonads in different aquatic ecosystems underlines their capacity to adapt to environments with different trophic levels. Several studies have shown that the phenospecies Aeromonas hydrophila is prevalent in cleaner water, whereas Aeromonas caviae is prevalent in water with a high level of fecal pollution; the frequencies of the other phenospecies appear to be unrelated to environmental conditions (3,15,17,23).These bacteria have also been isolated from chlorinated and unchlorinated drinking water and from bottled mineral water, which shows that they are able to withstand long periods of nutrient limitation (6,16,19,20,29,31,46,50). The survival of aeromonads in these ecosystems can be correlated with their capacity to produce and live within biofilms on the surfaces of pipes and bottles (26); on the other hand, it is known that Aeromonas spp. can cope with nutrient limitation conditions by entering into a starvation survival state (33).The growing interest in these organisms addresses aquatic environments, because these environments represent an important reservoir of aeromonads. It is assumed that huma...