A total of 35 samples (1000 ml each) of pasteurized milk and 25 samples (100 g each) of white cheese purchased at supermarkets in Rio de Janeiro were analyzed for the presence of Aeromonas. Strains of Aeromonas were isolated from 28.5% of pasteurized milk and 32% of white cheese samples. Standard Plate counts in the pasteurized milk samples ranged from 7.2 × 10* to 2.5 × 105 CFU/ml. Total and fecal coliform counts in white cheese samples ranged from 1.9 × 10* to 2.4 × 105 most probable number per g and 3.2 × 102 to 1.2 × 105 most probable number per g, respectively. It was possible to identify Aeromonas caviae (58.9%), Aeromonas hydrophila (12.8%), and Aeromonas schubertii (2.5%) among the cultures isolated from pasteurized milk samples. Twenty-five percent of the strains could only be classified as Aeromonas spp. In white cheese samples, unclassified strains were the most frequent isolates (61.5%) followed by A. hydrophila (26.9%), A. caviae (7.6%) and Aeromonas sobria (3.8%). Only strains of A. hydrophila and A. sobria showed high rate of positive results when tested for the production of hemolysin, cytotoxin, and staphylolytic activity. Heat-stable enterotoxin and autoagglutination test did not correlate as virulence factors. The presence of Aeromonas species in refrigerated food samples suggests that this microorganism could be a potential foodborne pathogen, and dairy products may represent an important vehicle of its transmission.
Aeromonas spp. are associated with intestinal and extra-intestinal infections. However, the virulence factors of A. caviae remain, for the most part, poorly known. This study examined the interactions involved in the adherence of A. caviae isolates Ae56, Ae391 and Ae398 to HEp-2 cells. All strains expressed high levels of aggregative adherence. Maximum adhesion occurred with bacteria grown at 228C, but transmission electron microscopy did not reveal the presence of ®mbrial structures on the bacterial cell surface. Outer-membrane proteins (OMPs) extracted from isolate Ae398, grown at 228C and 378C, showed similar SDS-PAGE protein pro®les. Most proteins were < 60 kDa. A major 43-kDa protein was seen only in the boiled OMP extract. The biotinylated 43-kDa protein bound speci®cally to HEp-2 cells. Microbeads coated with the 43-kDa protein were also adherent to HEp-2 cells, and anti-43-kDa protein antibody blocked adherence of 43-kDa protein-coated latex beads. These data suggest that the 43-kDa OMP functions as an adhesin in A. caviae.
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