Preliminary studies on pathologic conditions in the testis, epididymis, and the accessory sex glands of cattle have demonstrated that vesiculitis is the most common inflammatory condition in the genitals of Danish bulls. 5 Occasionally, this condition has an acute onset that produces clinical signs and then becomes a chronic disease. 18 Four-polled Hereford bulls approximatedly 1 year of age (1-2 years old) from a farm in southern Brazil were examined by rectal palpation. During this procedure, enlargement of the seminal vesicles was detected. The animals were slaughtered, and samples were collected for bacteriologic and histopathologic examination. Macroscopically, the seminal vesicles were enlarged and firm and contained foci of yellow exudate. The histopathologic examination revealed interstitial seminal vesiculitis with areas of lymphocytic and plasma cell infiltration surrounding alveoli containing suppurative exudate. Varying degrees of fibrosis were found in the glands. Samples of a selected group of organs were available for sectioning.For bacteriologic examination, fragments of seminal vesicles were inoculated asseptically onto 5% (w/v) sheep blood agar and incubated aerobically at 37 C for 24-48 hours. Microorganisms from all seminal vesicles were isolated in pure culture. The colonies were beta-hemolytic, smooth, small, and white and had characteristics of the genus Aeromonas (gram-negative rods, oxidase positive, fermentative metabolism,

The genus Aeromonas comprises Gram negative rods found mainly in aquatical environments that may infect humans and animals (JM Janda 1991 Clin Microbiol Rev 4: 397-410). In humans, some Aeromonas species have been associated with intestinal and extraintestinal infections and enterotoxins, cytotoxins as well as invasive mechanisms have been incriminated in the development of illness in the host (Janda loc. cit.). Bacteriocin-like substances (BLS) are protein compounds produced by some bacteria (G Ivanovics 1962 Bacteriol Rev 26: 108-118) showing antagonic activity against their own species (isoinhibitory activity -IA) or other non-related species (heteroinhibitory activity -HA). The use of the expression BLS is recommended to nominate bacterial products showing antagonic activity though not characterized (K Sandhu et al. 1983 J Clin Microbiol 17: 511-515). These substances have been widespread utilized in epidemiological studies as specific marker properties of bacteria, in the regulation of population dynamics in bacterial ecosystems and clinical treatment (V Fantinato & F Zelante 1991 Rev Microbiol 22: 49-51). As BLS have not been currently described in Aeromonas species, the purpose of this study was to investigate their production in strains isolated from animal, clinical and environmental sources.The assays for the production of BLS were performed according to Sandhu et al. (loc. cit.). The strains used as BLS producers and BLS indicators are listed in Table. Our results showed that among 32 Aeromonas strains, the BLS could be only demonstrated in a strain of A. hydrophila isolated from a water tank containing alligators. This strain demonstrated heteroinhibitory activity against four Staphylococcus aureus strains (one ATCC 6538 and three methicillin-resistant -MRSA). The heteroinhibitory activity was demonstrated after an incubation of 48 hr at 37°C and not at 25°C, conditions also observed for the BLS production in Serratia, Pseudomonas, Leuconostoc and Enterococcus strains (JD Foulds & D Shemin 1969