factors, including piliation, cytotoxin production, protease, 

 lipase, enterotoxin production and hemolysin. The more virulent 

 environmental isolates of Aeromonas ( LD50 for mice less than 10^ 

 cfu), generally possessed these virulence factors, whereas in the 

 less virulent isolates ( LD50 for mice greater than 10' cfu), 

 these were generally lacking (Daily et al . , 1981b). 



Aeromonas sp. have been reported to be associated with a 

 variety of clinical manifestations: septicemia ( Ketover et al., 

 1973); meningitis ( Quadri et al . , 1976); endocarditis (Davis et 

 al . , 1978); wound infection (Hanson et al., 1977); and acute 

 diarrheal disease (Ljungh et al., 1977). Moreover, infections 

 are frequently acquired as a result of exposure to waters 

 harboring Aeromonas species (Fulghum et al., 1978; Hanson et al., 

 1977; Joseph et al., 1979). Often Aeromonas species are 

 considered to be secondary opportunistic pathogens. However, 

 there are documented cases in which Aeromonas spp. were isolated 

 as the primary pathogen in a human infection. Joseph et al., 

 (1979), cite a case in which two species of Aeromonas , A. sobria 

 and A. hydrophila , were primary pathogens isolated from a leg 

 wound sustained by a diver conducting operations in the Anacostia 

 River. Both the A. sobria and A. hydrophila were beta hemolytic 

 for sheep erythrocytes and cytotoxic for Y-l adrenal cells. 

 Also, whole cells of A. sobria caused fluid accumulation in 

 ligated rabbit ileal loops. 



A follow-up survey at the site where the diver acquired the 

 infection yielded 193 Aeromonas isolates, of which 25% were 

 cytotoxic (Joseph et al . , 1979; Seidler et al., 1979). In 

 addition, Seidler et al. (1979) reported that biotypes and 

 antibiograms of Aeromonas spp. from the Anacostia River were 

 similar or identical to those which infected the diver's leg 

 wound. 



In a similar case, a previously healthy young man acquired 

 cellulitis after sustaining a laceration while diving in a 

 shallow water lake in the vicinity of an agricultural drainage 

 ditch (Hanson et al., 1977). A. hydrophila was isolated in large 

 numbers from the wound and was also shown to be the dominant 

 bacterial species in the lake where the injury occurred. Fecal 

 coliform counts along the shoreline of the lake were in the 

 marginally acceptable range and, therefore, wound contamination 

 by A. hydrophila can occur in water with acceptable numbers of 

 pollution indicator organisms. 



Legionella 



L egionella was first described as an important pathogen in 

 1977, following the L. pneumophila outbreak among the 

 legionnaires attending a convention in Philadelphia. Legionella 

 are nutritionally fastidious organisms with an active amino acid 

 metabolism. Morphologically they are indistinguishable from 



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