Aeromonas
Aeromonas
Aeromonas hydrophila
Aeromonas is a genus of Gram-negative, facultative anaerobic, rod-shaped bacteria that morphologically resembles members of the family Enterobacteriaceae. Most of the 14 described species have been associated with human diseases. The most important pathogens are A. hydrophila, A. caviae, and A. veronii biovar sobria. The organisms are ubiquitous in fresh and brackish water.They group with the gamma subclass of the Proteobacteria.Two major diseases associated with Aeromonas are gastroenteritis and wound infections, with or without bacteremia. Gastroenteritis typically occurs after the ingestion of contaminated water or food, whereas wound infections result from exposure to contaminated water. In it's most severe form, Aeromonas spp. can cause necrotizing fasciitis, which is life threatening, usually requiring treatment with antibiotics and even amputation. Although some potential virulence factors (e.g. endotoxins, hemolysins, enterotoxins, adherence factors) have been identified, their precise roles are unknown. Aeromonas species cause:
opportunistic systemic disease in immunocompromised patients
diarrheal disease in otherwise healthy individuals
wound infections
Antimicrobial therapy
Aeromonas species are resistant to penicillins, most cephalosporins, and erythromycin. Ciprofloxacin is consistently active against their strains in the U.S. and Europe, but resistant cases have been reported in Asia.
Plesiomonas shigelloides
Plesiomonas shigelloidesPlesiomonas shigelloides is a species of bacteria. It is a Gram-negative, rod-shaped bacterium which has been isolated from freshwater, freshwater fish, and shellfish and from many types of animals including cattle, goats, swine, cats, dogs, monkeys, snakes, and toads.
Infections from this organism cause gastroenteritis, followed by septicemia in immune deficient patients. It is placed among the Enterobacteriaceae. Some Plesiomonas strains share antigens with Shigella sonnei, and cross-reactions with Shigella antisera occur. Plesiomonas can be distinguished from Shigella in diarrheal stools by an oxidase test: Plesiomonas is oxidase positive and Shigella is oxidase negative. Plesiomonas is negative for DNAse; this and other biochemical tests distinguish it from Aeromonas sp.