Aeromonas Introduction Species of Aeromonas are Gram-negative, non-spore-forming, rod-shaped, facultatively anaerobic bacteria that occur ubiquitously and autochthonously in aquatic environments. The genus Aeromonas was part of the family Vibrionaceae until the mid-1980s when phylogenetic evidence from molecular studies supported separating out the genus as the family Aeromonadaceae. The species are principally associated with gastrointestinal infection in human. The present study was attempted to isolate and identify toxigenic Aeromonas spp. from environmental samples by conventional biochemical and molecular method in the Enteric and Food Microbiology Laboratory of International Centre for Diarrohoeal Disease Research, Bangladesh (ICDDR,B).A total six numbers (n=6) of isolates were randomly selected in this study based on their initial biochemical identification. These isolates were then subjected to extensive phenotypic, antibiogram and molecular characterization by polymerase chain reaction (PCR) for the detection of aerolysin gene (aerA). The antibotic susceptibility patterns of the isolates were determined against five commonly used antibiotics such as Ciprofloxacin, Erythromycin, Ampicillin, Gentamicin, Trimethoprim sulphamethoxazole, Furazolidone. All of the isolates were found to be resistant to Ampicillin (Amp) and showed sensitivity to other antibiotics. The aerolysin genes of Aeromonas spp. have frequently been targeted in molecular PCR methods. The result of which indicate the presence of virulence gene (aerA) in only two isolates. Aerolysin is a class of pore-forming cytotoxins that disrupt cell membranes. It is secreted as a 52-kDa protein called proaerolysin because it is inactive until it is proteolytically activated. Finally, the toxigenic property of the isolated strains was determined by molecular method. Thus, the detection of aerA gene by PCR suggest that the isolated Aeromonas strains was toxigenic
Discussion Aeromonas species are important pathogens of human. They are ubiquitous in the environment and naturally occurring inhabitants of aquatic environments, namely fresh waters, marine waters, and estuarine waters. However, Aeromonas also have been isolated from fish, shellfish, meats, dairy products, and fresh vegetables. Aeromonas spp. are associated with life threatening diseases of humans, such as bacteremia (Ko et al.,2000), meningitis (Lin and Cheng 1998), septicemia (Tabata et al., 1999), myonecrosis (Balasco et al., 1995), lung abscess (Hur et al., 1995), pulmonary infection (Leclerc et al., 1990) etc. It is one of the important agents associated with diarrhea. Aeromonas cause acute diarrheal disease of short duration or chronic loose stools in children, the elderly, or the immunocompromised. Aeromonas spp. associated diarrhea is usually mild and self-limiting (Holmberg et al.,1984). However, cholera like watery diarrhea (Champsaur et al., 1982) as well as dysentery-like syndrome (Rahman et al., 1980) is associated with aeromonad infection. Some Aeromonas spp. are opportunistic pathogens of humans, causing a wide variety of extra-intestinal infections and occasionally associated with gastrointestinal disease. An increasing number of epidemiological studies indicate that Aeromonas spp.may