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Applied and Environmental Microbiology, March 2007, p. 1444-1451, Vol. 73, No. 5
0099-2240/07/$08.00+0 doi:10.1128/AEM.01901-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
Persistence, Transmission, and Virulence Characteristics of Aeromonas Strains in a Duckweed Aquaculture-Based Hospital Sewage Water Recycling Plant in Bangladesh
Mokhlasur Rahman,1,2*
Geert Huys,3
Motiur Rahman,4
M. John Albert,4,5
Inger Kühn,1 and
Roland Möllby1
Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Box-280, SE-17177 Stockholm, Sweden,1 Department of Natural Science, Södertörns högskola University College, Alfred Nobles alle 7, SE-14189 Huddinge, Stockholm, Sweden,2 Laboratory of Microbiology, Faculty of Sciences, Ghent University, B-9000 Gent, Belgium,3 International Centre for Diarrhoeal Diseases Research, Dhaka 1000, Bangladesh,4 Department of Microbiology, Faculty of Medicine, Kuwait University, Kuwait City, Kuwait5
Received 9 August 2006/ Accepted 15 December 2006
The persistence and transmission of Aeromonas in a duckweed aquaculture-based hospital sewage water treatment plant in Bangladesh was studied. A total of 670 samples from different sites of the hospital sewage water treatment plant, from feces of hospitalized children suffering from diarrhea, from environmental control ponds, and from feces of healthy humans were collected over a period of three years. In total, 1,315 presumptive Aeromonas isolates were biochemically typed by the PhenePlate rapid screening system (PhP-AE). A selection of 90 representative isolates was further analyzed with PhenePlate (PhP) extended typing (PhP-48), fatty acid methyl ester analysis, and amplified fragment length polymorphism (AFLP) fingerprinting. In addition, the prevalence of the putative virulence factors hemolysin and cytotoxin and the presence of the cytolytic enterotoxin gene (AHCYTOEN) were analyzed. Aeromonas was found at all sites of the treatment plant, in 40% of the samples from environmental control ponds, in 8.5% of the samples from hospitalized children suffering from diarrhea, and in 3.5% of samples from healthy humans. A significantly high number of Aeromonas bacteria was found in duckweed, which indicates that duckweed may serve as a reservoir for these bacteria. PhP-AE typing allowed identification of more than 192 distinct PhP types, of which 18 major PhP types (MTs) were found in multiple sites and during several occasions. AFLP fingerprinting revealed the prevalence of genotypically indistinguishable Aeromonas isolates among certain PhP MTs recovered from different sampling occasions and/or at multiple sites. Hemolytic and cytotoxic activities were observed in 43% of the tested strains, whereas 29% possessed the cytolytic enterotoxin gene AHCYTOEN. Collectively, two specific MTs associated with diarrhea were shown to exhibit high cytotoxicity. Furthermore, all tested isolates of these major types were positive for the cytolytic enterotoxin gene. In conclusion, our data indicate that certain phenotypically and genotypically stable clonal lineages of Aeromonas have persisted in the treatment system for a prolonged period and might spread from the hospitalized children suffering from diarrhea to fish produced for human consumption through the sewage water treatment system.
* Corresponding author. Mailing address: Department of Natural Science, Södertörns högskola University College, Alfred Nobels alle 7, Flemingsberg, SE-14189 Huddinge, Stockholm, Sweden. Phone: 46 8 6084756. Fax: 46 8 6084510. E-mail: mokhlasur.rahman{at}sh.se.
Published ahead of print on 28 December 2006.
Applied and Environmental Microbiology, March 2007, p. 1444-1451, Vol. 73, No. 5
0099-2240/07/$08.00+0 doi:10.1128/AEM.01901-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
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