Molecular Detection, Quantification, and Toxigenicity Profiling of Aeromonas spp. in Source- and Drinking-Water



Boakai K Robertson*, 1, Carol Harden 1, Suresh B Selvaraju 2, Suman Pradhan 2, Jagjit S Yadav*
1 Department of Biological Sciences, Alabama State University, Montgomery, AL 36101.
2 Department of Environmental Health, University of Cincinnati College of Medicine, Cincinnati OH 45267-0056.


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© Robertson et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to these authors at the Microbial Pathogenesis Laboratory, Dept. of Environmental Health, University of Cincinnati Medical Center, 3223 Eden Avenue, Cincinnati OH 45267-0056; Tel: (513)558-4806; Fax: (513) 558-4397; E-mail: jagjit.yadav@uc.edu Department of Biological Sciences, Alabama State University, Montgomery, AL 36101-0271, USA. Tel: +334-229-4423; Fax: +334-229-1007; E-mail: brobertson@alasu.edu


Abstract

Aeromonas is ubiquitous in aquatic environments and has been associated with a number of extra-gastrointestinal and gastrointestinal illnesses. This warrants monitoring of raw and processed water sources for pathogenic and toxigenic species of this human pathogen. In this study, a total of 17 different water samples [9 raw and 8 treated samples including 4 basin water (partial sand filtration) and 4 finished water samples] were screened for Aeromonas using selective culturing and a genus-specific real-time quantitative PCR assay. The selective culturing yielded Aeromonas counts ranging 0 – 2 x 103CFU/ml and 15 Aeromonas isolates from both raw and treated water samples. The qPCR analysis indicated presence of a considerable nonculturable population (3.4 x 101 – 2.4 x 104 cells/ml) of Aeromonas in drinking water samples. Virulence potential of the Aeromonas isolates was assessed by multiplex/singleplex PCR-based profiling of the hemolysin and enterotoxin genes viz cytotoxic heat-labile enterotoxin (act), heat-labile cytotonic enterotoxin (alt), heat-stable cytotonic enterotoxin (ast), and aerolysin (aerA) genes. The water isolates yielded five distinct toxigenicity profiles, viz. act, alt, act+alt, aerA+alt, and aerA+alt+act. The alt gene showed the highest frequency of occurrence (40%), followed by the aerA (20%), act (13%), and ast (0%) genes. Taken together, the study demonstrated the occurrence of a considerable population of nonculturable Aeromonads in water and prevalence of toxigenic Aeromonas spp. potentially pathogenic to humans. This emphasizes the importance of routine monitoring of both source and drinking water for this human pathogen and role of the developed molecular approaches in improving the Aeromonas monitoring scheme for water.

Keywords: Aeromonas, drinking water, real-time qPCR, singleplex and multiplex PCR, virulence genes.