Vibrio cholerae has been diagnosed as the causative agent of several wound and ear infections in Austria since the beginning of this century (Huhulescu et al 2007). Interestingly, all of the domestically acquired V. cholerae infections were linked to recreational activities in the Eastern Austrian/Western Hungarian lake Neusiedler See/Fertö To. This lake has a moderate salinity (0.2-0.4%), and alkaline pH (8.5 – 8.9) and due to its shallowness (1.8 m max. depth) it can warm up to 30°C surface water temperature during summer, providing optimal growth conditions for V. cholerae (Kirschner et al 2008). There are two dominating crustacean zooplankton species present in high concentrations in the lake, one of which could be shown to promote the proliferation of V. cholerae (Kirschner et al 2011). Moreover the lake is highly turbid, due to wind induced sediment resuspension and is covered by 50% with reed (Phragmites australis). Large parts of the lake and other smaller alkaline lakes nearby (“Lacken”) are integrated into the national park Neusiedler See-Seewinkel, the largest bird protective area in Middle Europe.
Since 2009, a comprehensive project is being conducted, that studies the ecology, potential pathogenicity and genetic diversity of V. cholerae in the lake Neusiedler See. As a prerequisite new, culture independent methods for quantification of V. cholerae in challenging environmental water samples (high background, high concentrations of interfering substances) were developed:
- a cell-based method using a combination of enhanced fluorescence in situ hybridization and solid phase cytometry (CARD-FISH/SPC) (Schauer et al 2012).
- a quantitative real-time multiplex PCR using an internal inhibition control and targeting both total and toxigenic V. cholerae (Bliem et al 2015).
Both methods were applied on a large scale to the lake (5 stations) and 3 selected alkaline lakes over a 2 year cycle, with first results on the ecology and risk assessment being published recently (Schauer et al 2015).
A key topic of the project is to analyse the genetic diversity of the V. cholerae strains in the lake and the question what is driving this diversity. For this, Multi-locus Sequence Analysis (MLSA) was applied to > 500 strains isolated from different locations in the lake and compared to strains isolated from six other European countries. First results indicated a tremendous diversity of strains, mainly in the reed-covered part of the lake, and the potential Pan-European transport of strains via birds (Pretzer et al, in prep).
It can be assumed that V. cholerae (and other Vibrios) may play a role as human or animal pathogens in many Eastern European countries (e.g. Romania, Bulgaria, Poland), but due to financial constraints research and reporting on this topic from those countries is limited. It is thus an additional major task of our working group to integrate experts from Eastern European countries into the Vibrionet consortium in the next years.
Schauer S, Jakwerth S, Bliem R, Baudart J, Lebaron P, Huhulescu S, Kundi M, Herzig A, Farnleitner AH, Sommer R, Kirschner A (2015) Dynamics of Vibrio cholerae abundance in Austrian saline lakes, assessed with quantitative solid-phase cytometry. Environmental Microbiology 17: (doi: 10.1111/1462-2920.12861)
Bliem R, Schauer S, Plicka H, Obwaller A, Sommer R, Steinrigl A, Alam M, Reischer GH, Farnleitner AH, Kirschner A (2015) A Novel Triplex Quantitative PCR Strategy for Quantification of Toxigenic and Nontoxigenic Vibrio cholerae in Aquatic Environments. Appl Environ Microbiol 81(9): 3077-3085
Schauer S, R Sommer, AH Farnleitner and AKT Kirschner (2012) Rapid and Sensitive Quantification of Vibrio cholerae and Vibrio mimicus Cells in Water Samples by Use of Catalyzed Reporter Deposition Fluorescence In Situ Hybridization Combined with Solid-Phase Cytometry. Applied and Environmental Microbiology (78) 20: 7369-7375
Kirschner AKT, S Schauer, B Steinberger, I Wilhartitz, CJ Grim, A Huq, RR Colwell, A Herzig and R Sommer (2011) Interaction of Vibrio cholerae non-O1/non-O139 with Copepods, Cladocerans and Competing Bacteria in the Large Alkaline Lake Neusiedler See, Austria. Microbial Ecology 61: 496-506
Kirschner AKT, J Schlesinger, AH Farnleitner, R Hornek, B Süß, B Golda, A Herzig and B Reitner (2008) Rapid growth of planktonic Vibrio cholerae non-O1/non-O139 strains in a large alkaline lake in Austria: Dependence on temperature and dissolved organic carbon quality. Applied and Environmental Microbiology 74: 2004-2015
Huhulescu S, Indra A, Feierl G, Stoeger A, Ruppitsch W, Sarkar B, and Allerberger F (2007) Occurrence of Vibrio cholerae serogroups other than O1 and O139 in Austria. Wien Klin Wochenschr 119: 235-241.