Application of MALDI-TOF MS for environmental Vibrio surveillance programs

Application of MALDI-TOF MS for environmental Vibrio surveillance programs G. Gerdts1, R. Erler1, and A. Wichels1 1. Alfred Wegener Institute for Polar and Marine Research, Shelf Sea System Ecology, Kurpromenade 201, 27498 Helgoland, Germany Three mesophilic Vibrio species pose a serious threat for humans: V. cholerae, V. parahaemolyticus and V. vulnificus. Due to Global Warming an increase of Vibrio infections is expected in Northern Europe. Hence a fast and cost-effective approach for the identification of those potentially pathogenic strains is needed to evaluate this risk. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) fulfills these requirements and is therefore a promising analytical tool for environmental surveillance programs. Creation of a MALDI-TOF MS database filled with 1000 Vibrio reference spectra was crutial for this application. These isolates were characterized simultaneously with approved rpoB sequence data analysis. A comparative examination is getting performed to check the validity of MALDI-TOF identifications and the distinctness for closely related Vibrio species. First results reveal that species-specific groups found by the rpoB sequence analysis are equal to MALDI-TOF MS cluster. Congeneric species like V. vulnificus/V. navarrensis and V. cholerae/V. mimicus respectively can clearly be distinguished from each other. And in case of V. alginolyticus and V. vulnificus it was even possible to divide them into intraspecific groups. The first environmental application took place on a research cruise in July 2012. Agar plates were incubated with environmental samples like water or plankton. About 2100 single colonies were processed to obtain MALDI-TOF MS samples. Using the constructed reference database allows the species identification of these colonies which gives rise to conclusions about the species composition of Vibrio populations in the North and Baltic Sea. First results show high abundances of zoonotic vibrios like V. fluvialis, V. anguillarum and V. diazotrophicus. In contrast, putative human pathogenic vibrios were found rarely. However, MALDI-TOF MS identified the species of over 90 per cent of these environmental colonies. Hence, this technique can be a valuable tool in future surveillance programs