Preliminary identification of Salmonella serovar Enteritidis by MALDITOFMS

Abstract number: P1787

Sagel U., Kornschober C., Indra A., Blaschitz M., Springer B., Allerberger F.

Objectives: Human infections by Salmonella enterica subsp. enterica serovar Enteritidis (S. Enteritidis) are often due to the consumption of contaminated eggs or egg-products. Preliminary identification of this serovar may provide public health officers with a rapid indication of the source of infection. As many routine laboratories send their Salmonella isolates to reference laboratories for serotyping, definitive reports about the serovar may be delayed. We studied the applicability of matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI TOF MS) as a tool for rapid identification of S. Enteritidis.

Methods: From the most common serovars identified by the Austrian Reference Centre for Salmonella we tested 51 isolates (S. Enteritidis: 10, S. Typhimurium: 10, S. Infantis: 10, S. Hadar: 10, S. Saintpaul: 6, S. Agona: 5) using the mass spectrometer microflex™ LT MALDI-TOF (Bruker Daltonics, Bremen, Germany). Isolates were prepared for testing both by using a specific extraction method and by using the more convenient smear method. Using the MALDI Biotyper 2.0 software we analysed the mass spectra for peak differences between serovars and exported the peak list to STATA 10.1 (STATA Corp, College Station, TX, USA) for further statistical analysis. All m/z-values were rounded to±5, m/z-values of <600 were set as 600.

Results: All 51 isolates were correctly identified as Salmonella spp. using the MALDI Biotyper Automation Wizard with both preparation methods. S. Enteriditis often revealed peaks at about m/z 3020 and 6040 while other serovars often showed peaks at m/z 3005 and 6010. Thereof we derived the index = intensity at m/z 3020/intensity at m/z 3005 + intensity at m/z 6040/intensity at m/z 6010 Index values >2.0 point at S. Enteritidis, values leqslant R: less-than-or-eq, slant2.0 point to other serovars. Setting the threshold to 2.5, sensitivity and specificity were 90% (9/10) and 100% (41/41) if isolates were prepared according to the extraction method, and 70% (7/10) and 100% (41/41) for the smear method, respectively.

Conclusion: Preliminary testing for S. Enteritidis using MALDI TOF MS appears to be feasible for routine laboratories. Our diagnostical approach needs to be evaluated using more reference strains before application on a regular basis.

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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