| Summary: | <p>Abstract</p> <p>Background</p> <p>The <it>Cronobacter </it>genus (<it>Enterobacter sakazakii</it>) has come to prominence due to its association with infant infections, and the ingestion of contaminated reconstituted infant formula. <it>C. sakazakii </it>and <it>C. malonaticus </it>are closely related, and are defined according their biotype. Due to the ubiquitous nature of the organism, and the high severity of infection for the immunocompromised, a multilocus sequence typing (MLST) scheme has been developed for the fast and reliable identification and discrimination of <it>C. sakazakii </it>and <it>C. malonaticus </it>strains. It was applied to 60 strains of <it>C. sakazakii </it>and 16 strains of <it>C. malonaticus</it>, including the index strains used to define the biotypes. The strains were from clinical and non-clinical sources between 1951 and 2008 in USA, Canada, Europe, New Zealand and the Far East.</p> <p>Results</p> <p>This scheme uses 7 loci; <it>atp</it>D, <it>fus</it>A, <it>gln</it>S, <it>glt</it>B, <it>gyr</it>B, <it>inf</it>B, and <it>pps</it>. There were 12 sequence types (ST) identified in <it>C. sakazakii</it>, and 3 in <it>C. malonaticus</it>. A third (22/60) of <it>C. sakazakii </it>strains were in ST4, which had almost equal numbers of clinical and infant formula isolates from 1951 to 2008. ST8 may represent a particularly virulent grouping of <it>C. sakazakii </it>as 7/8 strains were clinical in origin which had been isolated between 1977 - 2006, from four countries. <it>C. malonaticus </it>divided into three STs. The previous <it>Cronobacter </it>biotyping scheme did not clearly correspond with STs nor with species.</p> <p>Conclusion</p> <p>In conclusion, MLST is a more robust means of identifying and discriminating between <it>C. sakazakii </it>and <it>C. malonaticus </it>than biotyping. The MLST database for these organisms is available online at <url>http://pubmlst.org/cronobacter/</url>.</p>
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