Whole genome sequencing as a tool to investigate a cluster of seven cases of listeriosis in Austria and Germany, 2011-2013.
A cluster of seven human cases of listeriosis occurred in Austria and in Germany between April 2011 and July 2013. The Listeria monocytogenes serovar (SV) 1/2b isolates shared pulsed-field gel electrophoresis (PFGE) and fluorescent amplified fragment length polymorphism (fAFLP) patterns indistinguishable from those from five food producers. The seven human isolates, a control strain with a different PFGE/fAFLP profile and ten food isolates were subjected to whole genome sequencing (WGS) in a blinded fashion. A gene-by-gene comparison (multilocus sequence typing (MLST)+) was performed, and the resulting whole genome allelic profiles were compared using SeqSphere(+) software version 1.0. On analysis of 2298 genes, the four human outbreak isolates from 2012 to 2013 had different alleles at ≤6 genes, i.e. differed by ≤6 genes from each other; the dendrogram placed these isolates in between five Austrian unaged soft cheese isolates from producer A (≤19-gene difference from the human cluster) and two Austrian ready-to-eat meat isolates from producer B (≤8-gene difference from the human cluster). Both food products appeared on grocery bills prospectively collected by these outbreak cases after hospital discharge. Epidemiological results on food consumption and MLST+ clearly separated the three cases in 2011 from the four 2012-2013 outbreak cases (≥48 different genes). We showed that WGS is capable of discriminating L. monocytogenes SV1/2b clones not distinguishable by PFGE and fAFLP. The listeriosis outbreak described clearly underlines the potential of sequence-based typing methods to offer enhanced resolution and comparability of typing systems for public health applications.
German-Austrian Binational Listeria Advisory Laboratory, Vienna, Austria.
D
D
Schmid
F
F
Allerberger
S
S
Huhulescu
A
A
Pietzka
C
C
Amar
S
S
Kleta
R
R
Prager
K
K
Preußel
E
E
Aichinger
A
A
Mellmann
D000368:Aged; D000369:Aged, 80 and over; D000483:Alleles; D001317:Austria / Q000453:epidemiology; D015373:Bacterial Typing Techniques / Q000379:methods*; D002611:Cheese / Q000382:microbiology; D004196:Disease Outbreaks; D005260:Female; D005516:Food Microbiology; D016680:Genome, Bacterial; D005858:Germany / Q000453:epidemiology; D006801:Humans; D007231:Infant, Newborn; D008089:Listeria monocytogenes / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D008088:Listeriosis / Q000453:epidemiology* / Q000382:microbiology*; D008461:Meat Products / Q000382:microbiology; D058885:Multilocus Sequence Typing; D065288:Serogroup; D012984:Software
Foodborne infections; Listeria; listeriosis; outbreaks; typing; whole genome sequencing; zoonoses