title: Population diversity of Listeria monocytogenes in quargel (acid curd cheese) lots recalled during the multinational listeriosis outbreak 2009/2010.
abstract: It has been possible to determine the genotype diversity of Listeria monocytogenes in the actual cheese lots of acid curd cheese that caused a multinational outbreak between 2009 and 2010. Following product recall in January 2010 all lots were investigated. A total of 422 L. monocytogenes isolates were characterized by genotyping. In a first approach the PCR serogroups were defined by multiplex-PCR assays. Subsequently, the isolates were subtyped by pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). Sequence types were assigned by submitting the DNA sequences to the Listeria MLST database at the Institute Pasteur. The serogroup PCR resulted in a homogeneous 1/2a - 3a (genetic linage II) cluster. The generated PFGE patterns divided the strains into two clusters (type 1 and 2) diverging at a homogeneity level of 74%. PFGE-type 2 was predominant, accounting for 98.3% (n = 415/422) of the isolates and was isolated during the whole period of acid curd cheese processing (01.12.2009-13.01.2010). 1.7% of all tested L. monocytogenes isolates (n = 7/422) belonged to PFGE-type 1 and were isolated from 28% of all cheese lots (n = 5/18) produced between the time span of 08.12.2009 to 13.01.2010. Furthermore, PFGE-type 1 and 2 showed the same PFGE patterns as the human outbreak strains (clone 1 and clone 2).
authors.affiliation: Institute of Milk Hygiene, Milk Technology and Food Science, Department of Veterinary Public Health and Food Science, University of Veterinary Medicine, Veterinärplatz 1, 1210 Vienna, Austria. Electronic address: dagmar.schoder@vetmeduni.ac.at.
authors.forename: D
authors.initials: D
authors.lastname: Schoder
authors.affiliation: Institute of Milk Hygiene, Milk Technology and Food Science, Department of Veterinary Public Health and Food Science, University of Veterinary Medicine, Veterinärplatz 1, 1210 Vienna, Austria.
authors.forename: B
authors.initials: B
authors.lastname: Stessl
authors.affiliation: Institute of Milk Hygiene, Milk Technology and Food Science, Department of Veterinary Public Health and Food Science, University of Veterinary Medicine, Veterinärplatz 1, 1210 Vienna, Austria.
authors.forename: K
authors.initials: K
authors.lastname: Szakmary-Brändle
authors.affiliation: Christian Doppler Laboratory for Molecular Food Analysis, University of Veterinary Medicine, Veterinärplatz 1, 1210 Vienna, Austria.
authors.forename: P
authors.initials: P
authors.lastname: Rossmanith
authors.affiliation: Institute of Milk Hygiene, Milk Technology and Food Science, Department of Veterinary Public Health and Food Science, University of Veterinary Medicine, Veterinärplatz 1, 1210 Vienna, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Wagner
mesh_terms: D001317:Austria / Q000453:epidemiology; D044822:Biodiversity; D002611:Cheese / Q000382:microbiology*; D004196:Disease Outbreaks; D005506:Food Contamination / Q000032:analysis*; D005838:Genotype; D006801:Humans; D008089:Listeria monocytogenes / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D008088:Listeriosis / Q000453:epidemiology / Q000382:microbiology*; D057051:Product Recalls and Withdrawals
keywords: Cheese; Listeria monocytogenes; Outbreak; Population diversity; Quargel