Background: Invasive listeriosis is a rare, life-threatening foodborne disease. Molecular subtyping and enhanced surveillance identified a cluster of possibly related listeriosis cases from 2006 to 2010 in the Lombardy Region of Northern Italy. Particularly, this major Pulsed-Field Gel Electrophoresis (PFGE) cluster (named 11) grouped 31 isolates, belonging to serotype 1/2a and Sequence Type (ST)38 as defined by Multi-Locus Sequence Typing (MLST). Our study expanded the previous investigation to include cases from 2011 to 2014 and to perform Multi-Virulence-Locus Sequence Typing (MVLST) on isolates in Cluster11/ST38 to better understand their epidemiology and possibly identify a common source outbreak clone. Materials and Methods: All collected human Listeria monocytogenes isolates were serotyped and subtyped with PFGE and MLST. MVLST was performed on all isolates in Cluster11/ST38. Demographic, clinical and microbiological data were collected using a standardized report form. Results: Of 338 L. monocytogenes human isolates collected during the period, 43 (12.7%) belonged to Cluster11/ST38. While this cluster was observed sporadically in 2006, 2008 and 2014 (2 cases/year each), and in 2013 (n=1), cases due to this cluster peaked in 2009, 2010 and 2011 (n=10, 16 and 10 cases respectively). Cases occurred in nine out of twelve Lombardy provinces, with the highest frequency observed in Bergamo and Milan. The 43 isolates in Cluster11/ST38 were split by MVLST into two Virulence Types (VTs), VT80 (n=12) and VT104 (n=31). VT104 cases were concentrated between 2009 and 2011 and in Bergamo and Milan provinces. For all Cluster11/ST38 cases, an epidemiological investigation was performed and in one case, a matching VT104 L. monocytogenes clone was isolated from a cheese sample (Taleggio) retrieved from a patient’s refrigerator. Based on both molecular and epidemiologic data, this cheese was identified as the implicated source. Conclusions: Our findings revealed a major listeriosis outbreak in Northern Italy linked to cheese in 2009-2011, which was undetected by local health authorities. Our study showed that integrating subtyping methods such as PFGE, MLST and MVLST with conventional epidemiologic investigations can help identify the source of outbreak clones of L. monocytogenes. Such information is useful in both terminating ongoing outbreaks and preventing future ones from occurring.

Molecular typing and epidemiological surveillance identified a major listeriosis Outbreak Clone linked to soft cheese in Northern Italy from 2009 to 2011 / E. Amato, V. Filipello, S. Lomonaco, A. Parisi, N. Losio, M. Gori, P. Huedo, M. Pontello, S. Knabel. ((Intervento presentato al 19. convegno Problems of Listeriosis tenutosi a Parigi nel 2016.

Molecular typing and epidemiological surveillance identified a major listeriosis Outbreak Clone linked to soft cheese in Northern Italy from 2009 to 2011

E. Amato
Primo
;
M. Gori;M. Pontello
Penultimo
;
2016

Abstract

Background: Invasive listeriosis is a rare, life-threatening foodborne disease. Molecular subtyping and enhanced surveillance identified a cluster of possibly related listeriosis cases from 2006 to 2010 in the Lombardy Region of Northern Italy. Particularly, this major Pulsed-Field Gel Electrophoresis (PFGE) cluster (named 11) grouped 31 isolates, belonging to serotype 1/2a and Sequence Type (ST)38 as defined by Multi-Locus Sequence Typing (MLST). Our study expanded the previous investigation to include cases from 2011 to 2014 and to perform Multi-Virulence-Locus Sequence Typing (MVLST) on isolates in Cluster11/ST38 to better understand their epidemiology and possibly identify a common source outbreak clone. Materials and Methods: All collected human Listeria monocytogenes isolates were serotyped and subtyped with PFGE and MLST. MVLST was performed on all isolates in Cluster11/ST38. Demographic, clinical and microbiological data were collected using a standardized report form. Results: Of 338 L. monocytogenes human isolates collected during the period, 43 (12.7%) belonged to Cluster11/ST38. While this cluster was observed sporadically in 2006, 2008 and 2014 (2 cases/year each), and in 2013 (n=1), cases due to this cluster peaked in 2009, 2010 and 2011 (n=10, 16 and 10 cases respectively). Cases occurred in nine out of twelve Lombardy provinces, with the highest frequency observed in Bergamo and Milan. The 43 isolates in Cluster11/ST38 were split by MVLST into two Virulence Types (VTs), VT80 (n=12) and VT104 (n=31). VT104 cases were concentrated between 2009 and 2011 and in Bergamo and Milan provinces. For all Cluster11/ST38 cases, an epidemiological investigation was performed and in one case, a matching VT104 L. monocytogenes clone was isolated from a cheese sample (Taleggio) retrieved from a patient’s refrigerator. Based on both molecular and epidemiologic data, this cheese was identified as the implicated source. Conclusions: Our findings revealed a major listeriosis outbreak in Northern Italy linked to cheese in 2009-2011, which was undetected by local health authorities. Our study showed that integrating subtyping methods such as PFGE, MLST and MVLST with conventional epidemiologic investigations can help identify the source of outbreak clones of L. monocytogenes. Such information is useful in both terminating ongoing outbreaks and preventing future ones from occurring.
Settore MED/42 - Igiene Generale e Applicata
Molecular typing and epidemiological surveillance identified a major listeriosis Outbreak Clone linked to soft cheese in Northern Italy from 2009 to 2011 / E. Amato, V. Filipello, S. Lomonaco, A. Parisi, N. Losio, M. Gori, P. Huedo, M. Pontello, S. Knabel. ((Intervento presentato al 19. convegno Problems of Listeriosis tenutosi a Parigi nel 2016.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/463969
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