Listeria monocytogenes is a ubiquitous bacterium that causes a food-borne infection called listeriosis in humans. For susceptible individuals, like immunocompromised individuals, pregnant women, newborns and elderly, invasive listeriosis is a potentially life-threatening disease. During the period from 3rd June to 6th November 2017, 11 cases of invasive listeriosis have been reported in the province of Pavia. Microbiological analyses were performed to isolate and identify the bacteria. The genomes of the 11 strains were obtained through Whole Genome Sequencing (WGS). For all the strains sequence type (ST), resistance and virulence genes profiles and genetic distance from the other strains were determined. Five different STs were found (ST1, ST2, ST8, ST37 and ST224) and the analysis of coreSNPs of the strains belonging to each ST showed that only two strains were part of the same phylogenetical cluster, while one strain was correlated to another isolate found in the province of Pavia in 2015. From our investigation we proved that the source of infection, even if it was not identified, has been different from each patient. The use of WGS based methods applied to epidemiological investigation allow to improve surveillance and outbreak detection.
Listeria monocytogenes è un batterio ubiquitario nell’ambiente che causa listeriosi una tossinfezione alimentare. Per i soggetti suscettibili, come gli individui immunocompromessi, le donne in gravidanza, i neonati e gli anziani, la malattia si manifesta nella forma invasiva con esito potenzialmente letale. Durante il periodo 3 giugno - 6 novembre 2017 si sono verificati 11 casi di listeriosi invasiva in provincia di Pavia. L’isolamento e l’identificazione degli isolati dai pazienti è stata effettuata con metodi microbiologici. Il genoma di tutti gli isolati è stato ottenuto mediante Whole Genome Sequencing (WGS). Per ciascun ceppo è stato determinato il sequence type (ST), il profilo dei geni di virulenza e resistenza, e la distanza genomica rispetto gli altri ceppi. Cinque ST sono stati identificati (ST1, ST2, ST8, ST37 e ST224) e l’analisi dei coreSNPs dei ceppi appartenenti a ciascun ST ha evidenziato che solo due degli 11 ceppi appartenevano allo stesso cluster filogenetico, mentre un altro ceppo è risultato filogeneticamente vicino ad un ceppo isolato nella provincia di Pavia nel 2015. La nostra indagine ha dimostrato che la fonte di infezione, seppure non individuata, è stata diversa per tutti i pazienti. L’applicazione delle tecniche basate sul WGS unita all’analisi epidemiologica permette di migliorare la surveillance e la rilevazione di outbreak.
Epidemiologia genomica per l’analisi di infezioni da Listeria monocytogenes nella provincia di Pavia
DELLA ROCCA, JENNIFER
2017/2018
Abstract
Listeria monocytogenes is a ubiquitous bacterium that causes a food-borne infection called listeriosis in humans. For susceptible individuals, like immunocompromised individuals, pregnant women, newborns and elderly, invasive listeriosis is a potentially life-threatening disease. During the period from 3rd June to 6th November 2017, 11 cases of invasive listeriosis have been reported in the province of Pavia. Microbiological analyses were performed to isolate and identify the bacteria. The genomes of the 11 strains were obtained through Whole Genome Sequencing (WGS). For all the strains sequence type (ST), resistance and virulence genes profiles and genetic distance from the other strains were determined. Five different STs were found (ST1, ST2, ST8, ST37 and ST224) and the analysis of coreSNPs of the strains belonging to each ST showed that only two strains were part of the same phylogenetical cluster, while one strain was correlated to another isolate found in the province of Pavia in 2015. From our investigation we proved that the source of infection, even if it was not identified, has been different from each patient. The use of WGS based methods applied to epidemiological investigation allow to improve surveillance and outbreak detection.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
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https://hdl.handle.net/20.500.14239/19062