Tracing sources ofListeriacontamination in traditional Italian cheese associated with a US outbreak: investigations in Italy

Abstract

In 2012 a US multistate outbreak of listeriosis was linked to ricotta salata imported from Italy, made from pasteurized sheep's milk. Sampling activities were conducted in Italy to trace the source of Listeria monocytogenes contamination. The cheese that caused the outbreak was produced in a plant in Apulia that processed semi-finished cheeses supplied by five plants in Sardinia. During an 'emergency sampling', 179 (23·6%) out of 758 end-products tested positive for L. monocytogenes, with concentrations from <10 c.f.u./g to 1·1 × 106 c.f.u./g. Positive processing environment samples were found in two out of four processing plants. A 'follow-up sampling' was conducted 8 months later, when environmental samples from three out of six plants tested positive for L. monocytogenes and for Listeria spp. PFGE subtyping showed 100% similarity between US clinical strains and isolates from ricotta salata, confirming the origin of the outbreak. The persistence of strains in environmental niches of processing plants was demonstrated, and is probably the cause of product contamination. Two PFGE profiles from clinical cases of listeriosis in Italy in 2011, stored in the MSS-TESSy database, were found to have 100% similarity to one PFGE profile from a US clinical case associated with the consumption of ricotta salata, according to the US epidemiological investigation (sample C, pulsotype 17). However, they had 87% similarity to the only PFGE profile found both in the US clinical case and in 14 ricotta cheese samples collected during the emergency sampling (sample B, pulsotype 1). Sharing of molecular data and availability of common characterization protocols were key elements that connected the detection of the US outbreak to the investigation of the food source in Italy. Simultaneous surveillance systems at both food and human levels are a necessity for the efficient rapid discovery of the source of an outbreak of L. monocytogenes.

Identification of a major Listeria monocytogenes outbreak clone linked to soft cheese in Northern Italy – 2009-2011

“…Interestingly, the PFGE profiles of isolates in Cluster11 were closely related to the pulsotype ( Asc I.0087) of one clinical case involved in the 2012 US outbreak linked to ricotta salata produced in Southern Italy and of two clinical cases detected in Lombardy in 2011 [24]. The isolates linked to the ricotta salata outbreak were typed as VT80 [19, 25], while the two Italian cases were subtyped as ST101, which is grouped in the same Clonal Complex (CC) as ST38 (i.e.…”

A case of haemolytic uraemic syndrome (HUS) revealed an outbreak of Shiga toxin-2-producing Escherichia coli O26:H11 infection in a nursery, with long-lasting shedders and person-to-person transmission, Italy 2015

“…Nel 2012, l'attivazione della rete Enter-Net Italia ed il coinvolgimento della rete gemella EnterVet a seguito di un'allerta europea per S. Stanley (ECDC, 2014;Kinros et al, 2014), consentì non solo di identificare l'esistenza di casi d'infezione in Italia ma di verificare anche che alcuni campioni di carne di tacchino esaminati poco prima nel nostro Paese risultavano contaminati da ceppi di S. Stanley dello stesso pulsotipo del ceppo epidemico (Comunicazione personale Antonia Ricci). Nel 2013, un'allerta internazionale relativa ad una grave epidemia di Listeriosi negli Stati Uniti (Heimaan et al, 2016), attraverso il ricollegamento della rete Enter-Net Italia con le attività analitiche condotte sulle matrici alimentari (latticini) e coordinate dal LNR per la L. monocytogenes, ha permesso di accertare l'assenza di casi epidemici in Italia e di rivelare l'origine della contaminzione della fonte epidemica (latticini prodotti in Italia ed esportati negli USA) (Acciari et al, 2016). Attività analoghe a quelle descritte sono state condotte attarverso le reti Enter-Net Italia e il Registro SEU nel 2011, per l'allerta relativa ad un focolaio di infezione da S. Stratchona associata al consumo di pomodori pachino di produzione italiana che era stata oggetto anche di un'allerta RASFF (Rapid Alert System for Food and Feed) (Müller et al, 2013).…”

Prevalence, Pathogenicity, Virulence, Antibiotic Resistance, and Phylogenetic Analysis of Biofilm-Producing Listeria monocytogenes Isolated from Different Ecological Niches in Egypt: Food, Humans, Animals, and Environment

“…Although the genus Listeria includes many species, due to the pathogenicity of L. monocytogenes in human hosts and its ability to flourish in hostile environments, earlier research implicating genome sequencing were to a great extent concentrated on L. monocytogenes [7][8][9][10][11]. L. monocytogenes is implicated with human listeriosis and in the present decennium, numerous serious outbreaks of foodborne listeriosis have been recorded in different countries and continents [11][12][13][14][15][16], causing serious manifestations in the form of septicemia and meningitis, principally in the immunocompromised and old populaces in addition to pregnant women, who may bring forth stillborn babies or seriously contaminated infants [4,9,[17][18][19][20][21][22][23][24][25][26].…”