Tracing sources of Listeria contamination in traditional Italian cheese associated with a US outbreak: investigations in Italy.

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.

T cell response in acute motor axonal neuropathy.

There is evidence that in the acute axonal motor neuropathy (AMAN) subtype of Guillain-Barré syndrome antibodies to gangliosides, produced through molecular mimicry by antecedent Campylobacter jejuni (C. jejuni) infection, attack gangliosides expressed in human peripheral nerve axolemma, inducing a primary axonal damage. The aim of this study is to investigate whether the T cell response has a role in AMAN pathogenesis. We isolated monocytes from 4 healthy subjects and 5 AMAN patients with antecedent C. jejuni infection and antibodies to GM1 and/or GD1a gangliosides. Immature dendritic cells expressing CD1 molecules cultured with autologous T cells were stimulated with 2 lipopolysaccharides (LPSs) extracted from C. jejuni strains containing GM1 and GD1a-like structures and with GM1 and GD1a. The T cell response to LPSs and to gangliosides was determined by measuring the release of IFN-gamma and TNF-alpha. We observed a T cell response to both LPSs in controls and AMAN patients, whereas only AMAN patients showed T cell reactivity to gangliosides GM1 and GD1a with a tight correlation between T cell reactivity to the ganglioside and individual antibody responses to the same ganglioside. T cells responding to gangliosides were CD1c-restricted CD8 positive and CD27 negative. These findings indicate a contribution of cellular immunity in the pathogenesis of AMAN. A possible role for ganglioside-reactive T cells might be to facilitate the production of antibodies against gangliosides.

Hygienic quality and freshness of shell eggs collected at retail outlets in Italy.

Shell eggs sampled at retail outlets in two large Italian cities were tested to assess their freshness, food safety and the presence of veterinary drug residues. Some samples were found to be irregular due to lack of compliance with freshness requirements or shells were tainted by micro-cracks and foreign material. The most severe case of non-compliance was due to the presence of veterinary drug residues that either exceeded either the maximum acceptable residue limits or drugs that were prohibited.

Surveillance system and rapid tracing of primary sources in food-borne outbreaks by Salmonella spp. Part II: Molecular characterisation of some strains of Salmonella enterica serovars Enteritidis and Typhimurium.

Salmonella enterica serovars Enteritidis and Typhimurium are the serotypes most frequently isolated from human cases. Traditional surveillance systems, based on serological characterisation and epidemiology, are not able to identify these common strains that cause outbreaks in humans. Innovative techniques are therefore necessary to accurately characterise these serotypes and hence accelerate the identification of the primary sources. Within a larger study, the goal of which was to develop an active surveillance system for outbreaks of food-borne diseases, characterisation of 42 Salmonella strains was performed using molecular techniques (pulsed field gel electrophoresis [PFGE] and random amplified polymorphic DNA [RAPD]), together with the Kirby-Bauer antibiotic assay. Results showed that both techniques were unable to satisfactorily characterise the Enteritidis serotype, while only PFGE identified the Typhimurium serotype.

Surveillance system and rapid tracing of primary sources in foodborne outbreaks by Salmonella spp. Part I: Identification of outbreaks in the Abruzzo region of Italy.

The determination of the origin of foodborne diseases is one of the top priorities for the world health community. Gastroenteritis caused by zoonotic Salmonella serovars is one of the major threats to human health. It is essential that surveillance systems are able to monitor the incidence of human cases and to provide useful data to plan and implement effective prevention strategies. Surveillance systems generate information that is of value both for the early detection of infection and for the identification of epidemiological trends and risk factors. The authors describe a surveillance system for the identification of the sources of infection foodborne disease outbreaks caused by Salmonella in the Abruzzo region of Italy between April 2000 and October 2002.

Use of innovative methods in the eradication of bovine tuberculosis.

During final phases of eradication programmes, strains of Mycobacterium sp. not belonging to the tuberculosis complex increase their relative frequency and are responsible for positive skin test reactions. Moreover, the specificity of any indirect diagnostic test, such as the skin test, is never completely accurate, therefore even when tuberculosis infection is completely eradicated, a number of false positive reactions are to be expected. The aim of this paper is to evaluate the performances of traditional isolation/typing techniques, automatic isolation/typing techniques based on fluorimetric detection of bacterial growth (Bactec), skin tests and the -interferon test. Samples examined for the evaluation of test sensitivities originated from 154 infected animals belonging to 32 infected herds. Samples used as negative controls in the evaluation of test specificities originated from 86 animals of nine officially infection-free herds. The automatic isolation/typing technique based on fluorimetric detection of bacterial growth showed higher sensitivity than the traditional isolation typing technique. Moreover, it allowed a safer processing of bacterial cultures, decreasing the risk for laboratory workers. The observed performance of the gamma-interferon test was considered beneficial in that it increased the sensitivity of individual diagnosis within an infected herd, especially in 'problem herds', but its poor specificity did not improve detection of infected herds compared to the skin test.