Outbreak of unusual Salmonella enterica serovar Typhimurium monophasic variant 1,4 [5],12:i:-, Italy, June 2013 to September 2014

Abstract

Monophasic variant of Salmonella enterica subspecies enterica serovar Typhimurium (monophasic S. Typhimurium), with antigenic structure 1,4,[5],12:i:-, appears to be of increasing importance in Europe. In Italy, monophasic S. Typhimurium represented the third most frequent Salmonella serovar isolated from human cases between 2004 and 2008. From June 2013 to October 2014, a total of 206 human cases of salmonellosis were identified in Abruzzo region (Central Italy). Obtained clinical isolates characterised showed S. Typhimurium 1,4,[5],12:i:- with sole resistance to nalidixic acid, which had never been observed in Italy in monophasic S. Typhimurium, neither in humans nor in animals or foods. Epidemiological, microbiological and environmental investigations were conducted to try to identify the outbreak source. Cases were interviewed using a standardised questionnaire and microbiological tests were performed on human as well as environmental samples, including samples from fruit and vegetables, pigs, and surface water. Investigation results did not identify the final vehicle of human infection, although a link between the human cases and the contamination of irrigation water channels was suggested.

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

“…Tra le regioni che nel periodo di studio hanno invece notificato ad Enter-Net Italia con minore regolarità, la Campania mostrava tasso di isolamenti di S. Typhimurium elevato, mentre in Veneto prevaleva S. Enteritidis (dati limitati al periodo 2010-2013). Napoli anno L'elevata frequenza di isolamento di S. Typhimurium variante monofasica, S. Berta e S. Enteritidis, in Abruzzo, rispettivamente negli anni 2010, 2013 e 2014, è associata al verificarsi di eventi epidemici (Cito et al, 2016;Di Giannatale et al, 2012; Di Giannatale, dati non pubblicati).…”

“…Nel 2014, per un focolaio che ha coinvolto diverse scuole in Lombardia dovuto a S. Napoli (Huedo et al, 2016) e per l'epidemia di S. Thypimurium var. monofasica in Abruzzo (Cito et al, 2016). Nel 2015, in occasione del grave focolaio epidemico di Listeriosi nella regione Marche (Marini et al, 2016).…”

A note from the editors: impact of anthropogenic changes to water on human pathogens

“…The challenges of outbreaks potentially caused by microbial contamination of water are first illustrated in a report from Italy, where an outbreak of monophasic Salmonella Typhimurium 1,4 [5],12:i:-with sole resistance to nalidixic acid is described [19]. Attempts to determine the source of this outbreak led to extensive environmental investigations.…”

“…While its cause could not be ascertained, a number of surface water samples in the outbreak area, including of water used for growing fruit and vegetables, were positive for the outbreak strain. Moreover some water samples from local sewage treatment plants also tested positive, thus leading to the hypothesis that wastewater may have contaminated irrigation water [19]. The epidemiological investigation was complicated and the origin of the outbreak strain and how this strain acquired its resistance to nalidixic acid remain unresolved.…”

“…As illustrated by some of the above studies [19,21], adequate management of wastewater is crucial. Indeed, water contaminated by wastewater can subsequently cumulate in larger water bodies such as lakes or the ocean.…”