Outbreak of Salmonella Newport associated with internationally distributed raw goats' milk cheese, France, 2018

Abstract

Raw milk cheeses are commonly consumed in France and are also a common source of foodborne outbreaks (FBOs). Both an FBO surveillance system and a laboratory-based surveillance system aim to detect Salmonella outbreaks. In early August 2018, five familial FBOs due to Salmonella spp. were reported to a regional health authority. Investigation identified common exposure to a raw goats' milk cheese, from which Salmonella spp. were also isolated, leading to an international product recall. Three weeks later, on 22 August, a national increase in Salmonella Newport ST118 was detected through laboratory surveillance. Concomitantly isolates from the earlier familial clusters were confirmed as S. Newport ST118. Interviews with a selection of the laboratory-identified cases revealed exposure to the same cheese, including exposure to batches not included in the previous recall, leading to an expansion of the recall. The outbreak affected 153 cases, including six cases in Scotland. S. Newport was detected in the cheese and in the milk of one of the producer's goats. The difference in the two alerts generated by this outbreak highlight the timeliness of the FBO system and the precision of the laboratory-based surveillance system. It is also a reminder of the risks associated with raw milk cheeses.

Keywords: Outbreaks; Salmonella; raw milk collection; surveillance.

Fig. 1.

(a) Chronological order of outbreak events; (b) chronology of the distribution and recall of implicated products; (c) epicurve of S. Newport ST118 cases by day of onset of symptoms, France, 2018 (n = 37; letter indicates cluster case belongs to); (d) epicurve of S. Newport ST118 cases by day of sampling, France, 2018 (n = 133, one late case with sampling date of 27 September not shown); (e) epicurve of S. Newport ST118 cases by date of validation of serotype by the FNRC-ESS, France, 2018 (n = 109, cases with date of validation after September 7 (n = 25) not shown).

Fig. 2.

Phylogenetic tree of 172 S. Newport ST118 isolates analysed by WGS at the FNRC-ESS in France and the SMiRL in Scotland, UK, in 2018. The tree was made by using the ‘create SNP project’ tool in EnteroBase and was based on 5042 non-repetitive SNPs. The tips are coloured according to the country of isolation and outbreak status.