Investigation and management of an outbreak of Salmonella Typhimurium DT8 associated with duck eggs, Ireland 2009 to 2011

Abstract

>Salmonella Typhimurium DT8 was a very rare cause of human illness in Ireland between 2000 and 2008, with only four human isolates from three patients being identified. Over a 19-month period between August 2009 and February 2011, 34 confirmed cases and one probable case of Salmonella Typhimurium DT8 were detected, all of which had an MLVA pattern 2-10-NA-12-212 or a closely related pattern. The epidemiological investigations strongly supported a link between illness and exposure to duck eggs. Moreover, S. Typhimurium with an MLVA pattern indistinguishable (or closely related) to the isolates from human cases, was identified in 22 commercial and backyard duck flocks, twelve of which were linked with known human cases. A range of control measures were taken at farm level, and advice was provided to consumers on the hygienic handling and cooking of duck eggs. Although no definitive link was established with a concurrent duck egg-related outbreak of S. Typhimurium DT8 in the United Kingdom, it seems likely that the two events were related. It may be appropriate for other countries with a tradition of consuming duck eggs to consider the need for measures to reduce the risk of similar outbreaks.

Increased phage resistance through lysogenic conversion accompanying emergence of monophasic Salmonella Typhimurium ST34 pandemic strain

“…Clade α exhibited a significantly greater R i than clade β ( P= 3.9×10 −7 )(), indicating greater phage resistance of broad-host-range livestock-associated lineages. Five lineages from clade α exhibited greater resistance to phage, with R i values from ~0.6–1, while clades containing strains exhibiting host-adaptation or host-restriction [1] exhibited lower mean Ri values (0.14–0.76) with duck-associated clade β2 being the only lineage from clade β with R i values in the upper-mid range (0.7–1) () [64]. The R i of four successive dominant clones (DT9, DT204, DT104, and monophasic S .…”

“…Five lineages from clade α exhibited greater resistance to phage, with R i values from ~0.6-1, while clades containing strains exhibiting host-adaptation or host-restriction [1] exhibited lower mean Ri values (0.14-0.76) with duck-associated clade β2 being the only lineage from clade β with R i values in the upper-mid range (0.7-1) (Fig. 1c) [64]. The R i of four successive dominant clones (DT9, DT204, DT104, and monophasic S. Typhimurium ST34, predominantly DT193 and DT120) over the last 60 years in Europe, had a trend to greater or equal resistance to phage with each successive clone (Fig.…”