Human salmonella isolates 2010

Annual summary 2010

There were 1195 human Salmonella isolates confirmed in 2010 (2009 n= 1176). S. Typhimurium phage type 160 remained the predominant serotype, representing 9% of total isolates (9% 2009). Several Salmonella serotypes showed an increase this year in comparison with 2009 with the most significant increase observed in S. Typhimurium phage type 135 (1.7% in 2009 to 4% in 2010) and RDNC-May 06 (3.7% in 2009 to 7% in 2010). The most significant decrease was seen in S. Typhimurium phage type 1 (from 8% in 2009 to 3% in 2010).

Significant Outbreaks and Clusters:

Salmonella Infantis: An increase in S. Infantis was first reported in December 2009. PFGE analysis was performed on all S. Infantis isolates confirmed by ERL during the months of November 2009 right through February 2010. Cases with outbreak PFGE profile were further investigated. Most cases were from the Auckland (14) or South Canterbury region (10 cases). Epidemiological investigations linked the outbreak in the Auckland region to a food premise.

Salmonella Typhimurium RDNC-May 06: A significant increase in numbers of S. Typhimurium RDNC-May 06 was observed over the months of July through September in the North Island, mainly in the Auckland region. Of the 46 cases confirmed in the North Island, 21 were from the Auckland region and 29 were from children aged 6 years of age or younger (15 in the Auckland region). This phage type is one of our most common phage types in New Zealand.

Salmonella Typhimurium phage type 155: An outbreak of S. Typhimurium phage type 155 was reported in South Canterbury. The common food source was the mousse filling of two chocolate cakes (made to order) purchased from a South Canterbury café. The mousse filling contained uncooked egg whites. The eggs were from a small supplier who does not have a Risk Management Program. New Zealand Food Safety Authority was informed.

Salmonella Typhimurium phage type 135: Twenty-three S. Typhimurium phage type 135 were confirmed in the Otago region between September and December 2010. Twenty were from children aged 7 years old or younger.

Salmonella subsp I ser. 4,[5],12 : i : - : Five Salmonella 4,[5],12 : i : - were confirmed in the Auckland region in July, including a household cluster (2 cases). Salmonella enterica serotype 4,[5],12 : i : – is considered a monophasic variant of S. Typhimurium (4,[5],12 : i : 1,2) due to antigenic and genotypic similarities between the two serotypes. Overseas, the prevalence of this serotype among human salmonellosis cases has increased considerably since the mid-1990s.

Change of phage type designation:

After further testing by the Enteric Reference Laboratory, two phage type designations have been amended.
S. Typhimurium phage type 108/170: This phage type was previously known as S. Typhimurium phage type 12a variant 09. This new designation reflects the situation overseas where this phage type pattern is known as either DT 108 or 170.
S. Typhimurium phage type 185: This phage type was previously known as S. Typhimurium phage type RDNC-Aug 08.