Human salmonella isolates 2013

Annual summary 2013

There were 1216 human Salmonella isolates confirmed in 2013 (2012 n= 1106). S. Typhimurium phage type 56 variant remained the predominant serotype, representing 10% of total isolates (6.6% 2012). Several Salmonella serotypes showed an increase this year in comparison with 2012 with the most significant increase observed in: S. Brandenburg (3.1% in 2012 to 4.3% in 2013), S. Saintpaul (2.4% in 2012 to 3.5% in 2013), S. Thompson (0.2% in 2012 to 1.3% in 2013), and S. Typhimurium phage type 56 variant (6.6% in 2012 to 10.0% in 2013). Up until 2009, Salmonella Typhimurium represented over 50% of the Salmonella cases confirmed by ERL. Since the 2010, this serotype has represented less than 50% of the total human Salmonella serotypes confirmed by ERL.

Salmonella Typhimurium phage type 56 variant was known as S. Typhimurium phage type RDNC-May06 prior to July 2013. Further characterisation work undertaken by the Salmonella Reference Unit at Colindale (Public Health England) identified this phage type as a 56 variant.

Significant Outbreaks and/or Clusters:

S. Infantis
An increase in S. Infantis was reported in the Auckland and Northland regions during the months of April and May. PFGE analysis was performed on the human isolates as well as a S. Infantis isolated from a ham and egg sandwich. The results indicated that the Northland cases and the “ham and egg sandwich” from the implicated premise had an indistinguishable PFGE profile, suggesting a common source outbreak. The Auckland cases, although similar, were distinguishable from the Northland cluster.

S. Paratyphi A
Four cases of S. Paratyphi A were confirmed during the month of June.  These cases were linked to the cluster of enteric diseases in Auckland school children who had recently returned from Asia – (Source: ARPHS).

S. Typhimurium phage type 56 variant
During the month of July, 16 isolates of S. Typhimurium phage type 56 variant were confirmed. This compared with 6 human isolates during the same period last year.
An increase in this phage type was also confirmed in animal isolates. Since 01 July 2013, 29 animal isolates were confirmed (compared to 3 for the same period last year). 15/23 were isolated from cats and 9/23 from horses.

S. Brandenburg
An increase in the number of S. Brandenburg isolates (4 in August 2012 versus 10 in August 2013) was reported during the months of August and September. Occurrence of S. Brandenburg infection in humans is a seasonal phenomenon in the southern half of the South Island (Baker et al Epidemiol Infect 2007; 135:76-83) and is often linked with occurrence of the serotype in livestock. Salmonella Brandenburg has caused periodic epidemics of disease in sheep flocks in Otago and Southland since 1997.
See also: http://www.stuff.co.nz/business/farming/sheep/9090477/Bacterial-outbreak-killing-South-Island-sheep(external link)

S. Enteritidis
During the month of September, 15 isolates of S. Enteritidis of various phage types were confirmed. This compares with 6 cases during the same period last year. Forty percent (6/15 cases) of the cases had reported recent overseas travel.

S. Montevideo
A cluster of 5 cases of S. Montevideo was confirmed in the Bay of Plenty region during the month of November. PFGE analysis showed that all cases had undistinguishable PFGE profile. The profile was distinguishable to the PFGE profile from samples of imported tahini implicated in a similar outbreak in 2012. Local environmental investigations at the food premises did not identified any food control failures or sick food handlers that could account for the source of these infections.