Human Salmonella Isolates, 2016 No. 3, March

The number of isolates (n=119) confirmed this month showed an increase in comparison to the number of isolates confirmed in March 2015 (n=95). Salmonella Enteritidis phage type 11 (6.3% in March 2015 vs 8.4% in March 2016) and S. Stanley (2.1% in March 2015 vs 8.4% in March 2016) were the most common serotypes confirmed this month. Uncommon serotypes confirmed this month included S. Enteritidis phage type 7 (12 human cases since it was first confirmed in New Zealand in 2004), S. Haifa (11 human cases since it was first confirmed in New Zealand in 1988) and S. Ruiru (10 human cases since it was first confirmed in New Zealand in 2004).

Increase in Salmonella Stanley in Tairawhiti DHB (Source: EpiSurv, Tairawhiti DHB, Ministry for Primary Industries, Ministry of Health)

• Tairawhiti DHB in conjunction with the Ministry of Health, Ministry for Primary Industries and ESR have been investigating an increase in S. Stanley notifications.  From 01 February to 05 April 2016 there have been 11 cases reported, a significant increase compared to the same period in previous years (no cases reported previously).
• None of the 11 cases had travelled overseas during the incubation period. In 2015 there were 26 cases of S. Stanley reported in New Zealand, of which 87.0% (20 of the 23 cases with known travel history) were overseas acquired infections.
• Pulsed-Field Gel Electrophoresis (PFGE) was performed on a selection of case isolates of S. Stanley confirmed this year and included 10 from Tairawhiti DHB. A common profile, and a profile with one band difference was identified among the Gisborne cluster which suggests that cases may have been exposed to the same source of infection. One case from Auckland DHB was also found to have the outbreak profile. This case has confirmed they were in Gisborne during the incubation period. All other cases had PFGE profiles distinguishable from the outbreak cluster.
• Although uncommon in New Zealand, S. Stanley is one of the most common serovars associated with human infection in South East Asia.  Sources for outbreaks documented overseas include alfalfa sprouts, peanuts, soft cheese, turkey meat (See: http://ecdc.europa.eu/en/publications/Publications/salmonella-stanley-multi-country-outbreak-assessment-8-May-2014.pdf) and raw cashew cheese (http://www.cdc.gov/salmonella/stanley-01-14/).
• The ERL has previously identified S. Stanley from overseas products, environmental and food sources between 1988 and 1998.