Human Salmonella Isolates, 2014

The number of Salmonella isolates confirmed this year (n=1022) showed a decrease in comparison with 2013 (n= 1216). Salmonella Typhimurium phage type 56 variant remained the predominant serotype, representing 7.1% of total isolates (10% 2013). Salmonella serotypes showing an increase this year in comparison with 2013 included: S. Enteritidis phage type 11 (from 2.2% to 3.8%) and phage type RDNC (from 0.6% to 3.0%), and S. Typhimurium phage type 101 (from 2.1% to 4.0%) and phage type 193 (from 0.8% to 1.7%). Several serotypes showed a decrease this year in comparison with 2013 and included: S. Enteritidis phage type 1b (from 1.2% down to 0.5%), S. Saintpaul (from 3.6% down to 2.5%), S. Typhimurium phage type 56 variant (from 10.0% down to 7.1%) and phage type 160 (from 5.7% down to 2.6%).

Significant outbreaks and clusters:

Salmonella Infantis (Source: EpiSurv, ARPHS, ERL)

• Eleven cases of S. Infantis were confirmed in the Auckland region during the months of February and March; this compared to three cases during the same period last year.
• Auckland Regional Public Health Service interviewed eight cases of S. Infantis reported from 01 Feb to 19 March 2014. Illness onset dates ranged between 30 Jan to 26 Feb and five cases were hospitalised.
• No overseas travel was identified. No clustering was seen by age, ethnic group or geographic location.
• A common takeout meal consumed by four cases was a suspected source although no common food commodity or food outlet was identified amongst all eight of the cases interviewed.

Salmonella Typhimurium phage type 120 - Associated with resistance to multiple antibiotics

• Four isolates of S. Typhimurium phage type 120 were confirmed during the month of April. All four cases were reported from the Wellington region.
• This phage type has been associated with resistance to multiple antibiotics overseas.
• These four isolates were referred to the Antibiotic Reference Laboratory (ARL) at ESR and were shown to be susceptible to the antibiotics tested. Pulsed-field gel electrophoresis analysis was also performed and showed an indistinguishable profile shared by the isolates.

Salmonella Typhimurium phage type 193 - Associated with resistance to multiple antibiotics

• Seventeen isolates of S. Typhimurium phage type 193 were confirmed this year; this compared with a total of 10 cases in 2013.
• This phage type is associated with resistance to multiple antibiotics overseas. These isolates were tested by ARL at ESR and were shown to be sensitive to all antibiotics tested.

Seasonal increase in S. Brandenburg

• Occurrence of Salmonella Brandenburg infection in humans is a seasonal phenomenon in the southern half of the South Island (Baker et al. 2007 in Epidemiol. Infect. 135(1):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: http://www.stuff.co.nz/business/farming/sheep/9090477/Bacterial-outbreak-killing-South-Island-sheep

Salmonella Typhimurium phage type U307 – Uncommon in New Zealand (Source: ERL, EpiSurv)

• Salmonella Typhimurium phage type U307 was first isolated from two human cases in New Zealand in 2010. No further cases were reported until December this year, when six isolates were confirmed;
• Travel history was recorded for all six cases. Of these, five were in Australia during the incubation period. The case that did not travel had close contact with a case that had visited Australia.