A protracted outbreak of Salmonella Hessarek infection associated with one brand of eggs­South Australia, March 2017 - July 2018

Salmonella Hessarek is an uncommon serotype in Australia. We report on the investigation of a protracted outbreak of 25 cases of S. Hessarek gastroenteritis in which cases were defined as any laboratory confirmed case of Salmonella Hessarek notified to the South Australian Communicable Disease Control Branch from 1st March 2017 to 3 July 2018. We conducted a descriptive case series investigation interviewing all cases and 17 (68%) reported consuming brand X free-range eggs. Four samples of one-dozen brand X eggs were cultured for the presence of Salmonella spp. One out of the four samples returned positive for S. Hessarek in the contents of the eggs; Salmonella was not present in any of the whole egg rinses of the four samples. The high proportion of cases reporting the consumption of brand X free-range eggs and the isolation of S. Hessarek from sampling four dozen brand X eggs is an unusually strong signal implicating brand X eggs as the source of this outbreak. From a public health perspective, it is important to understand the behaviour of S. Hessarek including its ability to be present in the content of eggs and further research is recommended. The findings in this investigation into a rare Salmonella serotype highlight the need for continuous monitoring of the epidemiology of Salmonella in Australia including the epidemiology of egg-associated Salmonella outbreaks of human disease.

An outbreak and case-control study of Salmonella Havana linked to alfalfa sprouts in South Australia, 2018.

An epidemiological investigation and a retrospective case-control study were conducted into an outbreak of Salmonella Havana in alfalfa sprouts, in Adelaide, Australia. In total, 31 cases of S. Havana were notified during June and July 2018 and linked to the outbreak. Eighteen cases and 54 unmatched controls were included in a case-control study. Results from the case-control study indicated an increased risk of illness linked to the consumption of alfalfa sprouts; this was supported by trace-back, sampling and environmental investigations. This outbreak of S. Havana was caused by consumption of alfalfa sprouts from one local sprouts producer. It is unclear as to when in the production of alfalfa sprouts the contamination occurred. However, contaminated seeds and poor pest control are the most likely causes. This investigation highlights the importance of ensuring that producers take appropriate action to minimise the likelihood of contamination and to comply with legislation and standards for primary production and food safety.