The two additional cases were identified in June and are under investigation, they have not yet been typed by Multiple-Locus Variable number tandem repeat Analysis (MLVA) so results are pending.
The remains of the implicated lot from China, via the Netherlands are being withdrawn from the market.
Mung bean sprouts implicated
A Salmonella Enteritidis outbreak occurred mainly in the Pirkanmaa area during March to May.
Genetically identical strains have been isolated from 19 primary cases and the strain was multi-resistant to several antimicrobials.
In-depth interviews and a case control study implicated mung bean sprouts as the most likely vehicle.
Dr Katri Jalava said evidence for the 19 cases to be part of one cluster is fairly strong.
“They are well clustered in time, mostly end of March and also by geography. The strain is also characteristic, it has a particularly distinct antimicrobial resistance profile and the strains have a unique MLVA profile.
“We have epidemiological evidence for the mung beans sprouts for the 19 cases cluster, it is difficult to say separately for the remaining two.”
The largest Salmonella enterica serovar Newport outbreak ever reported in Germany (106 illnesses) occurred in October and November 2011 and 20 cases were reported in the Netherlands.
Unspecified Salmonella was detected in samples of mung bean sprouts at a producer in the Netherlands and mung bean sprouts contaminated with S. Newport were found during routine sampling at a sprout distributor in Germany.
Case control study findings
Dr Jalava said they asked specifically about sprouts in the case control study.
“Many of the cases named mung bean sprouts and could indicate the date of shopping. It was particularly strong, just before Easter and only a few shops of the same chain.
“Many of the cases were also vegetarians or keen on organic produce, so they were possibly even more aware people about what they ate. Some had consumed mung bean sprouts in one brand of restaurant. We traced back the mung bean sprout company doing the germination, and could identify one lot.”
The implicated sprouts were traced back to the importing companies, microbiological samples were taken from an implicated seed lot and hygienic practices were inspected.
“There was a particularly stringent hygienic inspection being done in the germination facility to rule out an infected food handler, other sources of mung bean seeds or eggs eaten by the food handlers. Finnish eggs are free of S. Enteritidis, so it is an unusual vehicle for S. Enteritidis here,” said Dr Jalava.
No positive samples have been identified as yet, but the investigation on microbiology of the seeds is on-going.
“We are still trying to isolate the Salmonella from the implicated lot of seeds. It is characteristic of sprout outbreaks that isolating the strain from the seeds is extremely difficult. We have estimated the beans germinated in this lot and the number of people fallen ill, and the level of contamination in these seeds is very low,” said Dr Jalava.
There were 1,656 Salmonella cases reported in 2015 in Finland and 1,583 strains were submitted for typing.
Of these, 20% (311 strains) of infections were acquired in Finland, and 59 were S. Enteritidis. Most were sensitive to tested antimicrobials (80%).