A case-control study by scientists from Robert Koch-Institut (RKI) showed a strong association with ham from an unnamed food chain for the largest cluster of S. Kottbus illnesses.
A smaller cluster of illnesses may be linked to quail eggs.
Surveillance found smaller outbreaks
RKI said it illustrates the importance of molecular subtyping of isolates at the National Reference Center for Salmonella (Nationalen Referenzzentrum für Salmonellen) by PFGE and whole genome analysis to discover and find out more about outbreaks.
Without the molecular typing of the S. Kottbus isolates, two other, smaller outbreaks would not have been detected, added the institute.
RKI said as the incidence of S. Kottbus has returned to the usual background rate of two cases per month the outbreak seems to be in remission or finished, especially in relation to cluster 1.
Illnesses started at the end of June and as of mid-September, 66 cases had been reported without foreign travel history.
Of 68 cases in the study, 37 (54%) had exposure in the states of Schleswig-Holstein (SH), Hamburg (HH) and Mecklenburg-Vorpommern (MV). Reporting incidence was highest in Schleswig-Holstein.
Three sequence clusters were identified by PFGE and whole genome sequencing (WGS) analysis.
Cluster 1 (27 isolates) was by far the most common (74%) and was the outbreak strain - this strain was not detected in previous years.
Five isolates belonged to cluster 2 and three isolates were typed in cluster 3. Another sequence type was detected only once.
Cluster 1 investigation
In comparative isolates from animal and food, an isolate from pork sent to the NRL in April also belonged to Cluster 1.
This finding means it is likely that other pork products might be contaminated with S. Kottbus in addition to ham and could be further sources of infection, said RKI.
Cluster 1 cases occurred mainly in northern Germany (69% in SH, HH and MV). 56% were female and the age range was 0-91.
Of the five cluster 2 cases, four were female and were between 27-66 years old. All three cluster 3 cases were male and were 31, 55 and 76 years old.
In a case-control study in SH/HH/MV, 17 cases and 96 controls were surveyed - ten of these cases included those from Cluster 1.
A total of 14 of 17 cases had consumed raw/smoked ham the week before onset of disease; ten of these 14 had bought it at one supermarket chain.
On the basis of product pictures, nine of ten recalled the ham X1; the remaining case had the very similarly packed ham X2. Four cases also claimed to have had ham X3.
Hams X1 and X2 are similar packed products from the same manufacturer (H1) for the supermarket chain. The ham X3 was produced by another manufacturer (H3).
Of 14 cases interviewed in other states, six recalled the same or similar raw ham products from manufacturers H1 and H3.
In cluster 2, a link was established to quail eggs bought in two different supermarket chains (not chain X), but believed to be supplied by the same quail egg producer.
Campylobacter up and Salmonella down last year
Meanwhile, norovirus and Campylobacter were among the most commonly reported notifiable diseases in the country last year, according to the Infectious Disease Epidemiology Annual Report.
Almost 74,000 Campylobacter enteritis cases were reported including 477 outbreaks compared to 70,266 infections and 465 outbreaks in 2015.
For the almost 50,000 cases with strain data available C. jejuni accounted for 72%.
The report provides a summary of notifications of infectious diseases reported to RKI in 2016.
RKI said implementation of control measures in food production probably influenced the declining trend in salmonellosis cases.
Almost 13,000 cases were reported compared to 13,870 in 2015.
Serovar data was given for 76% of cases, with 41% S. Enteritidis and 36% S. typhimurium followed by S. Infantis (2.9%) and S. Derby (1.6%).
For an outbreak of listeriosis, ongoing since 2012 with indistinguishable PFGE typing profiles and identical sequence type (whole genome sequencing), a meat processing plant was identified as a possible source.
Listeria increased 7% to 707 infections and in 48 cases listeriosis was stated as the cause of death.
Other notable events were a botulism outbreak associated with consumption of roach involving four cases in Germany and two in Spain.