CDC issued a report on a 2015 outbreak of Salmonella Enteritidis associated with a Washington DC restaurant. There were 159 reported cases. Truffle oil was the most likely source based on the epidemiological investigation, but the organism was not isolated from the oil itself. "Six food items were significantly associated with case status (
Table 2), three of which (beef carpaccio, truffle mushroom croquette, and truffle risotto) contained truffle oil. When all truffle oil–containing items were combined into a single variable, including the three that were individually significant, consumption of a truffle oil–containing item was reported by 89% of case-patients compared with 57% of control subjects (p<0.001)."
While this Salmonella strain is normally associated with poultry and eggs, it was unusual that truffle oil was the likely source. And being a common pathogen, the report indicates that "Timely engagement of the public, health care providers, and local and federal public health officials, is particularly critical for early recognition of outbreaks involving common foodborne pathogens, such as
Salmonella Enteritidis" Basically, by really looking hard, investigators were able to determine that something different was going on, and in doing so, were able to determine the restaurant was involved. At that point, they closed the establishment thus preventing additional cases that would have most definitely occurred.
As far as testing "Truffle fries sampled from the deep fryer and uncooked truffle mushroom croquettes were among the samples collected on September 10; a truffle oil sample was collected on September 14." "DCPHL tested the truffle fries, which screened positive for Salmonella by using polymerase chain reaction (PCR), but Salmonella was not isolated during confirmatory testing. All other food and environmental samples were negative for Salmonella."
Another outbreak in the same restaurant chain indicated the issue may have originated in a NY commissary where the oil originated (but not sure if made there). It seems the commissary had gone through purge and sanitize procedure, so nothing was found there when investigators inspected that operation.
So before we throw truffle oil on the list per se, there should be additional information as to where it was made. This may be more of a commissary issue that a truffle issue.
CDC - MMWR
https://www.cdc.gov/mmwr/volumes/66/wr/mm6610a4.htm?s_cid=mm6610a4_e
Investigation of Salmonella Enteritidis Outbreak Associated with Truffle Oil — District of Columbia, 2015
Weekly / March 17, 2017 / 66(10);278–281