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Last week, CDC released two “Final Update” reports on Salmonella outbreak investigations within a 48-hour period.

The first report, released on January 17th, summarized the results of an investigation into a 10-month long outbreak of Salmonella Typhimurium associated with exposure to clinical and teaching microbiology laboratories. The second report, released on January 19th, presented the results of an investigation into a 2-month long multi-state outbreak of Salmonella Enteritidis infections linked to a restaurant chain.

These two outbreaks had very little in common with each other; the outbreak settings were different, the scope and duration of the outbreaks were different, and the source of the infections was different. Nevertheless, the two outbreaks have one very important thing in common.

CDC, in conjunction with at least some of its public health partners at the state and local level, has chosen to withhold important information from the public.

What information has CDC withheld, and why should this information be released? Here is a list of questions that I sent to my media contact at CDC on January 18th, the day after the Salmonella Typhimurium outbreak report was released.

  1. Is there a specific reason why CDC is not specifying the identity of the commercial strain of Salmonella Typhimurium that is associated with this outbreak (by the ATCC or NCTC strain number – not the commercial supplier)? Can you provide me with the strain number ID?
  2. Does CDC have any hypothesis as to the trigger for this outbreak? Most of the commercial strains have been in use in various labs for many years. What may have happened to initiate the increase in cases? What determined the start date? With a baseline rate for the outbreak strain of 0 to 4 reports/week, how were the start and ending date established for this outbreak?
  3. Were the outbreak cases all tied to the same commercial source of the S. Typhimurium “Strain X”?
  4. Were the outbreak cases tied to the use of a specific format of the commercial source (for example, Bacti-discs or pre-filled inoculation loops)?
  5. Have any cases involving this same strain been reported to CDC since the last “outbreak” case on June 29, 2011? If so, how has CDC differentiated those cases from the outbreak cases (keeping in mind the baseline of 0-4 cases per week mentioned in the CDC report).
  6. Were the bulk of the cases linked to student labs or to clinical labs?

To these questions, I would now add, “Were the clinical lab cases tied mainly to in-hospital labs, or to free-standing commercial clinical labs? If the latter, was any single commercial lab chain disproportionately involved?

When the Salmonella Enteritidis restaurant chain outbreak report hit the internet, I again contacted my CDC media liaison and asked, “Can you please explain why CDC has not revealed the name of the restaurant chain implicated in the above-mentioned outbreak? Even better, can you identify the chain by name?

I realize that both outbreaks are “over” and that at least some of this information now is academic. Nevertheless, I question CDC’s actions in withholding information that could influence purchasing decisions on the part of consumers and of medical and lab professionals.

CDC reported on January 19th that Restaurant Chain A’s handling and cooking processes likely ruled out ground beef as a source of the Salmonella Enteritidis outbreak. This is favorable to the restaurant chain, and would give consumers comfort that the restaurants belonging to this fast food chain are following appropriate food-handling procedures – if only CDC had released the name of the chain.

As for the lab-related outbreak, if I was still running a microbiology lab, I would certainly want to know whether a specific packaging or format of commercially available control culture was more prone to contaminating the lab surroundings than others. I would opt to avoid this format, if I had the information and the choice. Likewise, as a medical doctor, I would opt to avoid a commercial clinical lab chain that was prone to in-lab contamination.

If either of these outbreaks had been traced to a specific packaged food, the offending food would have been named. There is no logical reason for restaurant-linked outbreaks to be handled differently. There is no logical reason for a lab-related outbreak to be handled differently.

I would appreciate receiving substantive answers to my questions.

Sincerely yours,

Phyllis Entis, MSc., SM(NRCM)