“I’d like to see Cronobacter sakazakii elevated to something that we track and becomes a notifiable disease."
- Benjamin Chapman, Ph.D., Professor and Department Head, Agricultural Human Sciences, North Carolina State University
“I believe that the FDA has failed to prioritize the safety of all foods that are sold on our market."
- Rosa DeLauro, U.S. Representative (Connecticut), Chair, House Committee on Appropriations
On February 28, 2022, Abbott Nutrition voluntarily recalled three of its powdered infant formulas following the deaths of two infants who drank formula that was contaminated with the bacterium Cronobacter sakazakii. The tragic deaths of these infants precipitated the shutdown of the company’s Michigan-based plant, which in turn exacerbated an already existing weakened supply chain leading to a nationwide shortage of infant formula. Although the shortage has since been resolved, the recall raised questions about who’s in charge of food safety in America? And for some, including me, it also precipitated the question, “What on Earth is C. sakazakii?” In this Germ Gems post, I provide background on this cunning microbe and discuss food safety issues that surfaced in the wake of this tragic outbreak.
The science and clinical impact of C. sakazakii? First, a confession: until learning of this outbreak of baby formula-related infections in four neonates (two of whom died), I had never heard of this bacterium. You might wonder, how’s that possible after more than four decades of practice as an infectious disease specialist?
First, as an internist I cared for adults, and most of the cases of C. sakazakii infection occur in infants. Additionally, as was the case in this outbreak, powdered baby formula is a common vehicle for C. sakazakii infection—a food that is seldom, if ever, eaten by adults. Moreover, Cronobacter infections are rare. The Center for Disease Control and Prevention (CDC) is notified of about four cases per year, 50%-80% of which are fatal.
Despite its low profile and infection rates, C. sakazakii is a common microbe. It is found in the environment, including in soil and in homes on countertops and other surfaces. It is also found in the gut microbiome of healthy adults where it is kept in check by other members of the gut flora. But, in newborns or immunocompromised adults, it is a different story. In these groups of people C. sakazakii can penetrate the wall of the gut and get into the bloodstream causing severe “sepsis.” And as it travels through the body, it may end up in the brain causing bacterial meningitis, that contributes to the high mortality rate.
C. sakazakii is a member of the Enterobacteriaceae family of rod-shaped organisms with whip-like appendages, that help these microorganisms move towards nutrients and other targets. One particularly elegant feature of this bacterium is that it is exceptionally hardy—viable bacteria have been discovered in powdered formula left on the shelf for up to two years.
Scientists have discovered that C. sakazakii contains seven copies of an “osmotolerane” gene that encodes a protein that helps protect it in low-moisture environments. In addition to being desiccation resistant, C. sakazakii forms a “biofilm,” a sugary matrix that protects a whole community of bacterial cells. According to microbiologist and food safety specialist, Benjamin Chapman, “The fact that it survives in arid environments for a long time is really special. This trait renders traditional food safety strategies like drying food to inhibit bacterial growth useless against C. sakazakii.”
Foodborne infection. The CDC is responsible for tracking outbreaks of foodborne infections (defined as an incident in which two or more persons experience a similar illness after ingestion of a common food or meal and epidemiologic evaluation implicates the meal or food as the source of illness). Given the rarity of C. sakazakii infections, the bacterium rarely comes to the attention of the CDC as a cause of foodborne infection outbreaks. According to the CDC, 48 million Americans are victims of foodborne illness per year, and of the 17 outbreaks the CDC investigated in 2021, C. sakazakii was not among them. (The October 27, 2021 Germ Gems post, “For Crying Out Loud: Salmonella in Onions,” dealt with the most common cause of foodborne-related hospitalizations and deaths, that is Salmonella, albeit from an uncommon food source [onions] in that particular case).
C. sakazakii is in fact a very rare pathogen, and oversight of baby formula is a top priority in preventing most infections. The CDC does, however, recognize people with compromised immunity as a high-risk group for C. sakazakii infection. Because of the phenomenon of immunosenescence (waning of immunity associated with aging), I thought there would be cases reported in elderly adults. But in my review of the literature, the one and only case report I found was of a C. sakazakii fallopian tube infection in a 70-year-old woman (see, BMC Womens Health, April, 2021).
Foodborne infections in baby boomers. In my search for cases of C. sakazakii in elderly adults, I found an interesting article posted in FoodSafety.gov that targeted baby boomers: “Baby Boomers and Food Safety.” (“Boomers” are people born between 1946 and 1964, some of whom are now considered “elderly”—defined as 65 years of age or older). As you would imagine, neither C. sakazakii nor powdered milk formula is mentioned as a risk to “boomers.” Listeria monocytogenes, is, however, highlighted. This pathogen is notorious for causing serious infections in immunocompromised people. For the estimated 76.4 million American baby boomers, the CDC advises avoiding foods that have a high risk of contamination from Listeria such as soft cheeses, raw or undercooked meat, poultry, eggs or seafood, and unpasteurized milk. The CDC also provides recommendations regarding proper food preparation in order to stay clear of this opportunistic pathogen.
Who then is responsible for food safety? One of the major roles of the CDC is to make food safer. In doing so, it focuses primarily on determining the sources of foodborne illnesses and investigating multistate foodborne disease outbreaks with the goal of preventing illnesses and stopping outbreaks. But the CDC is not alone. As its name implies, the Food and Drug Administration (FDA) is also charged with the responsibility for investigating foodborne infection outbreaks with the aim to learn how to prevent similar outbreaks from happening in the future.
So, who was blamed for dereliction in this recent outbreak of powdered milk formula-related C. sakazakii infections? According to a June 11, 2022 article in The Lancet, the FDA was held responsible, “US infant formula crisis increases scrutiny of the FDA.” During his testimony before the U.S. House of Representatives’ Committee on Oversight and Investigation, the FDA Commissioner, Robert Califf, admitted that it took too long to inspect the plant after receiving a whistle-blower complaint. He told the committee, “we let you down and we are going to do everything we can to earn your trust.”
On June 3, U.S. Congresswoman Rosa DeLauro proposed legislation intended to close several of the regulatory gaps that the formula shortage had uncovered. She stated, “I don’t want to throw more money into a broken system, that’s why I want to change the system.” The role of the CDC in such a “changed system for food safety” was not spelled out. But a January 18, 2022 New York Times essay, “The C.D.C. and F.D.A. Can Work Better Together” (prompted by their sometimes working at cross-purposes during the COVID-19 pandemic), suggests that lessons learned from this very rare foodborne infection in newborns could be valuable in all areas where the FDA and CDC share responsibility for American public health. A closer, more coordinated partnership between the FDA and CDC in assuring food safety is certainly warranted and would benefit not only newborn babies and boomers, but all Americans.
Comments