A Cronobacter sakazakiithe bacterium responsible for withdrawing infant formula from the market, is less well known than other foodborne pathogens such as E. coli or a Salmonellabut it can affect vulnerable populations such as newborns or people with a compromised immune system.
Earlier this year, when two babies died in the US after drinking infant formula produced by the company Abbot Nutrition that was contaminated with this bacteria, the tragedy caused a widespread recall of the product from the market, eventually resulting in the closure of the company’s factory. in Michigan. In the US, parents and caregivers alike – who are already pressured by supply chain issues related to the pandemic – have struggled to feed their babies. The deaths and the shortages that followed have exposed the weaknesses of the food security system in the United States, especially when this system is confronted with a bacterium such as Cronobacter sakazakii.
Fortunately, cases of infection caused by this “nasty little worm” – which kills 50 to 80 percent of infected newborns – are relatively rare, with few cases identified annually in the US, according to Amy Edwards, a pediatrician and medical director at the Infection Control Department at Rainbow Babies & Children’s UH Hospital in Ohio. Amy Edwards has worked for 12 years in neonatal intensive care units and has encountered this bacterium about a dozen times. “But if you call and say your two-month-old is developing a culture of Cronobacter sakazakii, I get a little scared. Scares me more than E. coli” says Amy.
Named after Kronos – the titan god of Greek mythology who consumed his own children – and the Japanese microbiologist Riichi Sakazaki, who characterized the species, the Cronobacter sakazakii is a cunning bacterium that has developed a few tricks that help it thrive in conditions under which most of its congeners cannot survive.
This forces us to keep an eye out for this bacteria, says Benjamin Chapman, a microbiologist and food safety expert at the University of North Carolina.
What is the Cronobacter sakazakii?
Despite having a more discreet profile and relatively low infection rates, the C. sakazakii it is a common bacterium. “It’s in the soil and in the environment,” says Benjamin Chapman. It has also been detected in residential homes, including kitchen countertops, air filters and other surfaces. And despite now being tragically associated with powdered infant formula, this bacteria has appeared on everything – both now and in the past – in fresh produce, herbal teas and in wastewater.
“The bacterium C. sakazakii it’s also part of the normal human flora, which resides in the gut in small amounts and is controlled by other bacteria,” says Amy Edwards. The gut microbiome involves a community of (mostly) beneficial microbes that ensure the body functions optimally. For healthy children or adults, small amounts of pathogenic bacteria “do not really cause problems”.
Erika Claud – a neonatologist at the University of Chicago who studies the effects of an intestinal disease that is often brought on by C. sakazakii – agrees with Amy’s words. “Think of your microbiome as if it were an ecosystem, a forest or a lake: all the elements keep everything else in check.” When this system is in balance, good bacteria can prevent bad bacteria from adhering to human cells. They also compete for available nutrients, preventing harmful microbes from flourishing.
when does the Cronobacter sakazakii is it dangerous?
Newborns, however, with still-developing immune systems and immature gut microbiomes, can be quickly overwhelmed by pathogens such as C. sakazakiiwhich are usually introduced into your body through powdered formulas or through the birth canal during birth.
One of the typical routes of attack by this bacterium, says John Swartzberg, professor emeritus of infectious diseases at the University of California at Berkeley, is the gastrointestinal tract. Normally, pathogens get trapped in the mucus layer that separates what’s inside the intestines from the rest of the body. “However, in neonates or immunocompromised adults, the Cronobacter sakazakii can penetrate the mucosal wall, enter the bloodstream and travel to the rest of the body.”
Amy Edwards adds that this bacterium can then trigger sepsis, a generalized inflammatory response of the body, causing various organs, such as the heart and kidneys, to begin to fail.
Another of the favorite targets of the C. sakazakii it’s the brain. “This bacterium has a predilection for the lining of the brain, or the meninges, causing bacterial meningitis,” explains John Swartzberg. If the child manages to survive the infection, the consequences are often dire – including seizures, cognitive impairment and developmental delays.
science of Cronobacter sakazakii
These bacteria, which are part of the family Enterobacteriaceaeare rod-shaped organisms with whip-like appendages that help them move toward nutrients and other targets.
In addition to this bacterium being mobile, the C. sakazakii it is also particularly resistant; viable bacteria were discovered in powdered formulas stored for two years. “Surviving in arid environments for a long time is important,” says Benjamin Chapman. This characteristic makes traditional strategies used in food safety, such as dehydrating food to inhibit bacterial growth, useless in the fight against C. sakazakii.
The bacteria’s secret lies in its genome, according to Roy Sleater, a molecular biologist at the Munster University of Technology in Ireland. Roy Sleater and his team discovered that the C. sakazakii contains seven copies of an osmotolerant gene – which encodes a protein that helps protect bacteria in low-humidity environments – while other bacteria only have one copy. This allows the C. sakazakii produce much more of this protective protein compared to other bacteria that are less resistant to dehydration. “And this protection extends to other forms of stress, like high temperatures and high pressures,” says Roy Sleater, referring to previous research that found that bacteria that can survive in low-humidity conditions also become more resistant to stress. heat.
A C. sakazakii it also manages to form a biofilm, a community of bacteria that coexist in a sugary matrix produced by its members, says Erika Claud. This biofilm can adhere to surfaces such as countertops or hospital equipment, including organic matter such as a baby’s intestinal cells. “It’s a case where the union is the strength, because a biofilm is much more than the sum of its parts – the bacteria inside it communicate with each other and adapt to changes in the environment.” This flexibility makes biofilm layers particularly difficult to destroy.
Benjamin Chapman hopes that the events of recent months in the US will put the C. sakazakii in the spotlight. “So far, it hasn’t made the list of things we’re tracking – like the E. coli or a Salmonella. But the impact on babies who rely on powdered formula as their only source of nutrition can be enormous. I liked to see the Cronobacter sakazakii elevated to something that we monitor, and that is considered a notifiable disease.”