Profiling Cronobacter sakazakii (Enterobacter sakazakii)

Cronobacter sakazakii (formerly known as Enterobacter sakazakii) is a rare, though often fatal, cause of meningitis in newborns and infants.

Some history

Cronobacter sakazakii has gone through more than one name change. It was first described as a yellow-pigmented Enterobacter cloacae, then – in 1980 – assigned the species name Enterobacter sakazakii (Farmer, J.J. III, et al. 1980. Enterobacter sakazakii: A new species of “Enterobacteriaceae” isolated from clinical specimens. Internat. J. Systemic Bacteriol. 30(3): 569-584). The pathogen was linked to cases of neonatal meningitis for the first time in 1961 in a British report (Urmenyi, AM & Franklin, AW. 1961. Neonatal death from pigmented coliform infection. Lancet 1(7172): 313-315), and for the second time in a 1965 report from Denmark (Joker, R.N., et al. 1965. A case of neonatal meningitis caused by a yellow enterobacter. Dan. Med. Bull. 12:128-130).

What is Cronobacter sakazakii, and where is its natural habitat?

Cronobacter sakazakii is an opportunistic pathogen, affecting mainly newborns, and causes neonatal necrotizing enterocolitis and neonatal meningitis. In older infants, children and adults, it can cause sepsis and/or respiratory illness. The microbe has been found in many countries around the world, and has been recovered from Mexican fruit flies and the larvae of stable flies. It is found in food production facilities and households, and has been detected at low levels in powdered infant formulas in a number of countries.

How is Cronobacter sakazakii transmitted? What is the incubation period of the infection?

Cronobacter sakazakii infections of newborns have been traced to the use of reconstituted powdered infant formula, especially in hospital settings where formula is prepared in bulk and stored for several hours under refrigeration until needed. In neonatal intensive care units (NICU), feedings can take several hours, during which time the reconstituted formula remains at room temperature – a recipe for microbial multiplication. The incubation period for a Cronobacter sakazakii infection may be as short as one day or as long as three weeks; typically, infections show themselves within one week.

What illnesses are caused by Cronobacter sakazakii? How long does it take to develop?

Cronobacter sakazakii is a cause of necrotizing enterocolitis and meningitis in newborns. In older babies, children and adults, this opportunistic pathogen can cause respiratory infections and sepsis.

What are the symptoms of Cronobacter sakazakii infections?

Symptoms in newborns include fever, rapid heart rate, seizures and other neurological abnormalities.

What is the prognosis of Cronobacter sakazakii infections?

Cronobacter sakazakii infections are often fatal in newborns. The death rate has been reported to be as high as 40-80%.

What foods carry Cronobacter sakazakii?

Cronobacter sakazakii has been found at low levels in powdered infant formulas. It also can be found in water and the environment.

How can susceptible people protect themselves from infection?

The Illinois Department of Public Health offers the following advice:

Clean utensils

  • Wash hands, forearms and fingernails thoroughly before handling any feeding materials or preparing formula.
  • All bottles, nipples, caps and rings should be washed in hot, soapy water with thorough rinsing.

Preparing formula

  • Before use, powdered formula should be kept dry in an airtight container with a firm cap or lid and stored in a cool, dark area. Make sure the expiration date has not passed.
  • During formula preparation, bring water to a bubbling boil for two minutes and allow the water to cool before mixing.
  • Do not use a microwave oven to warm the formula.

Storing formula

  • Formula should be prepared in small amounts immediately before feeding time to minimize the need for storing reconstituted formula.
  • Reconstituted formula should not be stored at room temperature for more than one hour or more than four hours in the refrigerator after preparation.
  • Throw out any formula left in a bottle after feeding.

You can find more information on Cronobacter sakazakii and other food-borne pathogens in Food Safety: Old Habits, New Perspectives.


30 thoughts on “Profiling Cronobacter sakazakii (Enterobacter sakazakii)

  1. I am a microbiology technologist and have been since 1974. Sandy, these bacteria have probably existed for millenia. I was reporting out Enterobacter cloacae when I first started in microbiology. We were using simple tubed media identification in those days. We prepared the identification media at our lab, racks and racks of different types.

    In the late 70’s, new commercial identification methods were marketed to micro labs that gave more reactions. They took much less room to store, and most labs quit making their own identification media. I would guess that this trend started the investigations with the two different morphologies of E. cloacae, which ended up producing a name change, as they found that the yellow-pigmented E. cloacae gave some different reactions in the new ID strips.

    I have gone from identifying gram negative bacteria (of which E. cloacae and E. sakazakii/Cronobacter are included) with five reactions to the newest version of automated identifications that consist of 64 reactions in my 37 year lab career. We use a new instrument called the Vitek2 and, just in the last two years, many bacterial names have changed due to the infinite statistical variations in reactions. Testing at the molecular level will also change many bacteria in the near and far future, as that is the way microbiological testing is heading.

    In layman’s terms, it’s as if you, Sandy, legally changed your name to Jane, and then, for some reason, had to change your name again to Joanne. You’re the same person; you just have had two names in the past.

    Believe me, you cannot control sterility absolutely in every situation. Bacteria are in the environment and all around us. Unless you live like Bubble Boy, there are bacteria everywhere. The trick is to minimize the impact of the pathogens by taking the precautions in preparing formula each and every time.


      1. You’re quite welcome. I’ve been following the Cronobacter issue with interest and have posted some CDC links on Facebook. A FB friend, who is a pathologist in his 70’s, was remarking on the name changes and I found your blog researching information on the bug for him. I have worked in medical microbiology my entire career, but food micro has always been a side interest, although I am ignorant of procedures used in the food industry to track down pathogens. What few requests we get for identifying possible pathogens in food go straight to our Health Department, per our procedures, and we do not get involved in culturing food at all. Hope to learn something from this blog. :-).



  2. J.J. Farmer’s paper in the International Journal of Systematic Bacteriology of July 1980 pages 569-584 entitled, “Enterobacter sakazakii: A New Species of ‘Enterobacteriaceae’ Isolated from Clinical Specimens”
    He states, “The proposed change in the classification of this organism is based on differences between E. cloacae and E. sakazakii in deoxyribonucleic acid (DNA)-DNA hybridization, biochemical reactions, pigment production, and antibiotic susceptibility. By DNA hybridization, E. sakazakii was about 50% related to E. cloacae…”


    1. And that’s why he proposed that the “YELLOW-PIGMENTED VARIETY OF ENTEROBACTER CLOACAE” should be reclassified as Enterobacter sakazakii. By the way, Escherichia coli (E. coli) was named originally “Bacterium coli”. Its original discovery is dated by when it was first discovered, NOT when it was last renamed. Likewise, Enterobacter sakazakii was not “discovered” by Farmer – just renamed. It has since been renamed (again) as Cronobacter sakazakii, thanks to additional information on its genetic relatedness to other microbes as a result of new technologies. That doesn’t mean Cronobacter sakazakii was just discovered either.

      When the city of Bombay reverted to its old name “Mumbai”, was it discovered as of the date of the renaming for the first time???????

      This is ABSOLUTELY my last word on this discussion. Believe what you will, Cronobacter sakazakii (formerly Enterobacter sakazakii, formerly yellow-pigmented Enterobacter cloacae) was first associated with neonatal meningitis in a 1961 report.



  3. Phyllis,
    This is from a peer reviewed medical journal called, “Surgical Infections,” 2008 October;9(5):533-539 entitled “Enterobacter sakazakii: An Emerging Pathogen in Infants and Neonates,” by Catherine J. Hunter et al.

    “Enterobacter sakazakii (ES) is a member of the Enterobacteriaceae family that was described as a new species in 1980. Initially, it was noted to be an opportunistic pathogen responsible for neonatal sepsis and meningitis [1–3]. Necrotizing enterocolitis (NEC) is the most common gastrointestinal surgical emergency in neonatal populations, which results in a mortality rate of 40–100% in the most severely affected patients [4].”

    It is renamed because it was considered a “new” species…I believe that there are people who would consider this discovery not simply renaming.


    1. Valerie, you need to read the complete article. I quote from the body of the same article, as follows: “The first two known cases of neonatal meningitis caused by ES, classified initially asEnterobacter cloacae, were reported in 1961.” and, “Enterobacter sakazakii was formerly referred to as yellow-pigmented E. cloacae,and was characterized as a unique species almost 30 years ago.”

      This pathogen was not “discovered” in 1980. It was RENAMED in 1980.



  4. According to the Nick Stein Law Office on the International Cronobacter Conference, John James Farmer III, made a number of discoveries, included among the many discoveries is Enterobacter sakazakii. The article says, “new clinically significant genera and species.” Farmer was the keynote speaker at the first Cronobacter Conference. This is a biography of the participants.


    1. Valerie,

      With all due respect to the Nick Stein Law Office, I do not consider personal injury attorneys – no matter how reputable or ethical they may be – to be the “last word” in a science-based discussion. I say that even though I have great respect for several attorneys who specialize in this area of litigation. The bottom line is the science, as found in the original PEER REVIEWED scientific literature. JMO.



  5. Everyone else: Keep your heads screwed on. This trio of C. sakazakii infections in infants is presently only of interest to the parents of those infants, epidemiologists and press outlets that are quite aware the combination of food-borne illness, babies and death makes for good stories. It’s like hitting the trifecta of sensationalistic journalism. This blog’s writer — with whom I am in no way affiliated — is attempting to provide an informative resource of sensible tone for the information of the interested public. Mucking up the comments with misinformation in support of wild conspiracy theories is reckless: You do far more harm than good promoting unfounded, unverified claims bereft of anything better than scant anecdotal evidence.


  6. Sandy: A percentage of infant mortality has been reported as caused by infectious and/or toxic agents passed from mother to child via breast milk. Now me, I suggest we let neonates starve to death — helps keep the population down — but I doubt you’d find that a tenable arrangement. However, it still brings up the question: What would you feed infants when EVERYTHING we feed them has been linked to their deaths in statistically significant numbers? Huh?


    1. I have no doubt this is how our government is controlling our population. As I am sure you know that milk from breastfeeding is consumed with whatever is in the foods the mother is eating, so if she is not aware that she is consuming genetically engineered foods then she is not aware that she is poisoning her baby. Now, granted some mothers are too selfish to even careless one way or the other as their addictions rule them. Labeling of genetic engineered foods would at least allow mothers to make the choice so that if genetic engineering is not the cause we can definitely rule this out as time goes on as an unlikely cause of generating a deadly bacterial infection in neonates.


      1. Sandy, if you look at CDC data, half the cases, practically all with known M&M, are neonates with gestational ages <40 weeks — save one, with a gestational age of 41 weeks. I won't argue the larger picture of intended or unintended collateral effects of so-called genetically engineered food products — bear in mind "genetic engineering" of food predates recorded history, via hybridization, and other agricultural and animal husbandry methods. But in the case of C. sakazakii, it's just flat not a genetically engineered food issue. Combine preterm neonates, who are notorious for trying to die, most often by infection, with feeding procedures that leave formula at higher temperatures for long periods of time. It's a setup. Yet it's still very, very rare.

        "Healthy eating" fads that carry over to infant nutrition are responsible for infant deaths, too. For example, infant botulism was unheard of in the modern first world until the 1960s, when the natural foods craze started people feeding their infants honey. Before honey earned a reputation as a superfood, and the sweetener of choice for the nutrition-conscious, very few mothers fed their babies honey. From the 1960s on, infant botulism in the US has remained quite rare, but from one case in a decade to as many as 70 in a year, that's a pretty big jump in incidence rate. This had nothing to do with processed food, genetically engineered food, or any such thing. It was everything to do with process, a process which formerly didn't really exist. Not in the kind of numbers that would make even a blip on national epidemiological statistics. But then there it was, thanks to health-food devotees who were GOING OUT OF THEIR WAYS to feed their infants so-called natural foods that were allegedly SO MUCH BETTER FOR THEM than processed foods. Except, oops, many infant guts — especially preterm, but it's a generalized risk — don't have the flora to destroy C. botulinum after it erupts from its spores and beings to propagate.


  7. Valerie: CDC 0743–75 dates to a confirmed foot wound infection in 1975, predating Dow’s patent by a decade. I’m not wasting my whole morning finding you a citation from the 16th century, but C. sakazakii infections predate genetic modification processes in which the endpoint is a product used in commercial foods. Further, using a polysaccharide product of an organism doesn’t mean contamination with the origin organism unless there’s a production process break down. Otherwise, we wouldn’t have most vaccines. Which of course you probably think are responsible for every disease known to man. So enjoy your coffee and pertussis. I’m going to have my coffee black.


  8. J. J. Farmer is considered the “discoverer” of enterobacter sakazakii. His discovery was printed in journals in 1980. From the International Journal of Systematic Bacteriology (July 1980), “The proposed change in the classification of this organism is based on differences between E. cloacae and E. sakazakii in deoxyribonucleic acid (DNA)-DNA hybridization, biochemical reactions, pigment production and antibiotic susceptibility.
    This paper was entitled,
    Enterobacter sakazakii: A New Species of ‘Enterobacteriaceae’ Isolated from Clinical Specimens.” So I cannot fathom how this new organism found in 1980 is considered responsible for neonatal meningitis in 1961. Did they preserve the bacteria? I would like to read the article that you mention in which enterobacter sakazakii was linked to neonatal meningitis in 1961. Would you give me the citation for that article? Thank you.


    1. Valerie, J.J. Farmer is not the “discoverer” of Enterobacter sakazakii. He and his co-authors published a proposed renaming of the microbe based on updated knowledge of its genetics, physiology and biochemistry in 1980. In that publication, Farmer acknowledged the earlier reports of neonatal meningitis that were published in 1961 and 1965, and attributes those reports as being most likely due to Enterobacter sakazakii. I have added the relevant three literature citations to my profile of Cronobacter sakazakii (click on the Pathogen Profiles tab to navigate to the article most conveniently).

      It is not unusual for microbes to undergo name changes as more is learned about them and about their genetic relationship to other microbes. This does not mean that the microbe is “discovered” each time it’s name has changed.



  9. One precious life taken from a preventative situation is one too many. A percentage of infant deaths have been reported caused by ingesting powdered baby formula. I can’t fathom why this product is allowed, legally, to be sold to the public to feed new born babies. Do the labels on these products state a warning that feeding your baby powdered formula may lead to serious illness causing death? Gentetically altered foods have not been tested to know what bacteria will become active and deadly under any circumstances and if Baby Avery had a weakened immune system that could have very well gone undetected for a couple of weeks or months we still won’t know if a genetically altered ingredient that may have been altered using c. sakazakii or a strain of this bacteria was in fact the cause. Why is the seriousness of this fact being ignored, especially when precious, innocent lives are being lost at such an early age?


  10. I think you too readily dismiss genetic engineering as a possible problem in cases regarding enterobacter sakazakii.. Neonatal meningitis can be caused by other pathogens besides cronobacter/enterobacter sakazakii. Enterobacter sakazakii was not “discovered” until 1980, so there would have been no test to determine that e. sakazakii was the cause of neonatal meningitis. It can be presumed that it was the problem but not truly known.
    Dow Chemical owns a patent called, “Heteropolysaccharide produced by Enterobacter sakazakii,”, patent #4806636 filed in 1985 in which they used this pathogen to create a hetereopolysaccharide “to be used as a suspending, thickening, or stabilizing agent, and as a frictional drag reduction agent in aqueous systems.” This would be used in foods and mutants of this organism were part of this patent. What do consumers really know regarding the use of bacteria to create “novel” foods? And can we say without hesitation that this has nothing to do with genetic engineering?


    1. Valerie, I must differ with your date. Enterobacter sakazakii was first linked to neonatal meningitis in a 1961 peer-reviewed article. It’s existence and identity were known well before 1980, even though it might have been known under another name (not unusual in microbiology – even Salmonella has undergone name changes).


  11. Has any research causing cronobacter sakazakii been conducted on the companies making powdered infant formula and their use of genetically altered ingredients? After learning about the process used to genetically alter cells in plants such as corn, soy and canola, I am convinced this is why this deadly bacteria is present and predominantly found in the powdered baby formulas.


    1. Sandy,

      The issue of Cronobacter sakazakii (formerly known as Enterobacter sakazakii predates the issue of genetically altered ingredients. Reports of fatal cases of neonatal meningitis date back to the early 1960s. The pathogen also can be found at low levels in powdered milk. In a hospital setting (such as a neonatal ICU), powdered formula is prepared in batches and may fed orally over a period of several hours. At least one outbreak was traced to the extended time that the reconstituted formula remained at room temperature during a feeding. The powdered formula was found to contain C. sakazakii, but it likely would not have had the chance to cause the infections if the microbe didn’t have several hours at room temperature at which to grow.

      If you are interested in reading more on the C. sakazakii background, check your local university, college or public library for my book (Food Safety: Old Habits, New Perspectives). I discuss Cronobacter sakazakii in Chapter 1 (Old Habits Die Hard)

      Thanks for visiting.

      Phyllis (aka foodbuglady)


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