Cronobacter, an emerging opportunistic foodborne pathogen, is posing an increased risk to the health of neonates, persons with immunocompromising conditions, the elderly, and even healthy adolescents and adults. This gram-negative, anaerobic, motile, and rod shaped bacteria exists in the environment and can survive in a variety of dry conditions. Due to the rarity of infections and wide variety of symptoms caused by Cronobacter, the bacterium is under-reported and not well understood in the United States.

The Evolution of Cronobacter
There is a long taxonomic history involving multiple nomenclature changes for this pathogen.

  • In late 1929, the organism was first discovered in a case of septicemia in an infant and named “yellow-pigmented Enterobacter cloacae”.
  • From the 1930’s through the mid 1970’s four additional names were used for the bacteria, including: “Urmenyi and Franklin bacillus”, “yellow coliform”, “yellow Enterobacter”, and “pigmented cloacae A”.
  • In 1980, the organism was officially renamed and defined as its own distinct species, Enterobacter sakazakii (under the family Enterobacteriaceae) in honor of the Japanese bacterial taxonomist and microbiologist, Riichi Sakazaki.  During this era, it was noted that the organism E. sakazakii possibly represented multiple species.
  • In 2007, due to the emergence of molecular biology identification and detection methods, E. sakazakii was re-classified as five species within a new genus, named Cronobacter.
  • Over the past few years, additional species under the genus Cronobacter have been discovered.

Emerging pathogen?
Since its initial discovery, Cronobacter infections have been most commonly researched and associated with infants due to the severity of infections and elevated mortality rates, reaching as high as 40-50% in newborns. The bacterium has also been associated with life-threatening cases of meningitis, necrotizing enterocolitis, and sepsis in premature and full-term infants. The U.S. Centers for Disease Control and Prevention (CDC) estimates that 1.8 in 100,000 infants are infected each year. The natural habitat for Cronobacter is unknown, but the bacterium has been found in a variety of foods including powdered infant formula, milk powder, herbal teas, and even waste water. For infants, the only confirmed transmission of the infection is through consumption of reconstituted infant powder and milk powder. Since Cronobacter is ubiquitous, contamination has occurred at infant formula factories, as well as homes and other locales after products were opened.

According to a recent CDC study, Cronobacter infections may be more prevalent than originally thought in adolescent, adult, and elderly populations. Set to be published in the September issue of the CDC’s Emerging Infectious Diseases, the study, for the first time, will analyze rates of Cronobacter infections in groups other than infants. The study estimates around 3.9 out of every 100,000 people older than 65 are infected on a yearly basis, more than double the estimated infection rate in infants. While cases are less severe in adolescents, adults, and the elderly, infections of the blood and urinary tract have been associated with the pathogen. When it comes to the increased number of infections in adolescents and adults, the vehicle for transmission is still unknown and next on the CDC’s research agenda. On a positive note, there have been no confirmed reports of Cronobacter infections spreading from person-to-person contact.

To add to the heightened awareness of this emerging pathogen, a recently published FDA ruling, which went into effect September 8, 2014, requires all infant formula producers to test for Cronobacter and Salmonella.

Should you have any questions or concerns around these new testing requirements, please contact us for additional information.

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