Food Quality Magazine
ISSUE 02 | AUTUMN 2014
Cronobacter: Opportunistic Microorganism
of Growing Industry Concern
Seth Keller, Silliker Inc.
Cronobacter is an opportunistic
foodborne
pathogen
posing
an increased risk to the health
of neonates, persons with
immunocompromising conditions,
and the elderly. The organism has
been isolated from a wide variety of
sources including waste water, wheat,
soy, corn, herbs, fruits, vegetables,
powdered infant formula, and
powdered milk. The only confirmed
transmission of infections in humans
has been through powdered infant
formula and powdered dairy
products, making Cronobacter a
key food safety consideration to the
infant formula and dairy sectors.
Due to the small size of the overall
population studied and rarity of
infection, data regarding Cronobacter
spp. infections in the United States
prior to the early 2000’s is somewhat
unreliable. There is no national
surveillance program for Cronobacter
infections, and such infections are
only required to be reported in the
state of Minnesota. Additionally,
due to the wide variety of symptoms
caused by the pathogen, it is
believed multiple additional cases
have gone unreported. However,
recent studies have shown that
infections from this organism may
be higher than expected, even in
healthy adolescents and adults.
It is important to understand the
background of this microorganism.
Cronobacter is a group of gramnegative, anaerobic, motile, rod
shaped bacteria classified under
the family Enterobacteriaceae. The
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microorganism was first discovered
and named “yellow-pigmented
Enterobacter cloacae” in 1929 during
a case of septicemia in an infant.
In 1980, due to a close relation to
the phenotypic traits of organisms
in the Enterobacter and Citrobacter
genera, the bacteria was re-defined
as Enterobacter sakazakii species
in honor of Japanese bacterial
taxonomist and microbiologist Riichi
Sakazaki. However, during the time
period the bacterium was classified
as a single species, it was noted that
E. sakazakii possibly represented
multiple species.
In 2007, research using amplified
fragment-length polymorphism,
phenotypic arrays, automated
ribotyping, 16S rRNA gene
sequencing,
and
DNA-DNA
hyrbridization resulted in a
nomenclature change from the
species E. sakazakii to five species
under a new genus, Cronobacter.
Over the past few years, additional
species have been discovered
under this genus. The source of the
bacteria is unknown, but the most
probable origin and ecological niche
is within dry environments and plant
material.
Since its 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 pathogen is
extremely dangerous. Once it enters
the digestive system, it quickly
causes death to portions of the
intestines and has been associated
with life-threatening cases of
meningitis, necrotizing enterocolitis,
and sepsis in premature and fullterm infants. The U.S. Centers for
Disease Control and Prevention
(CDC) recently estimated that 1.8
in 100,000 infants are infected each
year, slightly higher than the overall
incidence rate which is estimated at
0.66 cases per 100,000 people.
As stated previously, the only
confirmed transmission of infection
is through the 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 and
reconstituted. It is estimated that
1 million infants in the U.S. are
fed formula from birth; by threemonths, formula is a regular dietary
component of about 2.7 million
newborns.
In an effort to reduce future
Cronobacter outbreaks among
infants, the Food and Drug
Administration (FDA) recently
published a new ruling, setting
standards for infant formula
manufacturer. Under the new
rule, which went into effect
September 8, 2014, infant formula
producers must establish good
manufacturing practices (GMPs)
specifically designed for infant
formula, including required testing
for Cronobacter and Salmonella.
Moreover, manufacturers must be
able to demonstrate that their infant
formula promotes normal physical
growth including nutritional content
testing in the final product stage,
before entering the market, and at
the end of the product shelf life.
Apart from FDA o