cloacaedistinguishable from other members of the species by production
of a yellow water diffusible pigment on tryptone soy agar. In 1980 it was
renamed Enterobacter sakazakii in honour of the eminent Japanese
bacterial taxonomist Riichi Sakazaki.
It is a typical mesophile and can grow between 6oand 47oC. As with
many species, its heat resistance varies between strains. Some workers
have described the heat sensitivity as similar to other Enterobacteriaceae
while others have reported slightly higher resistance. A typical published
D value measured in reconstituted dried milk at 60oC was 2.5 minutes
with a z value of 5.8oC.Ent. sakazakiiappears to be relatively more
resistant to low awstress than other Enterobacteriaceae and this may be a
significant factor in its transmission.
7.7.3 Pathogenesis and Clinical Features
Ent. sakazakiiis the recognised cause of severe infections in infants
characterised by meningitis, cerebritis, bacteraemia and necrotising
enterocolitis. Infection is associated with a high mortality rate of 50%
or more and severe long term, irreversible sequelae occur in most
survivors. These include quadriplegia and impaired sight or hearing.
The most common predisposing factors for infection are low birth-
weight or premature birth.
7.7.4 Isolation and Identification
The severity of the illness and an apparently low infectious dose have
led to very stringent criteria applying to the presence/absence ofEnt.
sakazakiiin powdered infant formulae. Thus cultural detection follows a
similar scheme toSalmonella detection involving pre-enrichment, and
selective enrichment stages prior to the use of selective agars. Agar media
can be selective and diagnostic for Enterobacteriaceae in general followed
by biochemical testing to confirm the identity of isolates, although
selective media have also been developed to detect a key biochemical
characteristic of the organism such as its ability to producea-glucosidase.
A variety of molecular methods have also been developed for the
identification and typing based on PCR and ribotyping, pulsed-field gel
electrophoresis (PFGE) and random amplification of polymorphic DNA
(RAPD)
7.7.5 Association with Foods
Ent. sakazakiiappears widespread in the environment and has been
isolated from water, soil and vegetation as well as the contents of
household vacuum cleaners. Powdered infant formula foods have been
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