Chapter reviewed and updated in December 2017. A description of changes can be found at Updates to the Communicable Disease Control Manual.


New Zealand Epidemiology

Cronobacter species were previously known as E. sakazakii.

Cronobacter spp. is naturally present in the environment and has been known to cause disease in people of all ages. The particular concern underlying the decision to make Cronobacter spp invasive disease notifiable is disease in premature neonates, including meningitis, necrotising enterocolitis and sepsis, often resulting in death, as a consequence of low-level Cronobacter spp contamination in powdered infant formula. In August 2004 all neonatal units were advised to cease using powdered infant formula, and instead use the prepared ‘ready-to-feed’ (RTF) infant formula that is recommended by the Ministry of Health and Ministry for Primary Industries.

More detailed epidemiological information is available on the Institute of Environmental Science and Research (ESR) surveillance website.

Case definition

Clinical description

Severe illness, usually in neonates and occasionally in elderly and immunocompromised, frequently presenting with hypo- or hyperthermia, lethargy, tachycardia, periods of apnoea and one or more of the following:

  • meningitis including seizures
  • encephalitis
  • necrotising enterocolitis
  • severe diarrhoea
  • severe sepsis
  • respiratory distress.

Only disease in infants less than 1 year old is notifiable.

Laboratory test for diagnosis

Laboratory definitive evidence for a confirmed case requires isolation of Cronobacter spp. from a normally sterile site, for example, blood, cerebrospinal fluid, or aspirated urine.

All invasive isolates of Cronobacter spp. or yellow-pigmented Enterobacter species (if unable to further speciate) from neonates or infants should be referred to the Enteric Reference Laboratory at ESR for confirmation.

Case classification

  • Under investigation: A case that has been notified, but information is not yet available to classify it as probable or confirmed.
  • Probable: Clinical deterioration with isolation of the organism from a non-sterile site, for example, faeces.
  • Confirmed: A clinically compatible illness accompanied by laboratory definitive evidence.
  • Not a case: A case that has been investigated and subsequently found not to meet the case definition.

Spread of infection

Incubation period

Not yet determined. In neonatal cases symptoms normally appear a few days after birth.

Mode of transmission

Cronobacter spp. has been known to contaminate infant formula through:

  • the raw materials used for producing the formula
  • contamination of the formula or other dry ingredients after pasteurisation
  • contamination of the formula as it is being reconstituted by the caregiver just before feeding.

Period of communicability

Although faecal carriage may last for 8–18 weeks, secondary transfer is not known to occur.


Notification procedure

Attending medical practitioners or laboratories must immediately notify the local medical officer of health of suspected cases. Notification should not await confirmation.

Only disease in infants less than 1 year old is reportable.

See Appendix 5: Escalation pathways for more information

Management of case


Obtain a history of pregnancy, medical co-morbidity and ingestion of potentially contaminated foodstuffs, in particular infant feed. Use the specific food-source questionnaire available through ESR to identify possible sources of contamination.

Ensure samples from the symptomatic patient and any foodstuffs, especially implicated infant feed, have been cultured for Cronobacter spp. Molecular subtyping should be used to determine the association between isolates from cases and any foodstuffs that test positive for Cronobacter spp. All invasive isolates of Cronobacter spp. should be referred to the Enteric Reference Laboratory at ESR for confirmation.

Where food/food businesses are thought to be involved inform the Ministry for Primary Industries.




The case and caregiver should be advised on the transmission of the infection and the symptoms.

Management of contacts


All neonates who have been exposed to the same food material suspected to be the source of infection, especially infant feed.


Investigate contacts who are symptomatic.

Restriction and prophylaxis



Close observation of neonatal contacts.

Other control measures

Identification of source

Liaise with the Ministry for Primary Industries.



Health education

New Zealand Government policy advice on infant feeding is:

  • breast milk is the best source of nutrition for newborn babies and breastfeeding benefits both the mother and the baby (Ministry of Health 2008).
  • where a decision is made to use infant formula, the most important considerations are as follows:
    • powdered infant formula is not sterile, which means it may contain bacteria; however, these bacteria very rarely cause illness as long as the formula is prepared and stored properly (refer to Ministry of Health booklet Feeding Your Baby Infant Formula)
    • healthy full-term (37–42 weeks) babies have an extremely low risk of infection by Cronobacter spp. from powdered infant formula
    • if formula is being used, a dairy-based powdered infant formula is recommended
    • when preparing dairy-based powdered infant formula, it is recommended you only prepare the amount you need for your baby’s next feed and that you prepare formula as close as possible to feeding time.

The following recommendations are made for premature, low birth weight and sick babies (admitted to neonatal units).

  • Breast milk is best for these babies too, but some may need formula
  • If not breastfed, these babies who are more vulnerable to infection should be fed ready-to-feed liquid formula instead of powdered infant formula. Ready-to-feed liquid formula is sterilised in the bottle, which means there is no risk of infection for babies given this formula.
  • If no alternative to powdered formula is available, then strict preparation and administration guidelines should be followed to minimise infection risk. Parents of premature babies should check with their neonatal unit staff.


National reporting

Ensure complete case information is entered into EpiSurv.

If any cases occur, contact 0800GETMOH - CD option, and outbreak liaison staff at ESR, and complete the Outbreak Report Form.

Further information