Invasive Cronobacter infection Among Infants
2024 Case Definition

Background

Cronobacter spp. belong to the order Enterobacterales, which are Gram-negative bacteria.¹ Cronobacter spp. are opportunistic pathogens linked to illnesses and outbreaks of life-threatening necrotizing enterocolitis, meningitis, and sepsis in neonates, infants, and other susceptible populations.² In 2008, the bacteria were reclassified under the genus Cronobacter which replaced the former single species Enterobacter sakazakii.³ To date, the most clinically relevant species are C. sakazakii and C. malonaticus, which are recognized as causing invasive disease in infants.²

Clinical Criteria

In the absence of a more likely alternative diagnosis, an acute illness in an infant characterized by an invasive infection, including but not limited to meningitis, cerebral abscess, sepsis, necrotizing enterocolitis, or urinary tract infection.

Laboratory Criteria

Confirmatory Laboratory Evidence:

• Isolation by culture of Cronobacter in a clinical specimen from a normally sterile site (e.g., blood or cerebrospinal fluid).

Supportive Laboratory Evidence:

• Isolation of Cronobacter spp. in a clinical specimen from a non-sterile site (e.g., stool or rectum, urine, skin, respiratory secretions, or broncho-alveolar lavage, etc.)*.

Note: The categorical labels used here to stratify laboratory evidence are intended to support the standardization of case classifications for public health surveillance. The categorical labels should not be used to interpret the utility or validity of any laboratory test methodology.
* Whether and how public health conducts follow-up for isolation of Cronobacter spp. from a non-sterile site in the absence of clinical disease is at the discretion of the jurisdiction.

Epidemiologic Linkage

Epidemiologic risk factors within 7 days prior to illness onset in an infant:

• Consumption of powdered infant formula (PIF) implicated as the source of infection, OR
• Exposure to a non-PIF product, such as breast milk, implicated as the source of infection, OR
• Residing in a congregate setting (e.g., a neonatal intensive care unit [NICU]) with an active Cronobacter outbreak.

Criteria to Distinguish a New Case from an Existing Case

A new case should be enumerated when:

• An infant was previously reported but not enumerated as a confirmed, probable, or suspect case, but now meets the criteria for a confirmed, probable, or suspect case, OR
• An infant most recently enumerated as a suspect case with supportive laboratory evidence with specimen collection date for that classification within 90 days‡ prior but now meets the confirmed case classification, OR
• WGS results indicate that a new positive specimen and a prior positive specimen are genetically distinct.

‡This time frame may be revised in future position statements if more information indicates a different period is more appropriate.

Suspect

• Meets clinical criteria AND supportive laboratory evidence, OR
• Meets clinical criteria AND epidemiologic linkage criteria.

Probable

• Meets clinical criteria AND epidemiologic linkage criteria AND supportive laboratory evidence.

Confirmed

• Meets clinical criteria AND confirmatory laboratory evidence.