Cronobacter sakazakii Isolated in Two Infants in New Mexico, 2008
In the October 30, 2009, edition of its weekly MMWR publication, the Centers for Disease Control and Prevention (CDC) reported on an investigation in November, 2008, when the Cronobacter sakazakii bacteria was isolated in two different infants. As recognized by the CDC, isolation of this organism from human specimens is rare and makes these cases notable. Cronobacter sakazakii (formerly Enterobacter sakazakii) are rare causes of infant septicemia and meningitis, resulting in death in approximately 40% of cases. Since 1958, 120 cases of Cronobacter sakazakii infection in infants have been reported, an average of fewer than three cases per year worldwide. Powdered infant formula (PIF), which is not sterile, has been implicated repeatedly as a vehicle of Cronobacter infection. This report provides important additional information regarding this elusive pathogen, and updates the CDC’s recommendations regarding safer PIF preparation, storage, and handling.
The Cronobacter sakazakii bacteria were isolated from two non-hospitalized, unrelated infants in November, 2008, in New Mexico. The CDC and FDA investigators determined that the female infant had been infected with Cronobacter sakazakii, and that the male infant had been colonized with Cronobacter sakazakii, without clear evidence of infection. Ingestion of PIF was the only identified risk factor for Cronobacter sakazakii exposure for the two infants. The two infants had consumed the same brand of PIF but had no other common exposures. The female infant had documented Cronobacter sakazakii infection that led to severe brain injury and hydrocephalus. Although a Cronobacter sakazakii organism was isolated from the male infant at autopsy, the role of that organism in the infant's apparent death from SIDS is unknown.
The two infants had consumed the same brand of formula, but their clinical Cronobacter sakazakii isolates had different Pulsed Field Gel Electrophoresis (PFGE) patterns. None of the samples obtained from the home of the female infant yielded Cronobacter sakazakii. Samples taken from the home of the male infant, however, provided positive results for Cronobacter sakazakii. An opened can of PIF yielded a Cronobacter sakazakii isolate with a PFGE pattern that was indistinguishable from the clinical Cronobacter sakazakii isolate from the male infant. Additionally, the vacuum cleaner filter from the home of the male infant also yielded Cronobacter sakazakii, but with a different PFGE pattern than the PFGE pattern isolated in both the male infant and the open PIF can.
The CDC reaffirmed in this report that prior investigations have found Cronobacter sakazakii cultured from prepared formula, unopened PIF containers, and the environment where PIF was reconstituted, clearly implicating PIF as the source of outbreaks. Other than an improperly prepared intravenous nutrition solution implicated in one outbreak, no other clear source of Cronobacter sakazakii infection has been identified to date. Accordingly, the report recommended that preparers should be aware that PIF is not sterile and can contain pathogenic organisms, such as Cronobacter sakazakii. The report also recommended that WHO guidelines for preparation of PIF, including reconstitution with water hot enough to inactivate Cronobacter sakazakii, be adopted, for safer PIF preparation, storage, and handling. In the United States and elsewhere, present recommendations are: to breastfeed infants when possible; to use sterile liquid infant formula in high-risk settings (e.g., neonatal intensive-care units and hospital nurseries); and to adhere to the safest available PIF preparation procedures. Interestingly, the CDC report noted that the manufacture of sterile powdered infant formula, perhaps by using irradiation in combination with other techniques, could prevent infant disease. Finally, the CDC stated that further precautions to prevent extrinsic contamination of PIF are needed, including the engineering of PIF packaging to prevent introduction of contaminated hands, scoops, or other items.
The complete report is accessible at MMWR. 2009:58;1179-1183.
Biography: Dr. Han Joosten is a Senior Scientist at the Nestle Research Center in Lausanne, Switzerland. At Nestle since 1996, he is responsible for providing scientific guidance on various research projects and early identification of emerging microbiological safety issues. He also provides advice to the business and quality management on analytical methods, hurdle technology, safety assessments and HACCP.
Editor's Note: This is another report on the presentations that were made in Dublin earlier this year at the 1st International Meeting on Cronobacter (Enterobacter Sakazakii).
Professor Fanning received an Honours BSc in Biochemistry from NUI, Cork, where he also completed his PhD in Microbiology and Molecular Genetics. Current research interests include the application of molecular methods to Food Safety to control zoonotic microorganisms associated with human disease. A significant part of this work relates to the characterization of the genetic mechanisms contributing to the emergence of multiple drug resistance (MDR); the role of membrane bound efflux pumps in MDR and virulence and how these phenotypes are regulated at a local and global level. 