Rapid Method Detects Enterobacter Sakazakii in Infant Formula

A rapid new method now detects Enterobacter sakazakii (E sazakii) and other Enterobacteriaceae in infant food formulas and milk powders. The method utilizes cationic (positively charged) paramagnetic particles.

Matrix MicroScience (Newmarket, UK) has launched a method that takes only 23 hours from sampling to final colonies on selective agars. The currently used method takes more than four days. The new method, which uses the Pathatrix pooling strategy, provides an increase in sample throughput, and the size of the sample tested can be increased up to 500 g, as opposed to the current test limit of 100 g.

The Pathatrix system relies on the use of antibody-coated paramagnetic particles to selectively bind and purify the target organism from complex food matrices. Once these are captured and concentrated, a variety of detection methods can be used: direct plating onto the appropriate selective medium, in this case violet red bile glucose agar (VRBGA), serology, polymerase chain reaction (PCR), enzyme-linked immunosorbant assay (ELISA), and/or a DNA probe.

The Pathatrix pooling principle relies on the pooling of up to five 50-ml samples to create a single 250 ml composite that can then be analyzed by a range of end-point detection technologies. Negative samples are quickly screened out and any positive samples can be quickly analyzed.

Cationic particles can capture other Enterobacteriaceae, including Citrobacter diversus, C freundii, Klebsiella oxytoca, K pneumoniae, K aerogenes, Serratia marcescens, Salmonella enteritidis, S typhimurium, and S poona. It is therefore necessary to conduct an initial Enterobacteriaceae screen followed by specific tests for E sakazakii or Salmonella spp.

E sakazakii is an emergent pathogen associated with ingestion of infant formula milk that can lead to neonatal meningitis and necrotizing enterocolitis. The International Commission for Microbiological Specifications for Foods (ICMSF) has ranked E sakazakii as "Severe hazard for restricted populations, life-threatening or substantial chronic sequelae, or long duration.” Therefore, as there is no accepted standard methodology, the correct definition and identification of E sakazakii is important for powdered infant formula manufacturers, as well as regulators, clinicians, and epidemiologists.



Related Links:
Matrix MicroScience
ICMSF