Rapid, specific detection of Enterobacter sakazakii in infant formula using a real-time PCR assay.
Enterobacter sakazakii is a rare cause of invasive infection with high mortality rates in neonates. Powdered milk-based infant formulas have been associated with the E. sakazakii-related outbreaks in premature or other immunocompromised infants. In this study, an assay was developed for the specific detection of E. sakazakii in infant formula using an application of the fluorogenic 5' nuclease assay (TaqMan). A set of primers and probe was designed using the E. sakazakii partial macromolecular synthesis operon: the rpsU gene 3' end and the primase (dnaG) gene 5' end. The specificity of the assay was evaluated using 68 Enterobacter and 55 non-Enterobacter strains. The newly developed assay enables us to detect 100 CFU/ ml in pure culture and in reconstituted infant formula in 50 cycles of PCR without enrichment. The assay was specific enough to discriminate E. sakazakii from all other Enterobacter and non-Enterobacter strains tested. The developed real-time PCR assay could save up to 5 days and eliminate the need for plating samples on selective or diagnostic agars and for biochemical confirmation steps. The real-time PCR assay could be used to rapidly screen infant formula samples for E. sakazakii and would be a boon to food industries and regulatory agencies.
Seo
K H
KH
Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Plant and Dairy, Foods, and Beverages, College Park, Maryland 20740, USA. kseo@cfsan.fda.gov
Brackett
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RE
D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D044083:Cronobacter sakazakii / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D017931:DNA Primers / Q000737:chemistry; D015342:DNA Probes / Q000737:chemistry; D005506:Food Contamination / Q000032:analysis*; D005516:Food Microbiology; D006801:Humans; D007223:Infant; D007225:Infant Food / Q000382:microbiology*; D041943:Infant Formula; D007231:Infant, Newborn; D016133:Polymerase Chain Reaction / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013045:Species Specificity; D013997:Time Factors
D017931:DNA Primers; D015342:DNA Probes