title: A comparison of polymerase chain reaction and international organization for standardization methods for determination of Enterobacter sakazakii contamination of infant formulas from Chinese mainland markets.
abstract: Enterobacter sakazakii is an emerging foodborne pathogen associated with meningitis, necrotizing enterocolitis, and sepsis in infants. One of the main transmission vehicles is the commercially available infant formulas. To provide efficient options and direction for detecting E. sakazakii in infant formulas, evaluation of different polymerase chain reaction (PCR) assays targeting the 16S-23S rDNA internal transcribed spacer (ITS), the ompA gene, and the alpha-1,4-glucosidase gene (gluA) of this organism, were compared to the International Organization for Standardization (ISO) method for detecting E. sakazakii in the 243 commercial infant formula samples. Twelve samples were found to be positive for E. sakazakii by all the PCR assays used, followed by sequencing of PCR products. Ten samples were found to be positive by the ISO method, and all 10 gave positive signals for all the PCR amplifications. In contrast, four false-positive results were generated by single-PCR of the ITS region and one false-positive result targeting the ompA gene, while two false-negative results occurred with the ISO method. Combined with selective enrichment step(s), duplex-PCR targeting ITS and ompA and targeting ompA and gluA genes or single-PCR of the gluA gene can be used to test for contamination by E. sakazakii in infant formulas before they enter the market. PCR techniques will be helpful for routine monitoring and risk assessment for large-scale screenings.
authors.affiliation: South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.
authors.forename: Yingwang
authors.initials: Y
authors.lastname: Ye
authors.forename: Qingping
authors.initials: Q
authors.lastname: Wu
authors.forename: Lin
authors.initials: L
authors.lastname: Yao
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Dong
authors.forename: Kui
authors.initials: K
authors.lastname: Wu
authors.forename: Jumei
authors.initials: J
authors.lastname: Zhang
mesh_terms: D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D002681:China; D044083:Cronobacter sakazakii / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D004269:DNA, Bacterial / Q000737:chemistry; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005516:Food Microbiology; D006801:Humans; D007223:Infant; D007225:Infant Food / Q000382:microbiology*; D041943:Infant Formula; D057230:Limit of Detection; D016133:Polymerase Chain Reaction / Q000379:methods*; D011933:Reagent Kits, Diagnostic; D017422:Sequence Analysis, DNA; D013997:Time Factors; D000520:alpha-Glucosidases / Q000235:genetics / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D004269:DNA, Bacterial; D021903:DNA, Ribosomal Spacer; D011933:Reagent Kits, Diagnostic; C078167:OMPA outer membrane proteins; D000520:alpha-Glucosidases