The phenotypic and genotypic characterization of Enterobacter sakazakii strains from infant formula milk

Abstract

Enterobacter sakazakii is an emerging foodborne pathogen associated with severe diseases in neonates. Infant formula milk (IFM) has been identified as one of the major contaminated sources and a transmission vehicle. To determine the phenotypic and genotypic characterization of this pathogen, 22 E. sakazakii strains isolated from IFM by an FDA-recommended method and PCR on the alpha-glucosidase gene were subtyped by random amplified polymorphic DNA (RAPD)-PCR, enterobacterial repetitive intergenic consensus (ERIC)-PCR, and antibiotic resistance patterns. At a similarity threshold of 80%, 16 ERIC-PCR fingerprint types were identified with a discriminatory power (D) of 0.933, and 18 RAPD-PCR types were identified with D of 0.973. Resistance to 9 antibiotics tested by disk diffusion assay revealed 6 antibiotic resistance patterns with D of 0.749. The comparison of characterization indicated that RAPD-PCR and ERIC-PCR have high discriminatory power showing genetic diversity of E. sakazakii isolates, and ERIC-PCR patterns showed a closer correlation than RAPD-PCR patterns to phenotypic characterization and the brands of IFM. Overall, the ERIC-PCR typing method could be used for tracing sources of E. sakazakii isolates in the food chain.

Investigation of the Use of a Cocktail of Lux-Tagged Cronobacter Strains for Monitoring Growth in Infant Milk Formulae

“…The phenotypic diversity of Cronobacter strains has also been demonstrated (3,32). These results indicate that strains of Cronobacter are not identical and may proliferate at different rates in different IMFs.…”

“…As for other bacteria, C. sakazakii strains are not genetically or phenotypically identical (3,13,32). There fore, studies aimed at developing novel IMF compositions should not focus solely on one strain but should include a collection of strains from different sources.…”

Isolation of Salmonella from Meat Samples and Characterization by Enterobacterial Repetitive Intergenic Consensus–Polymerase Chain Reaction and Antibiotics Test

“…for erythromycin) (CLSI, 2005;Kim et al, 2008). The index of discriminatory ability (D) was calculated as described by Ye et al (2010).…”

“…The PCR conditions were one cycle at 95°C for 5 min, followed by 30 cycles of 1 min at 94°C, 1 min at 46°C, and 4 min at 72°C, and the last extension at 72°C for 8 min. The ERIC-PCR fingerprinting was analyzed as described by Ye et al (2010), using Bionumerics 4.0 (Applied Maths).…”

Real-time PCR targeting OmpA gene for detection of Cronobacter spp. in powdered infant formula

“…These procedures take 6-7 days to confirm a definite result. The ordinary PCR method tends to be more rapid than biochemical methods and has been used for the detection of these pathogens (6,7), but its practical application has been limited by several factors, including low sensitivity, low specificity, and ease of contamination during gel electrophoresis (8).…”