• Journal of Microbiology and Biotechnology
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• v.20 no.4
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• pp.757-762
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• 2010

Cronobacter is a major foodborne pathogen in powdered infant formula and can lead to serious developmental after-effect and death to infants. The contamination of Cronobacter may be a high risk for the powdered foods. To isolate and identify Cronobacter from the powdered foods such as powdered infant formula and Saengsik in Korea, a conventional culture method, rapid identification system, PCR, and 16S rDNA sequencing were performed. As the results of isolation, seven Cronobacter spp. were isolated from seven out of 102 powdered infant formulas and 41 Cronobacter were isolated from 41 out of 86 Saengsiks. Forty-eight Cronobacter isolates were identified to be C. sakazakii and C. dublenisis by 16S rDNA sequence analysis. Most of the isolates were C. sakazakii and 13% of the isolates were C. dublinesis. One fourth of the C. sakazakii isolates showed different biochemical characteristics of negative nitrate reduction and nonmotility activities compared with the other strains reported previously.

• Journal of Food Hygiene and Safety
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• v.25 no.4
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• pp.341-345
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• 2010

Three-hundred samples of powdered infant formula milk and related products from four different manufacturers in 2010 were collected and surveyed their contaminations for aerobic bacteria, coliform, Enterobacter(Cronobacter) sakazakii, and food-borne pathogens. Fifteen samples of sterilized infant formula milk were all negative on these microorganisms. In all collected products of un sterilized infant formulas and follow-on infant formulas, aerobic bacteria were detected at 239 (83.9%) among 285 samples, and they all were found below $10^3$ cfu/g. Coliform bacteria were also detected at four among 285 samples. Salmonella spp. and Ent. sakazakii, weren't detected at the all samples. Bacillus cereus was detected at 24 (8.4%) among 285 samples. The level of B. cereus was below 100 cfu/g but it was suitable for the range of specification of B. cereus in infant formulas. Clostridium perjringens, Escherichia coli O157:H7, Staphylococcus aureus and Listeria monocytogenes weren't also detected. In consequence, it was suitable for total viable count, coliform and potential pathogen to the specification of infant formulas and related products.

• Food Science of Animal Resources
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• v.28 no.5
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• pp.555-561
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• 2008

Ninety-nine samples of powdered infant formula in a market were collected from the local market and their contaminations for total aerobic bacteria, coliform, FAO/WHO Category A, B, and C pathogens were analyzed. Total aerobic bacteria were detected in 92 of 99 samples (93%) at levels of $1.83{\pm}0.68\;Log\;MPN/g$. These levels were below legal levels specified for infant formulas except for one sample detected by 4.5 Log CFU/g. Coliform was detected in 12 of 99 samples (12%) at levels of $1.26{\pm}1.03\;Log\;MPN/g$ whereas non-detection was required according to the specification of coliform in infant formulas. Escherichia coli was detected in 1 of 99 samples by 0.48 Log MPN/g. Salmonella and Enterobacter sakazakii among Category A weren't detected in all the samples. Enterobacteriaceae, Category B group, were detected in 25 samples of total 99 samples (25%) by $0.83{\pm}1.37\;Log\;MPN/g$. Enterobacteriaceae identified by API 20E were Escherichia vulneris, Es. hermannii, Pantoea spp., Citrobacter koseri, Klebsiella pneumoniae, En. cloaceae. Bacillus cereus among Category C was highly detected in 29 of 99 samples (29%) at levels of $0.69{\pm}0.32\;Log\;MPN/g$ with the most probable number count method, which were below legal levels for the specification of B. cereus in infant formulas. Clostridium perfringens, E. coli O157, Staphyloccus aureus, Listeria monocytogenes, Yersinia enterocolitica, and Campylobacter jejuni/coli were not detected. Contamination level of major pathogens was low and falls within the range of specification of infant formulas. However, Enterobacteriaceae and B.cereus showed the high prevalence and some Enterobacteriaceae causing disease were detected. Therefore, it is necessary to monitor the potential pathogens continually and reduce them to improve the microbial quality of non-sterilized powdered infant formulas.

• Food Science and Biotechnology
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• v.15 no.1
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• pp.152-157
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• 2006

Enterobacter sakazakii, designated as an unique microbial species in 1980, may cause bacteremia, necrotizing enterocolitis and infant meningitis. The distribution and the thermostability of E. sakazakii in unprocessed ready-to-eat (RTE) agricultural products of 252 and in 25 powdered infant formulas (PIF) were analyzed. Eighty one, 50, 43, and 47% of brown rice, pumpkin, potato, and carrot samples, respectively, had aerobic plate counts (ARC) in the range of 5 log CFU/g or more. Almost all the other products sampled had APC of approximately 2 log CFU/g. Fifty three, 75, 67, and 68% of banana, pumpkin, soybean, and carrot had Enterobacteriaceae counts approximating 3 log CFU/g. Sixty six percent of the brown rice tested had Enterobacteriaceae counts approximating 5-6 log CFU/g. E. sakazakii was isolated from 3/25(12%), 4/23(17%), 1/24(4%), and 1/27(4%) of PIF, brown rice, laver, and tomato samples, respectively. D-values were 3.52-4.79 min at 60 and $D_{60}-values$ were similar as the isolates reported. Thermal inactivation of four thermovariant E. sakazakii strains during the rehydration of PIF with hot water were investigated. At $50^{\circ}C$, the levels of E. sakazakii decreased one log CFU/g for 4-6 min and thereafter the levels remained stable for 20 min. At $60^{\circ}C$, inactivation by about 2 log CFU/g occurred for 20 min. Therefore, the unprocessed agricultural products might be a source of contamination for PIF when used as an ingredient after drying and pulverization. Rehydration of PIF for infant feeding with a water temperature of $60^{\circ}C$ rather than $50^{\circ}C$, as recommended by the manufacturers, may be helpful in the reduction of potential E. sakazakii risk.

• Korean Journal of Veterinary Service
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• v.36 no.2
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• pp.67-71
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• 2013

Neonatal infection caused by Cronobacter species can result in serious illnesses such as bacteremia, septicemia, meningitis, and death in at-risk infants who are orally fed contaminated reconstituted powdered infant formulas. The objective of this study was to compare the virulence among three Cronobacter species strains by using an animal model for human neonatal Cronobacter species infections. We acquired timed-pregnant ICR mice and all owed them to give birth naturally. On postnatal day 3, each pup was administered orally a total dose of $1{\times}10^7$ CFU Cronobacter species strain 3439, CDC 1123-79, and 3231. Mice were observed twice daily for morbidity and mortality. At postnatal day 10, the remaining pups were euthanized, and brain, liver, and cecum were excised and analyzed for the presence of Cronobacter species. Cronobacter species were isolated from cecum and other tissues in inoculated mice. In the tissues of Cronobacter species infected mice, meningitis and gliosis were detected in the brain. In this study, we identified the virulence among Cronobacter species strains by using a neonatal mice model which was a very effective animal model for human neonatal Cronobacter species infections.

• Food Science of Animal Resources
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• v.31 no.6
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• pp.944-951
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• 2011

An improved cholesterol analysis method was developed for powdered infant formula by gas chromatographic separation after liquid-liquid extraction and partition. In the official Korea Food Standard method for cholesterol analysis, the water phase and solvent phase were not well separated in the case of emulsified foods such as powdered infant formulas and baby foods. For the rapid and simple sample preparation method, an optimized direct saponification condition was established for heating temperature, heating time, and KOH concentration. From the results, the optimum conditions were as follows: heating temperature $90^{\circ}C$, heating time 60 min, and 16 M KOH 10 mL for a 2 g infant formula sample; improved separation condition for gas chromatography was as follows: the initial oven condition was $250^{\circ}C$ for 25 min, the oven temperature was increased to $290^{\circ}C$ by $10^{\circ}C$/min ratio, and finally the oven temperature remained at $290^{\circ}C$for 9 min. The developed method could be implemented for the study of cholesterol, providing the advantages of reduced inspection time and cost in emulsified foods such as infant formula.

• Journal of Microbiology and Biotechnology
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• v.29 no.5
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• pp.696-703
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• 2019

Cronobacter sakazakii is an opportunistic pathogen causing serious infections in neonates. In this study, a bacteriophage ${\Phi}CS01$, which infects C. sakazakii, was isolated from swine feces and its morphology, growth parameters, and genomic analysis were investigated. Transmission electron microscopy revealed that ${\Phi}CS01$ has a spherical head and is 65.74 nm in diameter with a 98.75 nm contracted tail, suggesting that it belongs to the family Myoviridae. The major viral proteins are approximately 71 kDa and 64 kDa in size. The latent period of ${\Phi}CS01$ was shown to be 60 min, and the burst size was 90.7 pfu (plaque-forming units)/infected cell. Bacteriophage ${\Phi}CS01$ was stable at $4-60^{\circ}C$ for 1 h and lost infectivity after 1 h of heating at $70^{\circ}C$. Infectivity remained unaffected at pH 4-9 for 2 h, while the bacteriophage was inactivated at pH <3 or >10. The double-stranded ${\Phi}CS01$ DNA genome consists of 48,195 base pairs, with 75 predicted open reading frames. Phylogenetic analysis is closely related to that of the previously reported C. sakazakii phage ESP2949-1. The newly isolated ${\Phi}CS01$ shows infectivity in the host bacterium C. sakazakii, indicating that it may be a promising alternative to antibacterial agents for the removal of C. sakazakii from powdered infant formulas.