• Korean Journal of Food Science and Technology
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• v.41 no.6
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• pp.681-686
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• 2009

Cronobacter spp. (Enterobacter sakazakii) is known to be highly resistant to dry conditions than any other Enterobacteriaeae. In this study, one hundred and ten Korean Cronobacter isolates were characterized to find out their survival characteristics under conditions of desiccation and humidity. Thirty percentage strains of the isolates showed high resistance to desiccation exposed on the metal surface for eight hours by half survival of the initial number, whileas less than 10% strains showed dry sensitivity by less one log scale survival among seven log scales. Finally, more than 90% of the strains consisted of dry-resistant and dry-intermediate groups. The same tendencies were evident in a 15-day exposure. Dry-resistant and intermediate strain groups showed 3 log scale survival among 5 log initial numbers in the powdered infant formula for 30 days, which were more resistant than on the above metal surface exposed. So, almost the isolate strains showed high resistance to dry condition. Dry-resistant and intermediate groups exposed on the metal surface formed a biofilm at the beginning, and the dry-sensitive group showed biofilm formation mainly only after a 7-day exposure. However, without a time difference in formation of biofilm, the dry-resistant and sensitive isolates seemed to similar biofilm formation activity. Most of the isolates showed very low survival at 75% relative humidity in 48 hours; however, they showed high resistance by 60% survival at 40% relative humidity. The Cronobacter isolates showed high resistance to desiccation on the metal surface and in the powdered infant formula, but low survival at high relative humidity. Therefore, high humidity may be a control method for Cronobacter in food processing environments.

• Korean Journal of Food Science and Technology
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• v.40 no.1
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• pp.101-105
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• 2008

Enterobacter sakazakii is implicated in severe forms of neonatal infections such as meningitis and sepsis. This organism has been isolated from a wide range of foods, including cheese, vegetables, grains, herbs, and spices, but its primary environment is still unknown. Generally, dried infant milk formula has been epidemiologically identified as the source of E. sakazakii. Sunsik (a powdered mixture of roasted grains and other foodstuffs) is widely consumed in Korea as a side dish or energy supplement. Sunsik is consumed without heat treatment; thus, lacking an additional opportunity to inactivate foodborne pathogens. Therefore, its microbiological safety should be guaranteed. In this study, the prevalence of E. sakazakii was monitored in 23 different sunsik component flours, using FDA recommended methods; but E. sakazakii medium (Neogen) and Chromogenic E. sakazakii medium (Oxoid) were used as the selective media. In total, presumptive E. sakazakii strains were isolated from 8 different sunsik powders. Subsequently, an API 20E test was conducted, and 15 strains from 5 different sunsik flours (sea tangle, brown rice, non-glutinous rice, cheonggukjang, dried anchovy) were confirmed as E. sakazakii. Fifteen strains were again confirmed by PCR amplification, using three different primer sets (tDNA sequence, ITS sequence, 16S rRNA sequence), and compared to ATCC strains (12868, 29004, 29544, 51329). They were once again confirmed by their enzyme production profiles using an API ZYM kit. Finally, RAPD (random amplified polymorphic DNA)-genotyping was carried out as a monitoring tool to determine the contamination route of E. sakazakii during processing.