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RISS 인기검색어
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- 저자 : Dewanti-Hariyadi, Ratih (검색결과 5 건)
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Jameelah, Maryam,Dewanti-Hariyadi, Ratih,Nurjanah, Siti 한국식품과학회 2018 Food Science and Biotechnology Vol.27 No.3
Cronobacter spp. in powdered infant formula has been etiologically linked to meningitis and necrotizing enterocolitis in certain groups of infants. This study aimed to determine whether C. sakazakii Yrt2a strain experiencing desiccation stress could enter viable but nonculturable (VBNC) state as well as to examine the expression of genes associated with stress and virulence during the above states. Stress and VBNC conditions were determined based on viability and culturability assays. Expression of genes related to stress (rpoS) and virulence (hfq and ompA) was evaluated by real-time PCR. The results showed that C. sakazakii Yrt2a entered VBNC 24 days post exposure to 2 h of desiccation treatment. The expression of rpoS, hfq and ompA genes was up-regulated during stress conditions, suggesting that Cronobacter successfully managed stress to maintain its culturability while maintaining its virulence. The expression of the target genes decreased at VBNC state but remained higher than that of a normal state. These findings reinforce the assumption that C. sakazakii undergoing VBNC state maintains its pathogenicity.
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Maryam Jameelah,Ratih Dewanti-Hariyadi,Siti Nurjanah 한국식품과학회 2018 Food Science and Biotechnology Vol.27 No.3
Cronobacter spp. in powdered infant formula has been etiologically linked to meningitis and necrotizing enterocolitis in certain groups of infants. This study aimed to determine whether C. sakazakii Yrt2a strain experiencing desiccation stress could enter viable but nonculturable (VBNC) state as well as to examine the expression of genes associated with stress and virulence during the above states. Stress and VBNC conditions were determined based on viability and culturability assays. Expression of genes related to stress (rpoS) and virulence (hfq and ompA) was evaluated by real-time PCR. The results showed that C. sakazakii Yrt2a entered VBNC 24 days post exposure to 2 h of desiccation treatment. The expression of rpoS, hfq and ompA genes was up-regulated during stress conditions, suggesting that Cronobacter successfully managed stress to maintain its culturability while maintaining its virulence. The expression of the target genes decreased at VBNC state but remained higher than that of a normal state. These findings reinforce the assumption that C. sakazakii undergoing VBNC state maintains its pathogenicity.
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Stability and Growth Characteristics of GFPuv- Labeled Cronobacter sakazakii Isolated from Foods
Siti Nurjanah,Ratih Dewanti-Hariyadi,Sri Estuningsih,Maggy Thenawidjaja Suhartono 한국식품과학회 2014 Food Science and Biotechnology Vol.23 No.5
Stability of ultraviolet green fluorescent protein(GFPuv)-labeled Cronobacter sakazakii and C. muytjensiiisolated from foods and the effects of the plasmid GFPuv(pGFPuv) on growth were analyzed. PCR analysis andmicroscopic observation showed that C. sakazakii and C. muytjensii isolates took up the plasmid into cells andexpressed the GFPuv gene. All Cronobacter transformantsmaintained this plasmid after frozen storage and 2consecutive subcultures. The C. sakazakii FWHd16transformant was the most stable, while the C. muytjensiiFWHd11 transformant was the least stable. All transformantsshowed nearly identical growth curves during lag, log andstationary phases, compared to wild type parental isolates. The maximum bacterial growth rates (μmax) of thetransformants and parents were similar, indicating that thepresence of pGFPuv in transformants did not affect cellgrowth. Stable GFPuv-labeled Cronobacter has potentialfor use in tracking bacterial behavior during food handlingand drying.
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Maerani Maerani,Ratih Dewanti-Hariyadi,Siti Nurjanah 한국식품과학회 2020 Food Science and Biotechnology Vol.29 No.9
This research aimed to evaluate the effect of acidstress on the expression of stress regulator (grxB and rpoS)and virulence (ompA, hfq, and cpa) genes of Cronobactersakazakii Yrt2a. The results showed that C. sakazakii Yrt2aexperienced decrease in number during acid stress and wasno longer culturable 90 min post exposure to pH 3.0. During acid stress, the expression of grxB, rpoS, ompA, cpaand hfq was upregulated by 2.15; 2.19; 1.55; 1.1 and 1.41log, respectively. However, all genes expression wasdownregulated when the bacteria entered the unculturablestate. The expression of gene grxB, rpoS, ompA, cpadecreased to 1.04; 0.37; 0.84 and 1.71 log, respectively;while hfq gene expression reached a level lower than thatof control. This research implies a supposition that duringacid stress, C. sakazakii was capable of maintaining itsculturability and pathogenicity until they are no longerculturable.
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Dandy Yusuf,Lilis Nuraida,Ratih Dewanti-Hariyadi,Dase Hunaefi 한국미생물·생명공학회 2020 Journal of microbiology and biotechnology Vol.30 No.5
Indonesian kefir grains are potential sources of lactic acid bacteria (LAB) that may act as probiotics with specific functional properties. In this study we explored the potential of the probiotic and cholesterol-lowering effect of LAB isolated from Indonesian kefir grains obtained from Bogor, Bandung, Jakarta, and Yogyakarta. The results revealed that 10 isolates showed considerable survivability at low pH and bile salt with total cell reduction of ~3 log colony-forming units per milliliter after exposure to pH 2.5 and 0.5% (w/v) bile salt for 1 and 3 h, respectively. All strains exhibited strong antimicrobial activities against pathogenic bacteria and were sensitive to a wide spectrum of antibiotics but exhibited weak bile salt hydrolase activity. Identification based on 16S RNA suggested that nine isolates were Lactobacillus kefiri and one was Lactobacillus rhamnosus. The ability of the isolates to reduce cholesterol from the media varied, ranging from 22.08% to 68.75% with the highest reduction shown by L. kefiri JK17. The ability to remove cholesterol from the media decreased greatly in resting and dead cells, ranging from 14.58% to 22.08% in resting cells and from 7.89% to 18.17% in dead cells. It can be concluded that Indonesian kefir grains contain LAB potentially acting as probiotics capable of reducing cholesterol. The cholesterol-lowering effect especially occurs when the cells are metabolically active.
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