• Journal of Microbiology and Biotechnology
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• v.17 no.2
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• pp.364-368
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• 2007

Enterobacter sakazakii may be related to outbreaks of meningitis, septicemia, and necrotizing enterocolitis, mainly in neonates. To reduce the risk of E. sakazakii in baby foods, thermal characteristics for Korean E. sakazakii isolates were determined at 52, 56, and $60^{\circ}C$ in saline solution, rehydrated powdered infant formula, and dried baby food. In saline solution, their D-values were 12-16, 3-5, and 0.9-1 min for each temperature. D-values increased to 16-20, 4-5, and 2-4 min in rehydrated infant formula and 14-17, 5-6, and 2-3 min in dried baby food. The overall calculated z-value was 6-8 for saline, 8-10 for powdered infant formula, and 9-11 for dried baby food. Thermal inactivation of E. sakazakii during rehydration of powdered infant formula was investigated by viable counts. Inactivation of cultured E. sakazakii in infant formula milk did not occur for 20 min at room temperature after rehydration with the water at $50^{\circ}C$ and their counts were reduced by about 1-2 log CFU/g at $60^{\circ}C$ and 4-6 log CFU/ml with the water at 65 and $70^{\circ}C$. However, the thermo stability of adapted E. sakazakii to the powdered infant formula increased more than two times. Considering that the levels of E. sakzakii observed in powdered infant formula have generally been 1 CFU/100 g of dry formula or less, contamination with E. sakazakii can be reduced or eliminated by rehydrating water with at least $10^{\circ}C$ higher temperature than the manufacturer-recommended $50^{\circ}C$.

• The Plant Pathology Journal
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• v.36 no.3
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• pp.244-254
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• 2020

Gom-chwi (Ligularia fischeri) is severely infected with Phytophthora drechsleri, the causal organism of Phytophthora root rot, an economically important crop disease that needs management throughout the cultivation period. In the present study, Phytophthora root rot was controlled by using bacterial isolates from rhizosphere soils collected from various plants and screened for antagonistic activity against P. drechsleri. A total of 172 bacterial strains were isolated, of which, 49 strains showed antagonistic activities by dual culture assay. In the seedling assay, six out of the 49 strains showed a predominant effect on suppressing P. drechsleri. Among the six strains, the ObRS-5 strain showed remarkable against P. drechsleri when treated with seed dipping or soil drenching. The ObRS-5 strain was identified as Enterobacter asburiae based on 16S ribosomal RNA gene sequences analysis. The bacterial cells of E. asburiae ObRS-5 significantly suppressed sporangium formation and zoospore germination in P. drechsleri by 87.4% and 66.7%, respectively. In addition, culture filtrate of E. asburiae ObRS-5 also significantly inhibited sporangium formation and zoospore germination by 97.0% and 67.6%, respectively. Soil drenched bacterial cells, filtrate, and culture solution of E. asburiae ObRS-5 effectively suppressed Phytophthora root rot by 63.2%, 57.9%, and 81.1%, respectively. Thus, E. asburiae ObRS-5 could be used as a potential agent for the biological control of Phytophthora root rot infecting gom-chwi.

• The Journal of the Korean Society for Microbiology
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• v.22 no.3
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• pp.251-258
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• 1987

A total of 58 strains of Enterobacter species isolated from clinical specimens at Kyungpook National University Hospital in Taegu and Yonsei University Hospital in Seoul were tested for the molecular characterization to investigate the nosocomial infection through the study of R plasmids which might spread among Gram negative organisms regardless of their originated strains. All strains resistant to ampicillin, cefoxitin and cephalothin but susceptible to moxalactam were subjected to the further test for the determination of in detail MIC value against 23 drugs of common use including beta-lactam antibiotics and R plasmid profile analysis. The reistance frequency of strains against carbenicillin (53.4%) was similar to those against chloramphenicol, tobramycin, and sulfisomidine. Though the MIC values of resistance criteria against ceftazidime, aztreonam, imipenem, and norfloxacine in NCCLS manual were not available but MIC ranges of strains tested were very low. There were differences in patterns and frequencies of resistance between the strains isolated in Seoul and Taegu isolates. Seoul isolates showed a tendency of higher multiplicity of resistance than those of Taegu isolates. The resistances against cefoxitin, cephalothin, cefoperazone, cefotaxime, nalidixic acid, and rifampin were not conferred to the conjugally transferable R plasmid. The approximate molecular size of conjugally transferable R plasmids ranged 30 to 151 megadalton, and one or 2 to 3 R plasmids were identified in each transconjugants.

• Journal of Dairy Science and Biotechnology
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• v.39 no.3
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• pp.104-112
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• 2021

This study was conducted to evaluate the efficacy of commercial disinfectants at inactivating Enterobacter sakazakii (Cronobacter spp.) in water. Disinfectant I contained 6.15% sodium hypochlorite, and disinfectant II contained both 2.25% n-alkyl dimethylbenzyl ammonium chloride and 2.25% n-alkyl ethylbenzyl ammonium chloride. Disinfectant I was added to distilled water to obtain a range of residual chloride concentrations at 50 ppm intervals with a maximum of 1-1,000 ppm. Disinfectant II was prepared at concentrations ranging from 1-200 ppm with 5 ppm intervals. Exposure time for all solutions was 10 min. In total, 58 E. sakazakii (Cronobacter spp.) strains were tested in this study. Nine isolates were obtained from clinical samples, and 49 isolates were obtained from environmental samples. Seven strains (6 clinical and 1 environmental) were able to survive in 100 ppm disinfectant I, and a maximum of 5 ppm of disinfectant II. Fifty one strains (3 clinical and 48 environmental) were not killed in 10 ppm of disinfectant I and 1 ppm of disinfectant II in water. In conclusion, this study demonstrated that clinical E. sakazakii (Cronobacter spp.) strains displayed 5- to 10-fold higher resistance to disinfectants than environmental E. sakazakii (Cronobacter spp.) strains. Disinfectant II, containing quaternary ammonium compounds, was shown to be more potent in inactivating E. sakazakii (Cronobacter spp.) in water used to clean infant formula manufacturing equipment than disinfectant I.

• Journal of Dairy Science and Biotechnology
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• v.41 no.3
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• pp.103-112
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• 2023

This study aimed to assess the effectiveness of 10 different pre-enrichment methods using Real-Time polymerase chain reaction (PCR) in support of the FDA method. When the initial Cronobacter spp. (Enterobacter sakazakii) inoculation was 7.2 CFU/g, the Ct values were observed in the following order: 21.37 (Enterobacteriaceae enrichment [EE] broth), 21.95 (brain heart infusion [BHI]), 22.72 (tryptic soy broth [TSB]), 23.02 (violet red bile lactose [VRBL]), 22.31 (TSB-0.1% sodium pyruvate [SP]), 23.43 (distilled water [DW]), 24.34 (phosphate buffered saline [PBS]), 24.95 (nutrient broth [NB]), 25.82 (TSB-0.6% yeast extract [YE]), and 28.27 (violet red bile glucose [VRBG]). For an inoculation of 1.82% CFU/g of Cronobacter spp. (E. sakazakii), the Ct values were recorded in this sequence: 20.34 (EE broth), 22.16 (TSB-0.6% YE), 22.37 (BHI), 22.71 (VRBL), 22.88 (TSB), 23.01 (DW), 23.19 (NB), 23.79 (TSB-0.1% SP), 24.66 (VRBG), and 24.70 (PBS). Finally, when the inoculum of Cronobacter spp. (E. sakazakii) was 0.182 CFU/g, the Ct values followed this order: 21.93 (VRBL), 23.07 (TSB-0.6% YE), 23.31 (DW), 23.47 (PBS), 23.70 (BHI), 24.14 (TSB-0.1% SP), 25.14 (TSB), 29.00 (VRBG), 31.55 (EE broth), and were undetected in the case of NB. Consequently, these results indicate that there were no significant differences among the 10 different pre-enrichment broths. Future studies should focus on exploring pre-enrichment broths that can improve the limit of detection at very low Cronobacter spp. (E. sakazakii) concentrations and enhance the selective recovery of Cronobacter spp. (E. sakazakii) under acid, antibiotic, cold, and heat damage conditions.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.1
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• pp.67-73
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• 2013

Purpose: Recently, bacterial contamination of equipment and accessories required for vision correction has become a main causal factor in ophthalmic diseases. Thus, We investigated on both the actual condition of bacterial contamination from glasses of vision correction. Methods: Investigation of microorganisms was carried out with a group of 145 glasses wearers, composed of 36 elementary school students, 37 middle school students, 38 high school students, 10 college students, and 32 aged men. Results: Seventeen species of bacteria are detected from glasses of vision correction: B. cereus, B. licheniformis, Bacillus sp., CNS, Enterococcus sp., Escherichia coli, Proteus sp., Pseudomonas sp., Serretia sp., Streptococcus sp., Staphylococcus epidermidis, Staphylococcus aureus, Streptococcus hemolyticus,, Acinetobacter sp., Enterobacter cloacae, GNR, and Pseudomonas aeruginosa. Among 17 species of bacteria, there are some potential causative agents for keratitis, corneal ulcer, Acute dacryocystitis, Orbital cellulitis, Periphlebitis retinae, Marginal blepharitis, and Acute conjunctivitis. Enterobacter cloacae, Pseudomonas aeruginosa and Staphylococcus epidermidis cause keratitis. Pseudomonas sp., and Staphylococcus aureus cause corneal ulcer. Staphylococcus aureus causes acute dacryocystitis, orbital cellulitis, periphlebitis retinae, marginal belpharitis. Streptococcus hemolyticus causes acute conjunctivitis. Conclusions: In summation, it is verified that hazardous, opportunistic and infectious microorganisms exist in glasses for vision correction. Ophthalmic diseases are predicted. Therefore, supplementary research on the development of a cleaning solution to cleanse the infection and of an effective method to remove microorganisms is required.

• Korean Journal of Microbiology
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• v.47 no.1
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• pp.66-73
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• 2011

Bacterial density distributions of gut microbes in the digestive organs of Harmonia axyridis collected from three different sources (JK, CK, and CJ) were $6.0{\times}10^4$ CFU/gut under aerobic culture condition and $8.0{\times}10^6$ CFU/gut under anaerobic culture condition. Seven colony types were observed under aerobic condition and three types of similarity were detected under anaerobic condition. In total, 116 strains, including 34 strains under aerobic condition, were isolated from the digestive organs of H. axyridis. Based on the analysis of the 16S rRNA gene sequence, aerobic gut microbes were assigned to the Proteobacteria, Actinobacteria, Firmicutes, and Deinococcus-Thermus. A large number of isolates belonged to the genus Bacillus and Staphylococcus of the Firmicutes commonly found in H. axyridis from different sites. Anaerobic gut microbes were found to be similar according to colony morphological, phylogenetic analysis using ARDRA. Eighty-two anaerobic gut microbes were clustered into 17 different ARDRA types according to HaeIII. Representative anaerobic gut microbes in each ARDRA group were divided into five species of ${\gamma}$-Proteobacteria based on 16S rRNA gene sequence analysis; Hafnia alvei, Enterobacter ludwigii, Enterobacter kobei, Pseudomonas oryzihabitans and Pseudomonas koreensis. Phylogenetic analysis indicated that about 70% of the isolates belonged to ${\gamma}$-Proteobacteria, suggesting predominance of gut microbes.

• Korean Journal of Food Science and Technology
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• v.39 no.3
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• pp.295-298
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• 2007

In order to sterilize Bacillus cereus and Enterobacter sakazakii in rice flour, hot-air drying ($65^{\circ}C$/15 min, HT) and microwave drying (700 watt/30 sec, MT) treatments were evaluated and a storage study performed. Color changes (${\Delta}E$) appeared to be less in the MT rice flour than in HT treated rice flour. The effectiveness of the MT treatment showed reduced growth rates for B. cereus (0.54 log CFU/g) and E. sakazakii (1.45 log CFU/g). The populations of B. cereus in the control (NT) rice flour greatly increased during storage at 4, 10 and $20^{\circ}C$ as storage times increased. However, the growth of B. cereus was minimized in the MT rice flour. In conclusion, MT treatment is considered to be a good drying method when substituted for HT treatment to assure microbial safety in rice flour.

• Journal of Applied Biological Chemistry
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• v.54 no.4
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• pp.252-257
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• 2011

To remove excess nitrate from the agricultural environments, Enterobacter amnigenus GG0461 has been isolated as a bacterial strain having high capability of nitrate uptake activity. This strain was able to remove nitrate more than 3,000 ppm (50 mM) in the Pseudomonas agar F (PAF) medium. Therefore, it could be a candidate strain for a nitrate scavenger in the various contaminated environments, such as agricultural soils, livestock sewage, and industrial wastewater. In order to develop medium for the large-scale production of the strain GG0461, each component of PAF medium was replaced with the corresponding commercial product and the optimal conditions for bacterial growth and nitrate uptake activity were measured. Glycerol was replaced with the commercially available product and the nitrogen source was substituted with commercial tryptone, yeast extract, soybean meal, and fermented fish extract. Bacterial growth and nitrate uptake activity were maximal in the media containing 2% tryptone, followed by yeast extract, soybean meal, and fermented fish extract. The pH of the growth medium containing 2% tryptone was decreased by the bacterial nitrate uptake, suggesting that the nitrate uptake is mediated by a nitrate/proton antiporter. This result shows that the medium containing commercial tryptone was good enough for the physiological activity of the strain GG0461. Each component of PAF medium was successfully replaced with the corresponding commercial product except peptone. In conclusion, the composition of medium for the cultivation of the strain GG0461 was determined as 2% tryptone, 1% glycerol, plus required salts according to the composition of PAF medium.

• Korean Journal of Microbiology
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• v.32 no.1
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• pp.91-95
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• 1994

EagBI is a type II restriction endonuclease from Enterobacter agglomerans strain CBNU45 isolated from soil. EagBI was partially purified by DEAE-cellulose, phosphocellulose P11 and hydroxylapatite column chromatography. EagBI recognizes and cleaves the sequence 5'-CGAT${\downarrow}$CG-3' and generates 2-base 3'-protruding cohesive ends. The optimal reaction conditions of EagBI are 10 mM Tris-HCl (pH 7.8), 6-10 mM $MgCl_2$, at 37 ${\circ}C$. The enzyme is maximally active in the absence of NaCl, able to cleave both $dam^-$ and $dam^+$ DNAs, and sensitive to heat treatment (at 65 ${\circ}C$ for 10 min). Therefore, although EagBI is an isoschizomer of PvuI, it is more useful than PvuI in respect of the NaCl requirement and heat-stability.