Profiling Total Viable Bacteria in a Hemodialysis Water Treatment System

( Lihua Chen ),( Xuan Zhu ),( Menglu Zhang ),( Yuxin Wang ),( Tianyu Lv ),( Shenghua Zhang ),( Xin Yu ) 한국미생물 · 생명공학회 2017 Journal of microbiology and biotechnology Vol.27 No.5

Culture-dependent methods, such as heterotrophic plate counting (HPC), are usually applied to evaluate the bacteriological quality of hemodialysis water. However, these methods cannot detect the uncultured or viable but non-culturable (VBNC) bacteria, both of which may be quantitatively predominant throughout the hemodialysis water treatment system. Therefore, propidium monoazide (PMA)-qPCR associated with HPC was used together to profile the distribution of the total viable bacteria in such a system. Moreover, high-throughput sequencing of 16S rRNA gene amplicons was utilized to analyze the microbial community structure and diversity. The HPC results indicated that the total bacterial counts conformed to the standards, yet the bacteria amounts were abruptly enhanced after carbon filter treatment. Nevertheless, the bacterial counts detected by PMA-qPCR, with the highest levels of 2.14 × 107 copies/100 ml in softener water, were much higher than the corresponding HPC results, which demonstrated the occurrence of numerous uncultured or VBNC bacteria among the entire system before reverse osmosis (RO). In addition, the microbial community structure was very different and the diversity was enhanced after the carbon filter. Although the diversity was minimized after RO treatment, pathogens such as Escherichia could still be detected in the RO effluent. In general, both the amounts of bacteria and the complexity of microbial community in the hemodialysis water treatment system revealed by molecular approaches were much higher than by traditional method. These results suggested the higher health risk potential for hemodialysis patients from the up-to-standard water. The treatment process could also be optimized, based on the results of this study.

전자선 조사에 의한 신선굴(Crassostrea gigas) 중 휴먼노로바이러스 GⅡ. 4의 저감화

김지윤,전은비,최만석,박신영 한국수산과학회 2021 한국수산과학회지 Vol.54 No.1

This study investigated the reduction in human norovirus (HNV) GII. 4 count in pacific oyster Crassostrea gigas using electron beam irradiation. Infectious HNV GII. 4 was detected using RT-qPCR (real time reverse transcriptionquantitative polymerase chain reaction) with PMA (propidium monoazide)/sarkosyl. At electron beam doses 1, 5, 7, and 10 kGy, the count of HNV GII. 4 was 2.74, 2.37, 2.06, and 1.55 log copies/μL (control, 3.01 log copy/μL), respectively, confirming that as the irradiation dose increased, norovirus count reduced significantly (P<0.05). After PMA/ sarkosyl treatment, the counts further reduced at the same irradiation dose, and 10 kGy showed significant differences between the non-treated and PMA/sarkosyl-treated samples (P<0.05). The Ed (decimal reduction dose of electron beam) value based on the first-order kinetic model was 7.33 kGy (R2=0.98). No significant difference was observed in the pH values of the control (6.2) and electron beam-irradiated samples at all doses (6.1). For sensory evaluation, the non-treated sample scored the highest in all categories (5.25-6.17), while the samples treated with 10 kGy showed the lowest score (4.67-5.33), although without statistical significance (P>0.05). Overall, our results suggest that 7 kGy electron beam is sufficient for the non-thermal sterilization of oysters without causing significant changes in quality.

Inactivation efficiency and mechanism of UV-TiO₂ photocatalysis against murine norovirus using a solidified agar matrix

Park, D.,Shahbaz, H.M.,Kim, S.H.,Lee, M.,Lee, W.,Oh, J.W.,Lee, D.U.,Park, J. Elsevier Science Publishers 2016 International journal of food microbiology Vol.238 No.-

<P>Human norovirus (HuNoV) is the primary cause of viral gastroenteritis worldwide. Fresh blueberries are among high risk foods associated with norovirus related outbreaks. Therefore, it is important to assess intervention strategies to reduce the risk of foodborne illness. The disinfection efficiency of decontamination methods is difficult to evaluate for fruits and vegetables due to an inconsistent degree of contamination and irregular surface characteristics. The inactivation efficiency and mechanism of murine norovirus 1 (MNV-1, a surrogate for HuNoV) was studied on an experimentally prepared solidified agar matrix (SAM) to simulate blueberries using different wavelengths (A, B, C) of UV light both with and without TiO2 photocatalysis (TP). MNV-1 was inoculated on exterior and interior of SAM and inactivation efficiencies of different treatments were investigated using a number of assays. Initial inoculum levels of MNV-1 on the SAM surface and interior were 52 log PFU/mL. UVC with TiO2 (UVC-TP) achieved the highest level of viral reduction for both externally inoculated and internalized MNV-1. Externally inoculated MNV-1 was reduced to non-detectable levels after UVC-TP treatment for 5 min while there was still a 0.9 log viral titer after UVC alone. For internalized MNV-1, 32 log and 2.7 log reductions were obtained with UVC-TP and UVC alone treatments for 10 min, respectively. The Weibull model was applied to describe the inactivation behavior of MNV-1, and the model showed a good fit to the data. An excellent correlation between the steady-state concentration of OH radicals ([(OH)-O-center dot](ss)) and viral inactivation was quantified using a para-chlorobenzoic acid (pCBA) probe compound, suggesting that OH radicals produced in the UV-TP reaction were the major species for MNV-1 inactivation. Transmission electron microscopy images showed that the structure of viral particles was completely disrupted with UVC-TP and UVC alone. SDS-PAGE analysis showed that the major capsid protein VP1 was degraded after UVC-TP and UVC alone. Real-time RT-qPCR analysis showed that UVC-TP and UVC alone caused a reduction in the level of viral genomic RNA. Propidium monoazide (PMA) pretreatment RT-qPCR analysis showed that UVC-TP caused. damage to the viral capsid protein in addition to viral genomic RNA. UVC both with and without TiO2 was more effective for MNV-1 inactivation than UVB and UVA. Thus, UVC-TP disinfection aimed to reduce levels of food-borne viruses can inactivate viruses present on the surface and internalized in the interior of blueberries. (C) 2016 Elsevier B.V. All rights reserved.</P>

난배양성(viable but non-culturable; VBNC) Edwardsiella piscicida의 특성 연구

김아현,이윤항,노형진,허영웅,김남은,김도형 한국어병학회 2024 한국어병학회지 Vol.37 No.1

A viable but non-culturable (VBNC) state is a survival strategy adopted by bacteria when faced with unfavorable environmental conditions, rendering them unable to grow on nutrient agar while maintaining low metabolic activity. This study explored the impact of temperature and nutrient avail-ability on inducing VBNC state in Edwardsiella piscicida, the most important bacterial fish pathogen, and assessed its pathogenicity at VBNC state. E. piscicida was suspended in filtered sterile seawater and exposed to three different temperatures (4, 10, and 25°C) to induce the VBNC state. Subsequently, the induced VBNC cells were subjected to resuscitation by either raising the temperature to 28°C or inoculating them in brain heart infusion broth supplemented with 1% NaCl. A propidium monoazide (PMA)-qPCR method was also developed to selectively quantify live (VBNC or culturable) E. piscicida cells. The results showed that the bacteria entered the VBNC state after approximately 1 month at 4°C and 25°C, and 2 months at 10°C. The VBNC E. piscicida cells were successfully revived within 3 days in a nutrient-rich environment at 28°C, highlighting the significance of temperature and nutrition in inducing and resuscitating the VBNC state. In pathogenicity tests, resuscitated E. piscicida cells exhibited high pathogenicity in olive flounder comparable to cultured bacteria, while VBNC cells showed no signs of infection, suggesting they are unlikely to resuscitate in fish. In conclusion, this study contributes to our understanding of fish pathogen ecology by investigating the characteristics of the VBNC state under varying temperature and nutrition conditions.

Amplification Characteristics of Various Endospores by qPCR Before and After PMAxxTM Treatment for the Development of a Noble Sterilization Test Method

Jaewon RYU,Sanghwa PARK,Jung-Beom KIM,Keug Tae KIM 한국생물공학회 2023 한국생물공학회 학술대회 Vol.2023 No.10