1
|
Dinu LD, Al-Zaidi QJ, Matache AG, Matei F. Improving the Efficiency of Viability-qPCR with Lactic Acid Enhancer for the Selective Detection of Live Pathogens in Foods. Foods 2024; 13:1021. [PMID: 38611327 PMCID: PMC11012224 DOI: 10.3390/foods13071021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 03/22/2024] [Accepted: 03/25/2024] [Indexed: 04/14/2024] Open
Abstract
Pathogenic Escherichia coli are the most prevalent foodborne bacteria, and their accurate detection in food samples is critical for ensuring food safety. Therefore, a quick technique named viability-qPCR (v-qPCR), which is based on the ability of a selective dye, such as propidium monoazide (PMA), to differentiate between alive and dead cells, has been developed. Despite diverse, successful applications, v-qPCR is impaired by some practical limitations, including the ability of PMA to penetrate the outer membrane of dead Gram-negative bacteria. The objective of this study is to evaluate the ability of lactic acid (LA) to improve PMA penetration and, thus, the efficiency of v-qPCR in detecting the live fraction of pathogens. The pre-treatment of E. coli ATCC 8739 cells with 10 mM LA greatly increased PMA penetration into dead cells compared to conventional PMA-qPCR assay, avoiding false positive results. The limit of detection when using LA-PMA qPCR is 1% viable cells in a mixture of dead and alive cells. The optimized LA-PMA qPCR method was reliably able to detect log 2 CFU/mL culturable E. coli in milk spiked with viable and non-viable bacteria. Lactic acid is cheap, has low toxicity, and can be used to improve the efficiency of the v-qPCR assay, which is economically interesting for larger-scale pathogen detection applications intended for food matrices.
Collapse
Affiliation(s)
- Laura-Dorina Dinu
- Faculty of Biotechnology, University of Agricultural Sciences and Veterinary Medicine, 011464 Bucharest, Romania; (Q.J.A.-Z.); (A.G.M.); (F.M.)
| | - Quthama Jasim Al-Zaidi
- Faculty of Biotechnology, University of Agricultural Sciences and Veterinary Medicine, 011464 Bucharest, Romania; (Q.J.A.-Z.); (A.G.M.); (F.M.)
| | - Adelina Georgiana Matache
- Faculty of Biotechnology, University of Agricultural Sciences and Veterinary Medicine, 011464 Bucharest, Romania; (Q.J.A.-Z.); (A.G.M.); (F.M.)
| | - Florentina Matei
- Faculty of Biotechnology, University of Agricultural Sciences and Veterinary Medicine, 011464 Bucharest, Romania; (Q.J.A.-Z.); (A.G.M.); (F.M.)
- Faculty of Food Industry and Tourism, Transilvania University of Brasov, 500015 Brasov, Romania
| |
Collapse
|
2
|
Dhar BC, Delgado Santander R, Aćimović SG. Improved Canker Processing and Viability Droplet Digital PCR Allow Detection of Erwinia amylovora Viable Nonculturable Cells in Apple Bark. Microorganisms 2024; 12:376. [PMID: 38399780 PMCID: PMC10893025 DOI: 10.3390/microorganisms12020376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Revised: 02/02/2024] [Accepted: 02/07/2024] [Indexed: 02/25/2024] Open
Abstract
The bacterium Erwinia amylovora causes fire blight and continues to threaten global commercial apple and pear production. Conventional microbiology techniques cannot accurately determine the presence of live pathogen cells in fire blight cankers. Several factors may prevent E. amylovora from growing on solid culture media, including competing microbiota and the release of bacterial-growth-inhibitory compounds by plant material during sample processing. We previously developed a canker processing methodology and a chip-based viability digital PCR (v-dPCR) assay using propidium monoazide (PMA) to bypass these obstacles. However, sample analysis was still time-consuming and physically demanding. In this work, we improved the previous protocol using an automatic tissue homogenizer and transferred the chip-based v-dPCR to the BioRad QX200 droplet dPCR (ddPCR) platform. The improved sample processing method allowed the simultaneous, fast, and effortless processing of up to six samples. Moreover, the transferred v-ddPCR protocol was compatible with the same PMA treatment and showed a similar dynamic range, from 7.2 × 102 to 7.6 × 107 cells mL-1, as the previous v-dPCR. Finally, the improved protocol allowed, for the first time, the detection of E. amylovora viable but nonculturable (VBNC) cells in cankers and bark tissues surrounding cankers. Our v-ddPCR assay will enable new ways to evaluate resistant pome fruit tree germplasm, further dissect the E. amylovora life cycle, and elucidate E. amylovora physiology, epidemiology, and new options for canker management.
Collapse
Affiliation(s)
- Bidhan Chandra Dhar
- Alson H. Smith Jr. Agricultural Research and Extension Center, School of Plant and Environmental Sciences, Virginia Polytechnic Institute and State University, 595 Laurel Grove Rd, Winchester, VA 22602, USA;
| | - Ricardo Delgado Santander
- Irrigated Agriculture Research and Extension Center, College of Agricultural, Human and Natural Resource Sciences, Washington State University, Prosser, WA 99350, USA;
| | - Srđan G. Aćimović
- Alson H. Smith Jr. Agricultural Research and Extension Center, School of Plant and Environmental Sciences, Virginia Polytechnic Institute and State University, 595 Laurel Grove Rd, Winchester, VA 22602, USA;
| |
Collapse
|
3
|
Wang G, Nie X, Yang L, Liao H. A comparative analysis of quantitative detection methods for viable food-borne pathogens using RT-qPCR and PMA-qPCR. Lett Appl Microbiol 2023; 76:ovad120. [PMID: 37793793 DOI: 10.1093/lambio/ovad120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2023] [Revised: 09/25/2023] [Accepted: 10/03/2023] [Indexed: 10/06/2023]
Abstract
The accurate quantification of viable pathogens in food is crucial for ensuring food safety. This study mainly aimed to investigate the quantification of viable pathogens using PMA-qPCR and RT-qPCR, taking into account bacterial species, food matrices, and inactivation methods. The detection limit of PMA-qPCR for Salmonella serovars in simple matrices, such as culture broth, lake, or tap water, was found to be 102 cells per ml. Regarding the detection of Staphylococcus aureus and Escherichia coli in culture broth, as well as Salmonella in more complex matrices, such as juices and lab-made broth, both methods exhibited a detection limit of 103 cells per ml. Besides that, in adverse situations, there was a risk of overestimating the number of viable pathogens using PMA-qPCR. In addition, a conspicuous discrepancy between the results of PMA-qPCR/RT-qPCR and those of the plate counting assay was observed when Salmonella was exposed to isopropanol, H2O2, NaClO, sonication, or thermosonication. This suggests that it may survive in a viable but non-culturable state and poses a challenge for accurate quantification of viable cells using plate counting assay. Therefore, the results obtained by RT-qPCR were more objective compared to PMA-qPCR due to potential influences from bacteria species, surrounding media, and inactivation methods.
Collapse
Affiliation(s)
- Guoxiong Wang
- School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, 214122, China
| | - Xinyin Nie
- School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, 214122, China
| | - Lihong Yang
- School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, 214122, China
| | - Hongmei Liao
- School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, 214122, China
| |
Collapse
|
4
|
Thilakarathna SH, Stokowski T, Chui L. An Improved Real-Time Viability PCR Assay to Detect Salmonella in a Culture-Independent Era. Int J Mol Sci 2022; 23:ijms232314708. [PMID: 36499040 PMCID: PMC9738789 DOI: 10.3390/ijms232314708] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 11/21/2022] [Accepted: 11/22/2022] [Indexed: 11/26/2022] Open
Abstract
Viability PCR (vPCR) uses a DNA intercalating dye to irreversibly bind double-stranded DNA from organisms with compromised cell membranes. This allows the selective amplification of DNA from intact cells. An optimized vPCR protocol should minimize false positives (DNA from compromised cells not fully removed) and false negatives (live cell DNA bound by the dye). We aimed to optimize a vPCR protocol using PMAxx™ as the intercalating agent and Salmonella Enteritidis as the target organism. To do this, we studied (1) single vs. sequential PMAxx™ addition; (2) a wash step post-PMAxx™ treatment; (3) a change of tube post-treatment before DNA extraction. The single vs. sequential PMAxx™ addition showed no difference. Results signified that PMAxx™ potentially attached to polypropylene tube walls and bound the released DNA from PMA-treated live cells when lysed in the same tube. A wash step was ineffective but transfer of the treated live cells to a new tube minimized these false-negative results. Our optimized protocol eliminated 108 CFU/mL heat-killed cell DNA in the presence of different live cell dilutions without compromising the amplification of the live cells, minimizing false positives. With further improvements, vPCR has great potential as a culture-independent diagnostic tool.
Collapse
Affiliation(s)
- Surangi H. Thilakarathna
- Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, AB T6G 1C9, Canada
| | - Taryn Stokowski
- Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, AB T6G 1C9, Canada
| | - Linda Chui
- Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, AB T6G 1C9, Canada
- Alberta Precision Laboratories, Public Health Laboratory (ProvLab), Edmonton, AB T6G 2J2, Canada
- Correspondence:
| |
Collapse
|
5
|
Guo J, Wang W, Zhao H, Luo Y, Wan M, Li Y. A new PMA-qPCR method for rapid and accurate detection of viable bacteria and spores of marine-derived Bacillus velezensis B-9987. J Microbiol Methods 2022; 199:106537. [DOI: 10.1016/j.mimet.2022.106537] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 06/29/2022] [Accepted: 06/30/2022] [Indexed: 12/27/2022]
|
6
|
Hong W, Xiong J, Nyaruaba R, Li J, Muturi E, Liu H, Yu J, Yang H, Wei H. Rapid determination of infectious SARS-CoV-2 in PCR-positive samples by SDS-PMA assisted RT-qPCR. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 797:149085. [PMID: 34293609 PMCID: PMC8285242 DOI: 10.1016/j.scitotenv.2021.149085] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 07/05/2021] [Accepted: 07/13/2021] [Indexed: 05/02/2023]
Abstract
The ongoing COVID-19 pandemic has generated a global health crisis that needs well management of not only patients but also environments to reduce SARS-CoV-2 transmission. The gold standard RT-qPCR method is sensitive and rapid to detect SARS-CoV-2 nucleic acid, but does not answer if PCR-positive samples contain infectious virions. To circumvent this problem, we report an SDS-propidium monoazide (PMA) assisted RT-qPCR method that enables rapid discrimination of live and dead SARS-CoV-2 within 3 h. PMA, a photo-reactive dye, can react with viral RNA released or inside inactivated SARS-CoV-2 virions under assistance of 0.005% SDS, but not viral RNA inside live virions. Formation of PMA-RNA conjugates prevents PCR amplification, leaving only infectious virions to be detected. Under optimum conditions, RT-qPCR detection of heat-inactivated SARS-CoV-2 resulted in larger than 9 Ct value differences between PMA-treated and PMA-free groups, while less than 0.5 Ct differences were observed in the detection of infectious SARS-CoV-2 ranging from 20 to 5148 viral particles. Using a cutoff Ct difference of 8.6, this method could differentiate as low as 8 PFU live viruses in the mixtures of live and heat-inactivated virions. Further experiments showed that this method could successfully monitor the natural inactivation process of SARS-CoV-2 on plastic surfaces during storage with comparable results to the gold standard plaque assay. We believe that the culture-free method established here could be used for rapid and convenient determination of infectious SARS-CoV-2 virions in PCR-positive samples, which will facilitate better control of SARS-CoV-2 transmission.
Collapse
Affiliation(s)
- Wei Hong
- CAS Key Laboratory of Emerging Pathogens and Biosafety, Centre for Biosafety Mega-Sciences, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jin Xiong
- CAS Key Laboratory of Emerging Pathogens and Biosafety, Centre for Biosafety Mega-Sciences, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
| | - Raphael Nyaruaba
- CAS Key Laboratory of Emerging Pathogens and Biosafety, Centre for Biosafety Mega-Sciences, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Junhua Li
- CAS Key Laboratory of Emerging Pathogens and Biosafety, Centre for Biosafety Mega-Sciences, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
| | - Elishiba Muturi
- CAS Key Laboratory of Emerging Pathogens and Biosafety, Centre for Biosafety Mega-Sciences, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Huan Liu
- CAS Key Laboratory of Emerging Pathogens and Biosafety, Centre for Biosafety Mega-Sciences, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Junping Yu
- CAS Key Laboratory of Emerging Pathogens and Biosafety, Centre for Biosafety Mega-Sciences, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Hang Yang
- CAS Key Laboratory of Emerging Pathogens and Biosafety, Centre for Biosafety Mega-Sciences, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Hongping Wei
- CAS Key Laboratory of Emerging Pathogens and Biosafety, Centre for Biosafety Mega-Sciences, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| |
Collapse
|
7
|
Lin X, Jin X, Du W, Shan X, Huang Q, Fu R, Lv W, Yang H, Su Y, Huang G. Quantitative and specific detection of viable pathogens on a portable microfluidic chip system by combining improved propidium monoazide (PMAxx) and loop-mediated isothermal amplification (LAMP). ANALYTICAL METHODS : ADVANCING METHODS AND APPLICATIONS 2021; 13:3569-3576. [PMID: 34286728 DOI: 10.1039/d1ay00953b] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
An accurate and specific detection of viable Candida albicans (C. albicans) in vaginal discharge is crucial for the diagnosis of vulvovaginal candidiasis (VVC) and assessment of antifungal effects. In this study, improved propidium monoazide (PMAxx) and loop-mediated isothermal amplification (LAMP) were used for the first time to distinguish between viable and dead C. albicans. A portable microfluidic chip system was developed to detect multiple viable pathogens in parallel. The consumption of samples and reagents in per reaction cell were only 0.94 μL, less than 1/25 of the conventional 25 μL Eppendorf tubular test method, both significantly reducing testing cost and greatly simplifying the detection of multiple viable pathogens. The concentration of PMAxx was optimized against C. albicans at 4.0 log CFU mL-1 to 5.0 log CFU mL-1, and 1 μM PMAxx was proven to be suitable for the detection of C. albicans in clinical samples. When testing mixtures containing different ratios of viable to dead C. albicans, PMAxx-LAMP could circumvent the signal arising from dead cells and, therefore, reflected the abundance of viable cells precisely. Furthermore, the suitability of this technique to evaluate the effects of antifungal agents, including clotrimazole, miconazole, and tioconazole, was assessed. Finally, the viability of Escherichia coli (E. coli) and C. albicans were detected on the portable microfluidic chip system. PMAxx-LAMP based portable microfluidic chip system was determined to be a feasible technique for assessing the viability of multiple pathogens in gynecology and might provide insights into new VVC treatment strategies.
Collapse
Affiliation(s)
- Xue Lin
- Department of Biomedical Engineering, The School of Medicine, Tsinghua University, Beijing 100084, P. R. China.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Shi X, Yu L, Lin C, Li K, Chen J, Qin H. Biotin exposure-based immunomagnetic separation coupled with sodium dodecyl sulfate, propidium monoazide, and multiplex real-time PCR for rapid detection of viable Salmonella Typhimurium, Staphylococcus aureus, and Listeria monocytogenes in milk. J Dairy Sci 2021; 104:6588-6597. [PMID: 33715855 DOI: 10.3168/jds.2020-19887] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 01/28/2021] [Indexed: 11/19/2022]
Abstract
In this study, we established a rapid and sensitive method for the detection of viable Salmonella Typhimurium, Staphylococcus aureus, and Listeria monocytogenes in milk using biotin-exposure-based immunomagnetic separation (IMS) combined with sodium dodecyl sulfate (SDS), propidium monoazide (PMA), and multiplex real-time PCR (mRT-PCR). We used IMS to lessen the assay time for isolation of target bacteria. We then optimized the coupling conditions and immunomagnetic capture process. The immunoreaction and incubation times for 5 μg of mAb coupled with 500 μg of streptavidin-functionalized magnetic beads using a streptavidin-biotin system were 90 and 30 min, respectively. Treatment with SDS-PMA before mRT-PCR amplification eliminated false-positive outcomes from dead bacteria and identified viable target bacteria with good sensitivity and specificity. The limit of detection of IMS combined with the SDS-PMA-mRT-PCR assay for the detection of viable Salmonella Typhimurium, Staph. aureus, and L. monocytogenes in spiked milk matrix samples was 10 cfu/mL and remained significant even in the appearance of 106 cfu/mL of nontarget bacteria. The entire detection process was able to identify viable bacteria within 9 h. The combination of biotin-exposure-mediated IMS and SDS-PMA-mRT-PCR has potential value for the rapid and sensitive detection of foodborne pathogens.
Collapse
Affiliation(s)
- Xiuquan Shi
- Xiangya School of Public Health, Central South University, Changsha 410078, P. R. China
| | - Liang Yu
- Research and Development Office, Hunan First Normal University, Changsha 410205, P. R. China
| | - Cui Lin
- Xiangya School of Public Health, Central South University, Changsha 410078, P. R. China
| | - Ke Li
- College of Food Science and Technology, Hunan Agricultural University, Changsha 410128, P. R. China
| | - Jihua Chen
- Xiangya School of Public Health, Central South University, Changsha 410078, P. R. China
| | - Hong Qin
- Xiangya School of Public Health, Central South University, Changsha 410078, P. R. China.
| |
Collapse
|
9
|
Abstract
The development of viability quantitative PCR (v-qPCR) has allowed for a more accurate assessment of the viability of a microbial sample by limiting the amplification of DNA from dead cells. Although valuable, v-qPCR is not infallible. One of the most limiting factors for accurate live/dead distinction is the length of the qPCR amplicon used. However, no consensus or guidelines exist for selecting and designing amplicon lengths for optimal results. In this study, a wide range of incrementally increasing amplicon lengths (68 to 906 base pairs [bp]) was used on live and killed cells of nine bacterial species treated with a viability dye (propidium monoazide [PMA]). Increasing amplicon lengths up to approximately 200 bp resulted in increasing quantification cycle (Cq) differences between live and killed cells while maintaining a good qPCR efficiency. Longer amplicon lengths, up to approximately 400 bp, further increased the Cq difference but at the cost of qPCR efficiency. Above 400 bp, no valuable increase in Cq differences was observed. IMPORTANCE Viability quantitative PCR (v-qPCR) has evolved into a valuable, mainstream technique for determining the number of viable microorganisms in samples by qPCR. Amplicon length is known to be positively correlated with the ability to distinguish between live and dead bacteria but is negatively correlated with qPCR efficiency. This trade-off is often not taken into account and might have an impact on the accuracy of v-qPCR data. Currently, there is no consensus on the optimal amplicon length. This paper provides methods to determine the optimal amplicon length and suggests an amplicon length range for optimal v-qPCR, taking into consideration the trade-off between qPCR efficiency and live/dead distinction.
Collapse
|
10
|
Escherichia coli Capacity to Repopulate Microcosms Under Osmotic/U.V. Synergic Stress in Tropical Waters. Curr Microbiol 2021; 78:756-764. [PMID: 33462632 DOI: 10.1007/s00284-020-02319-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 12/07/2020] [Indexed: 10/22/2022]
Abstract
In both Brazilian and European regulations, the impact assessment of sewage discharges into coastal waters is based on microbiological analyses of fecal indicators such as Escherichia coli, frequently used in prevision hydrodynamic models. However, the decay rates of E. coli vary depending on environmental conditions, and analysis may lead to inaccurate conclusions. This study aimed to analyze the decay of culturable and viable (but not culturable) E. coli in outdoor conditions, by creating microcosms inoculated with pre-treated sewage. The microcosms were filled with 9.88 L of filtered water (0.22 μm membrane), 3.5% salt, 0.1-0.2% BHI, and 1% bacterial suspension obtained by reverse filtration. PMA-qPCR of E. coli uidA gene and Colilert measurements were applied to evaluate population counts after 2 h, 4 h, and 26 h. After nine hours of exposure to solar radiation, the viable cells decreased to 2.76% (interpolated value) of the initial population, and the cultivable fraction of the viable population accounted for 0.50%. In the dark period, the bacteria grew again, and viable cells reached 8.54%, while cultivable cells grew to 48.14% of initial population. This behavior is possibly due to the use of nutrients recycled from dead cells. Likewise, populations of E. coli in sewage outfalls remain viable in the sediments, where resuspension can renew blooming.
Collapse
|
11
|
Codony F, Dinh-Thanh M, Agustí G. Key Factors for Removing Bias in Viability PCR-Based Methods: A Review. Curr Microbiol 2019; 77:682-687. [DOI: 10.1007/s00284-019-01829-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 11/29/2019] [Indexed: 11/24/2022]
|
12
|
Quantitative detection of viable Escherichia coli O157:H7 using a photoreactive DNA-binding dye propidium monoazide in irrigation water. Biochem Eng J 2019. [DOI: 10.1016/j.bej.2019.107354] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
|
13
|
Kragh ML, Thykier M, Truelstrup Hansen L. A long-amplicon quantitative PCR assay with propidium monoazide to enumerate viable Listeria monocytogenes after heat and desiccation treatments. Food Microbiol 2019; 86:103310. [PMID: 31703859 DOI: 10.1016/j.fm.2019.103310] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 06/16/2019] [Accepted: 08/20/2019] [Indexed: 01/22/2023]
Abstract
The objective of this study was to develop a qPCR method for specific enumeration of viable Listeria monocytogenes in food processing facilities and heat treated products. Primers specific for L. monocytogenes were designed to amplify a short (199 bp) or long (1561 bp) fragment of the listeriolysin (hly) gene. The short- and long-amplicon qPCR methods with and without propidium monoazide (PMA) treatment of the cells were tested for their ability to discriminate between viable (no heat) and heat-killed cells (90 °C, 10 min). The PMA-qPCR methods were subsequently used to assess the survival of L. monocytogenes during desiccation (33% RH, 15 °C) on stainless steel surfaces for ten days with and without prior biofilm formation. The long-amplicon qPCR method had a limit of quantification (LOQ) of 1.32 log CFU/reaction (efficiency 92%, R2 = 0.991), while the LOQ for the short-amplicon qPCR method was 1.44 log CFU/reaction (efficiency 102%, R2 = 0.991). PMA was essential for detection of viable cells, and the long-amplicon PMA-qPCR significantly (p < 0.05) reduced the signal from heat-killed cells compared to the short-amplicon method. L. monocytogenes survival during desiccation without biofilm formation was accurately enumerated with the long-amplicon PMA-qPCR method. However, when L. monocytogenes had formed biofilm prior to desiccation, the long-amplicon PMA-qPCR accurately measured the log fold inactivation but underestimated the number of viable cells even with use of an optimized DNA extraction method. This long-amplicon PMA-qPCR method can aid in the detection and enumeration of viable L. monocytogenes cells to further the understanding of its survival and persistence in food processing facilities. The developed method was demonstrated to work on both heat and desiccation treated cells and highlights the importance of amplicon size in viability-qPCR.
Collapse
Affiliation(s)
- Martin Laage Kragh
- National Food Institute, Technical University of Denmark, Kemitorvet, DK-2800, Kgs. Lyngby, Denmark
| | - Mikala Thykier
- National Food Institute, Technical University of Denmark, Kemitorvet, DK-2800, Kgs. Lyngby, Denmark
| | - Lisbeth Truelstrup Hansen
- National Food Institute, Technical University of Denmark, Kemitorvet, DK-2800, Kgs. Lyngby, Denmark.
| |
Collapse
|
14
|
Dong L, Liu H, Meng L, Xing M, Lan T, Gu M, Zheng N, Wang C, Chen H, Wang J. Short communication: Quantitative PCR coupled with sodium dodecyl sulfate and propidium monoazide for detection of culturable Escherichia coli in milk. J Dairy Sci 2019; 102:6914-6919. [PMID: 31202653 DOI: 10.3168/jds.2018-15393] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 04/22/2019] [Indexed: 11/19/2022]
Abstract
Escherichia coli has been frequently reported as a major foodborne bacterium contaminating raw milk or pasteurized milk. Therefore, the aim of this study was to explore a quantitative real-time PCR (qPCR) technique combined with sodium dodecyl sulfate (SDS) and propidium monoazide (PMA) to detect culturable E. coli in milk. An internal amplification control was also added into this reaction system as an indicator of false-negative results. The inclusivity and exclusivity of the primers were tested using DNA from 7 E. coli and 14 other bacterial strains. The concentrations of SDS and PMA were determined according to plate counts and quantitative cycle values of qPCR, respectively. A standard curve was established using series diluted E. coli DNA. The reliability and specificity of this method were further determined by the detection of E. coli in spiked milk. The results showed that the optimal concentrations of SDS and PMA were 100 µg/mL and 40 μM, respectively. A standard curve with a good linear relationship (coefficient of determination = 0.997; amplification efficiency = 100.5%) was obtained. Compared with conventional PCR and PMA-qPCR, the SDS-PMA-qPCR assay was more specific and sensitive in culturable E. coli detection. Therefore, we evaluated and improved the SDS-PMA-qPCR method for detecting culturable E. coli in milk.
Collapse
Affiliation(s)
- Lei Dong
- Laboratory of Quality and Safety Risk Assessment for Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, P. R. China; Milk and Dairy Product Inspection Center of Ministry of Agriculture and Rural Affairs, Beijing 100193, P. R. China; College of Food Science and Engineer, Qingdao Agricultural University, Qingdao 266109, P. R. China
| | - Huimin Liu
- Laboratory of Quality and Safety Risk Assessment for Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, P. R. China; Milk and Dairy Product Inspection Center of Ministry of Agriculture and Rural Affairs, Beijing 100193, P. R. China; Institute of Quality Standard and Testing Technology, Xinjiang Academy of Agricultural Sciences, Urumqi 830091, P. R. China
| | - Lu Meng
- Laboratory of Quality and Safety Risk Assessment for Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, P. R. China; Milk and Dairy Product Inspection Center of Ministry of Agriculture and Rural Affairs, Beijing 100193, P. R. China
| | - Mengru Xing
- Laboratory of Quality and Safety Risk Assessment for Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, P. R. China; Milk and Dairy Product Inspection Center of Ministry of Agriculture and Rural Affairs, Beijing 100193, P. R. China; College of Food Science and Engineer, Qingdao Agricultural University, Qingdao 266109, P. R. China
| | - Tu Lan
- Laboratory of Quality and Safety Risk Assessment for Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, P. R. China; Milk and Dairy Product Inspection Center of Ministry of Agriculture and Rural Affairs, Beijing 100193, P. R. China; Institute of Quality Standard and Testing Technology, Xinjiang Academy of Agricultural Sciences, Urumqi 830091, P. R. China
| | - Mei Gu
- Laboratory of Quality and Safety Risk Assessment for Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, P. R. China; Milk and Dairy Product Inspection Center of Ministry of Agriculture and Rural Affairs, Beijing 100193, P. R. China
| | - Nan Zheng
- Laboratory of Quality and Safety Risk Assessment for Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, P. R. China; Milk and Dairy Product Inspection Center of Ministry of Agriculture and Rural Affairs, Beijing 100193, P. R. China
| | - Cheng Wang
- Institute of Quality Standard and Testing Technology, Xinjiang Academy of Agricultural Sciences, Urumqi 830091, P. R. China
| | - He Chen
- Institute of Quality Standard and Testing Technology, Xinjiang Academy of Agricultural Sciences, Urumqi 830091, P. R. China
| | - Jiaqi Wang
- Laboratory of Quality and Safety Risk Assessment for Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, P. R. China; Milk and Dairy Product Inspection Center of Ministry of Agriculture and Rural Affairs, Beijing 100193, P. R. China.
| |
Collapse
|
15
|
Laidlaw AM, Gänzle MG, Yang X. Comparative assessment of qPCR enumeration methods that discriminate between live and dead Escherichia coli O157:H7 on beef. Food Microbiol 2019; 79:41-47. [DOI: 10.1016/j.fm.2018.11.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Revised: 11/05/2018] [Accepted: 11/13/2018] [Indexed: 11/28/2022]
|
16
|
Zhao Y, Chen H, Liu H, Cai J, Meng L, Dong L, Zheng N, Wang J, Wang C. Quantitative Polymerase Chain Reaction Coupled With Sodium Dodecyl Sulfate and Propidium Monoazide for Detection of Viable Streptococcus agalactiae in Milk. Front Microbiol 2019; 10:661. [PMID: 30984156 PMCID: PMC6450196 DOI: 10.3389/fmicb.2019.00661] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Accepted: 03/15/2019] [Indexed: 12/14/2022] Open
Abstract
Streptococcus agalactiae is an important pathogen causing bovine mastitis. The aim of this study was to develop a simple and specific method for direct detection of S. agalactiae from milk products. Propidium monoazide (PMA) and sodium dodecyl sulfate (SDS) were utilized to eliminate the interference of dead and injured cells in qPCR. Lysozyme (LYZ) was adopted to increase the extraction efficiency of target bacteria DNA in milk matrix. The specific primers were designed based on cfb gene of S. agalactiae for qPCR. The inclusivity and exclusivity of the assay were evaluated using 30 strains. The method was further determined by the detection of S. agalactiae in spiked milk. Results showed significant differences between the SDS–PMA–qPCR, PMA–qPCR and qPCR when a final concentration of 10 mg/ml (R2 = 0.9996, E = 95%) of LYZ was added in DNA extraction. Viable S. agalactiae was effectively detected when SDS and PMA concentrations were 20 μg/ml and 10 μM, respectively, and it was specific and more sensitive than qPCR and PMA–qPCR. Moreover, the SDS–PMA–qPCR assay coupled with LYZ was used to detect viable S. agalactiae in spiked milk, with a limit of detection of 3 × 103 cfu/ml. Therefore, the SDS–PMA–qPCR assay had excellent sensitivity and specificity for detection of viable S. agalactiae in milk.
Collapse
Affiliation(s)
- Yankun Zhao
- Institute of Quality Standard and Testing Technology for Agro-Products, Xinjiang Academy of Agricultural Sciences, Urumqi, China.,Ministry of Agriculture and Rural Affairs-Laboratory of Quality and Safety Risk Assessment for Agro-Products, Urumqi, China.,Key Laboratory of Agro-Products Quality and Safety of Xinjiang, Urumqi, China
| | - He Chen
- Institute of Quality Standard and Testing Technology for Agro-Products, Xinjiang Academy of Agricultural Sciences, Urumqi, China.,Ministry of Agriculture and Rural Affairs-Laboratory of Quality and Safety Risk Assessment for Agro-Products, Urumqi, China.,Key Laboratory of Agro-Products Quality and Safety of Xinjiang, Urumqi, China
| | - Huimin Liu
- Institute of Quality Standard and Testing Technology for Agro-Products, Xinjiang Academy of Agricultural Sciences, Urumqi, China.,Ministry of Agriculture and Rural Affairs-Laboratory of Quality and Safety Risk Assessment for Agro-Products, Urumqi, China.,Key Laboratory of Agro-Products Quality and Safety of Xinjiang, Urumqi, China.,Ministry of Agriculture Laboratory of Quality and Safety Risk Assessment for Dairy Products (Beijing), Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Jianxing Cai
- Institute of Quality Standard and Testing Technology for Agro-Products, Xinjiang Academy of Agricultural Sciences, Urumqi, China.,Ministry of Agriculture and Rural Affairs-Laboratory of Quality and Safety Risk Assessment for Agro-Products, Urumqi, China.,Key Laboratory of Agro-Products Quality and Safety of Xinjiang, Urumqi, China
| | - Lu Meng
- Ministry of Agriculture Laboratory of Quality and Safety Risk Assessment for Dairy Products (Beijing), Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Lei Dong
- Ministry of Agriculture Laboratory of Quality and Safety Risk Assessment for Dairy Products (Beijing), Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Nan Zheng
- Ministry of Agriculture Laboratory of Quality and Safety Risk Assessment for Dairy Products (Beijing), Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Jiaqi Wang
- Ministry of Agriculture Laboratory of Quality and Safety Risk Assessment for Dairy Products (Beijing), Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Cheng Wang
- Ministry of Agriculture and Rural Affairs-Laboratory of Quality and Safety Risk Assessment for Agro-Products, Urumqi, China.,Key Laboratory of Agro-Products Quality and Safety of Xinjiang, Urumqi, China
| |
Collapse
|
17
|
Brosnahan CL, Georgiades E, McDonald C, Keeling SE, Munday JS, Jones B. Optimisation and validation of a PCR to detect viable Tenacibaculum maritimum in salmon skin tissue samples. J Microbiol Methods 2019; 159:186-193. [PMID: 30877014 DOI: 10.1016/j.mimet.2019.03.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 03/11/2019] [Accepted: 03/11/2019] [Indexed: 10/27/2022]
Abstract
A PCR protocol was optimised and validated for the detection of viable Tenacibaculum maritimum cells in salmon skin tissue. Viability conventional (vPCR) and quantitative PCR (v-qPCR) assays both had a limit of detection of 103 CFU mL-1 viable cells. The v-qPCR assay showed a linear quantification over 4 log units. Conventional vPCR showed complete signal suppression when only dead cells were present at concentrations lower than 106 CFU mL-1. While the v-qPCR did not result in complete suppression when only dead cells were present, a method was developed to determine if viable cells were present based on the % Δ in cycle threshold (Ct) value. The procedure was validated for high-throughput processing and an enrichment protocol was validated to reliably detect low concentrations of viable cells both with and without a high background of dead cells. Performing this protocol on naturally infected tissues showed that vPCR and v-qPCR reduced the potential for false positives compared to using conventional PCR and qPCR. The optimised protocol developed for this study provides an efficient, reliable and robust alternative for the detection of viable T. maritimum in skin tissue.
Collapse
Affiliation(s)
- C L Brosnahan
- Ministry for Primary Industries, Wellington, New Zealand; School of Veterinary Science, Massey University, Palmerston North, New Zealand.
| | - E Georgiades
- Ministry for Primary Industries, Wellington, New Zealand
| | - C McDonald
- Ministry for Primary Industries, Wellington, New Zealand
| | - S E Keeling
- Ministry for Primary Industries, Wellington, New Zealand
| | - J S Munday
- School of Veterinary Science, Massey University, Palmerston North, New Zealand
| | - B Jones
- Murdoch University, School of Veterinary and Life Sciences, Perth, WA, Australia
| |
Collapse
|
18
|
Development and application of a real-time polymerase chain reaction method for quantification of Escherichia coli in oysters (Crassostrea gigas). Food Microbiol 2019; 77:85-92. [DOI: 10.1016/j.fm.2018.08.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 07/30/2018] [Accepted: 08/31/2018] [Indexed: 11/17/2022]
|
19
|
Dong L, Liu H, Meng L, Xing M, Wang J, Wang C, Chen H, Zheng N. Quantitative PCR coupled with sodium dodecyl sulfate and propidium monoazide for detection of viable Staphylococcus aureus in milk. J Dairy Sci 2018; 101:4936-4943. [PMID: 29605335 DOI: 10.3168/jds.2017-14087] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 01/04/2018] [Indexed: 11/19/2022]
Abstract
Conventional quantitative PCR (qPCR) are unable to differentiate DNA of viable Staphylococcus aureus cells from dead ones. The aim of this study was to use sodium dodecyl sulfate (SDS) and propidium monoazide (PMA) coupled with lysostaphin to detect viable Staph. aureus. The cell suspensions were treated with SDS and PMA before DNA extraction. The SDS is an anionic surfactant, which can increase the permeability of dead cells to PMA without compromising the viability of live cells. The lysostaphin was applied to improve the effectiveness of DNA extraction. The reliability and specificity of this method were further determined by the detection of Staph. aureus in spiked milk. The results showed that there were significant differences between the SDS-PMA-qPCR and qPCR when a final concentration of 200 μg/mL of lysostaphin was added in DNA extraction. The viable Staph. aureus could be effectively detected when SDS and PMA concentrations were 100 µg/mL and 40 μM, respectively. Compared with conventional qPCR, the SDS-PMA-qPCR assay coupled with lysostaphin was more specific and sensitive. Therefore, this method could accurately detect the number of viable Staph. aureus cells.
Collapse
Affiliation(s)
- Lei Dong
- Ministry of Agriculture Laboratory of Quality and Safety Risk Assessment for Dairy Products (Beijing), Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, P. R. China; Ministry of Agriculture-Milk and Dairy Product Inspection Center (Beijing), Beijing 100193, P. R. China; College of Food Science and Engineer, Qingdao Agricultural University, Qingdao 266109, P. R. China
| | - Huimin Liu
- Ministry of Agriculture Laboratory of Quality and Safety Risk Assessment for Dairy Products (Beijing), Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, P. R. China; Ministry of Agriculture-Milk and Dairy Product Inspection Center (Beijing), Beijing 100193, P. R. China; Institute of Quality Standard and Testing Technology, Xinjiang Academy of Agricultural Sciences, Urumqi 830091, P. R. China
| | - Lu Meng
- Ministry of Agriculture Laboratory of Quality and Safety Risk Assessment for Dairy Products (Beijing), Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, P. R. China; Ministry of Agriculture-Milk and Dairy Product Inspection Center (Beijing), Beijing 100193, P. R. China
| | - Mengru Xing
- Ministry of Agriculture Laboratory of Quality and Safety Risk Assessment for Dairy Products (Beijing), Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, P. R. China; Ministry of Agriculture-Milk and Dairy Product Inspection Center (Beijing), Beijing 100193, P. R. China; College of Food Science and Engineer, Qingdao Agricultural University, Qingdao 266109, P. R. China
| | - Jiaqi Wang
- Ministry of Agriculture Laboratory of Quality and Safety Risk Assessment for Dairy Products (Beijing), Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, P. R. China; Ministry of Agriculture-Milk and Dairy Product Inspection Center (Beijing), Beijing 100193, P. R. China
| | - Cheng Wang
- Institute of Quality Standard and Testing Technology, Xinjiang Academy of Agricultural Sciences, Urumqi 830091, P. R. China
| | - He Chen
- Institute of Quality Standard and Testing Technology, Xinjiang Academy of Agricultural Sciences, Urumqi 830091, P. R. China
| | - Nan Zheng
- Ministry of Agriculture Laboratory of Quality and Safety Risk Assessment for Dairy Products (Beijing), Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, P. R. China; Ministry of Agriculture-Milk and Dairy Product Inspection Center (Beijing), Beijing 100193, P. R. China.
| |
Collapse
|
20
|
Agustí G, Fittipaldi M, Codony F. Optimization of a Viability PCR Method for the Detection of Listeria monocytogenes in Food Samples. Curr Microbiol 2018; 75:779-785. [DOI: 10.1007/s00284-018-1448-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 02/05/2018] [Indexed: 10/18/2022]
|
21
|
Scariot MC, Venturelli GL, Prudêncio ES, Arisi ACM. Quantification of Lactobacillus paracasei viable cells in probiotic yoghurt by propidium monoazide combined with quantitative PCR. Int J Food Microbiol 2018; 264:1-7. [DOI: 10.1016/j.ijfoodmicro.2017.10.021] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 10/16/2017] [Accepted: 10/17/2017] [Indexed: 12/21/2022]
|
22
|
Dinh Thanh M, Agustí G, Mader A, Appel B, Codony F. Improved sample treatment protocol for accurate detection of live Salmonella spp. in food samples by viability PCR. PLoS One 2017; 12:e0189302. [PMID: 29232387 PMCID: PMC5726647 DOI: 10.1371/journal.pone.0189302] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 11/23/2017] [Indexed: 11/19/2022] Open
Abstract
Culture-based detection is still considered as the standard way for detection of Salmonella in foods, although molecular methods, such as viability PCR (vPCR), have been introduced to overcome some disadvantages of traditional culture methods. Despite the success of the vPCR methodology, the problem of false-positive results is a major drawback, especially when applied to environmental samples, hindering the interpretation of the results. To improve the efficiency of vPCR, many approaches have been introduced by several authors during the last years. In the present work, the combination of PEMAX dye, double tube change, and double photo-activation step was established as a strategy to improve vPCR protocol. By combining these approaches, we developed an improved sample treatment protocol able to neutralize DNA signals of up to 5.0×107 dead cells/sample from both pure culture and artificially contaminated food samples. Our results indicate that vPCR can work reliable and has a potential for high throughput detection of live Salmonella cells in food samples, minimizing false-positive signals.
Collapse
Affiliation(s)
- Mai Dinh Thanh
- Freie Universität Berlin, Department of Biology, Chemistry and Pharmacy, Berlin, Germany
- German Federal Institute for Risk Assessment, Department Biological Safety, Berlin, Germany
| | | | - Anneluise Mader
- German Federal Institute for Risk Assessment, Department Biological Safety, Berlin, Germany
| | - Bernd Appel
- German Federal Institute for Risk Assessment, Department Biological Safety, Berlin, Germany
| | | |
Collapse
|
23
|
Takahashi H, Saito R, Miya S, Tanaka Y, Miyamura N, Kuda T, Kimura B. Development of quantitative real-time PCR for detection and enumeration of Enterobacteriaceae. Int J Food Microbiol 2017; 246:92-97. [PMID: 28270336 DOI: 10.1016/j.ijfoodmicro.2016.12.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Revised: 10/20/2016] [Accepted: 12/23/2016] [Indexed: 10/20/2022]
Abstract
The family Enterobacteriaceae, members of which are widely distributed in the environment, includes many important human pathogens. In this study, a rapid real-time PCR method targeting rplP, coding for L16 protein, a component of the ribosome large subunit, was developed for enumerating Enterobacteriaceae strains, and its efficiency was evaluated using naturally contaminated food products. The rplP-targeted real-time PCR amplified Enterobacteriaceae species with Ct values of 14.0-22.8, whereas the Ct values for non-Enterobacteriaceae species were >30, indicating the specificity of this method for the Enterobacteriaceae. Using a calibration curve of Ct=-3.025 (log CFU/g)+37.35, which was calculated from individual plots of the cell numbers in different concentrations of 5 Enterobacteriaceae species, the rplP-targeted real-time PCR was applied to 51 food samples. A <1log difference between the real-time PCR and culture methods was obtained in a majority of the food samples (81.8%), with good correlation (r2=0.8285). This study demonstrated that the rplP-targeted real-time PCR method could detect and enumerate Enterobacteriaceae species in foods rapidly and accurately, and therefore, it can be used for the microbiological risk analysis of foods.
Collapse
Affiliation(s)
- Hajime Takahashi
- Department of Food Science and Technology, Faculty of Marine Science, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan.
| | - Rumi Saito
- Department of Food Science and Technology, Faculty of Marine Science, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan
| | - Satoko Miya
- Department of Food Science and Technology, Faculty of Marine Science, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan
| | - Yuichiro Tanaka
- Department of Food Science and Technology, Faculty of Marine Science, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan
| | - Natsumi Miyamura
- Department of Food Science and Technology, Faculty of Marine Science, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan
| | - Takashi Kuda
- Department of Food Science and Technology, Faculty of Marine Science, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan
| | - Bon Kimura
- Department of Food Science and Technology, Faculty of Marine Science, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan
| |
Collapse
|