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Li L, Ren J, Zhang Q, Luo Y, Zhang Y, Qi J, Zhao X, Hu M, Liu Y. Development of Two Loop-Mediated Isothermal Amplification Assays for Rapid Detection of ermB and mefA Genes in Streptococcus suis. Foodborne Pathog Dis 2022; 19:817-822. [PMID: 36399616 DOI: 10.1089/fpd.2022.0034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Streptococcus suis is an important zoonotic pathogen that poses a serious threat to the pig industry and human health. The massive use of macrolides has led to the emergence of resistance in S. suis, and S. suis is suspected to be a reservoir of antimicrobial resistance genes. The mechanism to macrolide resistance in S. suis is mainly due to ermB and mefA. In this study, loop-mediated isothermal amplification (LAMP) methods were developed to detect ermB and mefA genes in S. suis through turbidimetry detection. The sensitivity and specificity of the LAMP reactions were determined. All results of LAMP and polymerase chain reaction (PCR) assay were compared to determine whether LAMP method was accurate and reliable. The results showed that all 100 nonstreptococcus clinical isolates tested negative, indicating the high specificity of LAMP assays. The detection limit of LAMP assay was 1 fg per reaction, and 102-104-fold lower than those of conventional PCR methods. Evaluation of the performance of the LAMP assay in S. suis clinical strains revealed a good consistency between LAMP and PCR assays. In conclusion, LAMP assays are specific, sensitive, and rapid methods to detect ermB and mefA in S. suis.
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Affiliation(s)
- LuLu Li
- Shandong Key Laboratory of Animal Disease Control and Breeding, Institute of Animal Science and Veterinary Medicine, Shandong Academy of Agricultural Sciences, Jinan, China.,Key Laboratory of Livestock and Poultry Multi-Omics of MARA, Jinan, China
| | - JinRui Ren
- Shandong Key Laboratory of Animal Disease Control and Breeding, Institute of Animal Science and Veterinary Medicine, Shandong Academy of Agricultural Sciences, Jinan, China.,Key Laboratory of Livestock and Poultry Multi-Omics of MARA, Jinan, China.,School of Life Sciences, Shandong Normal University, Jinan, China
| | - Qing Zhang
- Shandong Key Laboratory of Animal Disease Control and Breeding, Institute of Animal Science and Veterinary Medicine, Shandong Academy of Agricultural Sciences, Jinan, China.,Key Laboratory of Livestock and Poultry Multi-Omics of MARA, Jinan, China
| | - YanBo Luo
- Shandong Key Laboratory of Animal Disease Control and Breeding, Institute of Animal Science and Veterinary Medicine, Shandong Academy of Agricultural Sciences, Jinan, China.,Key Laboratory of Livestock and Poultry Multi-Omics of MARA, Jinan, China
| | - Yin Zhang
- Shandong Key Laboratory of Animal Disease Control and Breeding, Institute of Animal Science and Veterinary Medicine, Shandong Academy of Agricultural Sciences, Jinan, China.,Key Laboratory of Livestock and Poultry Multi-Omics of MARA, Jinan, China
| | - Jing Qi
- Shandong Key Laboratory of Animal Disease Control and Breeding, Institute of Animal Science and Veterinary Medicine, Shandong Academy of Agricultural Sciences, Jinan, China.,Key Laboratory of Livestock and Poultry Multi-Omics of MARA, Jinan, China
| | - XiaoNan Zhao
- Shandong Key Laboratory of Animal Disease Control and Breeding, Institute of Animal Science and Veterinary Medicine, Shandong Academy of Agricultural Sciences, Jinan, China.,Key Laboratory of Livestock and Poultry Multi-Omics of MARA, Jinan, China
| | - Ming Hu
- Shandong Key Laboratory of Animal Disease Control and Breeding, Institute of Animal Science and Veterinary Medicine, Shandong Academy of Agricultural Sciences, Jinan, China.,Key Laboratory of Livestock and Poultry Multi-Omics of MARA, Jinan, China
| | - YuQing Liu
- Shandong Key Laboratory of Animal Disease Control and Breeding, Institute of Animal Science and Veterinary Medicine, Shandong Academy of Agricultural Sciences, Jinan, China.,Key Laboratory of Livestock and Poultry Multi-Omics of MARA, Jinan, China
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Lin M, Li Z, Lin Q, Wang P, Liu W, Yuan J, Hong Z, Chen Y. Development and Clinical Application of a Rapid and Visual Loop-Mediated Isothermal Amplification Test for tetM gene in Clostridioides difficile Strains Cultured from Feces. Int J Infect Dis 2022; 122:676-684. [PMID: 35843495 DOI: 10.1016/j.ijid.2022.07.032] [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: 01/20/2022] [Revised: 04/23/2022] [Accepted: 07/09/2022] [Indexed: 10/17/2022] Open
Abstract
OBJECTIVES To develop a rapid and visual loop-mediated isothermal amplification (LAMP) assay targeting the tetM gene in Clostridioides difficile (C. difficile) strains cultured from feces. METHODS Primers were designed to recognize the tetM gene in C. difficile by LAMP, using turbidity and visual detection. The sensitivity and specificity of LAMP primers was determined. Besides, We conducted both LAMP and polymerase chain reaction (PCR) for the tcdA, tcdB, cdtA, cdtB, ermB, tetM genes in 300 toxigenic C. difficile strains cultured from feces. RESULTS The target DNA was amplified and visualized within 60 minutes at a temperature of 62°C. A total of 26 bacterial strains were found negative for tetM, which manifested high specificity of the primers. The detection limit of LAMP was 36.1 pg/µl, which was 100-fold more sensitive than PCR. The positive rate of tetM in toxigenic C. difficile strains cultured from feces was 93.3% by both LAMP and PCR. The proportion of toxin types in those C. difficile strains was 95.7% for A+B+CDT-, 4% for A-B+CDT-, and 0.3% for A+B+CDT+, respectively. CONCLUSIONS This is the first study examining tetM gene in C. difficile strains cultured from feces by LAMP. Its high specificity and sensitivity, as well as visual detection, make the new assay a powerful diagnostic tool for rapid testing.
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Affiliation(s)
- Minyi Lin
- Department of Infectious Diseases, The Fifth Affiliated Hospital, Sun Yat-Sen University, 52 East Meihua Road, Zhuhai, 519000, China
| | - Zitong Li
- Department of Gastroenterology, Guangdong Provincial Key Laboratory of Gastroenterology, State Key Laboratory of Organ Failure Research, Nanfang Hospital, Southern Medical University, 1838 North Guangzhou Ave. Guangzhou, China
| | - Qianyun Lin
- Department of Gastroenterology, Beijing Friendship Hospital, Capital Medical University, No. 95, Yong An Road, Xi Cheng District, Beijing, 100050, China
| | - Pu Wang
- Department of Gastroenterology, Guangdong Provincial Key Laboratory of Gastroenterology, State Key Laboratory of Organ Failure Research, Nanfang Hospital, Southern Medical University, 1838 North Guangzhou Ave. Guangzhou, China
| | - Wei Liu
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, 20 Dongda Street, Fengtai District, Beijing, 100071, China
| | - Jing Yuan
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, 20 Dongda Street, Fengtai District, Beijing, 100071, China
| | - Zhongsi Hong
- Department of Infectious Diseases, The Fifth Affiliated Hospital, Sun Yat-Sen University, 52 East Meihua Road, Zhuhai, 519000, China.
| | - Ye Chen
- Department of Gastroenterology, Integrative Microecology Center, Shenzhen Hospital, Southern Medical University, 1333 New Lake Road, Shenzhen, 518100, China.
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Liu X, Zou D, Wang C, Zhang X, Pei D, Liu W, Li Y. Evaluation of loop-mediated isothermal amplification assays for rapid detection of blaKPC producing Serratia spp. in clinical specimens: A prospective diagnostic accuracy study. Exp Ther Med 2021; 21:308. [PMID: 33717251 PMCID: PMC7885079 DOI: 10.3892/etm.2021.9739] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Accepted: 12/10/2020] [Indexed: 11/12/2022] Open
Abstract
The prevalence of carbapenem-resistant Serratia spp. is increasing owing to the propagation of β lactamase Klebsiella pneumoniae carbapenemase (blaKPC) and it has become one of the major global health concerns. As effective therapies for such resistant pathogens are limited, there is a great need for the rapid and sensitive characterization of the pathogen. In the present study, a loop-mediated isothermal amplification (LAMP) method for the rapid detection of Serratia spp. with blaKPC in pure cultures and clinical specimens was developed. A calcein indicator and real-time turbidity recording system were used to assess the LAMP reaction. The LAMP assay was compared with conventional PCR and real-time PCR kits for the target pathogen. The desired amplification was achieved using selected primers and detection was possible using both the calcein indicator method and the real-time turbity recording system at 65˚C for 60 min. The sensitivity of the detection system for blaKPC-producing Serratia spp. reached a detection limit of 3.92 pg/µl DNA, which was 10 times more sensitive than conventional PCR. Specificity testing indicated that the primers were highly specific. Compared with conventional culture methods and real-time PCR, the LAMP assay was more sensitive, easier for laboratory staff to master and less influenced by the clinical specimen matrix. In conclusion, a LAMP assay for blaKPC-producing Serratia spp. that permitted rapid, sensitive and economical detection for this pathogen was successfully developed. Comparisons with alternative methods indicated that the LAMP assay was more feasible in a clinical setting.
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Affiliation(s)
- Xinwei Liu
- Department of Clinical Laboratory, Henan Province Hospital of Traditional Chinese Medicine, Zhengzhou, Henan 450002, P.R. China
| | - Dayang Zou
- Institute for Disease Prevention and Control, People's Liberation Army, Beijing 100071, P.R. China
| | - Chunxia Wang
- Department of Clinical Laboratory, Henan Province Hospital of Traditional Chinese Medicine, Zhengzhou, Henan 450002, P.R. China
| | - Xiaoqian Zhang
- Department of Clinical Laboratory, Henan Province Hospital of Traditional Chinese Medicine, Zhengzhou, Henan 450002, P.R. China
| | - Dongxu Pei
- Department of Clinical Laboratory, Henan Province Hospital of Traditional Chinese Medicine, Zhengzhou, Henan 450002, P.R. China
| | - Wei Liu
- Institute for Disease Prevention and Control, People's Liberation Army, Beijing 100071, P.R. China
| | - Yongwei Li
- Department of Clinical Laboratory, Henan Province Hospital of Traditional Chinese Medicine, Zhengzhou, Henan 450002, P.R. China
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Jaroenram W, Cecere P, Pompa PP. Xylenol orange-based loop-mediated DNA isothermal amplification for sensitive naked-eye detection of Escherichia coli. J Microbiol Methods 2018; 156:9-14. [PMID: 30502368 DOI: 10.1016/j.mimet.2018.11.020] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Accepted: 11/28/2018] [Indexed: 12/12/2022]
Abstract
Loop-mediated isothermal amplification (LAMP) can amplify DNA specifically and sensitively. Under minimal buffering conditions, it produces hydrogen ions that lower the pH of the solution upon DNA amplification. This characteristic was applied to visually detect amplified DNA of Escherichia coli through the use of Xylenol Orange, a pH-dependent dye. Under the optimal conditions, 120 min at 63 °C, the Xylenol orange-dependent colorimetric LAMP revealed a detection limit as low as 1 CFU, namely 100,000 times more sensitive than typical multiplex PCR, and showed no cross-reactions with other foodborne pathogens. The colorimetric assay was successfully exploited to detect E. coli contaminations in milk samples, showing high reliability and the same high sensitivity with naked-eye readout. Together with robustness, simplicity, and visual detectability of amplification, this assay can serve as an alternative tool to PCR for detecting E. coli, which is suitable for both laboratory and on-field applications.
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Affiliation(s)
- Wansadaj Jaroenram
- Nanobiointeractions & Nanodiagnostics, Istituto Italiano di Tecnologia, Via Morego 30, Genova 16163, Italy
| | - Paola Cecere
- Nanobiointeractions & Nanodiagnostics, Istituto Italiano di Tecnologia, Via Morego 30, Genova 16163, Italy
| | - Pier Paolo Pompa
- Nanobiointeractions & Nanodiagnostics, Istituto Italiano di Tecnologia, Via Morego 30, Genova 16163, Italy.
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Xu X, Luo Y, Song X, Ying J, Ye J, Lu Y, Cai J, Ma J, Wang X, Yu W, Wang Y, Jin D. Evaluation of an UltraFast LabChip V280 assay for detection of toxigenic Clostridium difficile. Diagn Microbiol Infect Dis 2018; 92:279-283. [PMID: 30029809 DOI: 10.1016/j.diagmicrobio.2018.06.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 06/21/2018] [Accepted: 06/23/2018] [Indexed: 01/03/2023]
Abstract
In this study, we compared the performance of an UltraFast LabChip (UL) V280 system for Clostridium difficile detection in stool with that of Xpert C. difficile/Epi and VIDAS CDAB. Among 176 stool specimens, UL V280 detected toxigenic C. difficile in 22 (22/176, 12.5%) with a sensitivity, specificity, positive predictive value, negative predictive value (NPV) of 100.0%, 99.4%, 99.5% and 100.0%, respectively, which were higher than 95.2%, 97.4%, 83.3%, and 99.3% of Xpert C. difficile/Epi (P > 0.05). Notably, the sensitivity and NPV of ULV280 were significantly higher than those of VIDAS CDAB 52.4% (P < 0.001, odds ratio [OR] = 20.0, 95% confidence interval [CI] = 2.26-176.81) and 93.8% (P = 0.002, OR = 10.27, 95% CI = 1.30-81.17). UL V280 turnaround time (35 min) and cost (6.24 Dollars [$]) per specimen were less than those for Xpert C. difficile/Epi (47 min, 59.26 $) and VIDAS CDAB (65 min, 11.70 $). UL V280 possessed an analytical sensitivity limit of 2500 CFU/ml, 95% [CI] = (Ct: 30.76-34.90), and no cross-reactions with other pathogens were found. The study demonstrates that UL V280 based on a microfluidic chip is a rapid, accurate, easy, and cost-effective diagnostic test for toxigenic C. difficile in stool.
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Affiliation(s)
- Xingxing Xu
- Department of Laboratory Medicine, Zhejiang Chinese Medical University affiliated Hangzhou First Hospital, Hangzhou, Zhejiang, 310006, China; Department of Microbiology, Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, 310051, China
| | - Yun Luo
- Department of Microbiology, Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, 310051, China
| | - Xiaojun Song
- Department of Microbiology, Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, 310051, China
| | - Jianfei Ying
- Department of Laboratory Medicine, Ningbo Yinzhou People's Hospital, Ningbo, Zhejiang, 315040, China
| | - Julian Ye
- Department of Microbiology, Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, 310051, China
| | - Yong Lu
- Department of Laboratory Medicine, Ningbo Yinzhou People's Hospital, Ningbo, Zhejiang, 315040, China
| | - Jian Cai
- Department of Disease Control and Prevention, Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, 310051, China
| | - Jian Ma
- Department of Respiratory Medicine, Ningbo Yinzhou People's Hospital, Ningbo, Zhejiang, 315040, China
| | - Xianjun Wang
- Department of Laboratory Medicine, Zhejiang Chinese Medical University affiliated Hangzhou First Hospital, Hangzhou, Zhejiang, 310006, China
| | - Wanjun Yu
- Department of Respiratory Medicine, Ningbo Yinzhou People's Hospital, Ningbo, Zhejiang, 315040, China
| | - Yiping Wang
- Department of Laboratory Medicine, Ningbo Yinzhou People's Hospital, Ningbo, Zhejiang, 315040, China
| | - Dazhi Jin
- Department of Microbiology, Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, 310051, China.
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Wong YP, Othman S, Lau YL, Radu S, Chee HY. Loop-mediated isothermal amplification (LAMP): a versatile technique for detection of micro-organisms. J Appl Microbiol 2018; 124:626-643. [PMID: 29165905 PMCID: PMC7167136 DOI: 10.1111/jam.13647] [Citation(s) in RCA: 341] [Impact Index Per Article: 56.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 11/09/2017] [Accepted: 11/13/2017] [Indexed: 12/11/2022]
Abstract
Loop‐mediated isothermal amplification (LAMP) amplifies DNA with high specificity, efficiency and rapidity under isothermal conditions by using a DNA polymerase with high displacement strand activity and a set of specifically designed primers to amplify targeted DNA strands. Following its first discovery by Notomi et al. (2000Nucleic Acids Res 28: E63), LAMP was further developed over the years which involved the combination of this technique with other molecular approaches, such as reverse transcription and multiplex amplification for the detection of infectious diseases caused by micro‐organisms in humans, livestock and plants. In this review, available types of LAMP techniques will be discussed together with their applications in detection of various micro‐organisms. Up to date, there are varieties of LAMP detection methods available including colorimetric and fluorescent detection, real‐time monitoring using turbidity metre and detection using lateral flow device which will also be highlighted in this review. Apart from that, commercialization of LAMP technique had also been reported such as lyophilized form of LAMP reagents kit and LAMP primer sets for detection of pathogenic micro‐organisms. On top of that, advantages and limitations of this molecular detection method are also described together with its future potential as a diagnostic method for infectious disease.
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Affiliation(s)
- Y-P Wong
- Department of Medical Microbiology and Parasitology, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang, Malaysia
| | - S Othman
- Department of Medical Microbiology and Parasitology, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang, Malaysia
| | - Y-L Lau
- Department of Parasitology, Faculty of Medicine, Tropical Infectious Diseases Research and Education Centre (TIDREC), University of Malaya, Kuala Lumpur, Malaysia
| | - S Radu
- Centre of Excellence for Food Safety Research (FOSREC), Faculty of Food Science and Technology, Universiti Putra Malaysia, Serdang, Malaysia
| | - H-Y Chee
- Department of Medical Microbiology and Parasitology, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang, Malaysia
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Wang Y, Zhang B, Sun Y, Liu Y, Gu Y. Loop-Mediated Isothermal Amplification on Crude DNA as a Point-of-Care Test for the Diagnosis of Mycoplasma-Related Vaginitis During Early Pregnancy. Lab Med 2017; 49:59-67. [PMID: 29272448 DOI: 10.1093/labmed/lmx063] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Background Mycoplasma-related vaginitis gradually has been growing as a threat in adults-genitourinary infection contributes to funisitis, spontaneous abortion, and low birth weight. Until now, use of loop-mediated isothermal amplification (LAMP) to detect Ureaplasma urealyticum (UU), Mycoplasma hominis (MH), or Mycoplasma genitalium (MG) has been reported by some researchers. However, previous studies focused on purified DNA as the template for LAMP assay, which is usually extracted via commercial kit. Methods We developed a LAMP assay for rapid detection of UU, MH, and MG genital mycoplasmas using a simple boiling method for DNA extraction, in a cohort of pregnant women with mycoplasma-related vaginitis. We monitored amplicons with the naked eye using SYBR Green I. Results The cohort in our study showed a prevalence of 22.6% in pregnant women, as detected by UU-LAMP assay. Compared to the polymerase chain reaction (PCR) test with purified DNA, the sensitivity of the UU-LAMP in clinical specimens with crude DNA was 87.5% (95% confidence interval [CI], 64.6%->99.9). For crude DNA specimens, UU-LAMP was more sensitive and reliable than PCR, with a higher agreement rate (96.8%) and Youden index value (0.88). Conclusions As a point-of-care test, LAMP is a useful, specific, and efficient way to detect genital mycoplasmas in resource-limited settings, especially for crude DNA.
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Affiliation(s)
- Yichao Wang
- Medical Laboratory School, Tianjin Medical University, China
| | - Bumei Zhang
- Department of Family Planning, Second Hospital of Tianjin Medical University, China
| | - Yan Sun
- Tianjin Center for Control and Prevention of Aquatic Animal Infectious Disease, China
| | - Yunde Liu
- Medical Laboratory School, Tianjin Medical University, China
| | - Yajun Gu
- Medical Laboratory School, Tianjin Medical University, China
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Huang S, Yang Z, Zou D, Dong D, Liu A, Liu W, Huang L. Rapid detection of nusG and fadA in Fusobacterium nucleatum by loop-mediated isothermal amplification. J Med Microbiol 2016; 65:760-769. [PMID: 27339262 DOI: 10.1099/jmm.0.000300] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Fusobacterium nucleatum is associated with various human diseases such as periodontal disease and colorectal cancer (CRC); thus, F. nucleatum detection might serve as a novel diagnostic tool. Here, we describe the development of a sensitive and rapid molecular method for detecting two F. nucleatum genes: the highly conserved nusG and fadA, which encode a critical host colonization factor. Loop-mediated isothermal amplification (LAMP) primer sets for the rapid detection of nusG and fadA were designed and optimized. The nusG primers yielded consistent negative results for 20 non-F. nucleatum bacterial strains, confirming the high specificity of the primers. LAMP reaction primer sensitivity was determined, and its detection rate in comparison to conventional PCR was assessed using 57 clinical stool samples. The LAMP detection limit for nusG and fadA was 22.5 and 0.225 pg µl-1, respectively, indicating that the sensitivity of this method was 10-fold higher than that of conventional PCR. These results suggest that the LAMP technique is able to effectively identify F. nucleatum via nusG as well as detect its virulence factor. To the best of our knowledge, this study is the first to report the application of LAMP for the detection of nusG and fadA in F. nucleatum. The LAMP method constitutes a sensitive and specific visual assay for the rapid detection of the pathogen F. nucleatum.
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Affiliation(s)
- Simo Huang
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing, P. R. China
| | - Zhan Yang
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing, P. R. China
| | - Dayang Zou
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing, P. R. China
| | - Derong Dong
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing, P. R. China
| | - Anheng Liu
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing, P. R. China
| | - Wei Liu
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing, P. R. China
| | - Liuyu Huang
- Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing, P. R. China
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