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Abstract
Vibrio cholerae O1 is the causative agent of cholera, a severe diarrheal disease which can cause death if left untreated. In this study, a collection of clinical and environmental V. cholerae serogroup O1 isolates from Australia (1977 to 1987) (from local cases and cases acquired through international travel) and publicly available international isolates were characterized for genotypic features (virulence genes, mobile genetic elements [MGEs], and antimicrobial resistance gene profiles). Whole-genome sequencing (WGS) was used to investigate and compare the genetic relatedness between the 44 Australian and nine travel-associated isolates and the 60 publicly available international V. cholerae sequences representing pre-seventh-pandemic (pre-7PET) isolates and different waves of 7PET isolates. In this study, 36 (81%) Australian clinical and aquatic isolates harbored the cholera toxin-producing genes located in the CTX bacteriophage region. All the Australian environmental and clinical isolates lacked the seventh-pandemic virulence-associated genomic islands (VSP-I and -II). In silico multilocus sequence typing (MLST) classified all nine internationally acquired isolates as sequence type 69 (ST69), 36 clinical and aquatic isolates as ST70, and eight isolates from Australia as ST71. Most of the nontoxigenic clinical and aquatic isolates of ST71 had diverse genetic variations compared to ST70 Australian strains. The antimicrobial resistance-associated genes gyrA, parC, and parE had no mutations in all the environmental and clinical isolates from Australia. The SXT genetic element and class 1 integron gene sequences were not detected in Australian strains. Moreover, in this study, a Bayesian evolutionary study suggests that two distinct lineages of ST71 (new set of strains) and ST70 strains were prevalent around similar times in Australia, in ~1973 and 1969. IMPORTANCE Australia has its own indigenous V. cholerae strains, both toxigenic and nontoxigenic, that are associated with disease. Exotic strains are also detected in Australian patients returning from overseas travel. The clinical and aquatic V. cholerae O1 toxin gene-positive isolates from Australia responsible for cases in 1977 to 1987 were linked to acquisition from Queensland waterways but until now had not been characterized genetically. It is important to determine the genetic relatedness of Australian strains to international strains to assist in understanding their origin. This is the first extensive study to provide sequences and genomic analysis focused on toxigenic O1 V. cholerae clinical and environmental strains from Australia and its possible evolutionary relationship with other publicly available pre-7PET and 7PET V. cholerae strains. It is important to understand the population genetics of Australian V. cholerae from a public health perspective to assist in devising control measures and management plans for reducing V. cholerae exposure in Australia, given previous Australian disease clusters.
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Ramamurthy T, Pragasam AK, Taylor-Brown A, Will RC, Vasudevan K, Das B, Srivastava SK, Chowdhury G, Mukhopadhyay AK, Dutta S, Veeraraghavan B, Thomson NR, Sharma NC, Nair GB, Takeda Y, Ghosh A, Dougan G, Mutreja A. Vibrio cholerae O139 genomes provide a clue to why it may have failed to usher in the eighth cholera pandemic. Nat Commun 2022; 13:3864. [PMID: 35790755 PMCID: PMC9256687 DOI: 10.1038/s41467-022-31391-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 06/14/2022] [Indexed: 11/09/2022] Open
Abstract
AbstractCholera is a life-threatening infectious disease that remains an important public health issue in several low and middle-income countries. In 1992, a newly identified O139 Vibrio cholerae temporarily displaced the O1 serogroup. No study has been able to answer why the potential eighth cholera pandemic (8CP) causing V. cholerae O139 emerged so successfully and then died out. We conducted a genomic study, including 330 O139 isolates, covering emergence of the serogroup in 1992 through to 2015. We noted two key genomic evolutionary changes that may have been responsible for the disappearance of genetically distinct but temporally overlapping waves (A-C) of O139. Firstly, as the waves progressed, a switch from a homogenous toxin genotype in wave-A to heterogeneous genotypes. Secondly, a gradual loss of antimicrobial resistance (AMR) with the progression of waves. We hypothesize that these two changes contributed to the eventual epidemiological decline of O139.
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Bhandari M, Jennison AV, Rathnayake IU, Huygens F. Evolution, distribution and genetics of atypical Vibrio cholerae - A review. INFECTION GENETICS AND EVOLUTION 2021; 89:104726. [PMID: 33482361 DOI: 10.1016/j.meegid.2021.104726] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 01/07/2021] [Accepted: 01/15/2021] [Indexed: 12/21/2022]
Abstract
Vibrio cholerae is the etiological agent of cholera, a severe diarrheal disease, which can occur as either an epidemic or sporadic disease. Cholera pandemic-causing V. cholerae O1 and O139 serogroups originated from the Indian subcontinent and spread globally and millions of lives are lost each year, mainly in developing and underdeveloped countries due to this disease. V. cholerae O1 is further classified as classical and El Tor biotype which can produce biotype specific cholera toxin (CT). Since 1961, the current seventh pandemic El Tor strains replaced the sixth pandemic strains resulting in the classical biotype strain that produces classical CT. The ongoing evolution of Atypical El Tor V. cholerae srains encoding classical CT is of global concern. The severity in the pathophysiology of these Atypical El Tor strains is significantly higher than El Tor or classical strains. Pathogenesis of V. cholerae is a complex process that involves coordinated expression of different sets of virulence-associated genes to cause disease. We are yet to understand the complete virulence profile of V. cholerae, including direct and indirect expression of genes involved in its survival and stress adaptation in the host. In recent years, whole genome sequencing has paved the way for better understanding of the evolution and strain distribution, outbreak identification and pathogen surveillance for the implementation of direct infection control measures in the clinic against many infectious pathogens including V. cholerae. This review provides a synopsis of recent studies that have contributed to the understanding of the evolution, distribution and genetics of the seventh pandemic Atypical El Tor V. cholerae strains.
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Affiliation(s)
- Murari Bhandari
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, QLD, Australia; Public Health Microbiology, Forensic and Scientific Services, Queensland Department of Health, Brisbane, QLD, Australia
| | - Amy V Jennison
- Public Health Microbiology, Forensic and Scientific Services, Queensland Department of Health, Brisbane, QLD, Australia
| | - Irani U Rathnayake
- Public Health Microbiology, Forensic and Scientific Services, Queensland Department of Health, Brisbane, QLD, Australia
| | - Flavia Huygens
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, QLD, Australia.
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4
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Sabin NS, Calliope AS, Simpson SV, Arima H, Ito H, Nishimura T, Yamamoto T. Implications of human activities for (re)emerging infectious diseases, including COVID-19. J Physiol Anthropol 2020; 39:29. [PMID: 32977862 PMCID: PMC7517057 DOI: 10.1186/s40101-020-00239-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 09/16/2020] [Indexed: 12/12/2022] Open
Abstract
Since 1980, the world has been threatened by different waves of emerging disease epidemics. In the twenty-first century, these diseases have become an increasing global concern because of their health and economic impacts in both developed and resource-constrained countries. It is difficult to stop the occurrence of new pathogens in the future due to the interconnection among humans, animals, and the environment. However, it is possible to face a new disease or to reduce the risk of its spread by implementing better early warning systems and effective disease control and prevention, e.g., effective global surveillance, development of technology for better diagnostics, effective treatments, and vaccines, the global political will to respond to any threats and multidisciplinary collaboration involving all sectors in charge of good health maintenance. In this review, we generally describe some factors related to human activities and show how they can play a role in the transmission and spread of infectious diseases by using some diseases as examples. Additionally, we describe and discuss major factors that are facilitating the spread of the new pandemic known as COVID-19 worldwide.
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Affiliation(s)
- Nundu Sabiti Sabin
- Department of International Health and Medical Anthropology, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki, 852-8523, Japan
- Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
- Leading Program, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
| | - Akintije Simba Calliope
- Department of International Health and Medical Anthropology, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki, 852-8523, Japan
- Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
- Leading Program, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
| | - Shirley Victoria Simpson
- Department of International Health and Medical Anthropology, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki, 852-8523, Japan
- Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
- Leading Program, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
| | - Hiroaki Arima
- Department of International Health and Medical Anthropology, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki, 852-8523, Japan
- Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
| | - Hiromu Ito
- Department of International Health and Medical Anthropology, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki, 852-8523, Japan
| | - Takayuki Nishimura
- Department of Human Science, Faculty of Design, Kyushu University, Fukuoka, Japan
- Department of Public Health, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
| | - Taro Yamamoto
- Department of International Health and Medical Anthropology, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki, 852-8523, Japan.
- Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
- Leading Program, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
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5
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Ghosh R, Sharma NC, Halder K, Bhadra RK, Chowdhury G, Pazhani GP, Shinoda S, Mukhopadhyay AK, Nair GB, Ramamurthy T. Phenotypic and Genetic Heterogeneity in Vibrio cholerae O139 Isolated from Cholera Cases in Delhi, India during 2001-2006. Front Microbiol 2016; 7:1250. [PMID: 27555841 PMCID: PMC4977278 DOI: 10.3389/fmicb.2016.01250] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 07/27/2016] [Indexed: 11/29/2022] Open
Abstract
Incidence of epidemic Vibrio cholerae serogroup O139 has declined in cholera endemic countries. However, sporadic cholera caused by V. cholerae O139 with notable genetic changes is still reported from many regions. In the present study, 42 V. cholerae O139 strains isolated from 2001 to 2006 in Delhi, India, were retrospectively analyzed to understand their phenotype and molecular characteristics. The majority of isolates were resistant to ampicillin, furazolidone and nalidixic acid. Though the integrative conjugative element was detected in all the O139 isolates, the 2004–2006 isolates remained susceptible to co-trimoxazole, chloramphenicol, and streptomycin. Cholera toxin genotype 1 was present in the majority of the O139 isolates while few had type 3 or a novel type 4. In the cholera toxin encoding gene (ctx) restriction fragment length polymorphism, the majority of the isolates harbored three copies of CTX element, of which one was truncated. In this study, the ctx was detected for the first time in the small chromosome of V. cholerae O139 and one isolate harbored 5 copies of CTX element, of which 3 were truncated. The ribotype BII pattern was found in most of the O139 isolates. Three V. cholerae O139 isolated in 2001 had a new ribotype BVIII. Pulsed-field gel electrophoresis analysis revealed clonal variation in 2001 isolates compared to the 2004–2006 isolates. Molecular changes in V. cholerae O139 have to be closely monitored as this information may help in understanding the changing genetic features of this pathogen in relation to the epidemiology of cholera.
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Affiliation(s)
- Raikamal Ghosh
- Division of Bacteriology, National Institute of Cholera and Enteric Diseases Kolkata, India
| | | | - Kalpataru Halder
- Infectious Diseases and Immunology Division, Council of Scientific and Industrial Research-Indian Institute of Chemical Biology Kolkata, India
| | - Rupak K Bhadra
- Infectious Diseases and Immunology Division, Council of Scientific and Industrial Research-Indian Institute of Chemical Biology Kolkata, India
| | - Goutam Chowdhury
- Division of Bacteriology, National Institute of Cholera and Enteric Diseases Kolkata, India
| | - Gururaja P Pazhani
- Division of Bacteriology, National Institute of Cholera and Enteric Diseases Kolkata, India
| | - Sumio Shinoda
- Collaborative Research Center of Okayama University for Infectious Diseases in India, National Institute of Cholera and Enteric Diseases Kolkata, India
| | - Asish K Mukhopadhyay
- Division of Bacteriology, National Institute of Cholera and Enteric Diseases Kolkata, India
| | - G Balakrish Nair
- Center for Human Microbial Ecology, Translational Health Science and Technology Institute Faridabad, India
| | - Thadavarayan Ramamurthy
- Center for Human Microbial Ecology, Translational Health Science and Technology Institute Faridabad, India
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6
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The role of filamentous CTXphi bacteriophage in Vibrio cholerae genetics and diversity. ACTA ACUST UNITED AC 2015. [DOI: 10.1097/mrm.0000000000000017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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7
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Mukhopadhyay AK, Takeda Y, Balakrish Nair G. Cholera outbreaks in the El Tor biotype era and the impact of the new El Tor variants. Curr Top Microbiol Immunol 2014; 379:17-47. [PMID: 24710767 DOI: 10.1007/82_2014_363] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
Vibrio cholerae O1, the causative agent of the disease cholera, has two biotypes namely the classical and El Tor. Biotype is a subspecific taxonomic classification of V. cholerae O1. Differentiation of V. cholerae strains into biotype does not alter the clinical management of cholera but is of immense public health and epidemiological importance in identifying the source and spread of infection, particularly when V. cholerae is first isolated in a country or geographic area. From recorded history, till date, the world has experienced seven pandemics of cholera. Among these, the first six pandemics are believed to have been caused by the classical biotype whereas the ongoing seventh pandemic is caused by the El Tor biotype. In recent years, new pathogenic variants of V. cholerae have emerged and spread throughout many Asian and African countries with corresponding cryptic changes in the epidemiology of cholera. In this chapter, we describe the outbreaks during the seventh pandemic El Tor biotype era spanning more than five decades along with the recent advances in our understanding of the development, evolution, spread, and impact of the new variants of El Tor strains.
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Affiliation(s)
- Asish K Mukhopadhyay
- National Institute of Cholera and Enteric Diseases, P 33, CIT Road, Scheme XM, Beliaghata, Kolkata, 700010, India,
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8
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Abstract
Cholera is a global health problem as several thousands of cases and deaths occur each year. The unique epidemiologic attribute of the disease is its propensity to occur as outbreaks that may flare-up into epidemics, if not controlled. The causative bacterial pathogen Vibrio cholerae prevails in the environment and infects humans whenever there is a breakdown in the public health component. The Indian subcontinent is vulnerable to this disease due its vast coastlines with areas of poor sanitation, unsafe drinking water, and overcrowding. Recently, it was shown that climatic conditions also play a major role in the persistence and spread of cholera. Constant change in the biotypes and serotypes of V. cholerae are also important aspects that changes virulence and survival of the pathogen. Such continuous changes increase the infection ability of the pathogen affecting the susceptible population including the children. The short-term carrier status of V. cholerae has been studied well at community level and this facet significantly contributes to the recurrence of cholera. Several molecular tools recognized altering clonality of V. cholerae in relation with the advent of a serogroup or serotype. Rapid identification systems were formulated for the timely detection of the pathogen so as to identify and control the outbreak and institute proper treatment of the patients. The antimicrobials used in the past are no longer useful in the treatment of cholera as V. cholerae has acquired several mechanisms for multiple antimicrobial resistance. This upsurge in antimicrobial resistance directly influences the management of the disease. This chapter provides an overview of cholera prevalence in India, possible sources of infection, and molecular epidemiology along with antimicrobial resistance of V. cholerae.
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9
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Yu L, Zhou Y, Wang R, Lou J, Zhang L, Li J, Bi Z, Kan B. Multiple antibiotic resistance of Vibrio cholerae serogroup O139 in China from 1993 to 2009. PLoS One 2012; 7:e38633. [PMID: 22701685 PMCID: PMC3372494 DOI: 10.1371/journal.pone.0038633] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2012] [Accepted: 05/08/2012] [Indexed: 11/22/2022] Open
Abstract
Regarded as an emerging diarrheal micropathogen, Vibrio cholerae serogroup O139 was first identified in 1992 and has become an important cause of cholera epidemics over the last two decades. O139 strains have been continually isolated since O139 cholera appeared in China in 1993, from sporadic cases and dispersed foodborne outbreaks, which are the common epidemic types of O139 cholera in China. Antibiotic resistance profiles of these epidemic strains are required for development of clinical treatments, epidemiological studies and disease control. In this study, a comprehensive investigation of the antibiotic resistance of V. cholerae O139 strains isolated in China from 1993 to 2009 was conducted. The initial O139 isolates were resistant to streptomycin, trimethoprim-sulfamethoxazole and polymyxin B only, while multidrug resistance increased suddenly and became common in strains isolated after 1998. Different resistance profiles were observed in the isolates from different years. In contrast, most V. cholerae O1 strains isolated in the same period were much less resistant to these antibiotics and no obvious multidrug resistance patterns were detected. Most of the non-toxigenic strains isolated from the environment and seafood were resistant to four antibiotics or fewer, although a few multidrug resistant strains were also identified. These toxigenic O139 strains exhibited a high prevalence of the class I integron and the SXT element, which were rare in the non-toxigenic strains. Molecular subtyping of O139 strains showed highly diverse pulsed-field gel electrophoresis patterns, which may correspond to the epidemic state of sporadic cases and small-scale outbreaks and complex resistance patterns. Severe multidrug resistance, even resistance transfers based on mobile antibiotic resistance elements, increases the probability of O139 cholera as a threat to public health. Therefore, continual epidemiological and antibiotic sensitivity surveillance should focus on the occurrence of multidrug resistance and frequent microbial population shifts in O139 strains.
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Affiliation(s)
- Li Yu
- State Key Laboratory for Infectious Disease Prevention and Control, Department of Diarrheal Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People’s Republic of China
- Shandong Provincial Key Laboratory of Infectious Disease Control and Prevention, Shandong Center for Disease Control and Prevention, Jinan, China
| | - Yanyan Zhou
- State Key Laboratory for Infectious Disease Prevention and Control, Department of Diarrheal Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People’s Republic of China
| | - Ruibai Wang
- State Key Laboratory for Infectious Disease Prevention and Control, Department of Diarrheal Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People’s Republic of China
| | - Jing Lou
- State Key Laboratory for Infectious Disease Prevention and Control, Department of Diarrheal Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People’s Republic of China
| | - Lijuan Zhang
- State Key Laboratory for Infectious Disease Prevention and Control, Department of Diarrheal Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People’s Republic of China
| | - Jie Li
- State Key Laboratory for Infectious Disease Prevention and Control, Department of Diarrheal Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People’s Republic of China
| | - Zhenqiang Bi
- Shandong Provincial Key Laboratory of Infectious Disease Control and Prevention, Shandong Center for Disease Control and Prevention, Jinan, China
- * E-mail: (ZB); (BK)
| | - Biao Kan
- State Key Laboratory for Infectious Disease Prevention and Control, Department of Diarrheal Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People’s Republic of China
- * E-mail: (ZB); (BK)
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10
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Fazil MT, Bhanumathi R, Pandey H, Singh D. Characterization of Vibrio cholerae O139 belonging to multiple ribotypes and isolated from diarrhoeal patients in Kerala, southern India. INFECTION GENETICS AND EVOLUTION 2011; 11:454-9. [DOI: 10.1016/j.meegid.2010.12.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Revised: 12/07/2010] [Accepted: 12/15/2010] [Indexed: 11/30/2022]
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11
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Mantri CK, Mohapatra SS, Singh DV. Effect of storage and sodium chloride on excision of CTXPhi or pre-CTXPhi and CTXPhi from Vibrio cholerae O139 strains. INFECTION GENETICS AND EVOLUTION 2010; 10:925-30. [PMID: 20621579 DOI: 10.1016/j.meegid.2010.05.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2010] [Revised: 05/26/2010] [Accepted: 05/26/2010] [Indexed: 12/23/2022]
Abstract
We examined the effect of storage and sodium chloride on excision of CTXPhi or pre-CTXPhi and CTXPhi from Vibrio cholerae O139 strains. We found that one strain of V. cholerae O139 VO146P showed loss of the complete phage array, and other strain VO170P showed partial loss of the phage array giving rise to altered strains designated as VO146N and VO170N. Results of PCR and RFLP analysis revealed that both strains (VO146P and VO170P) possessed a single copy of pre-CTX(ET)Phi and two copies of CTXPhi comprising CTX(Class)Phi and CTX(Calc)Phi arranged in tandem, and integrated in the large chromosome. The presence of classical ctxB was detected in CTX(Calc)Phi of both V. cholerae O139 strains. Nucleotide sequencing of three housekeeping genes showed no difference between parent and altered strains of V. cholerae O139.
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Affiliation(s)
- Chinmay K Mantri
- Infectious Disease Biology, Institute of Life Sciences, Nalco Square, Bhubaneswar, Orrisa 751023, India
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12
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Raychoudhuri A, Mukherjee P, Ramamurthy T, Nandy RK, Takeda Y, Nair GB, Mukhopadhyay AK. Genetic analysis of CTX prophages with special reference to ctxB and rstR alleles of Vibrio cholerae O139 strains isolated from Kolkata over a decade. FEMS Microbiol Lett 2009; 303:107-15. [PMID: 20030720 DOI: 10.1111/j.1574-6968.2009.01856.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Chronological analysis of 125 Vibrio cholerae O139 strains isolated during 1993-2005 in Kolkata revealed the prevalence of two new genotypes of cholera toxin (CT) and novel combinations of ctxB and rstR alleles resulting in variant CTX prophages. One of the new genotypes of ctxB, which first appeared in 1996 with the re-emerged V. cholerae O139 strains that had CTX Calcutta phage, was designated as genotype 4. In 1998, another new genotype, designated as genotype 5, was detected that prevailed mostly in CTX phages with El Tor rstR. The prototype El Tor CTX phage with genotype 3 gradually disappeared in O139, and since 2002 the predominant CTX prophages in O139 are Calcutta phages with genotype 4 and El Tor phages with genotype 5. Results showed that V. cholerae O139 strains of Kolkata, isolated over a decade, harboured CTX prophages in the large chromosome having no RS1 downstream of CTX prophage. During the course of its intermittent incidence over a decade, five types of O139 strains were detected based on CT genotypes. Such abrupt genetic changes in O139 strains might not favour its continued prevalence in human cases in Kolkata, India.
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Affiliation(s)
- Amit Raychoudhuri
- Division of Bacteriology, National Institute of Cholera and Enteric Diseases, Kolkata, West Bengal, India
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Bakhshi B, Pourshafie M, Navabakbar F, Tavakoli A. Genomic organisation of the CTX element among toxigenic Vibrio cholerae isolates. Clin Microbiol Infect 2008; 14:562-8. [DOI: 10.1111/j.1469-0691.2008.01976.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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14
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Ledón T, Campos J, Suzarte E, Rodríguez B, Marrero K, Fando R. El Tor and Calcutta CTXΦ precursors coexisting with intact CTXΦ copies in Vibrio cholerae O139 isolates. Res Microbiol 2008; 159:81-7. [DOI: 10.1016/j.resmic.2007.11.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Revised: 11/15/2007] [Accepted: 11/19/2007] [Indexed: 10/22/2022]
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15
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Ghatak A, Majumdar A, Ghosh RK. Structural organization of the transfer RNA operon I of Vibrio cholerae: differences between classical and El Tor strains. J Biosci 2008; 30:469-74. [PMID: 16184008 DOI: 10.1007/bf02703720] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Nine major transfer RNA (tRNA) gene clusters were analysed in various Vibrio cholerae strains. Of these, only the tRNA operon I was found to differ significantly in V. cholerae classical (sixth pandemic) and El Tor (seventh pandemic) strains. Amongst the sixteen tRNA genes contained in this operon, genes for tRNA Gln3 (CAA) and tRNA Leu6 (CUA) were absent in classical strains as compared to El Tor strains. The observation strongly supported the view that the above two pandemic strains constitute two different clones.
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Affiliation(s)
- Atreyi Ghatak
- Molecular Biology Laboratory, Indian Institute of Chemical Biology, 4, Raja SC Mullick Road,Jadavpur, Kolkata 700 032, India
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McLeod SM, Kimsey HH, Davis BM, Waldor MK. CTXphi and Vibrio cholerae: exploring a newly recognized type of phage-host cell relationship. Mol Microbiol 2005; 57:347-56. [PMID: 15978069 DOI: 10.1111/j.1365-2958.2005.04676.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The genes encoding cholera toxin, one of the principal virulence factors of the diarrhoeal pathogen Vibrio cholerae, are part of the genome of CTXphi, a filamentous bacteriophage. Thus, CTXphi has played a critical role in the evolution of the pathogenicity of V. cholerae. Unlike the well-studied F pilus-specific filamentous coliphages, CTXphi integrates site-specifically into its host chromosome and forms stable lysogens. Here we focus on the CTXphi life cycle and, in particular, on recent studies of the mechanism of CTXphi integration and the factors that govern lysogeny. These and other processes illustrate the remarkable dependence of CTXphi on host-encoded factors.
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Affiliation(s)
- Sarah M McLeod
- Howard Hughes Medical Institute and Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
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17
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Ghatak A, Majumdar A, Ghosh RK. Molecular phylogenetic analysis ofVibrio cholerae O1 El Tor strains isolated before, during and after the O139 outbreak based on the intergenomic heterogeneity of the 16S-23S rRNA intergenic spacer regions. J Biosci 2005; 30:619-25. [PMID: 16388136 DOI: 10.1007/bf02703562] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We have cloned, sequenced and analysed all the five classes of the intergenic (16S-23S rRNA) spacer region (ISR) associated with the eight rrn operons (rrna-rrnh) of Vibrio cholerae serogroup O1 El Tor strains isolated before, during and after the O 139 outbreak. ISR classes 'a' and 'g' were found to be invariant, ISR-B (ISRb and ISRe) exhibited very little variation, whereas ISR-C (ISRc, ISRd, and ISRf) and ISRh showed the maximum variation. Phylogenetic analysis conducted with all three ISR classes (ISR-B, ISR-C and ISRh) showed that the pre-O 139 serogroup and post-O 139 serogroup O1 El Tor strains arose out of two independent clones, which was congruent with the observation made by earlier workers suggesting that analyses of ISR-C and ISR-h, instead of all five ISR classes, could be successfully used to study phylogeny in this organism.
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MESH Headings
- Cloning, Molecular/methods
- DNA, Intergenic/genetics
- DNA, Ribosomal Spacer/genetics
- Electrophoresis, Agar Gel
- Genetic Heterogeneity
- Genome, Bacterial/genetics
- Molecular Sequence Data
- Phylogeny
- Polymerase Chain Reaction
- RNA, Ribosomal, 16S/genetics
- RNA, Ribosomal, 23S/genetics
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Nucleic Acid
- Vibrio cholerae O1/classification
- Vibrio cholerae O1/genetics
- Vibrio cholerae O1/isolation & purification
- Vibrio cholerae O139/classification
- Vibrio cholerae O139/genetics
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Affiliation(s)
- Atreyi Ghatak
- Molecular Biology Laboratory, Indian Institute of Chemical Biology, 4, Raja SC Mullick Road, Jadavpur, Kolkata 700 032, India
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18
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Nusrin S, Khan GY, Bhuiyan NA, Ansaruzzaman M, Hossain MA, Safa A, Khan R, Faruque SM, Sack DA, Hamabata T, Takeda Y, Nair GB. Diverse CTX phages among toxigenic Vibrio cholerae O1 and O139 strains isolated between 1994 and 2002 in an area where cholera is endemic in Bangladesh. J Clin Microbiol 2005; 42:5854-6. [PMID: 15583324 PMCID: PMC535256 DOI: 10.1128/jcm.42.12.5854-5856.2004] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PCR surveillance of the rstR genes of CTX phages in Vibrio cholerae O1 and O139 showed no relationship between the incidence of disease and changes in the rstR but showed variations in their presence in O1 and O139 strains and the occurrence of multiple types in a few strains.
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Affiliation(s)
- Suraia Nusrin
- Laboratory Sciences Division, ICDDR,B Centre for Health and Population Research, Mohakhali, Dhaka-1212, Bangladesh.
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19
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Faruque SM, Chowdhury N, Kamruzzaman M, Ahmad QS, Faruque A, Salam MA, Ramamurthy T, Nair GB, Weintraub A, Sack DA. Reemergence of epidemic Vibrio cholerae O139, Bangladesh. Emerg Infect Dis 2003; 9:1116-22. [PMID: 14519249 PMCID: PMC3016788 DOI: 10.3201/eid0909.020443] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
During March and April 2002, a resurgence of Vibrio cholerae O139 occurred in Dhaka and adjoining areas of Bangladesh with an estimated 30,000 cases of cholera. Patients infected with O139 strains were much older than those infected with O1 strains (p<0.001). The reemerged O139 strains belong to a single ribotype corresponding to one of two ribotypes that caused the initial O139 outbreak in 1993. Unlike the strains of 1993, the recent strains are susceptible to trimethoprim, sulphamethoxazole, and streptomycin but resistant to nalidixic acid. The new O139 strains carry a copy of the Calcutta type CTXCalc prophage in addition to the CTXET prophage carried by the previous strains. Thus, the O139 strains continue to evolve, and the adult population continues to be more susceptible to O139 cholera, which suggests a lack of adequate immunity against this serogroup. These findings emphasize the need for continuous monitoring of the new epidemic strains.
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Affiliation(s)
- Shah M. Faruque
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
| | | | - M. Kamruzzaman
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
| | - Q. Shafi Ahmad
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
| | - A.S.G. Faruque
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
| | - M. Abdus Salam
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
| | - T. Ramamurthy
- National Institute of Cholera and Enteric Diseases, Beliaghata, Calcutta, India
| | - G. Balakrish Nair
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
| | | | - David A. Sack
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
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20
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Liang W, Wang S, Yu F, Zhang L, Qi G, Liu Y, Gao S, Kan B. Construction and evaluation of a safe, live, oral Vibrio cholerae vaccine candidate, IEM108. Infect Immun 2003; 71:5498-504. [PMID: 14500467 PMCID: PMC201064 DOI: 10.1128/iai.71.10.5498-5504.2003] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
IEM101, a Vibrio cholerae O1 El Tor Ogawa strain naturally deficient in CTXPhi, was previously selected as a live cholera vaccine candidate. To make a better and safer vaccine that can induce protective immunity against both the bacteria and cholera toxin (CT), a new vaccine candidate, IEM108, was constructed by introducing a ctxB gene and an El Tor-derived rstR gene into IEM101. The ctxB gene codes for the protective antigen CTB subunit, and the rstR gene mediates phage immunity. The stable expression of the two genes was managed by a chromosome-plasmid lethal balanced system based on the housekeeping gene thyA. Immunization studies indicate that IEM108 generates good immune responses against both the bacteria and CT. After a single-dose intraintestinal vaccination with 10(9) CFU of IEM108, both anti-CTB immunoglobulin G and vibriocidal antibodies were detected in the immunized-rabbit sera. However, only vibriocidal antibodies are detected in rabbits immunized with IEM101. In addition, IEM108 but not IEM101 conferred full protection against the challenges of four wild-type toxigenic strains of V. cholerae O1 and 4 micro g of CT protein in a rabbit model. By introducing the rstR gene, the frequency of conjugative transfer of a recombinant El Tor-derived RS2 suicidal plasmid to IEM108 was decreased 100-fold compared to that for IEM101. This indicated that the El Tor-derived rstR cloned in IEM108 was fully functional and could effectively inhibit the El Tor-derived CTXPhi from infecting IEM108. Our results demonstrate that IEM108 is an efficient and safe live oral cholera vaccine candidate that induces antibacterial and antitoxic immunity and CTXPhi phage immunity.
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MESH Headings
- Administration, Oral
- Animals
- Antibodies, Bacterial/blood
- Bacteriophages/genetics
- Base Sequence
- Cholera/immunology
- Cholera/prevention & control
- Cholera Toxin/genetics
- Cholera Toxin/immunology
- Cholera Vaccines/administration & dosage
- Cholera Vaccines/genetics
- Cholera Vaccines/isolation & purification
- Cholera Vaccines/pharmacology
- DNA, Bacterial/genetics
- Genes, Bacterial
- Rabbits
- Safety
- Vaccines, Attenuated/administration & dosage
- Vaccines, Attenuated/genetics
- Vaccines, Attenuated/isolation & purification
- Vaccines, Attenuated/pharmacology
- Vaccines, Synthetic/administration & dosage
- Vaccines, Synthetic/genetics
- Vaccines, Synthetic/isolation & purification
- Vaccines, Synthetic/pharmacology
- Vibrio cholerae/genetics
- Vibrio cholerae/immunology
- Vibrio cholerae/virology
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Affiliation(s)
- Weili Liang
- Priority Laboratory of Medical Molecular Bacteriology, Ministry of Health, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing 102206, People's Republic of China
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21
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Ramamurthy T, Yamasaki S, Takeda Y, Nair GB. Vibrio cholerae O139 Bengal: odyssey of a fortuitous variant. Microbes Infect 2003; 5:329-44. [PMID: 12706446 DOI: 10.1016/s1286-4579(03)00035-2] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Vibrio cholerae O139, the new serogroup associated with epidemic cholera, came into being in the second half of the year 1992 in an explosive fashion and was responsible for several outbreaks in India and other neighbouring countries. This was an unprecedented event in the history of cholera and the genesis of the O139 serogroup was, at that time, thought to be the beginning of the next or the eighth pandemic of cholera. However, with the passage of time, the O1 serogroup of the El Tor biotype again reappeared and displaced the O139 serogroup on the Indian subcontinent, and there was a feeling among cholera workers that the appearance of this new serogroup may have been a one-time event. The resurgence of the O139 serogroup in September 1996 in Calcutta and the coexistence of both the O1 and O139 serogroups in much of the cholera endemic areas in India and elsewhere, suggested that the O139 serogroup has come to stay and is a permanent entity to contend with in the coming years. During the past 10 years, intensive work on all aspects of the O139 serogroup was carried out by cholera researchers around the world. The salient findings on this serogroup over the past 10 years pertinent to its prevalence, clinico-epidemiological features, virulence-associated genes, rapid screening and identification, molecular epidemiology, and vaccine developments have been highlighted.
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Affiliation(s)
- Thandavarayan Ramamurthy
- National Institute of Cholera and Enteric Diseases, P-33, CIT Road, Scheme XM, Beliaghata, Calcutta 700 010, India.
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22
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Faruque SM, Sack DA, Sack RB, Colwell RR, Takeda Y, Nair GB. Emergence and evolution of Vibrio cholerae O139. Proc Natl Acad Sci U S A 2003; 100:1304-9. [PMID: 12538850 PMCID: PMC298768 DOI: 10.1073/pnas.0337468100] [Citation(s) in RCA: 140] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/09/2002] [Indexed: 11/18/2022] Open
Abstract
The emergence of Vibrio cholerae O139 Bengal during 1992-1993 was associated with large epidemics of cholera in India and Bangladesh and, initially, with a total displacement of the existing V. cholerae O1 strains. However, the O1 strains reemerged in 1994 and initiated a series of disappearance and reemergence of either of the two serogroups that was associated with temporal genetic and phenotypic changes sustained by the strains. Since the initial emergence of the O139 vibrios, new variants of the pathogen derived from multiple progenitors have been isolated and characterized. The clinical and epidemiological characteristics of these strains have been studied. Rapid genetic reassortment in O139 strains appears to be a response to the changing epidemiology of V. cholerae O1 and also a strategy for persistence in competition with strains of the O1 serogroup. The emergence of V. cholerae O139 has provided a unique opportunity to witness genetic changes in V. cholerae that may be associated with displacement of an existing serogroup by a newly emerging one and, thus, provide new insights into the epidemiology of cholera. The genetic changes and natural selection involving both environmental and host factors are likely to influence profoundly the genetics, epidemiology, and evolution of toxigenic V. cholerae, not only in the Ganges Delta region of India and Bangladesh, but also in other areas of endemic and epidemic cholera.
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Affiliation(s)
- Shah M Faruque
- Laboratory Sciences Division, International Centre for Diarrhoeal Disease Research, Mohakhali, Dhaka-1212, Bangladesh
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23
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Faruque SM, Kamruzzaman M, Sack DA, Mekalanos JJ, Nair GB. CTXphi-independent production of the RS1 satellite phage by Vibrio cholerae. Proc Natl Acad Sci U S A 2003; 100:1280-5. [PMID: 12529504 PMCID: PMC298764 DOI: 10.1073/pnas.0237385100] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The cholera toxin genes of Vibrio cholerae are encoded by the filamentous phage, CTXphi. Chromosomal CTXphi prophage DNA is often found flanked by copies of a related genetic element designated RS1, and RS1 DNA can be packaged into filamentous phage particles (designated RS1phi) by using the CTXphi morphogenesis genes. RS1phi is a satellite phage that further controls expression and dissemination of CTXphi. Here we describe a CTXphi-independent mechanism for production of RS1phi. A nontoxigenic environmental V. cholerae strain (55V71) was identified that supports production of RS1phi. However, newly infected CTX-negative strains did not produce RS1phi, indicating that additional 55V71 genes were involved in production of RS1phi. Analysis of nucleic acids from phage preparations of 55V71 revealed a 7.5-kb single-stranded DNA, whose corresponding replicative form was found in plasmid preparations. This DNA likely corresponds to the genome of a new filamentous phage, which we have designated KSF-1phi. The replicative form DNA of KSF-1phi was cloned into pUC18, and the resulting construct pKSF-1.1 supported the production of RS1phi particles by CTX-negative V. cholerae strains. RS1phi particles produced in this way infect recipient V. cholerae strains by a mechanism that is independent of the CTXphi receptor, the toxin-coregulated pilus. Thus, KSF-1phi is capable of facilitating the transfer of the RS1 element to strains that do not express toxin coregulated pilus. Given that RS1phi can enhance coproduction of CTXphi particles, KSF-1phi-mediated dissemination of RS1 may indirectly promote the spread of toxin genes among V. cholerae strains. This study also shows that filamentous phages can package diverse DNA elements and thus may play a role in horizontal transfer of more genes than previously appreciated.
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Affiliation(s)
- Shah M Faruque
- Molecular Genetics Laboratory, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka-1212, Bangladesh.
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24
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Davis BM, Kimsey HH, Kane AV, Waldor MK. A satellite phage-encoded antirepressor induces repressor aggregation and cholera toxin gene transfer. EMBO J 2002; 21:4240-9. [PMID: 12169626 PMCID: PMC126166 DOI: 10.1093/emboj/cdf427] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
CTXphi is a filamentous bacteriophage whose genome encodes cholera toxin, the principal virulence factor of Vibrio cholerae. We have found that the CTXphi-related element RS1 is a satellite phage whose transmission depends upon proteins produced from a CTX prophage (its helper phage). However, unlike other satellite phages and satellite animal viruses, RS1 can aid the CTX prophage as well as exploit it, due to the RS1-encoded protein RstC. RstC, whose function previously was unknown, is an antirepressor that counteracts the activity of the phage repressor RstR. RstC promotes transcription of genes required for phage production and thereby promotes transmission of both RS1 and CTXphi. Antirepression by RstC also induces expression of the cholera toxin genes, ctxAB, and thus may contribute to the virulence of V.cholerae. In vitro, RstC binds directly to RstR, producing unusual, insoluble aggregates containing both proteins. In vivo, RstC and RstR are both found at the cell pole, where they again appear to form stable complexes. The sequestration/inactivation process induced by RstC resembles those induced by mutant polyglutamine-containing proteins implicated in human neurodegenerative disorders.
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Affiliation(s)
| | | | - Anne V. Kane
- Howard Hughes Medical Institute, Division of Geographic Medicine and Infectious Diseases and
GRASP Center, Department of Medicine, Tufts-New England Medical Center and Tufts University School of Medicine, Boston, MA 02111, USA Corresponding author e-mail:
| | - Matthew K. Waldor
- Howard Hughes Medical Institute, Division of Geographic Medicine and Infectious Diseases and
GRASP Center, Department of Medicine, Tufts-New England Medical Center and Tufts University School of Medicine, Boston, MA 02111, USA Corresponding author e-mail:
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25
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Hochhut B, Lotfi Y, Mazel D, Faruque SM, Woodgate R, Waldor MK. Molecular analysis of antibiotic resistance gene clusters in vibrio cholerae O139 and O1 SXT constins. Antimicrob Agents Chemother 2001; 45:2991-3000. [PMID: 11600347 PMCID: PMC90773 DOI: 10.1128/aac.45.11.2991-3000.2001] [Citation(s) in RCA: 210] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2001] [Accepted: 07/30/2001] [Indexed: 01/01/2023] Open
Abstract
Many recent Asian clinical Vibrio cholerae E1 Tor O1 and O139 isolates are resistant to the antibiotics sulfamethoxazole (Su), trimethoprim (Tm), chloramphenicol (Cm), and streptomycin (Sm). The corresponding resistance genes are located on large conjugative elements (SXT constins) that are integrated into prfC on the V. cholerae chromosome. We determined the DNA sequences of the antibiotic resistance genes in the SXT constin in MO10, an O139 isolate. In SXT(MO10), these genes are clustered within a composite transposon-like structure found near the element's 5' end. The genes conferring resistance to Cm (floR), Su (sulII), and Sm (strA and strB) correspond to previously described genes, whereas the gene conferring resistance to Tm, designated dfr18, is novel. In some other O139 isolates the antibiotic resistance gene cluster was found to be deleted from the SXT-related constin. The El Tor O1 SXT constin, SXT(ET), does not contain the same resistance genes as SXT(MO10). In this constin, the Tm resistance determinant was located nearly 70 kbp away from the other resistance genes and found in a novel type of integron that constitutes a fourth class of resistance integrons. These studies indicate that there is considerable flux in the antibiotic resistance genes found in the SXT family of constins and point to a model for the evolution of these related mobile elements.
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Affiliation(s)
- B Hochhut
- Division of Geographic Medicine/Infectious Diseases, New England Medical Center, Tufts University School of Medicine, and Howard Hughes Medical Institute, Boston, Massachusetts 02111, USA
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26
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Mukhopadhyay R, Ghosh RK. Mechanism of phage PS166-mediated biotype conversion in Vibrio cholerae: role of the hlyA locus. Virology 2000; 273:44-51. [PMID: 10891406 DOI: 10.1006/viro.2000.0359] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Temperate phage PS166 lysogens of Vibrio eltor MAK757 biotype eltor belong to two major categories. Seventy percent of the lysogens acquire auxotrophy for glycine and histidine and maintain their parental biotype. About 10% of the lysogens become Cys(-) or Cys(-) Met(-) and are converted to the classical biotype with complete changes in all biotype-specific determinants. PCR and RFLP analysis revealed that in the latter lysogens, the phage genome integrated at the hlyA locus, whereas the same locus remained unaffected in lysogens that retained their parental biotype. These results suggest that the two types of lysogens arose due to integration of the phage genome at two different locations on the chromosome. A restriction map of the phage genome was constructed using AvaII and BglII. An 800-bp BglII fragment carrying the attP site, located at one of the termini of the phage genome, was used to distinguish the two classes of lysogen.
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Affiliation(s)
- R Mukhopadhyay
- Indian Institute of Chemical Biology, 4, Raja S.C. Mullick Road, Jadavpur, Calcutta, 700032, India
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27
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Davis BM, Waldor MK. CTXphi contains a hybrid genome derived from tandemly integrated elements. Proc Natl Acad Sci U S A 2000; 97:8572-7. [PMID: 10880564 PMCID: PMC26989 DOI: 10.1073/pnas.140109997] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
CTXphi is a filamentous, temperate bacteriophage whose genome includes ctxAB, the genes that encode cholera toxin. In toxigenic isolates of Vibrio cholerae, tandem arrays of prophage DNA, usually interspersed with the related genetic element RS1, are integrated site-specifically within the chromosome. We have discovered that these arrays routinely yield hybrid virions, composed of DNA from two adjacent prophages or from a prophage and a downstream RS1. Coding sequences are always derived from the 5' prophage whereas most of an intergenic sequence, intergenic region 1, is always derived from the 3' element. The presence of tandem elements is required for production of virions: V. cholerae strains that contain a solitary prophage rarely yield CTX virions, and the few virions detected result from imprecise excision of prophage DNA. Thus, generation of the replicative form of CTXphi, pCTX, a step that precedes production of virions, does not depend on reversal of the process for site-specific integration of CTXphi DNA into the V. cholerae chromosome. Production of pCTX also does not depend on RecA-mediated homologous recombination between adjacent prophages. We hypothesize that the CTXphi-specific proteins required for replication of pCTX can also function on a chromosomal substrate, and that, unlike the processes used by other integrating phages, production of pCTX and CTXphi does not require excision of the prophage from the chromosome. Use of this replication strategy maximizes vertical transmission of prophage DNA while still enabling dissemination of CTXphi to new hosts.
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Affiliation(s)
- B M Davis
- Howard Hughes Medical Institute and Division of Geographic Medicine and Infectious Diseases, New England Medical Center, and Tufts University School of Medicine, Boston, MA 02111, USA
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28
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Faruque SM, Saha MN, Bag PK, Bhadra RK, Bhattacharya SK, Sack RB, Takeda Y, Nair GB. Genomic diversity among Vibrio cholerae O139 strains isolated in Bangladesh and India between 1992 and 1998. FEMS Microbiol Lett 2000; 184:279-84. [PMID: 10713434 DOI: 10.1111/j.1574-6968.2000.tb09027.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
In order to assess the extent of genomic diversity among Vibrio cholerae O139 strains, restriction fragment length polymorphisms in two genetic loci, rrn and ctx, were studied. Analysis of 144 strains isolated from different regions of Bangladesh and India between 1992 and 1998 revealed the presence of at least six distinct ribotypes (B-I through B-VI) of which three were new ribotypes, and one of these was represented by a nontoxigenic O139 strain. Strains of ribotypes B-I through B-V shared 11 different CTX genotypes (A through K). Antimicrobial resistance patterns of the strains varied independently of their ribotypes and CTX genotypes. Results of this study suggest that V. cholerae O139 is undergoing rapid genetic changes leading to the origination of new variants, and temporal changes in antimicrobial resistance patterns may be contributing to the selection of different variants.
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Affiliation(s)
- S M Faruque
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
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29
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Basu A, Mukhopadhyay AK, Garg P, Chakraborty S, Ramamurthy T, Yamasaki S, Takeda Y, Nair GB. Diversity in the arrangement of the CTX prophages in classical strains of Vibrio cholerae O1. FEMS Microbiol Lett 2000; 182:35-40. [PMID: 10612727 DOI: 10.1111/j.1574-6968.2000.tb08869.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
This study reports the results of a molecular analysis of the CTX prophages in classical biotype strains of Vibrio cholerae O1 of clinical origin isolated between 1970 and 1979 in India. All strains were sensitive to group IV classical phage and polymyxin B but resistant to group 5 El Tor phage. These phenotypic traits are consistent to that exhibited by the classical biotype. PCR studies reconfirmed their biotype assignment and showed the presence of intact CTX prophages and the presence of the recently described toxin linked cryptic plasmid. Restriction fragment length polymorphism of rRNA genes and pulsed-field gel electrophoresis showed clonal diversity among the strains. The most notable observation was the finding that one strain (GP13) has three CTX prophages while another (GP147) has four CTX prophages. This is the first time heterogeneity is reported in the arrangement of the CTX prophages among classical strains of V. cholerae O1.
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Affiliation(s)
- A Basu
- Department of Microbiology, National Institute of Cholera and Enteric Diseases, P-33, CIT Road, Scheme XM, Beliaghata, Calcutta, India
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30
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Chakrabarti AK, Ghosh AN, Nair GB, Niyogi SK, Bhattacharya SK, Sarkar BL. Development and evaluation of a phage typing scheme for Vibrio cholerae O139. J Clin Microbiol 2000; 38:44-9. [PMID: 10618061 PMCID: PMC86014 DOI: 10.1128/jcm.38.1.44-49.2000] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The scenario of cholera that existed previously changed in 1992 and 1993 with the emergence of toxigenic Vibrio cholerae O139 in India. The genesis of the new serogroup formed the impetus to search for O139 phages in and around the country. A total of five newly isolated phages lytic to V. cholerae O139 strains were used for the development of this phage typing scheme. These phages differed from each other and also differed from the existing O1 phages in their lytic patterns, morphologies, restriction endonuclease digestion profiles, and immunological criteria. With this scheme, 500 V. cholerae O139 strains were evaluated for their phage types, and almost all strains were found to be typeable. The strains clustered into 10 different phage types, of which type 1 (38.2%) was the dominant type, followed by type 2 (22.4%) and type 3 (18%). Additionally, a comparative study of phage types in 1993 and 1994 versus those from 1996 to 1998 for O139 strains showed a higher percentage of phage type 1 (40.5%), followed by type 3 (18.8%) during the period between 1993 and 1994, whereas phage type 2 (32. 1%) was the next major type during the period from 1996 to 1998. This scheme comprising five newly isolated phages would be another useful tool in the study of the epidemiology of cholera caused by V. cholerae O139.
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Affiliation(s)
- A K Chakrabarti
- National Institute of Cholera and Enteric Diseases, Beliaghata, Calcutta-700 010, India
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Basu A, Garg P, Datta S, Chakraborty S, Bhattacharya T, Khan A, Ramamurthy S, Bhattacharya SK, Yamasaki S, Takeda Y, Nair GB. Vibrio cholerae O139 in Calcutta, 1992-1998: incidence, antibiograms, and genotypes. Emerg Infect Dis 2000; 6:139-47. [PMID: 10756147 PMCID: PMC2640858 DOI: 10.3201/eid0602.000206] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
We report results of surveillance for cholera caused by Vibrio cholerae O139 from September 1992, when it was first identified, to December 1998. V. cholerae O139 dominated as the causative agent of cholera in Calcutta during 1992-93 and 1996- 97, while the O1 strains dominated during the rest of the period. Dramatic shifts in patterns of resistance to cotrimoxazole, neomycin, and streptomycin were observed. Molecular epidemiologic studies showed clonal diversity among the O139 strains and continuous emergence of new epidemic clones, reflected by changes in the structure, organization, and location of the CTX prophages in the V. cholerae O139
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Affiliation(s)
- A Basu
- National Institute of Cholera and Enteric Diseases, Calcutta, India
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Davis BM, Kimsey HH, Chang W, Waldor MK. The Vibrio cholerae O139 Calcutta bacteriophage CTXphi is infectious and encodes a novel repressor. J Bacteriol 1999; 181:6779-87. [PMID: 10542181 PMCID: PMC94144 DOI: 10.1128/jb.181.21.6779-6787.1999] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
CTXphi is a lysogenic, filamentous bacteriophage. Its genome includes the genes encoding cholera toxin (ctxAB), one of the principal virulence factors of Vibrio cholerae; consequently, nonpathogenic strains of V. cholerae can be converted into toxigenic strains by CTXphi infection. O139 Calcutta strains of V. cholerae, which were linked to cholera outbreaks in Calcutta, India, in 1996, are novel pathogenic strains that carry two distinct CTX prophages integrated in tandem: CTX(ET), the prophage previously characterized within El Tor strains, and a new CTX Calcutta prophage (CTX(calc)). We found that the CTX(calc) prophage gives rise to infectious virions; thus, CTX(ET)phi is no longer the only known vector for transmission of ctxAB. The most functionally significant differences between the nucleotide sequences of CTX(calc)phi and CTX(ET)phi are located within the phages' repressor genes (rstR(calc) and rstR(ET), respectively) and their RstR operators. RstR(calc) is a novel, allele-specific repressor that regulates replication of CTX(calc)phi by inhibiting the activity of the rstA(calc) promoter. RstR(calc) has no inhibitory effect upon the classical and El Tor rstA promoters, which are instead regulated by their cognate RstRs. Consequently, production of RstR(calc) renders a CTX(calc) lysogen immune to superinfection by CTX(calc)phi but susceptible (heteroimmune) to infection by CTX(ET)phi. Analysis of the prophage arrays generated by sequentially integrated CTX phages revealed that pathogenic V. cholerae O139 Calcutta probably arose via infection of an O139 CTX(ET)phi lysogen by CTX(calc)phi.
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Affiliation(s)
- B M Davis
- Tufts University School of Medicine and Division of Geographic Medicine and Infectious Diseases, Tupper Research Institute, Boston, Massachusetts 02111, USA
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Thungapathra M, Sharma C, Gupta N, Ghosh RK, Mukhopadhyay A, Koley H, Nair GB, Ghosh A. Construction of a recombinant live oral vaccine from a non-toxigenic strain of Vibrio cholerae O1 serotype inaba biotype E1 Tor and assessment of its reactogenicity and immunogenicity in the rabbit model. Immunol Lett 1999; 68:219-27. [PMID: 10424424 DOI: 10.1016/s0165-2478(99)00076-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The disease cholera is an important cause of mortality in many developing countries. Though it can be controlled through improved sanitation, this goal is not easily attainable in many countries. Development of an efficacious vaccine offers the best immediate solution. A new oral candidate vaccine has been constructed from a non-toxigenic strain of Vibrio cholerae E1 Tor, Inaba, which is not only devoid of the cholera toxin (CT) virulence cassette but also is completely non-reactogenic in rabbit ileal loop assay. The strain, however, had toxR and tcpA genes. Through a series of manipulations, the ctxB gene of V. cholerae, responsible for the production of the 'B' subunit of the cholera toxin (CTB) was introduced into the cryptic hemolysin locus of the strain. The resulting strain, named vaccine attempt 1.3 (VA1.3), was found to be able to produce copious amounts of CTB. In the RITARD model this strain was found to be non-reactogenic and provided full protection against the challenge doses of both V. cholerae O1, classical and E1 Tor. In the immunized rabbit it invoked significant levels of anti-bacterial and anti-toxin immunity.
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Affiliation(s)
- M Thungapathra
- Institute of Microbial Technology, Sector 39A, Chandigarh, India
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Faruque SM, Siddique AK, Saha MN, Rahman MM, Zaman K, Albert MJ, Sack DA, Sack RB. Molecular characterization of a new ribotype of Vibrio cholerae O139 Bengal associated with an outbreak of cholera in Bangladesh. J Clin Microbiol 1999; 37:1313-8. [PMID: 10203477 PMCID: PMC84761 DOI: 10.1128/jcm.37.5.1313-1318.1999] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vibrio cholerae O139 Bengal initially appeared in the southern coastal region of Bangladesh and spread northward, causing explosive epidemics during 1992 and 1993. The resurgence of V. cholerae O139 during 1995 after its transient displacement by a new clone of El Tor vibrios demonstrated rapid changes in the epidemiology of cholera in Bangladesh. A recent outbreak of cholera in two north-central districts of Bangladesh caused by V. cholerae O139 led us to analyze strains collected from the outbreak and compare them with V. cholerae O139 strains isolated from other regions of Bangladesh and neighboring India to investigate their origins. Analysis of restriction fragment length polymorphisms in genes for conserved rRNA (ribotype) revealed that the recently isolated V. cholerae O139 strains belonged to a new ribotype which was distinct from previously described ribotypes of toxigenic V. cholerae O139. All strains carried the genes for toxin-coregulated pili (tcpA and tcpI) and accessory colonization factor (acfB), the regulatory gene toxR, and multiple copies of the lysogenic phage genome encoding cholera toxin (CTXPhi) and belonged to a previously described ctxA genotype. Comparative analysis of the rfb gene cluster by PCR revealed the absence of a large region of the O1-specific rfb operon downstream of the rfaD gene and the presence of an O139-specific genomic region in all O139 strains. Southern hybridization analysis of the O139-specific genomic region also produced identical restriction patterns in strains belonging to the new ribotype and those of previously described ribotypes. These results suggested that the new ribotype of Bengal vibrios possibly originated from an existing strain of V. cholerae O139 by genetic changes in the rRNA operons. In contrast to previously isolated O139 strains which mostly had resistance to trimethoprim, sulfamethoxazole, and streptomycin encoded by a transposon (SXT element), 68.6% of the toxigenic strains analyzed in the present study, including all strains belonging to the new ribotype, were susceptible to these antibiotics. Molecular analysis of the SXT element revealed possible deletion of a 3.6-kb region of the SXT element in strains which were susceptible to the antibiotics. Thus, V. cholerae O139 strains in Bangladesh are also undergoing considerable reassortments in genetic elements encoding antimicrobial resistance.
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Affiliation(s)
- S M Faruque
- Molecular Genetics Laboratory, Laboratory Sciences Division, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka-1212, Bangladesh.
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Abstract
Vibrio cholerae O139, the first non-O1 serogroup of V. cholerae to give rise to epidemic cholera, is characteristically resistant to the antibiotics sulphamethoxazole, trimethoprim, chloramphenicol and streptomycin. Resistances to these antibiotics are encoded by a 62 kb self-transmissible, conjugative, chromosomally integrating element designated the 'SXT element'. We found that the SXT element integrates site specifically into both V. cholerae and Escherichia coli K-12 into the 5' end of prfC, the gene encoding peptide chain release factor 3. Integration of the SXT element interrupts the chromosomal prfC gene, but the element encodes a new 5' end of prfC that restores the reading frame of this gene. The recombinant of prfC allele created upon element integration is functional. The integration and excision mechanism of the SXT element shares many features with site-specific recombination found in lambdoid phages. First, like lambda, the SXT element forms a circular extrachromosomal intermediate through specific recombination of the left and right ends of the integrated element. Second, chromosomal integration of the element occurs via site-specific recombination in a 17 bp sequence found in the circular form of the SXT element and a similar 17 bp sequence in prfC. Third, both chromosomal integration and excision of the SXT element were found to require an element-encoded int gene with strong similarities to the lambda integrase family. Based on the properties of the SXT element, we propose to classify this element as a CONSTIN, an acronym for a conjugative, self-transmissible, integrating element.
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Affiliation(s)
- B Hochhut
- New England Medical Center, Boston, MA, USA
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Khetawat G, Bhadra RK, Nandi S, Das J. Resurgent Vibrio cholerae O139: rearrangement of cholera toxin genetic elements and amplification of rrn operon. Infect Immun 1999; 67:148-54. [PMID: 9864209 PMCID: PMC96290 DOI: 10.1128/iai.67.1.148-154.1999] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/1998] [Accepted: 09/30/1998] [Indexed: 11/20/2022] Open
Abstract
The unprecedented genesis of a novel non-O1 Vibrio cholerae strain belonging to serogroup O139, which caused an epidemic in late 1992 in the Indian subcontinent, and its subsequent displacement by El Tor O1 vibrios after 18 months initiated a renewed investigation of the aspects of the organism that are related to pathogenesis. The reappearance of V. cholerae O139 with altered antibiotic sensitivity compared to O139 Bengal (O139B) in late 1996 has complicated the epidemiological scenario of V. cholerae and has necessitated an examination of possible rearrangements in the genome underlying such rapid changes in the phenotypic traits. With a view to investigating whether the phenotypic changes that have occurred are associated with alteration in the genome, the genome of the resurgent V. cholerae O139 (O139R) strains were examined. Pulsed-field gel electrophoresis analysis of NotI- and SfiI-digested genomic DNA of O139R isolates showed restriction fragment length polymorphism including in the cholera toxin (CTX) genetic element locus and with O139B isolates. Analyses of the organization of the CTX genetic elements in O139R strains showed that in contrast to two copies of the elements connected by two direct-repeat sequences (RS) in most of the genomes of O139B isolates, the genomes of all O139R strains examined, except strain AS192, have three such elements connected by a single RS. While the RS present in the upstream of the CTX genetic elements in the genome of O139R is of O139B origin, the RS connecting the cores of the elements has several new restriction sites and has lost the BglII site which is supposed to be conserved in all O1 strains and O139B. The endonuclease I-CeuI, which has sites only in the rrn operons in the genomes of all organisms examined so far, has 10 sites in the genomes of O139R strains, compared to 9 in the genomes of O139B strains. The recent isolates of V. cholerae O139 have thus gained one rrn operon. This variation in the number of rrn operons within a serogroup has not been reported for any other organism. The results presented in this report suggest that like the pathogenic El Tor O1 strains, the genomes of O139 strains are undergoing rapid alterations.
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Affiliation(s)
- G Khetawat
- Biophysics Division, Indian Institute of Chemical Biology, Calcutta
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Mukhopadhyay AK, Basu A, Garg P, Bag PK, Ghosh A, Bhattacharya SK, Takeda Y, Nair GB. Molecular epidemiology of reemergent Vibrio cholerae O139 Bengal in India. J Clin Microbiol 1998; 36:2149-52. [PMID: 9650989 PMCID: PMC105015 DOI: 10.1128/jcm.36.7.2149-2152.1998] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
We report the prevalence of the O139 serogroup in Calcutta, India, after its reemergence in August 1996 and the spread of the reemerged clone to other parts of the country by using previously established molecular markers. Phenotypically, the reemerged Vibrio cholerae O139 displayed a difference compared to those that appeared in late 1992 and 1993 in that the current O139 strains are sensitive to co-trimoxazole. Ribotyping with the enzyme BglI produced two rRNA restriction patterns in the O139 strains isolated after August 1996, and these patterns were identical to those exhibited by strains of O139 isolated in 1992. Three clones of V. cholerae O139 are currently prevailing in the country, with strains exhibiting three bands after HindIII digestion and hybridization with a ctxA probe being dominant. The reemergence of V. cholerae O139 in Calcutta after a 32-month quiescent period reestablishes the O139 serogroup as an entity which is likely to play a crucial role in the temporal antigenic variations among the serogroups of V. cholerae causing cholera.
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Affiliation(s)
- A K Mukhopadhyay
- National Institute of Cholera and Enteric Diseases, Beliaghata, Calcutta, India
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Basu A, Mukhopadhyay AK, Sharma C, Jyot J, Gupta N, Ghosh A, Bhattacharya SK, Takeda Y, Faruque AS, Albert MJ, Balakrish Nair G. Heterogeneity in the organization of the CTX genetic element in strains of Vibrio cholerae O139 Bengal isolated from Calcutta, India and Dhaka, Bangladesh and its possible link to the dissimilar incidence of O139 cholera in the two locales. Microb Pathog 1998; 24:175-83. [PMID: 9514639 DOI: 10.1006/mpat.1997.0186] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
After a lapse of 33 months, Vibrio cholerae O139, the new serogroup associated with cholera, has re-emerged in Calcutta, India and has become the dominant serogroup causing cholera from September 1996. In neighbouring Bangladesh, V. cholerae O1 biotype El Tor continues to be the dominant cause of cholera with the O139 serogroup accounting for only a small proportion of cases. Comparison of the phenotypic traits of representative O139 strains from Calcutta and Dhaka isolated between December 1996 and April 1997 showed similar phenotypic traits with the exception that Dhaka O139 strains were susceptible to streptomycin whilst Calcutta O139 strains were resistant. The Dhaka and Calcutta O139 strains displayed identical ribotypes but showed remarkable differences in the structure and organization of the CTX genetic element. In the Dhaka O139 strains, two copies of the CTX element were arranged in tandem and this resembled the pattern displayed by the 1992 epidemic strains of O139. The Calcutta O139 strains, in contrast, carried three copies of the CTX genetic element arranged in tandem with the loss of a conserved BglII restriction site in the RS1 element and the appearance of a new HindIII site in the same region. While there may be other factors, it appears that the reorganization of the CTX genetic element in the Calcutta O139 strains may have contributed to the resurgence of this serogroup in Calcutta.
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Affiliation(s)
- A Basu
- National Institute of Cholera and Enteric Diseases, Beliaghata, Calcutta-700 010, India
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