The complete genome sequence of Vibrio cholerae: a tale of two chromosomes and of two lifestyles. (73/1261)

Vibrio cholerae O1 has figured prominently in the history of infectious diseases as a cause of periodic global epidemics, an affliction of refugees in areas of social strife and as the disease first subjected to modern epidemiological analysis during the classic investigations of John Snow in mid-19th century London [1]. Thus, publication of the entire genome sequence of V. cholerae O1 (biotype El Tor) in Nature [2] by a consortium of investigators from The Institute for Genomic Research, the University of Maryland and Harvard Medical School is properly regarded as an historic event that will trigger a paradigm shift in the study of this organism.  (+info)

Human infection with Ascaris lumbricoides is associated with suppression of the interleukin-2 response to recombinant cholera toxin B subunit following vaccination with the live oral cholera vaccine CVD 103-HgR. (74/1261)

To investigate the potential immunomodulatory effects of concurrent ascariasis on the cytokine response to a live oral vaccine, we measured cytokine responses to cholera toxin B subunit (CT-B) following vaccination with the live oral cholera vaccine CVD 103-HgR in Ascaris lumbricoides-infected subjects randomized in a double-blind study to receive two doses of either albendazole or placebo prior to vaccination and in a group of healthy U.S. controls. Postvaccination cytokine responses to CT-B were characterized by transient increases in the production of interleukin-2 (IL-2; P = 0.02) and gamma interferon (IFN-gamma; P = 0.001) in the three study groups combined; however, postvaccination increases in IFN-gamma were significant only in the albendazole-treated A. lumbricoides infection group (P = 0.008). Postvaccination levels of IL-2 were significantly greater in the albendazole-treated group compared with the placebo group (P = 0.03). No changes in levels of Th1 and Th2 cytokines in response to control ascaris antigens were observed over the same period. These findings indicate that vaccination with CVD 103-HgR is associated with a Th1 cytokine response (IL-2 and IFN-gamma) to CT-B, that infection with A. lumbricoides diminishes the magnitude of this response, and that albendazole treatment prior to vaccination was able to partially reverse the deficit in IL-2. The potential modulation of the immune response to oral vaccines by geohelminth parasites has important implications for the design of vaccination campaigns in geohelminth-endemic areas.  (+info)

Comparison of Vibrio cholerae pathogenicity islands in sixth and seventh pandemic strains. (75/1261)

Epidemic Vibrio cholerae strains possess a large cluster of essential virulence genes on the chromosome called the Vibrio pathogenicity island (VPI). The VPI contains the tcp gene cluster encoding the type IV pilus toxin-coregulated pilus colonization factor which can act as the cholera toxin bacteriophage (CTXPhi) receptor. The VPI also contains genes that regulate virulence factor expression. We have fully sequenced and compared the VPI of the seventh-pandemic (El Tor biotype) strain N16961 and the sixth-pandemic (classical biotype) strain 395 and found that the N16961 VPI is 41,272 bp and encodes 29 predicted proteins, whereas the 395 VPI is 41,290 bp. In addition to various nucleotide and amino acid polymorphisms, there were several proteins whose predicted size differed greatly between the strains as a result of frameshift mutations. We hypothesize that these VPI sequence differences provide preliminary evidence to help explain the differences in virulence factor expression between epidemic strains (i.e., the biotypes) of V. cholerae.  (+info)

Endemic and epidemic dynamics of cholera: the role of the aquatic reservoir. (76/1261)

BACKGROUND: In the last decades, attention to cholera epidemiology increased, as cholera epidemics became a worldwide health problem. Detailed investigation of V. cholerae interactions with its host and with other organisms in the environment suggests that cholera dynamics is much more complex than previously thought. Here, I formulate a mathematical model of cholera epidemiology that incorporates an environmental reservoir of V. cholerae. The objective is to explore the role of the aquatic reservoir on the persistence of endemic cholera as well as to define minimum conditions for the development of epidemic and endemic cholera. RESULTS: The reproduction rate of cholera in a community is defined by the product of social and environmental factors. The importance of the aquatic reservoir depends on the sanitary conditions of the community. Seasonal variations of contact rates force a cyclical pattern of cholera outbreaks, as observed in some cholera-endemic communities. CONCLUSIONS: Further development on cholera modeling requires a better understanding of V. cholerae ecology and epidemiology. We need estimates of the prevalence of V. cholerae infection in endemic populations as well as a better description of the relationship between dose and virulence.  (+info)

The use of hospital-based nurses for the surveillance of potential disease outbreaks. (77/1261)

OBJECTIVE: To study a novel surveillance system introduced in Mpumalanga Province, a rural area in the north-east of South Africa, in an attempt to address deficiencies in the system of notification for infectious conditions that have the potential for causing outbreaks. METHODS: Hospital-based infection control nurses in all of Mpumalanga's 32 public and private hospitals were trained to recognize, report, and respond to nine clinical syndromes that require immediate action. Sustainability of the system was assured through a schedule of regular training and networking, and by providing feedback to the nurses. The system was evaluated by formal review of hospital records, evidence of the effective containment of a cholera outbreak, and assessment of the speed and appropriateness of responses to other syndromes. FINDINGS: Rapid detection, reporting and response to six imported cholera cases resulted in effective containment, with only 19 proven secondary cholera cases, during the two-year review period. No secondary cases followed detection and prompt response to 14 patients with meningococcal disease. By the end of the first year of implementation, all facilities were providing weekly zero-reports on the nine syndromes before the designated time. Formal hospital record review for cases of acute flaccid paralysis endorsed the value of the system. CONCLUSION: The primary goal of an outbreak surveillance system is to ensure timely recognition of syndromes requiring an immediate response. Infection control nurses in Mpumalanga hospitals have excelled in timely weekly zero-reporting, participation at monthly training and feedback sessions, detection of priority clinical syndromes, and prompt appropriate response. This review provides support for the role of hospital-based nurses as valuable sentinel surveillance agents providing timely data for action.  (+info)

New insights on the emergence of cholera in Latin America during 1991: the Peruvian experience. (78/1261)

After a century of absence, in late January 1991, Vibrio cholerae invaded the Western Hemisphere by way of Peru. Although a number of theories have been proposed, it is still not understood how that invasion took place. We reviewed the clinical records of persons attending hospital emergency departments in the major coastal cities of Peru from September through January of 1989/1990 and 1990/1991. We identified seven adults suffering from severe, watery diarrhea compatible with a clinical diagnosis of cholera during the four months preceding the cholera outbreak, but none during the previous year. The patients were scattered among five coastal cities along a 1,000 km coastline. We postulate that cholera vibrios, autochthonous to the aquatic environment, were present in multiple coastal locations, and resulted from environmental conditions that existed during an El Nino phenomenon. Once introduced into the coastal communities in concentrations large enough for human infection to occur, cholera spread by the well-known means of contaminated water and food.  (+info)

Role of sodium bioenergetics in Vibrio cholerae. (79/1261)

The ability of the bacterium to use sodium in bioenergetic processes appears to play a key role in both the environmental and pathogenic phases of Vibrio cholerae. Aquatic environments, including fresh, brackish, and coastal waters, are an important factor in the transmission of cholera and an autochthonous source. The organism is considered to be halophilic and has a strict requirement for Na(+) for growth. Furthermore, expression of motility and virulence factors of V. cholerae is intimately linked to sodium bioenergetics and to each other. Several lines of evidence indicated that the activity of the flagellum of V. cholerae might have an impact on virulence gene regulation. As the V. cholerae flagellum is sodium-driven and the Na(+)-NQR enzyme is known to create a sodium motive force across the bacterial membrane, it was recently suggested that the increased toxT expression observed in a nqr-negative strain is mediated by affecting flagella activity. It was suggested that the V. cholerae flagellum might respond to changes in membrane potential and the resulting changes in flagellar rotation might serve as a signal for virulence gene expression. However, we recently demonstrated that although the flagellum of V. cholerae is not required for the effects of ionophores on virulence gene expression, changes in the sodium chemical potential are sensed and thus alternative mechanisms, perhaps involving the TcpP/H proteins, for the detection of these conditions must exist. Analyzing the underlying mechanisms by which bacteria respond to changes in the environment, such as their ability to monitor the level of membrane potential, will probably reveal complex interplays between basic physiological processes and virulence factor expression in a variety of pathogenic species.  (+info)

Non-serogroup O:1 Vibrio cholerae bacteremia and cerebritis. (80/1261)

We describe a case of non-serogroup O:1 Vibrio cholerae bacteremia and cerebritis in a 41-year-old Thai man with alcoholism who presented with fever and cellulitis of the right ankle. He was successfully treated with parenteral cefotaxime and then was switched to treatment with oral ciprofloxacin.  (+info)