Individuals with Le(a+b−) Blood Group Have Increased Susceptibility to Symptomatic Vibrio cholerae O1 Infection

Cholera remains a severe diarrheal disease, capable of causing extensive outbreaks and high mortality. Blood group is one of the genetic factors determining predisposition to disease, including infectious diseases. Expression of different Lewis or ABO blood group types has been shown to be associated with risk of different enteric infections. For example, individuals of blood group O have a higher risk of severe illness due to V. cholerae compared to those with non-blood group O antigens. In this study, we have determined the relationship of the Lewis blood group antigen phenotypes with the risk of symptomatic cholera as well as the severity of disease and immune responses following infection. We show that individuals expressing the Le(a+b−) phenotype were more susceptible to symptomatic cholera, while Le(a–b+) expressing individuals were less susceptible. Individuals with the Le(a–b−) blood group had a longer duration of diarrhea when infected, required more intravenous fluid replacement, and had lower plasma IgA antibody responses to V. cholerae LPS on day 7 following infection. We conclude that there is an association between the Lewis blood group and the risk of cholera, and that this risk may affect the outcome of infection as well as possibly the efficacy of vaccination

Susceptibility to Vibrio cholerae Infection in a Cohort of Household Contacts of Patients with Cholera in Bangladesh

Vibrio cholerae is the bacterium that causes cholera, a severe form of diarrhea that leads to rapid and potentially fatal dehydration when the infection is not treated promptly. Cholera remains an important cause of diarrhea globally, and V. cholerae continues to cause major epidemics in the most vulnerable populations. Although there have been recent discoveries about how the bacterium adapts to the human intestine and causes diarrhea, there is little understanding of why some people are protected from infection with V. cholerae. This article describes several factors that are associated with the risk of developing V. cholerae infection among people living in the same household with a patient with severe cholera who are at high risk of contracting the infection. One of the findings is that IgA antibodies, a type of antibody associated with immunity at mucosal surfaces such as the intestine, that target several components of the bacteria are associated with immunity to V. cholerae infection. This article also describes genetic and nutritional factors that additionally influence susceptibility to V. cholerae infection

Strategies for Diagnosis and Treatment of Suspected Leptospirosis: A Cost-Benefit Analysis

Symptoms and signs of leptospirosis are non-specific. A number of diagnostic tests for leptospirosis are available. We compared the cost-benefit of 5 management strategies: 1) no patients tested or given antibiotic treatment; 2) all patients given empirical doxycycline treatment; patients given doxycycline when a patient is tested positive for leptospirosis using: 3) lateral flow; 4) MCAT; 5) latex test. Outcomes were measured in duration of fever which is then converted to productivity losses to capture the full economic costs. Empirical doxycycline treatment was found to be the most efficient strategy, being both the least costly alternative and the one that resulted in the lowest average duration of fever. The significantly higher relative cost of using a diagnostic test as compared with presumptive treatment, and the limited sensitivity of all the diagnostic tests implied that only the latex test could be considered cost-effective when compared with the no-antibiotic-treatment option, and that all three tests were still inferior to empirical treatment

Analysis of Salmonella enterica Serotype Paratyphi A Gene Expression in the Blood of Bacteremic Patients in Bangladesh

Salmonella enterica serotype Paratyphi A is a significant and emerging global public health problem and accounts for one fifth of all cases of enteric fever in many areas of Asia. S. Paratyphi A only infects humans, and the lack of an appropriate animal model has limited the study of S. Paratyphi A infection. In this study, we report the application of an RNA analysis method, Selective Capture of Transcribed Sequences (SCOTS), to evaluate which S. Paratyphi A genes are expressed directly in the blood of infected humans. Our results provide insight into the bacterial adaptations and modifications that S. Paratyphi A may need to survive within infected humans and suggest that similar approaches may be applied to other pathogens in infected humans and animals

A Comparative Study of Leptospirosis and Dengue in Thai Children

Two of the most common causes of acute febrile illnesses among children in the tropics are leptospirosis and dengue. Early in illness, these two conditions are often indistinguishable and rapid laboratory confirmation of the infecting pathogen is generally not available. An enhanced ability to distinguish leptospirosis from dengue in children would guide clinicians and public health personnel in the appropriate use of limited healthcare resources

Detection and Quantification of Leptospira interrogans in Hamster and Rat Kidney Samples: Immunofluorescent Imprints versus Real-time PCR

A major limitation in the clinical management and experimental research of leptospirosis is the poor performance of the available methods for the direct detection of leptospires. In this study, we compared real-time PCR (qPCR), targeting the lipL32 gene, with the immunofluorescent imprint method (IM) for the detection and quantification of leptospires in kidney samples from the rat and hamster experimental models of leptospirosis. Using a virulent strain of Leptospira interrogans serovar Copenhageni, a chronic infection was established in the rat model, which were euthanized 28 days post-infection, while the hamster model simulated an acute infection and the hamsters were euthanized eight days after inoculation. Leptospires in the kidney samples were detected using culture isolation, qPCR and the IM, and quantified using qPCR and the IM. In both the acute and chronic infection models, the correlation between quantification by qPCR and the IM was found to be positive and statistically significant (P<0.05). Therefore, this study demonstrates that the IM is a viable alternative for not only the detection but also the quantification of leptospires, particularly when the use of qPCR is not feasible

Interferon-γ and Proliferation Responses to Salmonella enterica Serotype Typhi Proteins in Patients with S. Typhi Bacteremia in Dhaka, Bangladesh

Salmonella enterica serotype Typhi infection is a significant global public health problem and the cause of typhoid fever. Salmonella are intracellular pathogens, and cellular immune responses are required to control and clear Salmonella infections. Despite this, there are limited data on cellular immune responses during wild type S. Typhi infection in humans. Here we report the assessment of cellular immune responses in humans with S. Typhi bacteremia through a screening approach that permitted us to evaluate interferon-γ and proliferation responses to a number of S. Typhi antigens. We detected significant interferon-γ CD4 and CD8 responses, as well as proliferative responses, to a number of recombinantly purified S. Typhi proteins as well as membrane preparation in infected patients. Antigen-specific interferon-γ responses were present at the time of clinical presentation in patients and absent in healthy controls. These observations could assist in the development of interferon-γ-based diagnostic assays for typhoid fever

Transmission of Vibrio cholerae Is Antagonized by Lytic Phage and Entry into the Aquatic Environment

Cholera outbreaks are proposed to propagate in explosive cycles powered by hyperinfectious Vibrio cholerae and quenched by lytic vibriophage. However, studies to elucidate how these factors affect transmission are lacking because the field experiments are almost intractable. One reason for this is that V. cholerae loses the ability to culture upon transfer to pond water. This phenotype is called the active but non-culturable state (ABNC; an alternative term is viable but non-culturable) because these cells maintain the capacity for metabolic activity. ABNC bacteria may serve as the environmental reservoir for outbreaks but rigorous animal studies to test this hypothesis have not been conducted. In this project, we wanted to determine the relevance of ABNC cells to transmission as well as the impact lytic phage have on V. cholerae as the bacteria enter the ABNC state. Rice-water stool that naturally harbored lytic phage or in vitro derived V. cholerae were incubated in a pond microcosm, and the culturability, infectious dose, and transcriptome were assayed over 24 h. The data show that the major contributors to infection are culturable V. cholerae and not ABNC cells. Phage did not affect colonization immediately after shedding from the patients because the phage titer was too low. However, V. cholerae failed to colonize the small intestine after 24 h of incubation in pond water—the point when the phage and ABNC cell titers were highest. The transcriptional analysis traced the transformation into the non-infectious ABNC state and supports models for the adaptation to nutrient poor aquatic environments. Phage had an undetectable impact on this adaptation. Taken together, the rise of ABNC cells and lytic phage blocked transmission. Thus, there is a fitness advantage if V. cholerae can make a rapid transfer to the next host before these negative selective pressures compound in the aquatic environment

Travel risk behaviours and uptake of pre-travel health preventions by university students in Australia

<p>Abstract</p> <p>Background</p> <p>Forward planning and preventative measures before travelling can significantly reduce the risk of many vaccine preventable travel-related infectious diseases. Higher education students may be at an increased risk of importing infectious disease as many undertake multiple visits to regions with higher infectious disease endemicity. Little is known about the health behaviours of domestic or international university students, particularly students from low resource countries who travel to high-resource countries for education. This study aimed to assess travel-associated health risks and preventative behaviours in a sample of both domestic and international university students in Australia.</p> <p>Methods</p> <p>In 2010, a 28 item self-administered online survey was distributed to students enrolled at the University of New South Wales, Sydney, Australia. Multiple methods of distributing links to the online survey were utilised. The survey examined the international travel history, travel intentions, infection control behaviours and self-reported vaccination history.</p> <p>Results</p> <p>A total of 1663 respondents completed the online survey, 22.1% were international students and 83.9% were enrolled at an undergraduate level. Half had travelled internationally in the previous 12 months, with 69% of those travelling only once during that time with no difference in travel from Australia between domestic and international students (<it>p </it>= 0.8). Uptake of pre-travel health advice was low overall with 68% of respondents reporting they had not sought any advice from a health professional prior to their last international trip. Domestic students were more likely to report uptake of a range of preventative travel health measures compared to international students, including diarrhoeal medication, insect repellent, food avoidance and condoms (<it>P </it>< 0.0001). Overall, students reported low risk perception of travel threats and a low corresponding concern for these threats.</p> <p>Conclusions</p> <p>Our study highlights the need to educate students about the risk associated with travel and improve preventative health-seeking and uptake of precautionary health measures in this highly mobile young adult population. Although immunisation is not an entry requirement to study at Universities in Australia, large tertiary institutions provide an opportunity to engage with young adults on the importance of travel health and provision of vaccines required for travel, including missed childhood vaccines.</p

Comparative Proteomic Analysis of the PhoP Regulon in Salmonella enterica Serovar Typhi Versus Typhimurium

Background: S. Typhi, a human-restricted Salmonella enterica serovar, causes a systemic intracellular infection in humans (typhoid fever). In comparison, S. Typhimurium causes gastroenteritis in humans, but causes a systemic typhoidal illness in mice. The PhoP regulon is a well studied two component (PhoP/Q) coordinately regulated network of genes whose expression is required for intracellular survival of S. enterica. Methodology/Principal Findings: Using high performance liquid chromatography mass spectrometry (HPLC-MS/MS), we examined the protein expression profiles of three sequenced S. enterica strains: S. Typhimurium LT2, S. Typhi CT18, and S. Typhi Ty2 in PhoP-inducing and non-inducing conditions in vitro and compared these results to profiles of $phoP^−/Q^−$ mutants derived from S. Typhimurium LT2 and S. Typhi Ty2. Our analysis identified 53 proteins in S. Typhimurium LT2 and 56 proteins in S. Typhi that were regulated in a PhoP-dependent manner. As expected, many proteins identified in S. Typhi demonstrated concordant differential expression with a homologous protein in S. Typhimurium. However, three proteins (HlyE, STY1499, and CdtB) had no homolog in S. Typhimurium. HlyE is a pore-forming toxin. STY1499 encodes a stably expressed protein of unknown function transcribed in the same operon as HlyE. CdtB is a cytolethal distending toxin associated with DNA damage, cell cycle arrest, and cellular distension. Gene expression studies confirmed up-regulation of mRNA of HlyE, STY1499, and CdtB in S. Typhi in PhoP-inducing conditions. Conclusions/Significance: This study is the first protein expression study of the PhoP virulence associated regulon using strains of Salmonella mutant in PhoP, has identified three Typhi-unique proteins (CdtB, HlyE and STY1499) that are not present in the genome of the wide host-range Typhimurium, and includes the first protein expression profiling of a live attenuated bacterial vaccine studied in humans (Ty800)