(Press-News.org) VIDEO:
See a time-lapse series showing hyper-replication of Salmonella bacteria (red) in epithelial cells from two to seven hours after infection.
Click here for more information.
New findings by National Institutes of Health scientists could explain how Salmonella bacteria, a common cause of food poisoning, efficiently spread in people. In a study published this week in the Proceedings of the National Academy of Sciences, researchers describe finding a reservoir of rapidly replicating Salmonella inside epithelial cells. These bacteria are primed to infect other cells and are pushed from the epithelial layer by a new mechanism that frees the Salmonella to infect other cells or be shed into the intestine.
The Centers for Disease Control and Prevention estimate that Salmonella infections sicken 40,000 people each year in the United States, though the actual number of infections is likely much higher because many cases are mild and not diagnosed or reported. Currently, Salmonella is the focus of an ongoing U.S. public health investigation into contaminated chicken eggs.
"Unfortunately, far too many people have experienced the debilitating effects of Salmonella, which cause disease via largely unexplained processes, including overactive inflammatory responses," says Anthony S. Fauci, M.D., director of NIH's National Institute of Allergy and Infectious Diseases (NIAID). "This elegant study provides new insight into the origins of that inflammatory disease process."
While much is known about the human infectious cycle of Salmonella, scientists have yet to understand how the bacteria escape the gut to spread infection. Epithelial cells line the outer and inner surfaces of the body, such as the skin and gut, and form a continuous protective tissue against infection. But Salmonella have learned how to live inside epithelial cells and use them for their benefit. Salmonella protect themselves within special membrane-bound compartments, called vacuoles, inside gut epithelial cells.
Using special high-resolution microscopes to view laboratory-grown human intestinal epithelial cells and laboratory mice infected with Salmonella, an NIAID research group led by Olivia Steele-Mortimer, Ph.D., in collaboration with Bruce Vallance, Ph.D., of the University of British Columbia in Vancouver, discovered a secondary population of Salmonella not confined within a vacuole, but instead moving freely inside the epithelial cells. This reservoir of Salmonella is distinct from vacuolar Salmonella. The bacteria multiply much faster; they have long tail-like projections, called flagella, used to move; and they exhibit a needle complex they use to pierce cells and inject their proteins. With these attributes, this population of Salmonella is genetically programmed to invade new cells.
The scientists observed that epithelial cells containing the hyper-replicating, invasive Salmonella are eventually pushed out of the intestinal tissue into the gut cavity, setting the Salmonella free. The mechanism used to push these Salmonella-infected cells into the body cavity resembles the natural mechanism humans use to shed dying or dead epithelial cells from their gut. The scientists believe that Salmonella have hijacked this mechanism to facilitate their own escape.
The human immune system, however, also senses that these are not normal, dying cells in the gut and triggers a response that includes release of interleukin-18, a small protein that sets off an inflammation cascade. Interleukin-18 also is prominent in chronic intestinal inflammation associated with autoimmune disorders, such as inflammatory bowel disease. The effects of interleukin-18 release provide an explanation for the acute intestinal inflammation associated with Salmonella infections.
The scientists hope their research leads to a treatment that prevents the spread of infection. They are focusing on how this specialized population of Salmonella escapes from its membrane-bound compartment to multiply and swim freely in the cell.
###
NIAID conducts and supports research—at NIH, throughout the United States, and worldwide—to study the causes of infectious and immune-mediated diseases, and to develop better means of preventing, diagnosing and treating these illnesses. News releases, fact sheets and other NIAID-related materials are available on the NIAID Web site at http://www.niaid.nih.gov.
The National Institutes of Health (NIH)—The Nation's Medical Research Agency—includes 27 Institutes and Centers and is a component of the U. S. Department of Health and Human Services. It is the primary federal agency for conducting and supporting basic, clinical and translational medical research, and it investigates the causes, treatments and cures for both common and rare diseases. For more information about NIH and its programs, visit http://www.nih.gov.
Reference: L Knodler et al. Dissemination of invasive Salmonella via bacterial-induced extrusion of mucosal epithelia. Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1006098107 (2010).
END
A cheetah lies still in the grass. Finally, a gazelle comes into view. The cheetah plunges forward, reaches sixty-five miles per hour in three seconds, and has the hapless gazelle by the jugular in less than a minute. Then it must catch its breath, resting before eating.
A blue whale surfaces, blasting water high from its blowhole. It breathes in great gasps, filling its thousand-gallon lungs with air. Then it descends again to look for krill, staying below for 10, 20, even 30 minutes before taking another breath.
Both animals need oxygen, of course. And both depend ...
Ames, Iowa - An Iowa State University researcher searched for new genes that are turned on during infection in a type of mosquito that is not only a pest, but transmits disease-causing pathogens.
Lyric Bartholomay, assistant professor of entomology, along with colleagues from around the world, infected the common southern house mosquito (Culex quinquefasciatus) with various pathogens to see which mosquito genes are activated in response to the infection.
Bartholomay is the first author on the paper, "Pathogenomics of Culex quinquefasciatus and Meta-Analysis of Infection ...
DARIEN, IL – A study in the Oct. 1 issue of the journal Sleep found that getting too little or too much sleep in early pregnancy is associated with elevated blood pressure in the third trimester. The study suggests that improving prenatal sleep hygiene may provide important health benefits.
Results show that the mean systolic blood pressure in the third trimester was 114 mm Hg in women with a normal self-reported nightly sleep duration of nine hours in early pregnancy, 118.05 mm Hg in women who reported sleeping six hours or less per night, and 118.90 mm Hg in women ...
SAN FRANCISCO, CA– Amblyopia, known as "lazy eye," is a major cause of vision problems in children and a common cause of blindness in people aged 20 to 70 in developed countries. In amblyopia the person's stronger eye is favored and his/her weaker eye gradually loses visual power as a result. When the condition is detected and treated before age 7, more than 75 percent of children achieve 20/30 vision or better, the Amblyopia Treatment Study reports. But parents and teachers can easily miss this problem–especially in very young children. Pediatric ophthalmologists (Eye ...
SAN FRANCISCO – For suicidal adolescents, the emergency department (ED) is most often the chosen portal to mental health services. New research, presented Friday, Oct. 1, at the American Academy of Pediatrics (AAP) National Conference and Exhibition in San Francisco, looks at what happens to the 30 percent of suicidal adolescents who are discharged from the ED and whether they go on to access additional mental health services.
In "Predictors of Mental Health Follow up Among Adolescents with Suicidal Ideation After Emergency Department Discharge," researchers followed ...
For the first time to date, research published in the October edition of the Journal of Thoracic Oncology (JTO) sought to determine the use of chemotherapy in a contemporary, diverse non-small cell lung cancer (NSCLC) population encompassing all patient ages. Prior population-based studies have shown that only 20 to 30 percent of advanced lung cancer patients receive chemotherapy treatment. These studies have previously relied on the Medicare-linked Surveillance, Epidemiology, and End Results (SEER) database, thus excluding the 30 to 35 percent of lung cancer patients younger ...
Featured in the October edition of the Journal of Thoracic Oncology (JTO), data from The Tarceva Lung Cancer Survival Treatment (TRUST) confirms the safety and efficacy profile of erlotinib, a highly potent oral active, reversible inhibitor of epidermal growth factor receptor (EGFR) tyrosine-kinase (TK) activity in a large heterogeneous non-small cell lung cancer (NSCLC) population.
Erlotinib has been shown to significantly increase survival for patients with previously treated advanced NSCLC. Certain groups of patients with NSCLC, such as those with a particular type ...
Forests of genetically altered trees and other plants could sequester several billion tons of carbon from the atmosphere each year and so help ameliorate global warming, according to estimates published in the October issue of BioScience.
The study, by researchers at Lawrence Berkeley National Laboratory and Oak Ridge National Laboratory, outlines a variety of strategies for augmenting the processes that plants use to sequester carbon dioxide from the air and convert it into long-lived forms of carbon, first in vegetation and ultimately in soil.
Besides increasing the ...
Researchers from the Arkansas Epilepsy Program found treatment with rufinamide results in a significant reduction in seizure frequency compared with placebo, for patients with uncontrolled partial-onset seizures (POS). Details of this study are now available online in Epilepsia, a journal published by Wiley-Blackwell on behalf of the International League Against Epilepsy.
Epilepsy affects up to 2% of the worldwide population according to the Centers for Disease Control and Prevention. More than half of these patients experience POS, or focal seizures, which are initiated ...
(Boston) – Researchers from Boston University School of Medicine (BUSM) and the VA Boston Healthcare System have conducted a study that failed to show a difference in efficacy between Bevacizumab (Avastin) and Ranibizumab (Lucentis) for the treatment of age-related macular degeneration (AMD). The study, which appears currently on-line in Eye, is believed to be the first study to describe one-year outcomes of a prospective, double-masked, randomized clinical trial directly comparing bevacizumab to ranibizuamab. Last October, these same researchers published early, six month ...
