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Typhoid carriers: a Salmonella gene mutation?
June 25, 2002Salmonella enterica causes approximately 16 million cases of typhoid fever worldwide, killing around 500,000 per year. One in thirty of the survivors, however, become carriers, such as Typhoid Mary who caused several typhoid outbreaks in New York City at the beginning of the last century. In carriers the bacteria remain hidden inside cells and the gall bladder, causing new infections as they are shed from an apparently healthy host.
The factors that enable the bacteria to establish chronic infection were unclear. However, in a paper published this week in the Proceedings of the National Academy of Science, researchers at the Institute of Food Research in Norwich and the Karolinska Institute in Sweden found that the change of a single base pair in one Salmonella gene can determine if the bacteria cause short-term illness or a long-term carrier state. The authors stumbled upon the striking change in infectivity while investigating a mutant strain that produces persistent infection in mice.
Tracing the mutation to the genome, the scientists found it caused a single base change in the gene coding for the enzyme polynucleotide phosphorylase (PNPase). This enzyme normally decreases the production of virulence factors by breaking down the messenger RNA essential for the translation of the genetic code into the Salmonella virulence factors. The mutant enzyme is less active, allowing greater production of virulence factors and, therefore, persistent infection.
Dr Jay Hinton of the Institute of Food Research said, "This is a new mechanism for controlling the expression of Salmonella virulence factors, and it's the first time that this type of gene regulation has been linked with the carrier state of typhoid."
Institute of Food Research
Dr Jay Hinton of the Institute of Food Research said, "This is a new mechanism for controlling the expression of Salmonella virulence factors, and it's the first time that this type of gene regulation has been linked with the carrier state of typhoid."
Institute of Food Research
Bacteria Current Events and Bacteria News RSSFactors from common human bacteria may trigger multiple sclerosis
Current research suggests that a common oral bacterium may exacerbate autoimmune disease. The related report by Nichols et al, "Unique Lipids from a Common Human Bacterium Represent a New Class of TLR2 Ligands Capable of Enhancing Autoimmunity," appears in the December 2009 issue of The American Journal of Pathology.
Exposure to both traffic, indoor pollutants puts some kids at higher risk for asthma later
New research presents strong evidence that the "synergistic" effect of early-life exposure to both outdoor traffic-related pollution and indoor endotoxin causes more harm to developing lungs than one or the other exposure alone.
New study finds MRSA on the rise in hospital outpatients
The community-associated strain of the deadly superbug MRSA-an infection-causing bacteria resistant to most common antibiotics-poses a far greater health threat than previously known and is making its way into hospitals, according to a study in the December issue of Emerging Infectious Diseases.
Researchers establish common seasonal pattern among bacterial communities in Arctic rivers
New research on bacterial communities throughout six large Arctic river ecosystems reveals predictable temporal patterns, suggesting that scientists could use these communities as markers for monitoring climate change in the polar regions.
Biologists discover bacterial defense mechanism against aggressive oxygen
Bacteria possess an ingenious mechanism for preventing oxygen from harming the building blocks of the cell.
Saving the single cysteine: new antioxidant system found
We've all read studies about the health benefits of having a life partner. The same thing is true at the molecular level, where amino acids known as cysteines are much more vulnerable to damage when single than when paired up with other cysteines.
Beyond sunlight: Explorers census 17,650 ocean species between edge of darkness and black abyss
Census of Marine Life scientists have inventoried an astonishing abundance, diversity and distribution of deep sea species that have never known sunlight - creatures that somehow manage a living in a frigid black world down to 5,000 meters (~3 miles) below the ocean waves.
Surface bacteria maintain skin's healthy balance
On the skin's surface, bacteria are abundant, diverse and constant, but inflammation is undesirable. Research at the University of California, San Diego School of Medicine now shows that the normal bacteria living on the skin surface trigger a pathway that prevents excessive inflammation after injury.
On the Trail of a Vaccine for Lyme Disease: Yale Researchers Target Tick Saliva
A protein found in the saliva of ticks helps protect mice from developing Lyme disease, Yale researchers have discovered. The findings, published in the November 19 issue of Cell Host & Microbe, may spur development of a new vaccine against infection from Lyme disease, which is spread through tick bites.
Cigarettes Harbor Many Bacteria Harmful to Human Health
Cigarettes are "widely contaminated" with bacteria, including some known to cause disease in people, concludes a new international study conducted by a University of Maryland environmental health researcher and microbial ecologists at the Ecole Centrale de Lyon in France.
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