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Archive - Mar 18, 2014

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China Halves Tuberculosis Prevalence in Just 20 Years

Over the last 20 years, China has more than halved its tuberculosis (TB) prevalence, with rates falling from 170 to 59 per 100 000 population. This unrivalled success has been driven by a massive scale-up of the directly observed, short-course (DOTS) strategy, from half the population in the 1990s to the entire country after 2000, according to findings from a 20-year-long analysis of national survey data, published online on March 18, 2014 in The Lancet. "One of the key global TB targets set by the Stop TB Partnership aims to reduce tuberculosis prevalence by 50% between 1990 and 2015. This study in China is the first to show the feasibility of achieving such a target, and China achieved this 5 years earlier than the target date," says study leader Dr. Yu Wang from the Chinese Center for Disease Control and Prevention in Beijing, China. "Huge improvements in TB treatment, driven by a major shift in treatment from hospitals to local public health centers implementing the DOTS strategy, were largely responsible for this success." China is a major contributor to the TB pandemic, with 1 million new TB cases every year, accounting for 11% of all new cases globally. Two national surveys of tuberculosis prevalence in 1990 and 2000 showed that levels of TB were reduced by around 30% in the 13 provinces where the DOTS program was adopted. However, national TB prevalence fell by just 19% over the decade. Another survey was done in 2010 to re-evaluate the national TB burden, providing an opportunity to assess the effect of the nationwide expansion of the DOTS program. Nearly 253,000 individuals aged 15 years and older were surveyed in 2010 at 176 investigation points chosen from all 31 mainland provinces. The results showed that between 2000 and 2010, national TB prevalence fell by 57%—tripling the reduction of the previous decade.

Antarctic Moss Comes Back to Life after 1,500 Years under Ice

Researchers from the British Antarctic Survey and the University of Reading reported online in the Cell Press journal Current Biology on March 17, 2014 that Antarctic mosses can essentially come back to life after 1,500 completely inactive years under the ice. Prior to this finding, direct regeneration from frozen plant material had been demonstrated after 20 years at most. Beyond that, only microbes had been shown to be capable of revival after so many years on hold. "These mosses were basically in a very long-term deep freeze," says Dr. Peter Convey of the British Antarctic Survey. "This timescale of survival and recovery is much, much longer than anything reported for them before." The findings in mosses have special relevance for Antarctic ecosystems and climate, Dr. Convey adds, because mosses are primary producers on land in both northern and southern polar regions. In the north in particular, mosses are responsible for storing most of the fixed carbon. If mosses can survive in this way for such long periods of time, then regrowth once the ice retreats wouldn't require long-distance, transoceanic colonization events. Dr. Convey and his colleagues primarily study polar moss cores because they provide a novel archive of past climate conditions. The researchers use them to assess growth rates over time and as proxies to reconstruct aspects of the environment and environmental change over time. The oldest moss banks of the type under study in the Antarctic date back 5,000 to 6,000 years. The one the researchers focused on in the current work is nearly 2,000 years old at its base. In the beginning, the researchers weren't sure that mosses frozen for more than a decade or two would remain viable. When they began to see the 1,500-year-old mosses start to regrow, it came as a real surprise.

Sequencing Reveals Genetic Diversity in Hospital-Acquired, Antibiotic-Resistant Klebsiella

Using genome sequencing, National Institutes of Health (NIH) scientists and their colleagues have tracked the evolution of the antibiotic-resistant bacterium Klebsiella pneumoniae sequence type 258 (ST258), an important agent of hospital-acquired infections. While researchers had previously thought that ST258 K. pneumoniae strains spread from a single ancestor, the NIH team showed that the strains arose from at least two different lineages. The investigators also found that the key difference between the two groups lies in the genes involved in production of the bacterium's outer coat, the primary region that interacts with the human immune system. Their results, which appeared online on March 17, 2014 in PNAS, promise to help guide the development of new strategies to diagnose, prevent. and treat this emerging public health threat. ST258 K. pneumoniae is the predominant cause of human infections among bacteria classified as carbapenem-resistant Enterobacteriaceae (CRE), which kill approximately 600 people annually in the United States and sicken thousands more. Most CRE infections occur in hospitals and long-term care facilities among patients who are already weakened by unrelated disease or have undergone certain medical procedures. In the new study, scientists from the NIH's National Institute of Allergy and Infectious Diseases (NIAID) and their colleagues sequenced the complete genomes of ST258 K. pneumoniae strains collected from two patients in New Jersey hospitals. By comparing these reference genomes with gene sequences from an additional 83 clinical ST258 K. pneumoniae isolates, the scientists found that the strains divided broadly into two distinct groups, each with its own evolutionary history.