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August 2012 tips from the journals of the American Society for Microbiology

August 23, 2012

Boost for Efforts to Prevent Microbial Stowaways on Interplanetary Spacecraft

Efforts to expunge micro-organisms from spacecraft assembly cleanrooms, and the spacecraft themselves, inadvertently select for the organisms that are often the most fit to survive long journeys in space. This has the risk of thwarting the goal of avoiding contaminating other celestial bodies, as well as samples brought back to earth, according to Myron La Duc of the Jet Propulsion Laboratory (JPL), California Institute of Technology, and his collaborators. Their research is published in the August issue of the journal Applied and Environmental Microbiology.

Mars, the Jovian moon, Europa, and a few other denizens of our solar system may harbor life, and might be capable of supporting some terrestrial microbes. Contaminating planets or moons that already support extraterrestrial life--a possibility on Mars, the big Jovian moon, Europa, and the tiny Saturnian moon, Enceladus--could interfere with efforts to understand that life, and its origins. For example, life on all of these orbs may have a common origin--likely on Earth or Mars--and contamination of samples could confound efforts to determine which planet was the source of life, and how life arose. For these reasons, sterilization processing of spacecraft bound for such planetary bodies is a very high priority for the National Aeronautics and Space Administration.

Species of bacteria have long been considered capable of surviving space travel, but examples of a fungal species that is capable of such survival have only recently been demonstrated, according to the report. Additionally, due to their extraordinary ability to withstand various extreme environments, some archaea "have been proposed as being capable of tolerating the Martian environment," the investigators write. "In light of this, the breadth of current spacecraft-associated microbial diversity assessments must expand to include eukaryotes and archaea."

Because of this, better methods are needed for determining microbial populations on surfaces that have a very low density of individual microbes. In this study, the researchers became the first to take the microbial census using so-called pyrosequencing studies. Pyrosequencing is a recent method of sequencing DNA from entire microbial communities that is much faster and simpler than other methods, and extremely thorough.

Further findings in the study pointed up the value of pyrosequencing in demonstrating where vigilance in sterilizing equipment is needed. Of most import, certain archaeal sequences, notably from the ammonia-oxidizing genus, Nitrososphaeraceae of the recently proposed phylum, Thaumarchaeota, appeared in ground support equipment samples, both before and after cleaning. Archaea of this phylum can survive on ammonia or urea, or other inorganic chemicals, enhancing their ability to survive extreme conditions, according to the report, so prevention of their transfer to the spacecraft is key.

"Methanobacteriaceae sequences were also observed in the spacecraft hardware samples," the researchers write. "This is particularly relevant for astrobiological issues, since members of this family have been reported to be obligate anaerobic, hydrogenotrophic, and methanogenic organisms and capable of utilizing carbon dioxide as their sole carbon source." The challenge for the JPL's spacecraft team is to ensure that the DNA sequences only arise from dead Methanobacteriaceae, and not from live ones.

(M.T. La Duc, P. Vaishampayan, H.R. Nilsson, T. Torok, and K. Venkateswaran, 2012. Pyrosequencing-derived bacterial, archaeal, and fungal diversity of spacecraft hardware destined for Mars. Appl. Environ. Microbiol. 78:5912-5922.)

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New Evidence for Polyomavirus BK Role in Prostate Cancer

Prostate cancer is the leading cause of cancer morbidity and the third greatest cause of cancer death among men in developed countries. A major question in cancer research has been whether virus infection plays a role in cancers of the genitourinary tract. Now a team of Swiss investigators has new evidence suggesting human polyomavirus BK is involved in maintaining and enhancing an environment suitable for prostate cancer growth. The research, published in the August Journal of Virology, could lead to preventive and/or therapeutic prostate cancer vaccines.

The researchers found somewhat different immune responses against the virus' large tumor antigen between seropositive patients with prostate cancers, those seropositive patients with benign prostatic hyperplasia (the benign enlargement of the prostate that is common in older males), and those without prostate abnormalities. In prostate cancer patients, especially those expressing the large tumor antigen in tumor tissue, and showing evidence of recurrence following treatment, the researchers found that this viral antigen seems to influence immune responses in ways that encourage development of the tumor, says principal investigator Maurizio Provanzano of the University of Zurich, Switzerland.

Provenzano lists three major reasons why polyomavirus BK might play a causal role in genitourinary tract cancers: the virus resides asymptomatically in the genitourinary tract of nearly 80 percent of young individuals; it is expressed in inflammatory lesions at very early stages of prostate cancer onset; and it binds and sequesters the tumor suppressor protein p53 in its wild-type form in the cytoplasm of infected cells.

Provenzano says that although the current results are not yet strong enough to prove that polyomavirus BK can cause prostate cancer, some findings suggest ways of fighting the cancer. For example, the strong association between the detection of the virus in prostate cancer and disease recurrence suggests that boosting their immune systems might protect virus-positive individuals.

(G. Sais, S. Wyler, T. Hudolin, I. Banzola, C. Mengus, L. Bubendorf, P.J. Wild, H.H. Hirsch, T. Sulser, G.C. Spagnoli, and M. Provanzano, 2012. Differential patterns of large tumor antigen-specific immune responsiveness in patients with BK polyomavirus-positive prostate cancer or benign prostatic hyperplasia. J. Virol. 86:8461-8471.)

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New Diagnostic Fast and Effective at Finding TB in Elephants: Benefits for Pachyderms and Public Health

A serological test is highly accurate at finding tuberculosis infection in elephants, and can determine such infection years before culture, according to a study in the August Clinical and Vaccine Immunology. The issue is critical not only for elephants, which are an endangered species, but for human public health, because elephants are among the very rare animal species which are commonly infected by human strains of tuberculosis, says first author Konstantin P. Lyashchenko of Chembio Diagnostic Systems, Inc., Medford, NY.

Elephants are unusual when it comes to diagnosing M. tuberculosis. Generally, bacterial infections can be diagnosed much earlier with culture than with serology. "Serology is considered to be a late diagnostic marker of tuberculosis in humans and various animal species," says Lyashchenko. "However, efforts to isolate M. tuberculosis from live, infected elephants have proven very disappointing, whereas antibody assays in such animals showed promise for early detection of TB," says Lyashchenko.

Lyashchenko and his collaborators first realized the promise of serology for diagnosing TB in elephants, in 2004, when they were asked to test serum samples from a zoo elephant that had been diagnosed with M. tuberculosis in 2000. They requested serum samples going back 10 years, and discovered the elephant had become antibody positive in 1996. Later, they found that all 26 elephants that had been culture confirmed as infected tested antibody positive for M. tuberculosis.

The novelty in the new paper is that instead of conducting serological tests in elephants that were known, via culture, to be infected with M. tuberculosis, the researchers began conducting serology in elephants that were not known to be infected, deflecting criticisms that interpretations of antibody test results might be biased by the knowledge that the elephants were infected, says Lyashchenko.

That is important, because the earlier research and development leading to approval of the Chembio antibody assays by the United States Department of Agriculture (USDA) in 2007, resulted in USDA's implementing a requirement by the USDA two years ago that all ~450 elephants in the US be tested annually using the Chembio serology. When elephants are diagnosed with tuberculosis, and confirmed by culture, their owners have a choice of treating, quarantining, or euthanising the elephants. Treatment takes around a year, and is very expensive, partly because such large animals require proportionately large quantities of drugs.

The incidence of TB appears to be higher in circus elephants than in zoos, says Lyashchenko. He notes that TB has more opportunity to spread among circus elephants than in zoo or sanctuary elephants, because they travel together more frequently and are both kept in closer proximity to, and exposed to greater numbers of people and other animals.

Positive cultures for M. tuberculosis are difficult to obtain because bacterial shedding occurs only intermittently, so that "trunk wash" samples, from which cultures are grown, must be taken repeatedly before success is achieved. Further slowing diagnosis, elephants can be infected with M. tuberculosis for a number of years before showing signs of disease.

"Very interesting and potentially right up my alley," says Suzan Murray, head veterinarian at the National Zoo. "We are beginning to do more field work with elephants and this could be very helpful."

(K.P. Lyashchenko, R. Greenwald, J. Esfandiari, S. Mikota, M. Miller, T. Moller, L. Vogelnest, K.P. Gairhe, HS. Robbe-Austerman, J. Gai, and W. Ray Waters, 2012. Field application of serodiagnostics to identify elephants with tuberculosis prior to case confirmation by culture. Clin Vaccine Immunol. 19:1269-1275.)

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Emerging Gastrointestinal Pathogen Linked With Human Fecal Contamination

A gastrointestinal pathogen associated with fecal contamination was present in 97 of 129 water samples taken from four beaches on the Lake Erie coast of Ohio according to research published in the August issue of Applied and Environmental Microbiology.

Substantial numbers of beach-goers may be sickened by this pathogen, says Jiyoung Lee of The Ohio State University, Columbus, who led the research. "We were actually quite shocked at the strength of the association between human fecal contamination and [the pathogen] Arcobacter," she adds.

There was ample precedent for the findings. In 2004, a major disease outbreak involving wastewater contamination of groundwater occurred at South Bass Island in Lake Erie, just off of the Ohio coast near Sandusky, causing 1,450 to become ill. The authors of a report on that incident stated that Arcobacter "should be considered as one of the emerging waterborne bacterial pathogens, and waters should be further monitored for this bacterium."

In the new study, Lee and collaborators found a fairly strong association between presence of Arcobacter and the number of days in which the density of E. coli, considered an indicator of fecal contamination, reached levels where a beach advisory is posted. Nonetheless, Arcobacter levels were often elevated on days when E. coli concentrations were too low to trigger beach advisories, raising concerns of contamination on some days with no beach advisories.

"HuBac was much better in our study at predicting Arcobacter densities than E. coli and it is likely that at Lake Erie beaches, human-associated fecal contamination may be more associated with pathogens than E. coli," says Lee. HuBac is a human-specific fecal contamination marker. The US EPA is revising the recreational water quality criteria, and Lee hopes these results will be taken into account.

"By reducing untreated human fecal inputs--by preventing sewage and septic system runoff--Arcobacter densities could be substantially reduced, leading to improved public health," says Lee.

(C. Lee, S. Agidi, J.W. Marion, and J. Lee, 2012. Arcobacter in Lake Erie beach waters: an emerging gastrointestinal pathogen linked with human-associated fecal contamination. Appl. Environ. Microbiol. 78:5511-5519.)

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American Society for Microbiology

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