Tips from the journals of the American Society for Microbiology

Detection of Campylobacter in Air Samples May Offer New Monitoring System for Broiler Flocks

New research from Denmark suggests a promising method using air samples to continuously monitor broiler flocks for the presence of the foodborne pathogen Campylobacter. The findings are reported in the April 2009 issue of the journal Applied and Environmental Microbiology.

Campylobacter is one of the most common cause of diarrheal illnesses in humans worldwide. Research estimates that about half of the cases of human Campylobacteriosis originate from livestock, with poultry considered to be the most important source of infection. The slow and complicated process of detecting Campylobacter through culture-based identification has emphasized the need for more efficient detection devices and methodologies.

In the study researchers used the PCR method to detect Campylobacter in feces, dust, and air samples during the lifetime of broiler flocks in two poultry houses. Results showed that the sensitivity of detection of Campylobacter in air samples was comparable to detection in the other sample materials. Further monitoring of airborne particles in six poultry houses suggested that aerodynamic conditions depended on the age of the chickens, but were very comparable among different poultry houses. Lastly, researchers found that Campylobacter could be detected by PCR method in air samples collected only during the hanging stage of the slaughter process.

“The exploitation of airborne dust in poultry houses as a sample material for the detection of Campylobacter and other pathogens provides an intriguing possibility, in conjunction with new detection technologies, for allowing continuous or semicontinuous monitoring of colonization status,” say the researchers.

(K.N. Olsen, M. Lund, J. Skov, L.S. Christensen, J. Hoorfar. 2009. Detection of Campylobacter bacteria in air samples for continuous real-time monitoring of Campylobacter colonization in broiler flocks. Applied and Environmental Microbiology, 75. 7: 2074-2078.)

New Highly Sensitive Method May Offer Early Detection of Dengue Virus

A new highly sensitive method may offer early diagnosis of dengue virus infection by detecting the viral components, such as RNA. The researchers from Gen-Probe Incorporated, San Diego, California and the Centers for Disease Control and Prevention, San Juan, Puerto Rico and Fort Collins, Colorado report their findings in the April 2009 issue of the Journal of Clinical Microbiology.

Dengue virus (DENV) is currently recognized as the most widely spread mosquito-borne virus. The World Health Organization reported between 50 million and 100 million cases of dengue-related disease in 2004. Mosquitoes’ expansion of their geographical distribution throughout the tropical regions of South East Asia and the Americas over the last two decades is largely attributed to population growth as well as increased international travel and trade.

Early diagnosis of DENV has proved challenging largely due to the undifferentiated fever and other unspecific symptoms that patients present with 5 to 7 days postinfection. Patients that present with acute dengue disease are viremic, but may not yet have developed detectable antibodies. Serological testing has been the main method used for diagnosing DENV, but this approach generally only confirms infection after the patient has recovered.

Reverse transcription (RT)-PCR testing has been used more frequently for diagnosing dengue virus, however sensitivity levels only range between 40% and 80% in serologically confirmed cases. Transcription-mediated amplification (TMA) is a highly sensitive blood screening method with detection limits of approximately 95%. In the study researchers compared the sensitivity of TMA to that of (RT)-PCR and found TMA to be 10 to 100 times more sensitive. Further testing showed that among samples from patients with serologically confirmed dengue infection, TMA detected DENV RNA in 80% of specimens that were negative according to the RT-PCR test used and in all specimens with positive RT-PCR results.

“Our results indicate that TMA detects DENV RNA in approximately 89% of acute-phase serum specimens and therefore may provide a useful diagnostic test for acute DENV infections,” say the researchers.

(J.L. Munoz-Jordan, C.S. Collins, E. Vergne, G.A. Santiago, L. Petersen, W. Sun, J.M. Linnen. 2009. Highly sensitive detection of dengue virus nucleic acid in samples from clinically ill patients. Journal of Clinical Microbiology, 47. 4: 927-931.)

New Ebolavirus Vaccine Protects Against Lethal Infection in Animal Models

A new experimental Ebola vaccine is one step closer to realization, having proven its ability to protect against lethal infections in animal models. The researchers report their findings in the April 2009 issue of the Journal of Virology.

Ebolaviruses (EBOVs), the cause of severe hemorrhagic fever in humans and nonhuman primates, are transmitted through direct contact of bodily fluids with infected individuals resulting in death up to 90% of the time. Due to its high pathogenicity and its ability to spread by aerosol droplets, EBOV and its sister virus, Marburgvirus, are classified as category A bioterrorism threats. Currently, no licensed vaccines or antivirals are available against EBOV.

In a previous study the researchers developed a replication-deficient, biologically contained EBOV, Ebola?VP30, vaccine candidate which lacks the essential VP30 gene. In this study they demonstrated its safety in STAT-1 knockout-mice and evaluated its protective efficacy in mice and guinea pigs. Results showed that mice receiving two inoculations with Ebola?VP30 were protected against lethal infection with a mouse-adapted EBOV and viral levels in the blood of vaccinated mice were noticeably lower that those in nonvaccinated mice. Additionally, guinea pigs immunized twice with Ebola?VP30 were also protected against lethal infection with a guinea pig adapted EBOV.

“Our study demonstrates the potential of the Ebola?VP30 virus as a new vaccine platform,” say the researchers. “As with other EBOV vaccine candidates, our vaccine would be of value to health care personnel, laboratory workers, and military personnel, as well as those at risk during outbreaks.”

(P. Halfmann, H. Ebihara, A. Marzi, Y. Hatta, S. Watanabe, M. Suresh, G. Neumann, H. Feldmann, Y. Kawaoka. 2009. Replication-deficient Ebolavirus as a vaccine candidate. Journal of Virology, 83. 8: 3810-3815.)

Repaired Gene Improves Commercial Lager Fermentation

A recent study shows that beer fermentation conducted with genetically modified brewer’s yeast may result in more efficient lager brewing and a lower environmental footprint. Researchers from VTT Technical Research Center of Finland report their findings in the April 2009 issue of the journal Applied and Environmental Microbiology.

The use of more concentrated, high gravity and very high gravity (VHG) brewer’s worts for the manufacture of beer has economic and environmental advantages. By using a special strain of brewer’s yeast and adding more sugar, commercial brewers can create a beer with a higher alcohol percentage using the same amount of ingredients. The resulting concentrated beer can be diluted with water to create a beer with the desired alcohol content. Current strains of brewer’s yeasts, however, ferment VHG worts slowly and incompletely, leaving undesirable byproducts in the final beers.

Current research suggests that lager yeast strains possess a faulty gene that causes the brewing problems. Researchers repaired the lager yeast’s genes by using DNA sequenced from an ale strain. The new yeast fermented VHG lager wort faster and more completely than unmodified strains, producing beers containing more ethanol and less unwanted byproducts.

“They [the transformed yeasts] fermented VHG wort faster and more completely, producing beers containing more ethanol and less residual maltose and maltotriose,” say the researchers.

(V. Vidgren, A. Huuskonen, H. Virtanen, L. Ruohonen, J. Londesborough. 2009. Improved fermentation performance of a lager yeast after repair of its AGT1 maltose and maltotriose transporter genes. Applied and Environmental Microbiology, 75. 8: 2333-2345.)

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