Tips from the Journals of the American Society for Microbiology

04/16/04

FERTILIZER, IRRIGATION CAUSE LONG-TERM CONTAMINATION OF SOIL AND VEGETABLES

Manure and irrigation water contaminated with salmonella may cause long-term contamination in soil and root vegetables say researchers from Georgia, Maryland and South Carolina. Their findings appear in the April 2004 issue of the journal Applied and Environmental Microbiology.

"Although manure is an obvious source of pathogens, two additional sources of pathogens that contaminate soil, water, crops, animals, and humans are runoff water from manure fields and irrigation water containing manure."

In the study, three manure compounds and irrigation water were contaminated with a nonpathogenic strain of Salmonella enterica to determine the life span of the bacteria in soils fertilized with the compounds as well as the water, and carrots and radishes grown in the contaminated soil. Researchers determined the bacteria stayed in soil samples for 203 to 231 days and for 84 to 203 days after radish and carrot seeds were planted.

"It is remarkable that a one-time application of contaminated irrigation water or compost can result in pathogen contamination of radishes and carrots well beyond their growing cycle," say the researches. "Our results indicate that contaminated irrigation water or manure compost may play an important role in contaminating vegetables and the soil in which they grow."

(M. Islam, J. Morgan, M.P. Doyle, S.C. Phatak, P. Millner, X. Jiang. 2004. Fate of Salmonella enterica serovar typhimurium on carrots and radishes grown in fields treated with contaminated manure composts and irrigation water. Applied and Environmental Microbiology, 70. 4: 2497-2502.)

IDENTIFICATION OF BACTERIA IN SAP MAY MAKE FOR BETTER MAPLE SYRUP

Canadian researchers have tested a new method of identifying bacteria in the sap of maple trees which may allow for increased contamination control. Their findings appear in the April 2004 issue of the journal Applied and Environmental Microbiology.

"This solution is known to be a good nutrient medium for microorganisms, and their growth in the sap will eventually effect the quality of maple syrup and other end products," say the researchers.

Bacterial contamination of maple sap usually occurs at the taphole. In the study, samples of sap were taken from the taphole of maple trees throughout two seasons and screened for bacteria. Amplified ribosomal DNA restriction analysis (ARDRA) was used to place the bacterial isolates in groups and a subset of each ARDRA group was established using 16S rRNA gene fragment sequencing. Results showed gram-negative organisms as the prevailing bacteria while y-Proteobacteria was identified most frequently. Also, bacterial contamination of the taphole increased to higher levels as the season progressed.

"These results are providing interesting insights into maple taphole microflora that will be useful for further investigations of phenomena related to microbial contamination and quality of maple products and also of microbial control strategies," say the researchers.

(L. Lagace, M. Pitre, M. Jacques, D. Roy. 2004. Identification of the bacterial community of maple sap by using amplified ribosomal DNA (rDNA) restriction analysis and rDNA sequencing. Applied and Environmental Microbiology, 70. 4: 2052-5060.)

DNA VACCINE MAY PROTECT AGAINST SMALLPOX

A DNA based vaccine may protect against smallpox say researchers from the United States Army Medical Research Institute of Infectious Diseases in Fort Detrick, Maryland. Their findings appear in the May 2004 issue of the Journal of Virology.

"All viruses in the genus Orthopoxvirus, family Poxviridae, including VACV (the virus used in the current smallpox vaccine), monkeypox virus (MPOV), and variola virus (the virus that causes smallpox), are highly similar in the majority of their nearly 200 proteins, which accounts superficially for the cross-protection among these viruses," say the researchers.

The researchers tested a DNA-based vaccine containing genes from the orthopox family of viruses. It successfully prevented monkeypox virus infection in monkeys, an indicator that it could protect against smallpox in humans. A DNA based vaccine would not have the adverse side effects commonly associated with the live vaccine, such as the dangerous heart inflammation that halted a recent clinical trial.

"We demonstrated here that a DNA vaccine compromised of four VACV genes and administered by gene gun is capable of protecting nonhuman primates against severe monkeypox," say the researchers. "Such a vaccine would contribute greatly to vaccination strategies aimed at reducing the health hazards of the present smallpox vaccine."

(J.W. Hooper, E. Thompson, C. Wilhelmsen, M. Zimmerman, M. Ait Ichou, S.E. Steffen, C.S. Schmaljohn, A.L. Schmaljohn, and P.B. Jahrling. 2004. Smallpox DNA vaccine protects nonhuman primates against lethal monkeypox. Journal of Virology, 78. 9: 4433-4443.)

Source: Eurekalert & others

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