Tips from the journals of the American Society for Microbiology

September 15, 2005

Combined Testing Methods May Rapidly Detect Hepatitis A in Strawberry and Green Onion Rinses

Two testing methods combined may be able to rapidly identify hepatitis A contamination in strawberries and green onions say researchers from Canada. Their findings appear in the September 2005 issue of the journal Applied and Environmental Microbiology.

Hepatitis A virus (HAV), which is endemic worldwide, is often transmitted to humans through contaminated food. Shellfish, fruits, and vegetables are commonly infected through contaminated water, surfaces, and food handlers and recent outbreaks have been specifically associated with strawberries and green onions. Detecting HAV in food has previously proven difficult due to the presence of inhibitory substances and low concentration of virus recovered.

In the study researchers combined real-time reverse transcription-PCR (a promising method for detecting HAV due to its sensitivity, specificity, speed, and ability to deliver quantitative data) and immunomagnetic separation (IMS) treatment (a method capable of addressing the limitations listed above) to detect for HAV in rinses from strawberries and green onions. Researchers were able to capture 20 times more HAV particles from both green onion and strawberry rinses receiving IMS treatment and complete the entire testing process within a six hour period.

"This study demonstrated for the first time the application of IMS combined with real-time RT-PCR for quantification of HAV in food rinses," say the researchers. "This procedure can be completed within six hours and has the potential to be applied for routine surveillance of HAV in fresh produce and environmental samples."

(X.C. Shan, P. Wolffs, M.W. Griffiths. 2005. Rapid and quantitative detection of hepatitis A virus from green onion and strawberry rinses by use of real-time reverse transcription-PCR. Applied and Environmental Microbiology, 71. 9: 5624-5626.)

Antimicrobial Peptides from Amphibian Skin May Inhibit Transmission of HIV

A topical solution containing antimicrobial peptides from amphibian skin may inhibit transmission of HIV say researchers. Their findings appear in the September 2005 issue of the Journal of Virology.

Antimicrobial peptides (AMPs) are the driving force behind the innate immune response in animals. Anuran amphibians, frogs and toads, are two of the richest sources of these peptides which are believed to generate antiviral activity against a variety of microbes. With sexual intercourse remaining as the most common mode of HIV infection throughout the world, a topical solution capable of inhibiting transmission of the virus at mucosal sites could significantly impact prevention efforts.

In the study fourteen peptides from various amphibian species were collected and tested for their ability to inhibit HIV infection. Researchers identified three peptides, caerin 1.1, caerin 1.9, and maculatin 1.1, capable of inhibiting infection within minutes of exposure to the virus. These same amphibian peptides were also found to be effective at inhibiting the transfer of HIV by dendritic cells (DCs) to T cells.

"These data suggest that amphibian-derived peptides can access DC-sequestered HIV and destroy the virus before it can be transferred to T cells," say the researchers. "Thus, amphibian-derived antimicrobial peptides show promise as topical inhibitors of mucosal HIV transmission and provide novel tools to understand the complex biology of HIV capture by DC's."

(S.E. VanCompernolle, R.J. Taylor, K. Oswald-Richter, J. Jiang, B.E. Youree, J.H. Bowie, M.J. Tyler, J.M. Conlon, D. Wade, C. Aiken, T.S. Dermody, V.N. KewalRamani, L.A. Rollins-Smith, D. Unutmaz. 2005. Antimicrobial peptides from amphibian skin potently inhibit human immunodeficiency virus infection and transfer of virus from dendritic cells to T cells. Journal of Virology, 79. 18: 11598-11606.)

New Method for Simultaneously Detecting Staphylococcal and Botulinum Toxins in Food

Researchers from Washington, DC have developed a new method that may allow for rapid simultaneous detection of staphylococcal and botulinum toxins in food. Their findings appear in the September 2005 issue of the journal Applied and Environmental Microbiology.

Staphylococcal enterotoxin B (SEB) and botulinum toxin A (BotA) are common causes of food poisoning in humans and pose high risk as potential biological warfare agents. In the study canned tomatoes, sweet corn, green beans, mushrooms and tuna were spiked with both toxins and left at room temperature for two hours. Researchers used the Naval Research Laboratory array biosensor to detect for the presence of SEB and BotA and found it capable of rapidly and simultaneously identifying both toxins in complex food matrices.

"Here we demonstrate the rapid, simultaneous dose-dependent detection of staphylococcal enterotoxin B and botulinum toxin A, as measured using the Naval Research Laboratory array sensor" say the researchers. "The ability to carry out multianalyte detection in complex samples is a clear advantage for screening food, water, or air samples for hazards either naturally occurring or deliberately introduced."

(K.E. Sapsford, C.R. Taitt, N. Loo, F.S. Ligler. 2005. Biosensor detection of botulinum toxoid A and staphylococcal enterotoxin B in food. Applied and Environmental Microbiology, 71. 9: 5590-5592.)

American Society for Microbiology

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