Tips from the journals of the American Society for Microbiology

December 18, 2009

New Nasal Vaccine Blocks Parasite Transmission to Mosquitoes

An experiemental nasally administered malaria vaccine prevented parasite transmission from infected mice to mosquitoes and could play an important role in the fight against human malaria. The researchers from Japan report their findings in the December 2009 issue of the journal Infection and Immunity.

Malaria is one of the most significant infectious diseases affecting developing countries and is often prominent in children. Mortality and morbidity levels are high and although antimalarial drug chemotherapy and insecticide-treated bed nets have somewhat reduced the number of malaria infections, additional prevention and treatment methods such as vaccines are needed for local elimination and ultimately complete eradication. Prior studies show that the ookinete-to-oocyst phase in the malaria life cycle, when the malarial parasite is fertilized in the mosquito's body, is one of the most vulnerable stages making it an ideal target for antitransmission vaccines.

In the study researchers developed a nasal vaccine based on ookinete-surface proteins (OSPs or also known as parasite antigens) and intranasally vaccinated mice infected with malaria. When given in conjunction with the cholera toxin adjuvant vaccinated mice developed a robust antibody response and completely prevented trasmission of the parasite to mosquitoes that were allowed to feed on them after infection.

"To our knowledge, this is the first time that mucosal vaccination has been demonstrated to be efficacious for directly preventing parasite transmission from vaccinated animals to mosquitoes, and the results may provide important insight into rational design of nonparenteral vaccines for use against human malaria," say the researchers.

(T. Arakawa, M. Tachibana, T. Miyata, T. Harakuni, H. Kohama, Y. Matsumoto, N. Tsuji, H. Hisaeda, A. Stowers, M. Torii, T. Tsuboi. 2009. Malaria ookinete surface protein-based vaccination via the intranasal route completely blocks parasite transmission in both passive and active vaccination regimens in a rodent model of malaria infection. Infection and Immunity, 77. 12: 5496-5500.)

Antimicrobial Peptide Discovered from Ancient Organism May Be Effective Against Multiresistant Human Pathogens Including MRSA

Researchers from Germany have identified a new antimicrobial peptide that demonstrates significant activity against a variety of bacteria, including multiresistant human strains such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). The discovery was made while investigating the ancient metazoan organism Hydra magnipapillata. The researchers from Christian-Albrechts-University and the University Medical Center Schleswig-Holstein Campus, Kiel, Germany report their findings in the December 2009 issue of the journal Antimicrobial Agents and Chemotherapy.

While occurrences of multidrug-resistant infections continue to increase, the discovery and development of drugs effective against these bacterial strains have slowed. Once commonly thought of as a hospital-acquired infection, MRSA has now spread to the community (now known as community acquired or CA-MRSA) and is infecting previously healthy young people who have not been recently hospitalized or undergone a medical procedure. Past research has proven that ancient organisms are well equipped at preventing infectious pathogens from entering the body and given the desperate need for new drug targets, further exploration of these organisms is warranted.

MRSA has already developed resistance to CA-MRSA human antimicrobial peptides and prior studies have shown antibacterial immune responses in the simple metazoan Hydra magnipapillata to include bactericidal peptides with novel structural features and modes of action. In the study researchers identified the antimicrobial peptide arminin 1a from Hydra and found that it exhibited significant and wide-spread activity against bacteria including MRSA and enterococci, a common cause of nosocomial infections that is also drug-resistant. Further observations revealed that bacteria are killed when the bacterial cell wall is disrupted and the antibacterial activity of arminin 1a isn't affected by exposure to salt in human blood. Finally, researchers determined that arminin 1a doesn't share any ancestry with any known antimicrobial peptides.

"Our data suggest that ancient metazoan organisms such as Hydra hold promise for the detection of novel antimicrobial molecules and the treatment of infections caused by the multiresistant bacteria," say the researchers.

(R. Augustin, F. Anton-Erxleben, S. Jungnickel, G. Hemmrich, B. Spudy, R. Podschun, T.C.G. Bosch. 2009. Activity of the novel peptide arminin against multiresistant human pathogens shows the considerable potential of phylogenetically ancient organisms as drug sources. Antimicrobial Agents and Chemotherapy, 53. 12: 5245-5250.)

New Filling, Cooling and Storage System May Prevent Bacterial Growth and Prolong Shelf Life of Orange Juice

Researchers from Brazil have estimated the growth timeline of a bacterium that causes orange juice spoilage during shelf life (approximately 6 months) and developed a safe and inexpensive filling, cooling, and storage protocol that inhibits bacterial growth and offers an alternative to other proposed treatments. They report their findings in the December 2009 issue of the journal Applied and Environmental Microbiology.

Alicyclobacillus sp. was first attributed to spoiled apple juice, or "off" flavors, in 1982 and Alicyclobacillus acidoterrestris is recognized as the most significant spoilage species within the family. Its ability to grow in a broad temperature range under acidic conditions and withstand heat allows for both survival during pasteurization and growth during juice storage and creates a continuous challenge for fruit juice and beverage industries worldwide.

Pasteurization followed by hot-fill or cold-fill processes are the two main methods used by the fruit juice industry to eradicate bacterial presence. Hot-filling, described as heating the product to approximately 200˚ Fahrenheit and holding for 15 to 20 seconds then filling into the package and cooling at room temperature, has been used extensively to process fruit drinks, however, the extended time that the product is maintained at room temperature allows for growth of bacteria such as A. acidoterrestris that can thrive in a wide temperature range. In the study researchers estimated and compared growth timelines of A. acidoterrestris in hot-filled orange juice following pasteurization that was cooled and stored in various conditions ranging from 68˚ to 95˚ Fahrenheit and inoculated with two different amounts of the bacterium. Only one treatment involving storage at 68˚ completely inhibited A. acidoterrestris growth for the full 6-month shelf life.

"In conclusion, treatment 5 (storage at 20˚ C) was more efficient than any of the others since in this case the A. acidoterrestris population remained inhibited for the entire shelf-life of the orange juice," say the researchers. "This measure can be considered a safe, easy, and inexpensive alternative procedure to avoid A. acidoterrestris growth during the orange juice shelf-life."

(A.C.N.F. Spinelli, A.S. Sant'Ana, S. Rodrigues-Junior, P.R. Massaguer. 2009. Influence of different filling, cooling, and storage conditions on the growth of Alicyclobacillus acidoterrestris CRA7152 in orange juice. Applied and Environmental Microbiology, 75. 23: 7409-7416.)

American Society for Microbiology

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