Tips from the Journals of the American Society for Microbiology

August 15, 2003


An antimicrobial cocktail consisting of phages and the bacteriocin, nisin, may prove effective at decontaminating fresh-cut produce say researchers from Maryland and West Virginia. Their findings appear in the August 2003 issue of the journal Applied and Environmental Microbiology.

Although the fresh-cut produce industry provides easily accessible and nutritious foods, consumers are more likely to contract illnesses associated with foodborne pathogens due to nutrients on cut surfaces and excessive handling. Listeria monocytogenes, a bacterium commonly found in fresh-cut fruits and vegetables, is believed to be the cause of many severe foodborne outbreaks.

In the study, honeydew melons and apples were artificially contaminated with L. monocytogenes and treated with lytic, L. monocytogenes-specific phages alone and in combination with the bacteriocin, nisin. Results showed that the phage cocktail independent of ,and in conjunction with nisin, reduced L. monocytogenes contamination on fresh-cut produce.

"Phage and nisin applications reduce pathogenic bacterial contamination and growth on produce, and when implemented can contribute to the microbial safety of fruits and vegetables."

(B. Leverentz, W.S. Conway, M.J. Camp, W.J. Janiesiewicz, T. Abuladze, M. Yang, R. Saftner, A. Sulakvelidze. 2003. Biocontrol of Listeria monocytogenes on fresh-cut produce by treatment with lytic bacteriophages and a bacteriocin. Applied and Environmental Microbiology, 69. 8: 4519-4526.)


A vaccine administered through the nasal passages may increase protection against pneumococcal disease compared to the current vaccine, say researchers from Albany Medical College in New York and the University of Alabama at Birmingham. Their findings appear in the August 2003 issue of the journal Infection and Immunity.

Streptococcus pneumoniae, a common cause of bacterial pneumonia, generally enters the body through the nose. While the current intramuscular immunizations are effective in fighting the disease, their ability to protect against bacterial carriage in the nasal passages is only fifty to sixty percent.

In the study, mice were immunized intranasally, treated with interleukin-12 to enhance mucosal immune response and then challenged with varying strains of S. pneumoniae. The researchers found a seventy-five percent survival rate of vaccinated mice as opposed to a rate of zero percent in those not vaccinated. Additionally, vaccinated mice showed fewer bacterial colonies in the upper respiratory tract.

"The nasal mucosa is the first point of contact for inhaled antigens, and as a consequence, intranasal immunization has emerged as potentially the most effective route of vaccination for both peripheral and mucosal immunity," say the researchers. "Intranasal vaccination may be a new approach that could be combined with standard vaccination strategies to give optimal protection both systemically and at mucosal surfaces."

(J.M. Lynch, D.E. Briles, D.W. Metzger. 2003. Increased protection against pneumococcal disease by mucosal administration of conjugate vaccine plus interleukin-12. Infection and Immunity, 71. 8: 4780-4788.)


Researchers from Germany have genetically engineered plants to produce particles of human papillomavirus (HPV) that could be used in the creation of vaccines or as edible vaccines themselves. They report their findings in the September 2003 issue of the Journal of Virology.

"Cervical cancer is linked to infection with HPV and is the third most common cancer among women worldwide. There is a strong demand for the development of an HPV preventive vaccine," say the researchers.

In the study, the researchers genetically engineered tobacco and potato plants to produce a major structural protein of HPV. When the protein was purified and administered to mice, it induced an immune response. When the potatoes were fed to mice, they also induced an immune response, though not as significant.

"Here, we demonstrated as a first step that it is possible to produce transgenic plants expressing the HPV-16 L1 protein in a form appropriate for immunization purposes," say the researchers.

(S. Biemelt, U. Sonnewald, P. Galmbacher, L. Willmitzer, and M. Muller. 2003. Production of human papillomavirus type 15 virus-like particles in transgenic plants. Journal of Virology, 77: 9211-9220.)

American Society for Microbiology

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