Tips from the Journals of the American Society for Microbiology

Blue Light and Hydrogen Peroxide May Effectively Treat Biofilms That Cause Cavities and Gum Disease Blue light commonly used by dentists to cure resin fillings and hydrogen peroxide (H₂O₂) combined may be capable of reaching and treating bacteria in deep layers of biofilms that can cause cavities and gingivitis. The researchers from Hebrew University, Hadassah, Jerusalem, Israel and the University of California San Francisco report their findings in the July 2008 issue of the journal Antimicrobial Agents and Chemotherapy.

Most bacteria in nature exist in communities of biofilms, structures that serve as physical barriers and severely limit the effect of antibacterial agents. Oral biofilms are commonly associated with infections such as cavities, gingivitis and periodontal disease. With antibiotic resistance continually on the rise, researchers are exploring alternative sterilization methods to effectively treat biofilms.

In the study biofilms of Streptococcus mutans were exposed to wavelengths of visible light consisting of 400 to 500 nm for 30 to 60 seconds while in the presence of 3 to 300 mM of hydrogen peroxide. Microbial counts from each treated sample were compared with those of the control and results showed that visible light and hydrogen peroxide combined successfully penetrated all layers of the biofilm creating an antibacterial effect.

"The ability of noncoherent visible light in combination with H₂O₂ to affect bacteria in deep layers of the biofilm suggests that this treatment may be applied in biofilm-related diseases as a minimally invasive antibacterial procedure," say the researchers.

(D. Steinberg, D. Moreinos, J. Featherstone, M. Shemesh, O. Feuerstein. 2008. Genetic and physiological effects of noncoherent visible light combined with hydrogen peroxide on Streptococcus mutans in biofilm. Antimicrobial Agents and Chemotherapy, 52. 7: 2626-2631.)

Rotavirus Infection May Accelerate Type 1 Diabetes in Mice

New research out of Australia suggests that rotavirus, a common childhood infection, may accelerate type 1 diabetes development in prediabetic mice. The findings are reported in the July 2008 issue of the Journal of Virology.

Type 1 diabetes is a common autoimmune disease that occurs when insulin-producing pancreatic cells are selectively destroyed. Rotaviruses are the major causative agents of severe, dehydrating diarrhea in infants and children and they have been previously implicated in the exacerbation of type 1 diabetes development.

Nonobese diabetic mice have been shown to develop a similar form of autoimmune diabetes to that of human type 1 diabetes making them an ideal model candidate. In the study nonobese diabetic mice up to 12 weeks old were inoculated with murine rotaviruses and the rhesus monkey rotavirus. Following infection results showed that diabetes onset was significantly accelerated. Researchers also observed that exposure of nonobese diabetic mice to mouse rotavirus in a natural experiment also resulted in accelerated diabetes.

"These data provide the first evidence that rotavirus infection can accelerate diabetes development in an animal model," say the researchers.

(K.L. Graham, N. Sanders, Y. Tan, J. Allison, T.W.H. Kay, B.S. Coulson. 2008. Rotavirus infection accelerates type 1 diabetes in mice with established insulitis. Journal of Virology, 82. 13: 6139-6149.)

New Vaccine May Protect Against All Four Strains of Dengue Virus

Researchers from Maryland and South Carolina have developed a novel four-component vaccine that protects monkeys against all four strains of dengue virus and may potentially offer protection to the millions of humans at risk worldwide. They report their findings in the July 2008 issue of the Journal of Virology.

There are four distinct but similar strains of dengue virus causing more than 100 million annual infections worldwide. Tropical regions are at especially high risk where illness may range from mild symptoms to potentially fatal forms of dengue hemorrhagic fever and dengue shock syndrome. With all four strains of the virus sharing similar clinical presentation, epidemiology, and distribution, development of a vaccine offering multi-faceted protection has become a global health priority.

In the study researchers developed a tetravalent dengue virus vaccine by combining genes and proteins from all four dengue virus types as well as incorporating an adenovirus agent. Following intramuscular vaccination, rhesus macaques showed high antibody levels that neutralized all four of the dengue virus types. To further test the sustainability of the protective immune response, two separate live-virus challenges were administered at 4 and 24 weeks after the final inoculation. Results showed complete protection against dengue types 1 and 3 and significant protection against types 2 and 4.

"Results reported here demonstrate that the tetravalent dengue vaccine elicited a neutralizing antibody response to all four dengue virus stereotypes and provided both short-term and long-term protection against challenges from each of the four serotypes," say the researchers.

(K. Raviprakash, D. Wang, D. Ewing, D.H. Holman, K. Block, J. Woraratanadharm, L. Chen, C. Hayes, J.Y. Dong, K. Porter. 2008. A tetravalent dengue virus vaccine based on a complex adenovirus vector provides significant protection in rhesus monkeys against all four serotypes of dengue virus. Journal of Virology, 82. 14: 6927-6934.)

Source: American Society for Microbiology