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Tips from the Journals of the American Society for Microbiology

American Society for Microbiology

New Test May Simultaneously Identify Herpesviruses, Enteroviruses, and Flaviviruses

Researchers from France may have developed a new method of simultaneously detecting viruses from three different families that cause diseases of the central nervous system in humans. Their findings appear in the August 2005 issue of the Journal of Clinical Microbiology.

Viruses afflicting the central nervous system are mostly caused by herpesviruses, enteroviruses, and flaviviruses. Human herpesvirus can lead to serious diseases such as encephalitis, myelitis, and meningitis. Eighty to ninety-two percent of aseptic meningitis cases are caused by human enteroviruses as well as several poliovirus serotypes. Tick-borne encephalitis and West Nile encephalitis are two of many viruses belonging to the flavivirus family.

In the study a new diagnostic tool that uses reactive primers to detect for each family of viruses followed by DNA probe technology to differentiate between virus species within each family was tested. Researchers were able to accurately identify herpesviruses, specifically herpes simplex virus type 1 and 2, all serotypes of human enteroviruses and five flaviviruses including West Nile, Dengue, and Langat virus.

"This approach, which used highly conserved consensus primers for amplification and specific sequences for identification, would be extremely useful for the detection of variants and would probably help solve some unexplained cases of encephalitis," say the researchers.

(J. Korimbocus, N. Scaramozzino, B. Lacroix, J.M. Crance, D. Garin, G. Vernet. 2005. DNA probe array for the simultaneous identification of herpesvirus, enteroviruses, and flaviviruses. Journal of Clinical Microbiology, 43. 8: 3779-3787.)

Olives May Successfully Transmit Beneficial Bacteria to Humans

Table olives may serve as a carrier for delivering beneficial bacteria to humans, according to researchers from Italy. Their findings appear in the August 2005 issue of the journal Applied and Environmental Microbiology.

Probiotic foods contain healthy bacteria intended to promote microbial balance, inhibit pathogens and protect humans from gastrointestinal diseases. Researchers are also investigating their role in reducing risk of cancer, preventing food allergies, and alleviating symptoms of lactose intolerance.

The researchers studied survival rates of various strains of four probiotic bacteria, Lactobacillus rhamnosus, Lactobacillus paracasei, Bifidobacterium bifidum, and Bifidobacterium longum, on table olives at room temperature. L. paracasei was noted for its survival on olives throughout the three month experiment and was recovered from fecal samples in four out of five volunteers who consumed 10 to 15 olives per day for 10 days.

"The results reported here suggest that table olives are a suitable substrate for delivering probiotic species, since populations of L. paracasei, a strain selected for its potential probiotic characteristics assessed in vitro and for its lengthy survival on olives, were detected in the feces of human volunteers," say the researchers. "This result meets one of the aims of the current research, that of finding new delivery systems ensuring the stability and viability of strains."

(P. Lavermicocca, F. Valerio, S.L. Lonigro, M.D. Angelis, L. Morelli, M.L. Callegari, C.G. Rizzello, A. Visconti. 2005. Study of adhesion and survival of lactobacilli and bifidobacteria on table olives with the aim of formulating a new probiotic food. Applied and Environmental Microbiology, 71. 8: 4233-4240.)

Oral Vaccine from Bacterial Ghosts May Protect Against E. coli

Researchers from Austria and Russia have developed an oral vaccine comprised of bacterial ghosts, or empty bacterial envelopes, which may protect against E. coli in animals and humans. Their findings appear in the August 2005 issue of the journal Infection and Immunity.

Enterohemorrhagic Escherichia coli (EHEC) is a bacterial pathogen associated with several life threatening diseases in humans. O157:H7, one of the most harmful and frequently studied strains of the bacteria can cause intestinal inflammation ranging from diarrhea to hemorrhagic colitis, with more severe cases afflicting children and the elderly. EHEC O157:H7 has also been identified as a bioterrorism agent. There is currently no specific treatment against EHEC infection and antibiotics are not recommended as they prompt the liberation of toxins which can worsen the clinical course of the disease.

Because the major reservoir for EHEC O157:H7 is cattle, researchers are focusing on a vaccine that will prevent infection in both humans and animals. In order to mimic the bacteria's natural route of infection they developed an oral vaccine in hopes of eliciting local immunity in the gut.

In the study production of the protein E-mediated lysis was controlled to produce EHEC bacterial ghosts, or non-living bacterial cell envelopes. They have the same surface components of live cells and are capable of inducing strong immune responses, but the lack of genetic material inhibits transfer of resistance genes. An oral vaccine containing the bacterial ghosts was administered to mice that were challenged with a lethal dose of the EHEC strain 55 days later. A single dose of the vaccine resulted in an 86 percent protection rate and mice receiving a booster after 28 days showed a 93 percent survival rate. Non-immunized mice challenged with the bacteria had a 26 to 30 percent rate of survival.

"Bacterial ghosts as candidate vaccines and carriers of foreign viral and/or bacterial antigens are under development as multivalent vaccines against diarrheal diseases of humans and might represent new, improved nonliving bacterial vaccines with excellent safety properties and high immunological potential," say the researchers.

(U.B. Mayr, C. Haller, W. Haidinger, A. Atrasheuskaya, E. Bukin, W. Lubitz, G. Ignatyev. 2005. Bacterial ghosts as an oral vaccine: a single dose of Escherichia coli O157:H7 bacterial ghosts protects mice against lethal challenge. Infection and Immunity, 73. 8: 4810-4817.)


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