Tipsheet: April journals of the American Society for Microbiology

Test distinguishes between animal and human bacterial pollution

Researchers from the University of Missouri have developed a test that can differentiate between human and animal sources of fecal bacterial pollution. They report their results in the April 2001 issue of the journal Applied and Environmental Microbiology.

The test, called ribotyping, is a DNA-based test used to identify and classify bacteria based on genetic differences. This type of test has been commonly used to identify bacteria but has only recently has it been enlisted to differentiate between human and animal sources of fecal bacteria.

In the study, the researchers tested the ability of ribotyping to not only distinguish between human and animal sources of fecal bacteria, but also to identify the source as one of seven different types of animals: cattle, swine, horses, chickens, turkeys, dogs and migratory geese. The test had an accuracy of over 97% in distinguishing between human and nonhuman sources, and had a high degree of accuracy identifying the animal source.

"Fecal polution of water resources is an environmental problem of increasing importance. Identification of individual host sources of fecal Escherichia coli, such as humans, pets, production animals and wild animals is a prerequisite to formulation of remediation plans," say the researchers. "Application of this technique to identification of host sources of fecal coliforms in water could assist in formulation of pollution reduction plans.

(C.A. Carson, B.L. Shear, M.R. Ellersieck and A. Asfaw. 2001. Identification of fecal Escherichia coli from humans and animals by ribotyping. Applied and Environmental Microbiology, 67: 1503-1507.)

Influenza treatment may enable resistance

The influenza virus may be developing resistance to a drug recently approved for the prevention and treatment of the disease, say researchers from Japan. They report their results in the April 2001 issue of the Journal of Clinical Microbiology.

The drug, known as amantadine, has only recently been approved for the prevention and treatment of influenza in Japan, but had been widely used for years to treat symptoms of Parkinson's disease and other neuropsychiatric disorders. The researchers studied Japanese patients on long-term amantadine therapy for these disorders who developed influenza. Two of the influenza viruses isolated were amantadine resistant.

"This is the first report of isolation of amantadine-resistant viruses from patients receiving long-term amantadine treatment for Parkinsonism, neurpsychiatric disorders and apathy due to cerebral infarction," say the researchers. "Our results indicate that the amantadine-resistant viruses may naturally circulate and emerge from patients receiving long-term treatment with amantadine."

In the United States, amantadine is also approved for treatment of Parkinson's and influenza. The drug is also currently being tested as a treatment for chronic hepatitis C.

(J. Iwahashi, K. Tsuji, T. Ishibashi, J. Kajiwara, Y. Imamura, R. Mori, K. Hara, T Kashiwagi, Y. Ohtsu, N. Hamada, H. Maeda, M. Toyoda, and T. Toyoda. 2001. Isolation of amantadine-resistant influenza A viruses (H3N2) from patients following administration of amantadine in Japan. Journal of Clinical Microbiology, 39: 1652-1653.)

Tuberculosis protein reactivates waning immunity

Researchers from Colorado State University have developed a strategy for bolstering the waning effectiveness of the current tuberculosis vaccine in adults. They report their findings in the April 2001 issue of the journal Infection and Immunity.

"For several decades the Mycobacterium-bovis-derived bacillus Calmette-Guerin (BCG) has been the only widely used vaccie for tuberculosis and accumulating data from clinical trials and subsequent meta-analysis have tended to reveal its general ineffectiveness in adults," say the researchers. "The mechanism underlying the gradual loss of effectiveness of BCG as the individual reaches 10 to 15 years of age is poorly understood."

The researchers believe that one possible reason for declining effectiveness is that the immune system's memory slowly declines over time. One way to reverse this effect, say the researchers, is to reintroduce the immune system to tuberculosis by exposing it to a harmless protein from the bacterium. They tested one of these proteins (Ag85A) on mice who had previously been vaccinated with BCG. Those mice that received the Ag85A booster before their immunity began to decline retained their ability to fight tuberculosis infection better than the mice who did not or received a mix of tuberculosis proteins instead.

"While there is a desperate need to develop new tuberculosis vaccines to deal with the global emergency in general, in more developed countries tuberculosis continues to be relatively common in elderly people," say the researchers. "While primary tuberculosis sometimes occurs in these individuals, the majority of cases are thought to be due to reactivation of latent disease acquired decades earlier. In view of this, the vaccine strategy espoused here may also have applications to prevention of reactivation tuberculosis in the elderly."

(J.V. Brooks, A.A. Frank, M.A. Keen, J.T. Bellisle and I.M. Orme. 2001. Boosting vaccine for tuberculosis. Infection and Immunity, 69: 2714-2717.)

Copies of the full articles referenced above can be accessed through the ASM Website at: http://www.asmusa.org/pcsrc/tip.htm.