American Society for Microbiology news tips for November 2000

November 15, 2000

Genetic diversity suggests congo as source of hiv epidemic

An extremely high level of genetic diversity among HIV isolates taken in the Democratic Republic of Congo (DRC) suggests that the HIV-1 pandemic originated in central Africa, say researchers from France, Congo and the United Kingdom in the November 2000 issue of the Journal of Virology. The most common form of the HIV virus, HIV-1 group M, is known to have at least 9 genetic variations, known as subtypes. In the study, the researchers tested 247 HIV isolates in the DRC (formerly known as Zaire) to determine the genetic diversity of HIV-1 infections in that part of Africa. While they found one specific subtype was dominant in the area, they found smaller populations infected with the other 8 subtypes. In contrast, only 3 of the subgroups are found at any significant level in surrounding African nations.

"Overall, the high number of HIV-1 subtypes cocirculating, the high intrasubtype diversity and the high numbers of possible recombinant viruses as well as different unclassified strains are all in agreement with an old and mature epidemic in the DRC, suggesting that this region is the epicenter of HIV-1 group M," say the researchers.

(N. Vidal, M. Peeters, C. Mulanga-Kabeya, N. Nzilambi, D. Robertson, W. Ilunga, H. Sema, K. Tshimanga, B. Bongo and E. Delaporte. 2000. Unprecedented degree of human immunodeficiency virus type 1 group M diversity in the Democratic Republic of Congo suggests that the HIV-1 pandemic orginated in central Africa. Journal of Virology: 74: 10498-10507.)

Chlamydia not a cause of multiple sclerosis after all

Contrary to previously published reports, the organism Chlamydia pneumoniae may not play a role in the development of multiple sclerosis after all. Researchers from the State University of New York in Brooklyn, Hahnemann University in Philadelphia and Umea University in Sweden report their findings in the November 2000 issue of the Journal of Clinical Microbiology. Multiple sclerosis (MS) is a disease of the central nervous system (CNS) in which the immune system attacks the insulation that protects nerve fibers and promotes nerve impulse transmission. The exact cause of the disease is not known but some recent studies had found high levels of C. pneumoniae in the CNS of patients with MS suggesting that the organism may play a role in the development of the disease. In the study published this month, the researchers studied brain tissues taken from both MS patients and controls post mortem and tested for the presence of C. pneumoniae. All results were negative. No specimens were found to be infected. "In conclusion our studies on brain tissues do no confirm the recent identification of C. pneumoniae in the cerebrospinal fluid of MS patients," say the researchers.

M. Hammerschlag, Z. Ke, F. Lu, P. Roblin, J. Boman and B. Kalman. 2000. Is Chlamydia pneumoniae in brain lesions of patients with multiple sclerosis? Journal of Clinical Microbiology, 38: 4274-4276.)

E. coli bacteria find their way inside apples

The virulent E.coli O157:H7 bacterium may burrow its way into the core of unblemished apples, evading standard disinfection treatments, say researchers from the University of Georgia in the November 2000 issue of the journal Applied and Environmental Microbiology.

In the study the researchers looked at the ability of the bacteria to infiltrate the internal structure of apples. The skin of the fruit was punctured and the apples placed in plastic bags containing E. coli O157:H7 bacteria. They were then tested for bacterial contamination at the puncture wounds, on intact skin and in the internal structures that make up the apple core. While puncture wounds predictably harbored greater numbers of bacteria than other sites tested, bacteria were found at all sites including in the core. The researchers believe that the bacteria entered the core through the floral tube at the base of the apple.

"E. coli O157:H7 infections associated in recent years with the consumption of nonpasteurized apple juice have raised interest in developing efficacious methods to kill human pathogens that may be on raw apples," say the researchers. "Among the obstacles in achieving this goal is the probability that pathogens infiltrate tissues within produce, giving them protection against chemical sanitizers, physical methods of removal such as brushing or high-pressure spraying, or other commonly used interventions for cleaning and sanitizing."

(S. Burnett, J. Chen and L. Beuchat. 2000. Attachment of Escherichia coli O157:H7 to the surfaces and internal structures of apples as detected by confocal scanning laser microscopy. Applied and Environmental Microbiology, 66: 4679-4687.)
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American Society for Microbiology

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