http://www.infectiousdiseasenews.com/200707/bartonella.asp


Researchers have identified a previously uncultured and unnamed Bartonella species, Bartonella rochalimae, after extensive analysis, using genetic phylogeny from isolates of an American tourist.

The investigation began after a 43-year-old American woman visited Peru for three weeks. Sixteen days after returning to the United States, she had a fever, insomnia, myalgia, nausea, headache and mild cough. A fever lasting more than four days reached 102°F. She was treated and recovered.

Researchers from the CDC, the University of California Medical School in San Francisco, Massachusetts General Hospital and Harvard Medical School contributed to the isolation, genetic analysis and new species identification. Both the route of infection and the potential burden of the new pathogen in humans are yet unknown.

A case report and explanation of the species identification appeared in The New England Journal of Medicine.

The woman visited Lima, Nazca and several other areas of Peru, including Machu Picchu, and concluded her tour in the Amazon Basin. She received numerous insect bites during the trip.

Her symptoms began 16 days after her return. Six days before presentation, she had a diffuse macular rash and sought clinical care eight days after her fever began. Microscopic examinations of blood smears showed no bacterial or malaria parasites within erythrocytes. A traveling companion showed no sign of illness.

Because of the woman’s symptoms and travel history, researchers assumed the infection was caused by a known Bartonella species, B. bacilliformis, which is endemic to Peru and causes Oroya fever.

A blood sample was cultured and an isolate was recovered. DNA was extracted from the isolate, and partial sequences of four genes were used to generate a phylogenic tree to determine the relation of the isolate to other species of Bartonella. The characterized isolate also was inoculated into a rhesus macaque to examine its ability to cause disease.

When viewed using electron microscopy, the new isolate appeared identical to B. clarridgeiae and B. bacilliformis. However, genetic analysis revealed a close relation to B. clarridgeiae, but not to B. bacilliformis. Furthermore, comparison of the sequences of several genes revealed that although the new Bartonella isolate is closely related to B. clarridgeiae, it represents a distinct new Bartonella species.

The Bartonella genus now includes 19 officially recognized and extant species and subspecies. In 1992, the genus consisted of only a single species. In the 1990s, B. henselae was identified as a new species. It causes bacteremia and bacillary angiomatosis in people with AIDS, and cat scratch disease in immunocompetent people.

The new species is described as a small, motile, fastidious gram-negative rod with multiple, unipolar flagella. It differs genetically from other Bartonella species because of its unique sequences of 16S rDNA, gltA and rpoB genes and 16S-23S intergenic spacer region.

B. rochalimae was named in honor of an early Brazilian researcher who studied rickettsial diseases, Henrique da Rocha Lima, MD.