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We previously wrote about diseases caused by Bartonella species that had been described in medical literature for more than a century before the bacteria that caused them were identified. For example, B. henselae was isolated from HIV patients experiencing unusual symptoms during the 1990s. Bartonella clarridgeiae and Bartonella koehlerae, two lesser known Bartonella species, were discovered as causative agents of bartonellosis during the same decade. They were first discovered in cats, then connected to humans, and eventually found in dogs as well.
Bartonella clarridgeiae
In the mid-1990s, the Veterans Affairs Medical Center in Houston, Texas, instituted a testing program for Bartonella species. In the first 16 months of testing they identified four infected people, two with HIV and two without. One of the patients with HIV was diagnosed with Bartonella henselae. When his new kitten was tested, an unidentified strain was found. This would later be called Bartonella clarridgeiae.
The first confirmed human case of B. clarridgeiae was reported in 1997. A veterinarian was bitten by a 6-week-old pet kitten and subsequently developed headache, fever and an inflamed lymph node. The cat tested seropositive for multiple strains of Bartonella, but the veterinarian did not. It took repeated cultures from the cat before the bacteria was isolated and found to be B. clarridgeiae.
Bartonella koehlerae
In 1999, a study of Bartonella samples collected from pet cats in the San Francisco Bay Area found two samples that were different from the rest of the samples, which contained Bartonella henselae. Researchers identified the samples as a new species which they named Bartonella koehlerae. Comparing it to the known Bartonella species, the researchers identified it as genetically closest to B. henselae.
The individual in the first human case was a 60-year-old man in Israel who had frequently fed stray cats. He reported fever and fatigue for eight months and then developed endocarditis. Simultaneous infections with Bartonella henselae (a cause of cat scratch disease) and Bartonella quintana (the cause of trench fever) were identified through an analysis of samples from his heart valves.
Because of the recent identification of Bartonella koehlerae in Israel, the case authors did further analysis of the bacteria sample. They found that rather than B. henselae, the man was infected with B. koehlerae. The case authors suggested performing DNA sequencing on PCR-positive samples to prevent mixing up Bartonella species. At Galaxy Diagnostics, this is exactly what we do after identifying a Bartonella species with our patented ePCR technology.
Conclusion
B. henselae and B. clarridgeiae are the primary species that cause cat scratch disease, but additional species of Bartonella continue to be identified right up to the current year. Unless PCR is confirmed with sequencing, it is possible that close variants of known species may come up in laboratory tests but not be correctly identified. When these species are identified, information about their pathogenic status remains to be investigated. Do they cause illness in the host in whom they were identified? Do they cause illness in other animals and humans? In the case of B. clarridgeiae and B. koehlerae, it took the combined work of attentive clinicians, laboratory professionals and researchers to identify them as pathogens.
References
Clarridge, III, J. E. et al. (1995). Strategy to detect and identify Bartonella species in routine clinical laboratory yields Bartonella henselae from Human Immunodeficiency Virus-positive patient and unique Bartonella strain from his cat. Journal of Clinical Microbiology, 33(8), 2107-2113. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC228344/pdf/332107.pdf
Kordick, D. L. et al. (1997). Bartonella clarridgeiae, a newly recognized zoonotic pathogen causing inoculation papules, fever, and lymphadenopathy (cat scratch disease). Journal of Clinical Microbiology, 35(7), 1813-1818. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC229848/pdf/351813.pdf
Gundi, V. A. K. B. et al. (2004). Bartonella clarridgeiae and B. henselae in dogs, Gabon. Emerging Infectious Diseases, 10(12), 2261-2262. doi:10.3201/eid1012.040359 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3323364/
Droz, S. et al. (1999). Bartonella koehlerae sp. nov., isolated from cats. Journal of Clinical Microbiology, 37(4), 1117-1122. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC88658/
Avidor, B. et al. (2004). Bartonella koehlerae, a new cat-associated agent of culture-negative human endocarditis. Journal of Clinical Microbiology, 42(8), 3462-3468. doi:10.1128/JCM.42.8.3462-3468.2004 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC497599/
Lashnits, E. et al. (2018). Bartonella seroepidemiology in dogs from North America, 2008-2014. Journal of Veterinary Internal Medicine, 32(1), 222-231. doi:10.1111/jvim.14890 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5787158/