The best antibiotics to treat Borrelia miyamotoi?
Borrelia miyamotoi, first described in Japan in 1995, is a relapsing fever spirochete which can cause hard tick-borne relapsing fever (HTBRF), an emerging infectious disease. The infection is transmitted by the same blacklegged tick which carries the Lyme disease pathogen. In “Antimicrobial susceptibility of Borrelia miyamotoi,” researchers examine the effectiveness of several antibiotic regimes in the treatment of HTBRF.
by Daniel J. Cameron, MD MPH
In the United States, as many as 15.4% of the blacklegged ticks were found to be infected with B. miyamotoi, compared with up to 4% in Europe and Japan, according to Koetsveld from the Center for Experimental and Molecular Medicine, Academic Medical Center, Amsterdam, the Netherlands. 
The B. miyamotoi spirochete is related to other relapsing fever spirochetes, such as Borrelia hermsii, Borrelia turicatae, and Borrelia recurrentis. But the clinical presentation differs from classical relapsing fevers. “Recurrent fever episodes have only been observed in 10% [of the cases] and spirochetemia is calculated to be low in patients infected with B. miyamotoi,” Koetsveld explains in Antimicrobial Agents Chemotherapy.  Fever episodes last for three days and are accompanied by flu-like symptoms such as headache, chills, abdominal discomfort, arthralgia and myalgia.Researchers find doxycycline, azithromycin & ceftriaxone are best at treating B. miyamotoi in vitro. Click To Tweet
Meningoencephalitis caused by B. miyamotoi has been described in 3 patients receiving B-cell depleting therapy in the Netherlands, Germany and the United States. Typically, the full clinical spectrum becomes clearer over time as tests become available and as doctors become more familiar with the disease.
Until now, there have been no treatment guidelines for B. miyamotoi and regimes have been empirically based on the treatment for Lyme disease. “The antimicrobial susceptibility of B. miyamotoi has not yet been elucidated, due to difficulties with cultivation of B. miyamotoi spirochetes in vitro,” according to Koetsveld.
“In this study we describe, to our knowledge for the first time, in vitro susceptibility of B. miyamotoi to the most commonly used antibiotics” in the treatment of B. miyamotoi and Lyme borreliosis.
The study authors demonstrated that B. miyamotoi is susceptible to doxycycline, azithromycin, and ceftriaxone but resistant to amoxicillin in vitro. The next step would be to show whether these drugs work in patients.
- Koetsveld J, Draga ROP, Wagemakers A, et al. In vitro susceptibility of the relapsing fever spirochete Borrelia miyamotoi to antimicrobial agents. Antimicrob Agents Chemother. 2017.