By Dean L. Winslow, MD, FACP, FIDSA

Professor of Medicine, Division of General Medical Disciplines, Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine

Dr. Winslow reports no financial relationships relevant to this field of study.

SYNOPSIS: Broad polymerase chain reaction screening followed by multilocus sequence typing is a useful method to understand the geographic distribution of Borrelia species causing human disease. Candidatus B. johnsonii (carried by bat ticks) was not known previously to infect humans. Its identification in a human patient suggests it may cause a relapsing fever syndrome.

SOURCE: Kingry LC, Anacker M, Pritt B, et al. Surveillance for and discovery of Borrelia species in U.S. patients suspected of tickborne illness. Clin Infect Dis 2018;66:1864-1871.

Providers throughout the United States submitted 7,292 de-identified blood and other body fluid specimens from patients who were suspected to have a tickborne disease to the U.S. Centers for Disease Control and Prevention (CDC). Researchers screened the specimens initially by employing a Borrelia genus-level TaqMan polymerase chain reaction (PCR) followed by characterizing the species and sequence types of Borrelia with multilocus sequence typing (MLST) using next-generation sequencing. Researchers identified five Borrelia species among these 7,292 specimens. The two species causing the clinical syndrome of Lyme borreliosis (LB) were Borrelia burgdorferi (n = 25) and Borrelia mayonii (n = 9). The three species causing the clinical syndrome of relapsing fever (RF) were Borrelia hermsii (n = 1), Borrelia miyamotoi (n = 8), and Candidatus Borrelia johnsonii (n = 1). The latter species was identified previously only in Carios kelleyi (bat ticks). The researchers found that sequence type (ST) diversity was greatest for specimens that were positive for B. burgdorferi, and these diverse STs were identified primarily in synovial fluids.

COMMENTARY

I found this to be a very interesting study. The novel species Candidatus B. johnsonii was identified in a human patient with a relapsing fever illness in Wisconsin. Previously, this species had been identified only in bat ticks from a farmhouse in Iowa. The one specimen positive for B. hermsii came from a patient in Montana. The B. miyamotoi-positive specimens came from patients in Minnesota, Wisconsin, and New Jersey. The B. mayonii-positive specimens all came from Minnesota or Wisconsin. Not surprisingly, the specimens of B. burgdorferi all originated from eight states in the regions of the Midwest, mid-Atlantic, and Northeast (Iowa, Maryland, Minnesota, Missouri, New Jersey, New York, Pennsylvania, Virginia, and Wisconsin). This study emphasizes the growing clinical importance of broad-range PCR and NGS to identify human pathogens.