Rickettsia amblyommatis sp. nov., a spotted fever group Rickettsia associated with multiple species of Amblyomma ticks in North, Central and South America

Abstract

In 1973, investigators isolated a rickettsial organism, designated strain WB-8-2T, from an adult Amblyomma americanum tick collected at Land Between the Lakes National Recreation Area, TN, USA. This organism is now recognized as highly prevalent in A. americanum, as well as several other Amblyomma species found throughout the Western hemisphere. It has been suggested that cross-reactivity to WB-8-2T and similar strains contributes to the increasing number of spotted fever cases reported in the USA. In 1995, investigators provided preliminary evidence that this strain, as well as another strain from Missouri, represented a distinct taxonomic unit within the genus Rickettsia by evaluating sequences of the 16S rRNA and 17 kDa protein genes. However, the bacterium was never formally named, despite the use of the designation ‘Rickettsia amblyommii’ and later ‘Candidatus Rickettsia amblyommii’, for more than 20 years in the scientific literature. Herein, we provide additional molecular evidence to identify strain WB-8-2T as a representative strain of a unique rickettsial species and present a formal description for the species, with the proposed name modified to Rickettsia amblyommatis sp. nov. to conform to the International Code of Nomenclature of Prokaryotes. We also establish a pure culture of strain WB-8-2T and designate it as the type strain for the species. The type strain is WB-8-2T (=CRIRC RAM004T=CSURP2882T).

Ticks and tick-associated spotted fever group Rickettsia from birds in the southwestern Brazilian Amazon

“…In these previous studies, R. amblyommatis was reported as R. amblyommii or 'Candidatus R. amblyommii'. However, a recent study reassessed the taxonomic status of this agent, which is now validated as R. amblyommatis (Karpathy et al, 2016). Despite a nearly widespread distribution of tick infection by these two rickettsial agents in South America, including the Amazon region, their role as human pathogens remains unknown.…”

Vector competence of Amblyomma americanum (Acari: Ixodidae) for Rickettsia rickettsii

“…In 1973, W. Burgdorfer and colleagues identified a novel spotted fever group Rickettsia in questing lone star ticks, which was provisionally designated as “ Rickettsia amblyommii ” (Burgdorfer et al, 1981b; Stothard and Fuerst, 1995). This endosymbiotic bacterium, only recently formally named Rickettsia amblyommatis (Karpathy et al, 2016), has since been detected in most of the examined populations of A. americanum with prevalence of infection often exceeding 40% (reviewed by Karpathy et al, 2016). As transovarial maintenance of multiple infections of Rickettsia spp.…”

Rickettsiasp. Strain NOD Infecting Ticks (Amblyomma nodosum) in an Endemic Area of Spotted Fever in Brazil

“…Rickettsia sp. strain NOD (Ogrzewalska et al 2009), Rickettsia bellii (Moerbeck et al 2016), and Rickettsia amblyommatis (¼Rickettsia amblyommii; Karpathy et al 2016) are rickettsial organisms known to infect A. nodosum. Although there are no records of human infestations by A. nodosum, evidence of rickettsial infections and wide distribution of their host species suggest A. nodosum as a potential vector in the enzootic cycle of rickettsiae (Guglielmone et al 2014).…”