Use of eschar swabbing for the molecular diagnosis and genotyping of Orientia tsutsugamushi causing scrub typhus in Quang Nam province, Vietnam

Abstract

BackgroundScrub typhus is a rickettsiosis which is caused by Orientia tsutsugamushi and occurs throughout the Asia-Pacific region. Molecular diagnosis of rickettsioses using eschar swabs has recently emerged, and may be very useful for the diagnosis of these diseases in tropical settings.Methodology/Principal findingsQuantitative polymerase chain reaction (qPCR) was used to detect O. tsutsugamushi DNA in whole blood and eschar swab specimens of 67 patients who were clinically suspected of scrub typhus in Quang Nam province, Vietnam. Among the 20 patients for whom both eschar and whole blood were obtained, 17 (85%) of the eschar specimens and 5 (25%) of the whole blood specimens tested positive for O. tsutsugamushi. Genetic analysis of the 56-kDa TSA gene sequences demonstrated that the 14 sequences obtained in this study, including 12 eschar swabs and 2 whole blood specimens, were related to 4 groups: Karp, Kawasaki, Gilliam (JG-v and TG-v) and TA716. The majority (9/14; 64.4%) of contemporary O. tsutsugamushi genotypes in Quang Nam province were related to the Karp group.ConclusionsThese results suggest that polyclonal antigen pools used for serological testing in the future should contain at least Karp, Kawasaki, Gilliam and TA716 antigens for Vietnamese patients, as well as patients who have traveled to Vietnam. qPCR after eschar swabbing should be considered for molecular diagnosis of scrub typhus in endemic patients as well as in travelers, since it is easy to perform and appears very useful for the rapid detection of Orientia tsutsugamushi in the early phase of infection.

Diagnosis of severe scrub typhus infection by next-generation sequencing:a case report

“…Scrub typhus is a natural epidemic caused by Orientia tsutsugamushi, spread globally, mainly in the Asia-Pacific region [1,3,5] and is considered as the world's leading rickettsial infection, threatening the health of one billion people every year and causing more than one million deaths [10]. The hosts of Orientia tsutsugamushi are larvae and rats, while it could also infect humans and spread through the sputum in grass or soil on the floor [2].…”

“…For example, the indirect fluorescent antibody test needs a four-fold rise in titers over a 14-day period [4]. Polymerase chain reaction testing is only used as confirmatory test, but not as a screening test, because of multiple pathogenic bacterium in the clinic [5]. The culture of Orientia tsutsugamushi was very difficult and dangerous, and should be accomplished at a special research institution [6].…”

A review of the global epidemiology of scrub typhus

“…Differing from past studies, current studies and case reports of scrub typhus in Vietnam have been focused on the northern part of the country. There was only one study in the central part of Vietnam, Quang Nam province, which identified that the main genotype in the area was the Karp group [ 180 ]. Recent studies of scrub typhus in North Vietnam demonstrated that the cumulative incidence of scrub typhus was about 1.1% among the general population, and ~3.5% among patients admitted to hospitals [ 103 , 105 ].…”

Tifus de los matorrales, una enfermedad emergente en Chile

“…El comportamiento de las diversas técnicas serológicas varía dependiendo de varios factores, entre ellos la cepa presente en cada localidad 18,19 . El cultivo requiere de instalaciones de bioseguridad III, por lo que la RPC constituye el mejor método de confirmación, siendo el material de la escara la muestra más recomendada, pues además de otorgar la mayor sensibilidad, permanece positiva aún varios días después de iniciado el tratamiento antimicrobiano 20,21 . Otros materiales para el diagnóstico molecular incluyen un hisopado de la base de la escara y el buffy coat (leucocitos separados de sangre con EDTA).…”