Evaluation of the Diagnostic Accuracy of Antibody Assays for Patients with Scrub Typhus.

This study was carried out to evaluate the accuracy of various antibody tests for scrub typhus, namely, the indirect immunofluorescence assay (IFA) from the Korea Centers for Disease Control and Prevention (KCDC) and four commercial kits (companies A to D). The test accuracy was based on the diagnosis of scrub typhus, as defined by a positive PCR or culture. In total, serum samples from 97 patients with scrub typhus and 200 non-scrub typhus patients were tested. The respective sensitivity and specificity of each test were as follows. For the KCDC IFA, sensitivity and specificity were 55.7% (95% confidence interval [CI], 45.2 to 65.8%) and 94.8% (95% CI, 90.4 to 97.3%) for IgM and 42.3% (95% CI, 32.3 to 52.7%) and 96.3% (95% CI, 92.6 to 98.5%) for IgG, with diagnostic cutoffs of ≥1:16 for IgM and ≥1:256 for IgG. For kit A, the sensitivity and specificity were 70.1% (95% CI, 59.8 to 78.8%) and 74.6% (95% CI, 67.6 to 80.6%) for total immunoglobulins, with a cutoff of ≥1:40. For kit B, the sensitivity and specificity were 64.3% (95% CI, 51.9 to 75.1%) and 94.9% (95% CI, 81.4 to 99.1%) for IgM and 67.1% (95% CI, 54.8 to 77.6%) and 74.4% (95% CI, 57.6 to 86.4%) for IgG. For kit C, the sensitivity and specificity were 53.6% (95% CI, 43.2 to 63.7%) and 99.5% (95% CI, 96.8 to 100%) for IgM and 36.1% (95% CI, 26.8 to 46.5%) and 100% (95% CI, 97.6 to 100%) for IgG. For kit D, the sensitivity and specificity were 73.2% (95% CI, 63.1 to 81.4%) and 89.5% (95% CI, 84.2 to 93.2%) for total immunoglobulins. These results are all unsatisfactory, highlighting an urgent need for the development of more highly sensitive and specific tests.

Molecular detection and identification of Culex flavivirus in mosquito species from Jeju, Republic of Korea.

BACKGROUND: Mosquito-borne flaviviruses are prime pathogens and have been a major hazard to humans and animals. They comprise several arthropod-borne viruses, including dengue virus, yellow fever virus, Japanese encephalitis virus, and West Nile virus. Culex flavivirus (CxFV) is a member of the insect-specific flavivirus (ISF) group belonging to the genus Flavivirus, which is widely distributed in a variety of mosquito populations. METHODS: Viral nucleic acid was extracted from adult mosquito pools and subjected to reverse transcriptase nested polymerase chain reaction (PCR) using target-specific primers for detecting CxFV nonstructural protein 5 (NS5). The PCR-positive samples were then sequenced, and a phylogenetic tree was constructed, including reference sequences obtained from GenBank. RESULTS: 21 pools, belonging to Culex pipiens pallens (Cx. p. pallens) were found to be positive for the CxFV RNA sequence, with a minimum infection rate of 14.5/1000 mosquitoes. The phylogenetic analysis of the NS5 protein sequences indicated that the detected sequences were closely related to strains identified in China, with 95-98% sequence similarities. CONCLUSION: Our findings highlight the presence of CxFV in Cx. p. pallens mosquito species in Jeju province, Republic of Korea. This is the first study reporting the prevalence of CxFV in Culex Pipiens (Cx. pipiens) host in the Jeju province, which can create possible interaction with other flaviviruses causing human and animal diseases. Although, mosquito-borne disease causing viruses were not identified properly, more detailed surveillance and investigation of both the host and viruses are essential to understand the prevalence, evolutionary relationship and genetic characteristic with other species.

Performance assessment of ASTA MicroIDSys, a new matrix assisted laser desorption ionization-time of flight mass spectrometry system, for identification of viridans group streptococci.

The performance of the ASTA MicroIDSys system (ASTA), a new matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) system, was evaluated for the identification of viridans group streptococci (VGS) and compared with the results obtained with the Bruker Biotyper system (Bruker Daltonics). A total of 106 Streptococcus reference strains belonging to 24 species from the bacterial strain bank was analyzed using the two MALDI-TOF MS systems. Of the 106 reference strains tested, ASTA MicroIDSys and Bruker Biotyper correctly identified 84.9% and 81.1% at the species level, 100% and 97.2% at the group level and 100% and 98.1% at the genus level, respectively. The difference between the two systems was not statistically significant (P = 0.289). Out of 24 species, 13 species were accurately identified to the species level with 100% accurate identification rates with both systems. The accurate identification rates at the species level of ASTA MicroIDSys and Bruker Biotyper were 100% and 87.5% for the S. anginosus group; 78.4% and 73.5% for the S. mitis group; 91.7% and 91.7% for the S. mutans group; and 100% and 100% for the S. salivarius group, respectively. The ASTA MicroIDSys showed an identification performance equivalent to that of the Bruker Biotyper for VGS. Therefore, it would be useful for the identification of VGS strains in clinical microbiology laboratories.

Follow-up investigation of antibody titers and diagnostic antibody cutoff values in patients with scrub typhus in South Korea.

BACKGROUND: Scrub typhus is a mite-borne infectious disease caused by Orientia tsutsugamushi. Few follow-up studies have assessed antibody titers using serologic tests from various commercial laboratories and the Korea Centers for Disease Control and Prevention (KCDC). METHODS: A prospective study to assess the antibody titers in patients with scrub typhus and seroprevalence in individuals undergoing health checkups was conducted using results of immunofluorescence antibody assays (IFAs) and serologic tests, used by the KCDC and commercial laboratories, respectively. The following tests were performed simultaneously: (i) indirect IFA used by the KCDC to detect immunoglobulin (Ig) M and IgG, (ii) IFA used by a commercial laboratory to detect total Ig, and (iii) antibody tests using two commercially available kits. RESULTS: When the IgM and IgG cutoff values (≥1:16 and ≥1:256, respectively) used in the IFA and the total IgG cutoff values (≥1:40) were used in prospective follow-up investigations, the antibody positivity rates of 102 patients with scrub typhus were 44.1, 35.3, and 57.6%, respectively, within 5 days of symptom onset. Among 91 individuals who recovered from scrub typhus, the follow-up IgM, IgG, and total Ig positivity rates for 13 years were 37.4% (34/91), 22.0% (20/91), and 76.9% (70/91), respectively. Among 216 individuals undergoing health checkups, the seroprevalence of IgM was 4.2% (9/216); no seroprevalence of IgG was observed. CONCLUSIONS: IFAs used by the KCDC and the commercial laboratory and rapid commercial kits could not distinguish between patients who had recovered from scrub typhus and those who are currently infected with O. tsutsugamushi. In South Korea and other countries, where low antibody cutoff values are used, upward adjustments of cutoff values may be necessary.

A case of SFTS coinfected with E. coli bacteremia.

BACKGROUND: Severe fever thrombocytopenia syndrome virus (SFTSV) is the causative agent of severe fever thrombocytopenia syndrome (SFTS). SFTS is an emerging infectious disease, characterized by high fever, gastrointestinal symptoms, leukopenia, thrombocytopenia, and a high mortality rate. Until now, little importance has been given to the association of SFTS with leukocytosis and bacterial co-infection. CASE PRESENTATION: A 51-year old man visited our hospital with fever and low blood pressure. He was a farmer by occupation and often worked outdoors. He had a Foley catheter inserted due to severe BPH. Laboratory tests revealed thrombocytopenia, elevated liver function, and elevated CRP levels. He had marked leukocytosis, proteinuria, hematuria, and conjunctival hemorrhage. Initially, we thought that the patient was suffering from hemorrhagic fever with renal syndrome (HFRS). However, we confirmed SFTS through PCR and increasing antibody titer. However, his blood culture also indicated E. coli infection. CONCLUSION: SFTS displays characteristics of fever, thrombocytopenia, elevated liver function, and leukocytopenia. We described a case of SFTS with leukocytosis due to coinfection with E. coli. Since patients with SFTS usually have leukocytopenia, SFTS patients with leukocytosis are necessarily evaluated for other causes of leukocytosis. Here, we report the first case of an SFTS with concurrent E. coli bacteremia.

The Effect of Long-lasting Permethrin Impregnated Socks on Tick Bite in Korea.

BACKGROUND: The risk of tick-borne diseases is decreased by increasing awareness and knowledge through prevention education. The aim of the present study was to evaluate the effect of long-lasting permethrin impregnated (LLPI) socks for tick bites. METHODS: A randomized open label study was conducted to determine the effectiveness of LLPI socks for prevention of tick bites among 367 adults living in a rural area. Participants completed questionnaires at the start of follow-up (July 2014) and at the end of follow-up (December 2014), and tick bites were reported. RESULTS: A total of 332 subjects completed the follow-up survey. The tick bite rate of the two groups was not significantly different (3.6% vs. 3.1%). But the tick bite rate of lower extremities of subjects wearing LLPI socks was significantly lower compared to that of subjects wearing general socks. CONCLUSION: The tick bite rate was not different between the two groups, but the tick bite rate of lower extremities of LLPI was significantly lower than general groups. Further study is needed to investigate the effect of LLPI clothes with larger populations.

Asymptomatic-anaplasmosis confirmation using genetic and serological tests and possible coinfection with spotted fever group Rickettsia: a case report.

BACKGROUND: Anaplasmosis is an emerging acute febrile disease that is caused by a bite of an Anaplasma phagocytophilum-infected hard tick. As for healthy patients, reports on asymptomatic anaplasmosis resulting from such tick bites are rare. CASE PRESENTATION: A 55-year-old female patient visited the hospital with a tick bite in the right infraclavicular region. The tick was suspected to have been on the patient for more than 10 days. PCR and an indirect immunofluorescence assay (IFA) were performed to identify tick-borne infectious diseases. The blood sample collected at admission yielded a positive result in nested PCR targeting Ehrlichia- or Anaplasma-specific genes groEL and ankA. Subsequent sequencing confirmed the presence of A. phagocytophilum, and seroconversion was confirmed by the IFA involving an A. phagocytophilum antigen slide. PCR detected no Rickettsia-specific genes [outer membrane protein A (ompA) or surface cell antigen 1 (sca1)], but seroconversion of spotted fever group (SFG) rickettsiosis was confirmed by an IFA. CONCLUSIONS: This study genetically and serologically confirmed an asymptomatic A. phagocytophilum infection. Although SFG rickettsiosis was not detected genetically, it was detected serologically. These findings indicate the possibility of an asymptomatic coinfection: anaplasmosis plus SFG rickettsiosis. It is, therefore, crucial for clinicians to be aware of potential asymptomatic anaplasmosis following a tick bite.

First identification of Anaplasma phagocytophilum in both a biting tick Ixodes nipponensis and a patient in Korea: a case report.

BACKGROUND: Human granulocytic anaplasmosis (HGA) is a tick-borne infectious disease caused by Anaplasma phagocytophilum. To date, there have been no reported cases of A. phagocytophilum infection found in both the biting tick and the patient following a tick bite. CASE PRESENTATION: An 81-year-old woman presented with fever following a tick bite, with the tick still intact on her body. The patient was diagnosed with HGA. The tick was identified as Ixodes nipponensis by morphological and molecular biological detection methods targeting the 16S rRNA gene. The patient's blood was cultured after inoculation into the human promyelocytic leukemia cell line HL-60. A. phagocytophilum growth was confirmed via culture and isolation. A. phagocytophilum was identified in both the tick and the patient's blood by Anaplasma-specific groEL- and ankA-based nested polymerase chain reaction followed by sequencing. Moreover, a four-fold elevation in antibodies was observed in the patient's blood. CONCLUSION: We report a case of a patient diagnosed with HGA following admission for fever due to a tick bite. A. phagocytophilum was identified in both the tick and the patient, and A. phagocytophilum was successfully cultured. The present study suggests the need to investigate the possible incrimination of I. nipponensis as a vector for HGA in Korea.

Scalp eschar and neck lymphadenopathy after tick bite (SENLAT) caused by Bartonella henselae in Korea: a case report.

BACKGROUND: Tick-borne lymphadenopathy (TIBOLA) is an infectious disease, mainly caused by species from the spotted fever group rickettsiae and is characterized by enlarged lymph nodes following a tick bite. Among cases of TIBOLA, a case of scalp eschar and neck lymphadenopathy after tick bite (SENLAT) is diagnosed when an eschar is present on the scalp, accompanied by peripheral lymphadenopathy (LAP). Only a few cases of SENLAT caused by Bartonella henselae have been reported. CASE PRESENTATION: A 58-year-old male sought medical advice while suffering from high fever and diarrhea. Three weeks before the visit, he had been hunting a water deer, and upon bringing the deer home discovered a tick on his scalp area. Symptoms occurred one week after hunting, and a lump was palpated on the right neck area 6 days after the onset of symptoms. Physical examination upon presentation confirmed an eschar-like lesion on the right scalp area, and cervical palpation revealed that the lymph nodes on the right side were non-painful and enlarged at 2.5 × 1.5 cm. Fine needle aspiration of the enlarged lymph nodes was performed, and results of nested PCR for the Bartonella internal transcribed spacer (ITS) confirmed B. henselae as the causative agent. CONCLUSION: With an isolated case of SENLAT and a confirmation of B. henselae in Korea, it is pertinent to raise awareness to physicians in other Asian countries that B. henselae could be a causative agent for SENLAT.

Usefulness of Nested Polymerase Chain Reaction with Clinical Specimens for Diagnosis of Leptospirosis: a Case Series and a Review of Literature.

A culture of the Leptospira species and the microscopic agglutination test (MAT) are considered as the reference standard for the diagnosis of leptospirosis, but both tests are imperfect for early diagnosis. We describe 4 patients diagnosed with leptospirosis using nested polymerase chain reaction (N-PCR) that targeted the 16S rRNA gene and the passive hemagglutination assay (PHA). In our 4 cases, Leptospira DNA in the urine, plasma, or cerebrospinal fluid (CSF), was detected by N-PCR in the early phase of leptospirosis, except in the sample from the buffy coat. Especially, case 3 showed that N-PCR with the urine and CSF was positive 8 days after symptom onset, but not for the plasma or buffy coat. We report 4 cases of leptospirosis that were diagnosed by N-PCR that targeted the 16S rRNA gene with urine, plasma, or CSF, but not the buffy coat. Three were cured by doxycycline but the case 4 was fatal. Detection of Leptospira DNA by PCR from the urine and CSF, in addition to plasma, may be helpful to confirm the diagnosis.

Molecular detection of viruses causing hemorrhagic fevers in rodents in the south-west of Korea.

Many pathogens causing hemorrhagic fevers of medical and veterinary importance have been identified and isolated from rodents in the Republic of Korea (ROK). We investigated the occurrence of emerging viruses causing hemorrhagic fevers, such as hemorrhagic fever with renal syndrome (HFRS), severe fever with thrombocytopenia syndrome (SFTS), and flaviviruses, from wild rodents. Striped field mice, Apodemus agrarius (n = 39), were captured during 2014-2015 in the south-west of ROK. Using molecular methods, lung samples were evaluated for SFTS virus, hantavirus, and flavivirus, and seropositivity was evaluated in the blood. A high positive rate of hantavirus (46.2%) was detected in A. agrarius lungs by reverse transcription-nested polymerase chain reaction (RT-N-PCR). The monthly occurrence of hantavirus was 16.7% in October, 86.7% in November, and 25% in August of the following year (p < 0.001). Moreover, 17.9% of blood samples were serologically positive for hantavirus antibodies. The most prevalent strain in A. agrarius was Hantaan virus. All samples were positive for neither SFTS virus nor flavivirus. Hantaan virus was detected in 86.7% of A. agrarius in November (autumn), and thus, virus shedding from A. agrarius can increase the risk of humans contracting HFRS. These findings may help to predict and prevent disease outbreaks in ROK.

Identifying the mechanism underlying treatment failure for Salmonella Paratyphi A infection using next-generation sequencing - a case report.

BACKGROUND: Salmonella is a notorious pathogen that causes gastroenteritis in humans and the emergence of resistance to third-generation cephalosporins and azithromycin have raised concern. There has been rare case of Salmonella Paratyphi A infection accompanied by spondylitis. Here, we report a case of initial antibiotic treatment failure in a Korean man with Salmonella Paratyphi A infection and conducted next-generation sequencing (NGS) to determine the cause of failure of initial treatment for Salmonella Paratyphi A infection. CASE PRESENTATION: A 70-year-old man was admitted to Chosun University Hospital with reported consistent low back pain with a history of having 5 days of chills and fever in another hospital a month ago. He was administered ceftriaxone (2 g daily) for 18 days including initial treatment to cover Salmonella enterica. The antimicrobial susceptibility test using MIC plate, found that the identified organism was resistant to ciprofloxacin and nalidixic acid. Moreover, the Salmonella Paratyphi A isolates were found to have an MIC > 16 mg/L for azithromycin, as he had resistance to both azithromycin and nalidixic acid, the treatment was switched to a combination of ciprofloxacin and cefotaxime. We carried out next-generation sequencing (NGS) to determine the cause of failure of initial treatment for Salmonella Paratyphi A infection. NGS showed that the amino acid substitution GyrA S83F and the expression of multiple RNA-family efflux pumps led to a high-level resistance to quinolone. No genes related to ceftriaxone resistance, such as CTX-M, CMY-2, or other extended-spectrum beta-lactamases were identified in Salmonella enterica Paratyphi A using NGS. The GyrA S83F mutation and the expression of multiple RNA-family efflux pumps may have contributed to the treatment failure of ceftriaxone, even though the MIC of the isolate to ceftriaxone was less than 1. CONCLUSION: This case involved a Salmonella Paratyphi A infection accompanied by spondylitis. To our knowledge, this is the first report to elucidate the mechanism underlying antimicrobial resistance using NGS.

Indicators of severe prognosis of scrub typhus: prognostic factors of scrub typhus severity.

BACKGROUND: Scrub typhus is an acute disease, characterized by symptoms of fever, which occurs due to infection by Orientia tsutsugamushi. In most cases, patients recover from the disease with appropriate treatment, but serious and fatal complications may occur. The present study examined laboratory findings and tumor necrosis factor-alpha (TNF-α) levels of scrub typhus patients to identify the prognostic predictors of disease severity. METHOD: Patients whose scrub typhus diagnosis was confirmed by elevated indirect fluorescent antibody (IFA) levels and positive polymerase chain reaction (PCR) results were classified according to disease severity into one of three groups; i.e., deceased (n = 7), severe (n = 15), and mild (n = 15) retrospectively registered. Additionally, the usefulness of modified Acute Physiology and Chronic Health Evaluation II (APACHE II) score, C-reactive protein (CRP) level, white blood cell (WBC) count, and TNF-α level as prognostic predictors were examined. RESULT: The mean TNF-α levels of the deceased, severe, and mild groups were 53.5 (range: 7.8-147.8), 26.0 (1.7-64.4), and 8.8 pg/mL (4.6-16.0), respectively. The results of Kruskal-Wallis tests showed statistically significant differences between the deceased and severe groups versus the mild group (p = 0.005). CRP level and Modified APACHE II score also differed significantly among the groups (p = 0.046 and 0.007, respectively); however, WBC count did not (p = 0.196). CONCLUSION: An elevated serum TNF-α level in patients with scrub typhus could predict a severe condition or death and may be useful in predicting patient prognosis.

Effects of Rifampin and Doxycycline Treatments in Patients With Uncomplicated Scrub Typhus: An Open-Label, Randomized, Controlled Trial.

Background: Doxycycline is currently the most frequently used treatment in patients with scrub typhus. However, doxycycline-resistant strains have been found, necessitating the development of a new treatment. Rifampin is known to be effective even for such strains. Our aim in this study was to compare the effects of rifampin and doxycycline treatment in patients with scrub typhus in areas in which resistance to doxycycline has not been reported. Methods: Patients admitted to Chosun University Hospital and regional network hospitals between 2007 and 2009 with a body temperature ≥37.5°C and suspected to have scrub typhus were randomly assigned to 1 of 2 treatment groups: a group administered doxycycline 100 mg twice daily for 5 days and a group administered rifampin 600 mg once daily for 5 days. For treatment outcomes, fever, headache, muscle ache, and rash clearance times were compared between the groups. Results: The rifampin and doxycycline groups showed equivalence in all treatment outcomes evaluated. The proportions of patients with fever clearance within 48 hours were similar between groups. Furthermore, there was no significant difference in the occurrence of side effects following drug administration between groups. Conclusions: On the basis of the finding that equivalent treatment effects and safety were found in patient groups that received 600 mg of rifampin and 200 mg of doxycycline, respectively, for 5 days to treat scrub typhus, rifampin may be considered an alternative treatment to doxycycline. Clinical Trials Registration: NCT00568711.

Seroprevalence of Severe Fever with Thrombocytopenia Syndrome Virus Antibodies in Rural Areas, South Korea.

We investigated 1,228 residents of 3 rural areas in South Korea and determined that 50 (4.1%) were positive for severe fever with thrombocytopenia syndrome virus antibodies. Fever and gastrointestinal symptoms in the previous 3 years and career duration were associated with virus seropositivity.

Hemorrhagic fever with renal syndrome accompanied by panhypopituitarism and central diabetes insipidus: a case report.

Central diabetes insipidus (DI) was detected in a patient with hemorrhagic fever with renal syndrome (HFRS) who had been molecularly and serologically diagnosed with Hantaan virus infection. We recommend that clinicians differentiate central DI in HFRS patients with a persistent diuretic phase even when pituitary MRI findings are normal.

Manifestation of anaplasmosis as cerebral infarction: a case report.

BACKGROUND: Human granulocytic anaplasmosis is a tick-borne zoonotic disease caused by Anaplasma phagocytophilum, an obligate intracellular granulocytotropic bacterium. CASE PRESENTATION: A 70-year-old female patient was admitted with the clinical signs of fever and an altered state of consciousness 1 week after experiencing a tick bite while planting lawn grass. Magnetic resonance imaging, performed at the time of admission, indicated cerebral infarction in the left basal ganglia, whereas increasing immunofluorescence assay antibody titers for A. phagocytophilum were also documented. A. phagocytophilum was identified using groEL and ankA targeted polymerase chain reaction and sequencing. Because of severe thrombocytopenia, only doxycycline was administered, without any antiplatelet agents. Subsequently, the symptoms improved without any focal neurologic sequela. CONCLUSION: This is the first reported case of cerebral infarction occurrence in an anaplasmosis patient.

A case report of scrub typhus complicated with myocarditis and rhabdomyolysis.

BACKGROUND: Scrub typhus is a zoonotic disease caused by Orientia tsutsugamushi, a gram-negative intracellular bacterium. Myocarditis and rhabdomyolysis are rare complications of scrub typhus. CASE PRESENTATION: We report a case of scrub typhus, which was simultaneously complicated with myocarditis and rhabdomyolysis. A 54-year-old woman presented to our hospital with myalgia in the upper and lower limbs, oedema and a fever of 7 days' duration. We confirmed the diagnosis of scrub typhus complicated with myocarditis by pericardial fluid analysis and cardiac magnetic resonance imaging results. The pericardial fluid showed characteristics of an exudate, an elevated immunofluorescence assay (IFA) IgG titer of 1:2048 and a positive 16S rRNA qPCR result. We also diagnosed rhabdomyolysis by the patient's presenting symptoms, elevated muscle enzyme levels and bone scan results. CONCLUSION: We report for the first time a case of scrub typhus complicated with both myocarditis and rhabdomyolysis, the causative agent of which was the Boryong genotype of O. tsutsugamushi.

Tenosynovitis caused by Scedosporium apiospermum infection misdiagnosed as an Alternaria species: a case report.

BACKGROUND: Scedosporium apiospermum, which can usually be isolated from soil, polluted stream water and decaying vegetation, is increasingly recognized as an opportunistic dematiaceous fungus. The mortality rate of infection in immunocompromised hosts is over 50%. S. apiospermum is commonly responsible for dermal and epidermal infections (i.e., mycetoma) after traumatic penetration. CASE PRESENTATION: A 73-year-old woman was admitted to our hospital complaining of painful swelling and tenderness on the dorsum of the proximal left wrist and hand. The symptoms had persisted for approximately 2 months. A physical examination revealed a 4 x 3 cm, poorly defined, erythematous papule, which was fluctuant, with pustules and crusts on the dorsum of the left hand. CONCLUSIONS: We report a very rare case of tenosynovitis caused by S. apiospermum infection. We identified the infectious agent via molecular DNA sequencing. The infectious agent was initially misidentified as an Alternaria species by microscopic examination with lactophenol cotton blue (LPCB) staining. The infection was successfully treated with debridement and adjuvant fluconazole therapy.

Accuracy of Conventional PCR Targeting the 16S rRNA Gene with the Ot-16sRF1 and Ot-16sRR1 Primers for Diagnosis of Scrub Typhus: a Case-Control Study.

We retrospectively evaluated the accuracy of conventional PCR targeting the 16S rRNA gene (16S C-PCR) using the Ot-16sRF1/Ot-16sRR1 primers for diagnosing scrub typhus. The diagnosis of Orientia tsutsugamushi infection by 16S C-PCR presented an increased sensitivity of 87.0% and specificity of 100% compared with those obtained with other targets and is thus a simple and clinically useful method with good diagnostic accuracy.