Use of monoclonal antibodies against Rickettsia tsutsugamushi Kawasaki for serodiagnosis by enzyme-linked immunosorbent assay.
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Monoclonal antibodies (MAbs) against Rickettsia tsutsugamushi Kawasaki were prepared. The crossreactivity tests of the MAbs performed by using antigenically distinct strains of R. tsutsugamushi in immunofluorescence and immunoblotting analyses indicated that the Kawasaki strain contains a strain-specific epitope and also contains a common epitope on the 56-kDa polypeptide cross-reactive with the Gilliam strain, group- and subgroup-specific epitopes on the 46-kDa polypeptide, and a subgroup-specific epitope on the 25-kDa polypeptide. By using the strain-specific MAb for serodiagnosis of tsutsugamushi disease (or scrub typhus fever), we have established a method which was designated the inhibition enzyme-linked immunosorbent assay. The principle of the method is to measure the percentage of inhibition of antigen absorption on a MAb-coated plate by antibody-positive sample sera which were mixed with the antigen suspension. The advantages of this test for practical use are that (i) crude antigen can be used, i.e., purification of the antigen is not required; (ii) the test is more sensitive than immunofluorescence; (iii) the final judgment of plus or minus is clear-cut; and (iv) rickettsial antigenic types in the patients can be distinguished by this test. (+info)
Scrub typhus during pregnancy and its treatment: a case series and review of the literature.
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Although scrub typhus is uncommon in pregnant women, when present, it can have serious repercussions for the mother and developing fetus. Since it is uncommon, the clinical impact of scrub typhus on pregnancy has not been elucidated and an effective and safe therapeutic regimen has not been validated. The medical records of pregnant women whose scrub typhus were treated at Chungnam National University Hospital were reviewed and their clinical outcomes were evaluated. A review of the literature was also performed on pregnant women with scrub typhus and their clinical outcomes. Eight pregnant women with scrub typhus were treated successfully with a single 500-mg dose of azithromycin, and no relapses were reported. They all delivered healthy babies at term, without congenital or neonatal complications. In the reviews, azithromycin was effective against scrub typhus and had favorable pregnancy outcomes. Ciprofloxacin and cefuroxime failed to treat scrub typhus and fetal loss resulted. A single 500-mg dose of azithromycin may be a reasonable treatment regimen for pregnant women with scrub typhus. Ciprofloxacin might not be advisable for the treatment of scrub typhus during pregnancy. Scrub typhus itself seems to have serious adverse effects on pregnancy if not appropriately controlled. (+info)
Rapid diagnosis of scrub typhus in rural Thailand using polymerase chain reaction.
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The aim of this study was to evaluate the use of polymerase chain reaction (PCR) amplification of the O. tsutsugamushi 16S rRNA gene for the diagnosis of scrub typhus in rural Thailand. A prospective study of acute febrile illness in Udon Thani, northeast Thailand, identified 183 patients as having scrub typhus on the basis of immunofluorescent antibody testing (IFA) of paired sera. A further 366 febrile patients admitted concurrently with a range of other diagnoses acted as negative controls. Diagnostic sensitivity and specificity of 16S rRNA PCR was 44.8% and 99.7%, respectively, compared with IFA. PCR positivity was related to duration of symptoms and presence of eschar (P < 0.001, both cases). PCR using primers to amplify a fragment of the 56-kd gene had a sensitivity and specificity of 29.0% and 99.2%, respectively. PCR has a high specificity but low sensitivity for the rapid diagnosis of scrub typhus in this endemic setting. (+info)
Scrub typhus in Himalayas.
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Himachal Pradesh state of India is situated in the outer Himalayan ranges. During the rainy season, several cases of acute febrile illness of unknown origin occurred. Orientia tsutsugamushi was identified as the causative agent by microimmunofluorescence and PCR. Two new genotypes of O. tsutsugamushi were identified in the region. (+info)
Comparative susceptibility to mouse interferons of Rickettsia tsutsugamushi strains with different virulence in mice and of Rickettsia rickettsii.
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Three strains of Rickettsia tsutsugamushi (Karp, Gilliam, and TA716, representing three virulence types in mice) were examined for their sensitivity to the inhibitory effects of recombinant gamma interferon (IFN-gamma) and purified IFN-alpha/beta in two cultured mouse fibroblast cell lines. The susceptibilities of another species, Rickettsia rickettsii, and of encephalomyocarditis virus (EMCV) were also tested for comparative purposes. IFN-gamma inhibited rickettsial replication in only one of the six combinations of R. tsutsugamushi strains and mouse cells (strain Gilliam and the BALB/c mouse-derived cell line). In contrast, R. rickettsii and EMCV replication were markedly inhibited in both cell types, but to a greater extent in the BALB/c line than in the C3H cells. IFN-alpha/beta (300 to 450 U/ml) was uniformly ineffective in three of the combinations of R. tsutsugamushi strains and mouse cells (Gilliam in C3H cells and Karp in both C3H and BALB/c cells); in the remaining sets, IFN-alpha/beta-mediated inhibition of rickettsial replication was variable and in no case was it very pronounced. The tests with R. rickettsii in both cell types also indicated slight, variable sensitivity to IFN-alpha/beta. EMCV, on the other hand, was very susceptible to IFN-alpha/beta, confirming the potency of the preparation used; as with IFN-gamma, virus replication was inhibited to a greater degree in the BALB/c cell line than in the C3H cultures. These results are discussed in terms of their relationship to the virulence properties of the R. tsutsugamushi strains in BALB/c and C3H mice and to the known IFN-sensitivities of the more widely studied Rickettsia prowazekii. (+info)
Scrub typhus serologic testing with the indirect immunofluorescence method as a diagnostic gold standard: a lack of consensus leads to a lot of confusion.
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A review was performed to determine the evidence base for scrub typhus indirect immunofluorescence assay (IFA) methodologies and the criteria for positive results. This review included a total of 109 publications, which comprised 123 eligible studies for analysis (14 publications included 2 substudies). There was considerable underreporting of the IFA methodology and seropositivity criteria used, with most studies using a defined cutoff titer rather than an increase in the titer in paired samples. The choice of positivity cutoff titer varied by country and purpose of the IFA test. This variation limits the comparability of seroprevalence rates between studies and, more seriously, raises questions about the appropriateness of the cutoffs for positive IFA results chosen for diagnosis of acute scrub typhus infection. We suggest that the diagnosis of scrub typhus using IFA should be based on a > or =4-fold increase in the titer in paired serum samples and should only be based on a single sample titer when there is an adequate local evidence base. (+info)
BACKGROUND: Acute disseminated encephalomyelitis (ADEM) is a monophasic demyelinating disease of the central nervous system, typically occurring after infections or vaccinations. To our knowledge, scrub typhus has not been described in association with ADEM. CASE REPORT: A 77-year-old man was admitted with fever, convulsions and an altered level of consciousness. On neurological examination, the patient was stuporous and had nuchal rigidity and left hemiparesis. A generalized tonic-clonic seizure was observed. Serum and cerebrospinal fluid samples were positive for anti-Orientia tsutsugamushi antibody. Despite a 10-day course of parenteral minocycline, his clinical condition deteriorated. Serial cranial magnetic resonance images demonstrated progressively extensive areas of signal hyperintensity on conventional T2-weighted and fluid attenuated inversion recovery sequence images, mainly affecting the periventricular white matter. After administration of intravenous high-dose corticosteroids, the patient had limited improvement. CONCLUSIONS: This is the first identifiable case of ADEM temporally associated with scrub typhus alone. (+info)
Preparation of recombinant antigen of O. tsutsugamushi Ptan strain and development of rapid diagnostic reagent for scrub typhus.
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Spring scrub typhus has frequently occurred in Pingtan Island, China, since 2000. In this study, we amplified a 1352-bp DNA fragment encoding a truncated 56-kDa outer membrane protein of the Ptan strain, which was isolated from a serum sample of a patient with spring scrub typhus, and cloned it into the pET28a vector for expression. The expression product was a recombinant polypeptide containing a His-tag to facilitate purification on a Ni2+ chromatography column. The recombinant protein was further identified by Western blotting and enzyme-linked immunosorbent assay (ELISA) and appeared to be a good diagnostic antigen candidate. A rapid colloidal gold immunochromatographic assay (CIA) for detecting serum total antibodies, IgG and IgM, which are anti-Orientia tsutsugamushi, was developed, using a mixture of the r56 of the Gilliam and Ptan strains as the diagnostic antigen. CIA performance was tested on a panel of 112 control sera from confirmed cases of scrub typhus. The detection sensitivities of CIA against anti-O. tsutsugamushi total antibodies, IgM, and IgG were 98.2%, 81.2%, and 94.6%, respectively, while that of IFA (using the lysate of the O. tsutsugamushi Gilliam-infected chicken yolk sac as the antigen) against IgG was 85.7%. One hundred five serum samples from healthy individuals and patients with other febrile diseases were tested with CIA as negative controls. Specificities of CIA against anti-O. tsutsugamushi total antibodies, IgM, and IgG were 98.1%, 100%, and 98.9%, respectively, while the specificity of IFA against IgG was 98.9%. These results indicated that CIA was a good assay and could substitute for conventional immunofluorescence assays for diagnosis of scrub typhus. (+info)