Clinical Evaluation of Rapid Diagnostic Test Kit for Scrub Typhus with Improved Performance

Diagnosis of scrub typhus is challenging due to its more than twenty serotypes and the similar clinical symptoms with other acute febrile illnesses including leptospirosis, murine typhus and hemorrhagic fever with renal syndrome. Accuracy and rapidity of a diagnostic test to Orientia tsutsugamushi is an important step to diagnose this disease. To discriminate scrub typhus from other diseases, the improved ImmuneMed Scrub Typhus Rapid Diagnostic Test (RDT) was evaluated in Korea and Sri Lanka. The sensitivity at the base of each IgM and IgG indirect immunofluorescent assay (IFA) in Korean patients was 98.6% and 97.1%, and the specificity was 98.2% and 97.7% respectively. The sensitivity and specificity for retrospective diagnosis at the base of IFA in Sri Lanka was 92.1% and 96.1%. ImmuneMed RDT was not reactive to any serum from seventeen diseases including hemorrhagic fever with renal syndrome (n = 48), leptospirosis (n = 23), and murine typhus (n = 48). ImmuneMed RDT shows superior sensitivity (98.6% and 97.1%) compared with SD Bioline RDT (84.4% at IgM and 83.3% at IgG) in Korea. The retrospective diagnosis of ImmuneMed RDT exhibits 94.0% identity with enzyme-linked Immunosorbent assay (ELISA) using South India patient serum samples. These results suggest that this RDT can replace other diagnostic tests and is applicable for global diagnosis of scrub typhus. This rapid and accurate diagnosis will be beneficial for diagnosing and managing scrub typhus.

Outbreak of scrub typhus in Puducherry & Tamil Nadu during cooler months.

Background & objectives: The southern part of India has witnessed an increase in scrub typhus (ST) during the past ten years. ST outbreaks occurred during winter months but at intervals of one to three years. With only a few reports of ST in Puducherry, this study was undertaken to look for the persistence of ST cases in Puducherry and Tamil Nadu in the winter months. Methods: During relatively cooler months of September, 2012 to March, 2013, a total of 45 patients with fever and clinical suspicion of ST and who provided both acute and convalescent blood samples were included. Total WBC, platelet counts, serum creatinine, liver enzymes levels and a rapid immunochromatographic test (RICT) for ST were first done. Paired serum samples were analysed by two specific tests - ST IgM and IgG ELISA- and a non-specific, but widely used Weil-Felix (WF) test. Results: Of the 45 patients, 21 adults and seven children were confirmed as ST based on clinical and laboratory findings, and positivity in specific serological test(s). Setting ST IgM and IgG ELISA as reference, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for RICT were 91.67, 85.71 per cent; 90.48, 100 per cent; 91.67, 100 per cent and 90.48, 80.95 per cent, respectively. Similarly, for WF the values were 83.33, 75 per cent; 95.24, 100 per cent; 95.24, 100 per cent and 83.33, 70.83 per cent, respectively. Interpretation & conclusions: ST continues to persist in the cooler months in Puducherry and neighbouring Tamil Nadu with fever and myalgia as prominent features. None of the tests evaluated in this study was found to be ideal, but ST IgM/IgG ELISA was useful for batch testing and the non-specific WF test can be used in resource poor settings.

Scrub Typhus Co-infection in an Adolescent Girl with Varicella.

Background: Co-infections with scrub typhus have been described quite frequently in adults but less frequently in children. Case characteristics: An adolescent girl with varicella infection who had persistent fever. Associated clinical features like pain abdomen, vomiting, and features of third space losses made us suspect a co-infection. IgM and IgG antibodies by ELISA in acute and convalescent serum were suggestive of scrub typhus. Outcome: She recovered following a course of oral doxycycline. Message: In unexplained prolonged fever or atypical clinical manifestations not explainable by the primary disease process, coinfection needs to be considered.

Early dengue diagnosis by nonstructural protein 1 antigen detection: Rapid immunochromotography versus two the enzyme-linked immunosorbent assay kits.

Dengue is known for its serious life-threatening complications. New rapid kits available recently in India target circulating non-structural protein (NS1) antigen from day one onwards. The sensitivity and specifi city of a newly introduced rapid combo kit against two conventional ELISA kits is assessed. The performance of this kit is quite satisfactory since excellent agreement of 94.26% was observed with particular reference to NS1 antigen detection among all three kits namely Rapid SD Bioline dengue Duo (SD Korea), InBios DENV Detect NS1 ELISA, USA and dengue Early ELISA, Panbio, Australia. The false positivity of the rapid kit is very low since its specifi city as for as NS1 antigen detection is concerned is 98.33%. The use of combination kit helps to detect additional cases of dengue, which are negative for NS1 antigen but positive for IgM and/or IgG antibodies, thus facilitating early diagnosis in remote areas and small laboratories.

Keratomycosis caused by Exserohilum rostratum.

We report a case of keratomycosis caused by Exserohilum rostratum. A 46-year-old farmer presented with history of pain, watery discharge and redness of the right eye for the past 2 weeks following trauma with vegetable matter. On ocular examination, a central corneal ulcer of about 8 mm with a greyish-white slough, feathery edges and diffuse corneal edema was seen in the right eye. KOH examination of corneal scrapings revealed thick, brown, branched, septate hyphae. Culture of corneal scrapings on Sabouraud dextrose agar showed velvety greenish-black colony with a black pigment on the reverse. The culture was identified as E. rostratum on the basis of microscopic morphology. The patient responded well to treatment with topical natamycin and oral itraconazole.

Detection of extended spectrum beta lactamases, ampc beta lactamases and metallobetalactamases in clinical isolates of ceftazidime resistant Pseudomonas Aeruginosa

We studied the prevalence of ceftazidime resistance in Pseudomonas aeruginosa and the rates of extended-spectrum β-lactamase (ESBL), AmpC β-lactamase (AmpC) and metallo-β-lactamase (MBL) production among the ceftazidime resistant Pseudomonas aeruginosa. A very high rate of MBL production was observed, which suggested it to be an important contributing factor for ceftazidime resistance among Pseudomonas aeruginosa.