We use cookies to understand how you use our site and to improve your experience. This includes personalizing content and advertising. To learn more, click here. By continuing to use our site, you accept our use of cookies. Cookie Policy.

Features Partner Sites Information LinkXpress
Sign In
Advertise with Us
Technopath Clinical Diagnostics

Download Mobile App




Events

ATTENTION: Due to the COVID-19 PANDEMIC, many events are being rescheduled for a later date, converted into virtual venues, or altogether cancelled. Please check with the event organizer or website prior to planning for any forthcoming event.
05 Sep 2020 - 09 Sep 2020
Virtual Venue

Immunoassays Compared for Diagnosis of Acute Murine Typhus Infections

By LabMedica International staff writers
Posted on 10 Sep 2019
Print article
Image: A photomicrograph of an immunofluorescence assay (IFA) for Rickettsia (Photo courtesy of Fuller Laboratories).
Image: A photomicrograph of an immunofluorescence assay (IFA) for Rickettsia (Photo courtesy of Fuller Laboratories).
Murine typhus is a disease transmitted by fleas and is caused by intracellular gram-negative bacteria called Rickettsia typhi, and manifested clinically with acute fever, chills, muscle pain, nausea, vomiting, stomach pain, cough and rash.

Appropriate rapid diagnostics are needed to distinguish it from other infections, as patient management varies. Due to low rickettsemia during acute illness, the sensitivity of real-time polymerase chain reaction (PCR) is highly variable. Thus, sero-diagnosis using immunofluorescence assay (IFA) remains the gold standard.

Scientists working with the Indonesia Research Partnership on Infectious Disease (Jakarta, Indonesia) obtained samples from eight government referral teaching hospitals in seven provincial capitals. Paired acute and convalescent plasma samples from 40 cases with confirmed R. typhi and 58 controls with another confirmed infection were used to evaluate the performance of commercial IgM and IgG enzyme-linked immunosorbent assay (ELISA) and IFA. The 58 paired plasma specimens that they used for controls were negative for R. typhi and Rickettsia spp., but positive for other pathogens by culture or molecular testing.

The immunofluorescence assay (IFA) was performed using kits from Focus Diagnostics (Cypress, CA, USA). The dilution for study samples was 1:64, and for provided positive controls was 1:32. Acute and convalescent specimens from each subject were performed simultaneously. Acute and convalescent plasma were tested simultaneously using ELISA kits from Fuller Laboratories (Fullerton, CA, USA). Microwells were coated with the outer surface membrane protein rOmp B purified from R. typhi. Optical density (OD) was measured at a wavelength of 450 nm.

The team reported that sensitivity and specificity of combined ELISA IgM and IgG anti-R. typhi using paired specimens were excellent (95.0% and 98.3%, respectively), comparable to combined IFA IgM and IgG (97.5% and 100%, respectively); sensitivity of ELISA IgM from acute specimens only was poor (45.0%), but specificity was excellent (98.3%). IFA IgM was more sensitive (77.5%), but less specific (89.7%) for single specimens. IgM was detected as early as day three of fever by ELISA and day four by IFA. Starting from day nine of illness, IgM was detected in all cases by IFA, while ELISA missed two specimens (days 10 and 25).

The authors concluded that their data supports the validity of ELISA in the diagnosis of R. typhi infection. As the specificity in acute specimens as well as sensitivity and specificity in convalescent specimens and paired specimens were excellent, ELISA is recommended when fluorescence microscopy is not feasible. However, IFA remains the method of choice if resources are available. ELISA is appropriate for resource-limited settings as it is easy to read, is objective, and has a high throughput. The study was published on August 26, 2019, in the journal Vector-Borne and Zoonotic Diseases.

Related Links:
Indonesia Research Partnership on Infectious Disease
Focus Diagnostics
Fuller Laboratories


Print article

Channels

Molecular Diagnostics

view channel
Image: Structure of the ACE2 (angiotensin-converting enzyme 2) protein (Photo courtesy of Wikimedia Commons)

Elevated Angiotensin 1–7/Angiotensin II Ratio Predicts Favorable Outcomes in Patients with Heart Failure with Potential Link to COVID-19 Patients

A high ratio of angiotensin 1-7 to angiotensin II (Ang 1–7/Ang II ratio), was found to be an independent and incremental predictor of beneficial outcomes, higher survival rate, and decreased hospitalization... Read more

Industry News

view channel
Image: ChemWell RPR Analyzer (Photo courtesy of Awareness Technology, Inc.)

Awareness Technology Announces ChemWell RPR Analyzer - The Most Significant Innovation in Syphilis Testing in Last 30 Years

Awareness Technology, Inc. (Palm City, FL, USA) has announced the most significant innovation in syphilis testing in the last 30 years with the launch of the ChemWell RPR automated nontreponemal analyzer... Read more
Copyright © 2000-2020 Globetech Media. All rights reserved.