Specific detection of dengue and Zika virus antibodies using envelope proteins with mutations in the conserved fusion loop

Detection of antibodies is widely used for the diagnosis of infections with arthropod-borne flaviviruses including dengue (DENV) and Zika virus (ZIKV). Due to the emergence of ZIKV in areas endemic for DENV, massive co-circulation is observed and methods to specifically diagnose these infections and differentiate them from each other are mandatory. However, serological assays for flaviviruses in general, and for DENV and ZIKV in particular, are compromised by the high degree of similarities in their proteins which can lead to cross-reacting antibodies and false-positive test results. Cross-reacting flavivirus antibodies mainly target the highly conserved fusion loop (FL) domain in the viral envelope (E-) protein, and we and others have shown previously that recombinant E-proteins bearing FL-mutations strongly reduce cross-reactivity. Here we investigate whether such mutant E-proteins can be used to specifically detect antibodies against DENV and ZIKV in an ELISA-format. IgM antibodies against DENV and ZIKV virus were detected with 100% and 94.2% specificity and 90.7% and 87.5% sensitivity, respectively. For IgG the mutant E-proteins showed cross-reactivity, which was overcome by pre-incubation of the sera with the heterologous antigen. This resulted in specificities of 97.1% and 97.9% and in sensitivities of 100% and 100% for the DENV and ZIKV antigens, respectively. Our results suggest that E-proteins bearing mutations in the FL-domain have a high potential for the development of serological DENV and ZIKV tests with high specificity

The importance of timely introduction of vancomycin therapy against methicillin-resistant Staphylococcus aureus (MRSA) bacteremia and severity of MRSA bacteremia at Teaching Hospital, Anuradhapura, Sri Lanka

Aim: Worldwide, an estimated 2 billion healthy people carry Staphylococcus aureus (SA) and of these, up to 53 million are thought to carry methicillin-resistant SA (MRSA). MRSA bacteremia patients are more critical to manage and timely introduction of antibiotics is life-saving. The aim of the study was to elucidate the prevalence of MRSA bacteremia in different units of Teaching Hospital, Anuradhapura (THA), Sri Lanka and assess the clinical characteristics and associated mortality related to timely introduction of vancomycin therapy. Materials and Methods: The data on MRSA bacteremia which were obtained from THA, for the period of March 2012 to December 2013 were statically analyzed emphasizing the unit-wise prevalence, severity, and comorbidity and timely introduction of vancomycin therapy. Results: The laboratory records of total 13,260 blood cultures were analyzed. Of those, MRSA bacteremia was detected in 61 cultures (9.3%). The highest prevalence of MRSA bacteremia was observed in the nephrology unit. The survival rate of the patients when the vancomycin therapy started before 24 h of receiving the blood culture report was 94.9% and in the instances of the treatment started after 24 h of blood culture report, the survival rate decreased down to 50%. High Pitt Bacteraemia score (PBS) (p<0.05) and initiation of vancomycin therapy after 24 h following the receipt of blood culture report (p<0.05) independently affected the MRSA bacteremic patient’s 7th day mortality. Having comorbidities have not shown significant impact on 7th day mortality. Conclusion: The start of vancomycin therapy as earlier as possible following arrival of antibacterial susceptibility test reduces the likelihood of mortality

Synthesis and antibacterial/antitubercular activity evaluation of symmetrical <i style="mso-bidi-font-style:normal">trans</i>-cyclohexane-1,4-diamine derivatives

1441-1450<span style="font-size:12.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-ansi-language:="" en-gb;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="" lang="EN-GB">A library of symmetrical trans-cyclohexane-1,4-diamine derivatives have been synthesized and evaluated for their activity against the M. tb H37Rv strain. Most of the synthesized compounds show moderate to weak activity against M. tb H37Rv strain. Out of twenty-seven compounds tested, four compounds having substitution at p-position on the aromatic ring exhibit activity with MIC99 value ranging from 12.5 - 25 µM. Compound 9u having i-propyl group substitution at p-position is found to be the most potent among all the tested compounds with MIC99 value of 12.5 µM against M. tb H37Rv strain. All these compounds have also been tested against <i style="mso-bidi-font-style: normal">Methicilin resistant Staphylococcus aureus (MRSA), and four of the compounds <b style="mso-bidi-font-weight: normal">9c, 9i, 9p and 9s possess good antibacterial activity with IC50 ranging from 128 mg/L – 256 mg/L.</span

Dengue virus IgM serotyping by ELISA with recombinant mutant envelope proteins

We developed an IgM-based ELISA that identifies the dengue virus serotype of recent infections. Dominant serotypes were detectable in 91.1% of samples from travelers and 86.5% of samples from residents of endemic regions; 97.1% corresponded to the serotype identified by PCR. This ELISA enables more accurate reporting of epidemiologic findings