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Vircell publications ECCMID 2018

Vircell publications ECCMID 2018

It is a pleasure to share with you our latest publications displayed in ECCMID 2018, held in Madrid, Spain.  

INVASIVE CANDIDIASIS (CAGTA) VIRCLIA® MONOTEST

  • Value of beta-D-glucan and CAGTA biomarkers in diagnosing invasive candidiasis among medical and surgical patients. Lo Cascio, G. et al. (2018)
  • Performance of the association of two markers for invasive candidiasis (IC): (1-3)-beta-D-glucan and Candida albicans germ tube antibodies (CAGTA). Marchi, E. et al. (2018)

Invasive candidiasis (IC) plays an important role as severe infection, constantly rising within hospital wards with intensive and medical-surgical regimen. Diagnosis and treatment are difficult because of the absence of pathognomonic symptoms and due to a low sensitive and time-consuming gold standard (blood culture). 

In order to overcome this and to avoid unnecessary and costly empirical antifungal therapies, non-culture-based microbiological assays are proposed as novel early markers of IC. 

In these studies, the detection of (1 → 3)-β-d-glucan (BDG) and antibodies against Candida (C. albicans germ tube antibodies, CAGTA) are analysed as single tests and in association. 

Lo Cascio, G. et al. evaluate whether the association of BDG and CAGTA can lead to an earlier and more specific diagnosis of IC in medicine and surgery wards patients and therefore a timely targeted therapy can be initiated.

The performance of the single tests BG and CAGTA in comparison to their combination and the gold standard (blood culture) showed an improvement in IC diagnosis, with a PPV of 65% and a NPV of 100% when BG and CAGTA are combined. 

Marchi, E. et al. also showed an increase in sensitivity and NPV when the two markers were associated (93% and 91%, respectively). The accuracy of the individual assays augmented up to 84%, when used in association. Moreover, the specificity of the association of the two markers (75%) was lower than that of CAGTA (89%) and higher than that of BDG (70%) taken alone. 

Both publications agree that INVASIVE CANDIDIASIS (CAGTA) VIRCLIA® IgG MONOTEST in combination with BDG considerably improves the IC diagnostics showing an enhanced NPV that may help to optimize the therapeutic strategies of antifungal management.

VIRCLIA® MONOTEST in the diagnosis of Q fever

  • Comparison of new chemiluminescent immunoassays with indirect immunofluorescence assay in the diagnosis of human Q fever. Ana Fernández-Blázquez et al. (2018)

Q fever is a zoonosis caused by Coxiella burnetii that presents with a wide spectrum of clinical manifestations. Serologic testing using indirect immunofluorescence assay (IFA) is the reference method for laboratory diagnosis. New methods based on chemiluminescent immunoassay (CLIA) technology are able to detect the amount of antibodies in serum using automated analytical platforms and shortening time responses.

In this study, Ana Fernández-Blázquez et al. evaluate the CLIA’s performance in the diagnosis of Q fever establishing comparisons between IgG indexes obtained by VirClia® Monotest and IgG titers observed by Vircell IFA.

After the analysis of this correlation, the authors conclude that:

  • VirClia’s IgG indexes are representative of IFA’s antibody quantification.
  • Confirmation by IFA remains necessary when CLIA’s IgG indexes are close to the threshold value, due to a possible prozone phenomenom present in sera with high IgG titers.
  • VirClia is an excellent diagnostic tool that enables a classification of probable Q fever cases and a rapid response in patients with acute Q fever.

AMPLIRUN®, a standard for quantification

  • Timely detection of sequence variations of three genes potentially associated with Mycoplasma genitalium treatment failures. Egli, K. et al. (2018)

Mycoplasma genitalium (MGEN) infection is a major cause of urethritis in men and is associated with cervicitis, pelvic inflammatory disease, preterm birth, and spontaneous abortion in women. The first-line treatment is the macrolide azithromycin (AZI) however, single nucleotide polymorphisms (SNPs) in the 23S rRNA gene of MGEN are held responsible for the worldwide emergence resistances towards this treatment. 

Here, Egli, K. et al. study the technical feasibility of determining the 23S rRNA gene sequence of MGEN directly from positive clinical specimens by real-time PCR and melting-curve analysis. In addition, the variability of gyrA and parC gene loci of MGEN are studied as a potential surrogate marker for quinolone resistance.

In this study, our AMPLIRUN® DNA controls were used as quantified DNA standards to determine the analytical sensitivities (LOD) of all targets.

Clinical specimens were screened for the presence of MGEN by the AnyplexII STI-7 assay (Seegene). SNPs in the 23S rRNA gene were analysed using "LightMix Modular Mycoplasma Macrolide" (TibMolbiol). Analytical sensitivities were excellent. Timely confirmation of MGEN wild-type 23S rRNA gene sequence directly from clinical specimens is feasible and may have impact on current treatment guidelines. For quinolones, the relatively high proportion of silent mutations found may limit this approach for predicting treatment failures.

VIRCELL IFA for Chagas detection

  • Epidemiological risk factors involved in vertical transmission of Chagas disease (CD). Simon Paez, M. et al. (2018)

It is estimated that the congenital transmission risk in newborns from mothers with CD is around 5%, but can vary from 0.7% to 28.6%, depending on geographic areas and other factors such as maternal factors.

In this study, Simon Paez, M. et al. evaluate possible epidemiological risk factors involved in vertical transmission of Chagas Disease.

144 T. cruzi-seropositive pregnant women and their 160 newborns were diagnosed differently:

  • Vircell CHAGAS IFA IgG+IgM® was used in combination with Abbott ARCHITECT Chagas® to diagnose women. 
  • Infants were considered infected when the parasite was detected by PCR and/or microhematocrite at any age, or when serology remained positive at 12 months of life. 

The authors conclude that all mothers who transmitted the infection to their newborn were Bolivian (since most of the mothers in the study came from this country that shows the greatest prevalence of CD). Younger women and women with less years of residence in Spain have more risk of transmitting the infection to their infants. It could be supposed that less time elapsed since they acquired the infection and women parasitemia would be higher.

VIRCELL CELL CULTURE

  • Comparison of quantitative real-time PCR and shell vial culture for CMV detection in urine. Coltella, L. et al. (2018)

Cytomegalovirus (CMV) infection is the most common cause of congenital infection. For years, the gold standard in the diagnosis of congenital CMV infection has been urine viral culture. Thanks to the real time PCR, CMV DNA detection has become a valid diagnostic tool. In immunocompromised patients it has replaced blood culture and pp65 antigen detection because of its higher sensitivity. 

In this study, Coltella, L. et al. support quantitative real time PCR on urine in comparison to shell vial culture. A retrospective study was conducted in a period of 5 years (2012-2017) on 255 urine samples belonging to patients admitted to Bambino Gesù Pediatric Hospital. 

Vircell´s MRC-5 cell line shell vial was used for quantitative and rapid tool for viral culture and it was compared with quantitative real time PCR (Artus CMV TM PCR Kit, Qiagen).

The authors conclude that quantitative real time PCR in comparison to shell vial culture provides standardization, simplicity and faster results.