HBHA-IGRA and cytotoxic mediators release assays for the diagnosis of cervical tuberculous lymphadenitis

IMPORTANCE

Cervical tuberculous lymphadenitis (CTL), the most frequent extrapulmonary form of tuberculosis, is currently a major health problem in Tunisia and in several regions around the world. CTL diagnosis is challenging mainly due to the paucibacillary nature of the disease and the potential misdiagnosis as cervical non-tuberculous lymphadenitis. This study demonstrates the added value of the heparin-binding hemagglutinin-interferon-gamma release assay as an immunoassay in the context of CTL.

Performance of GeneXpert ultra in the diagnosis of Tuberculous Cervical lymphadenitis in formalin fixed paraffin embedded tissues

The diagnosis of Tuberculous Cervical lymphadenitis (TCL) is challenging. The present study aimed to assess the performance of GeneXpert ultra (GXu) in the diagnosis of TCL on Formalin Fixed, Paraffin Embedded Tissues (FFPET). This study included 35 TCL cases confirmed by positive microbiology and/or positive GXu on Fresh Tissues (FT). The diagnostic performance parameters of GXu on FFPET were determined with reference to microbiology (positive Ziehl Neelsen and/or positive culture) and with reference to positive microbiology and/or positive GXu on FT. The GXu on FFPET was positive in 26/35 (74%) cases. With reference to positive ZN and or culture, the sensitivity, specificity, positive predictive value, and negative predictive value of GXu on FFPET were 63%, 100%, 100% and 71% respectively. With reference to positive microbiology and/or positive GXu on FT, these rates were 74%, 100%, 100% and 40% respectively. GXu on FFPET is a reliable tool for the detection of Mycobacterium tuberculosis complex particularly for cases where microbiological investigations have not been performed.

IS6110-5'3'FP: an automated typing approach for Mycobacterium tuberculosis complex strains simultaneously targeting and resolving IS6110 5' and 3' polymorphisms

OBJECTIVES

Fingerprinting of Mycobacterium tuberculosis complex strains based on the IS6110 insertion sequence would considerably gain in terms of discriminatory power and versatility if both 5' and 3' polymorphisms were simultaneously targeted, and if it benefited from automated capillary electrophoresis. In response to these requirements, we developed IS6110-5'3'FP (IS6110 5' and 3' fluorescent polymorphisms).

METHODS

IS6110-5'3'FP involves the construction of an M. tuberculosis genomic library in a plasmid vector using HincII endonuclease, which cuts within the IS6110 sequence. After amplification in Escherichia coli, the library is subjected to selective and simultaneous PCR amplification of IS6110 5' and 3' polymorphic fragments, using differentially labeled fluorescent primers. The resulting amplicons are then fractionated on a capillary sequencer and the signal peaks analyzed as digital data.

RESULTS

IS6110-5'3'FP consistently detected and resolved both 5' and 3' IS6110 polymorphic fragments (35% and 65%, respectively) with a high level of reproducibility. The method differentiated all M. tuberculosis strains, as did IS6110 restriction fragment length polymorphism (RFLP), the gold standard of IS6110-based typing. Strikingly, the potential of IS6110-5'3'FP to resolve more polymorphic fragments than IS6110 RFLP was demonstrated.

CONCLUSIONS

IS6110-5'3'FP demonstrated sufficient potential to be a promising automated alternative to IS6110 RFLP, amenable to high throughput analysis and inter-laboratory comparison.

Genotyping of French Bacillus anthracis strains based on 31-loci multi locus VNTR analysis: epidemiology, marker evaluation, and update of the internet genotype database

Background

Bacillus anthracis is known to have low genetic variability. In spite of this lack of diversity, multiple-locus variable-number tandem repeat (VNTR) analysis (MLVA) and single nucleotide polymorphisms (SNPs) including the canonical SNPs assay (canSNP) have proved to be highly effective to differentiate strains. Five different MLVA schemes based on a collection of 31 VNTR loci (MLVA8, MLVA15, MLVA20, MLVA25 and MLVA31) with increased resolving power have been described.

Results

MLVA31 was applied to characterize the French National Reference Laboratory collection. The total collection of 130 strains is resolved in 35 genotypes. The 119 veterinary and environmental strains collection in France were resolved into 26 genotypes belonging to three canSNP lineages and four MLVA clonal complexes (CCs) with particular geographical clustering. A subset of seven loci (MLVA7) is proposed to constitute a first line assay. The loci are compatible with moderate resolution equipment such as agarose gel electrophoresis and show a good congruence value with MLVA31. The associated MLVA and SNP data was imported together with published genotyping data by taking advantage of major enhancements to the MLVAbank software and web site.

Conclusions

The present report provides a wide coverage of the genetic diversity of naturally occurring B. anthracis strains in France as can be revealed by MLVA. The data obtained suggests that once such coverage is achieved, it becomes possible to devise optimized first-line MLVA assays comprising a sufficiently low number of loci to be typed either in one multiplex PCR or on agarose gels. Such a selection of seven loci is proposed here, and future similar investigations in additional countries will indicate to which extend the same selection can be used worldwide as a common minimum set. It is hoped that this approach will contribute to an efficient and low-cost routine surveillance of important pathogens for biosecurity such as B. anthracis.