Comparison of PNA probe-based real-time PCR and Cobas TaqMan MTB for detection of MTBC

Liquid-Crystal-Based Immunosensor for Diagnosis of Tuberculosis in Clinical Specimens

Tuberculosis (TB) is a serious global health problem, although it is easily preventable and curable. The prevalence of TB is caused by a lack of simple, rapid, cheap, and effective TB diagnostic tests. In this study, we have established a novel liquid crystal (LC)-based immunosensor to diagnose TB in clinical specimens. The clinical serum samples were incubated on a TB antigen-immobilized substrate, and their optical LC responses were observed using a polarized light microscope. Specific binding of anti-TB antibodies to the TB antigen-immobilized surface only occurred in clinical specimens from TB patients, inducing the disruption of the orientation of LCs. This was followed by the distinctive change in the optical appearance of LCs from uniform to random. However, when clinical serum samples from healthy people or latent TB patients were incubated, the orientation of LCs remained uniform. Through the change of optical LC images, in 76% of TB patients, this essay correctly identified the patients as having antibodies to TB in their serums. 91% of healthy people free of TB were correctly identified as not having antibodies to TB. Thus, this LC-based immunosensor is a promising platform, particularly in clinical TB diagnostics, which does not require complicated preparation of clinical specimens or complex instrumentation.

Separation of Mycobacterium abscessus into subspecies or genotype level by direct application of peptide nucleic acid multi-probe- real-time PCR method into sputa samples

Background

Recently, we introduced a novel peptide nucleic acid (PNA) multi-probe real time PCR method targeting the hsp65 gene (hsp65 PNA RT-PCR) to distinguish Mycobacterium abscessus groups.

Methods

Here, we evaluated the usefulness of the hsp65 PNA RT-PCR for the direct identification of the M. abscessus group at the subspecies and genotype levels from sputa samples. The method was applied to total sputa DNA from 60 different patients who were identified as having mycobacterial infections via rpoB PCR restriction analysis of the same cultures.

Results

The hsp65 PNA RT-PCR method had higher sensitivity than the multi-probe real-time PCR assay targeting hsp65 (HMPRT-PCR) for the detection of M. abscessus from sputum [96.7 % (29/30 samples) vs. 70 % (21/30 samples); 100 % specificity].

Conclusions

These results suggest that the PNA-based method is feasible for the detection of M. abscessus members not only from cultures but also directly from sputa.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-015-1076-8) contains supplementary material, which is available to authorized users.

Fluorescence melting curve analysis using self-quenching dual-labeled peptide nucleic acid probes for simultaneously identifying multiple DNA sequences

Previous fluorescence melting curve analysis (FMCA) used intercalating dyes, and this method has restricted application. Therefore, FMCA methods such as probe-based FMCA and molecular beacons were studied. However, the usual dual-labeled probes do not possess adequate fluorescence quenching ability and sufficient specificity, and molecular beacons with the necessary stem structures are hard to design. Therefore, we have developed a peptide nucleic acid (PNA)-based FMCA method. PNA oligonucleotide can have a much higher melting temperature (Tm) value than DNA. Therefore, short PNA probes can have adequate Tm values for FMCA, and short probes can have higher specificity and accuracy in FMCA. Moreover, dual-labeled PNA probes have self-quenching ability via single-strand base stacking, which makes PNA more favorable. In addition, this method can facilitate simultaneous identification of multiple DNA templates. In conventional real-time polymerase chain reaction (PCR), one fluorescence channel can identify only one DNA template. However, this method uses two fluorescence channels to detect three types of DNA. Experiments were performed with one to three different DNA sequences mixed in a single tube. This method can be used to identify multiple DNA sequences in a single tube with high specificity and high clarity.

Development of a peptide nucleic acid-based multiprobe real-time PCR method targeting the hsp65 gene for differentiation among Mycobacterium abscessus strains

Recently, the need to distinguish between members of the Mycobacterium abscessus group has gained increasing attention. Here, we introduced a novel peptide nucleic acid (PNA) real-time PCR method targeting the hsp65 gene in order to distinguish between four subspecies within the M. abscessus group (M. abscessus and 3 types of M. massiliense).