Amplified in situ hybridization with peptide nucleic acid probes for differentiation of Mycobacterium tuberculosis complex and nontuberculous Mycobacterium species on formalin-fixed, paraffin-embedded archival biopsy and autopsy samples.

The aim of this study was to evaluate sensitivity and specificity of in situ hybridization (ISH) using peptide nucleic acid (PNA) probes and tyramide-based amplification for the differentiation between Mycobacterium tuberculosis (MTB) and mycobacteria other than tuberculosis (MOTT) on formalin-fixed, paraffin-embedded tissue samples. We performed ISH simultaneously with both probes on 86 specimens from different organs: 70 obtained at autopsy and 16 by biopsy, all with a histologic evidence of mycobacterial infection confirmed by Ziehl-Neelsen-positive staining. Taking culture as the "gold standard," the sensitivity and the specificity of the MTB probe were 100% (41/41) and 95% (38/40), respectively. In only 2 cases ISH failed to identify mycobacteria. Culture results were not available in 3 cases. We propose ISH as a relatively simple and rapid method to differentiate mycobacteria on formalin-fixed, paraffin-embedded specimens (it is more specific than usual histologic stains) and as an alternative to polymerase chain reaction, allowing the morphologic evaluation of positive bacilli.

A one-step solid phase immunoassay for simultaneous detection of serum IgG and IgM antibodies to Borrelia burgdorferi.

A one-step immunoassay for simultaneous detection of serum IgG and IgM antibodies to Borrelia burgdorferi has been developed. The assay is based on C1q, which binds to immune complexes containing IgG and/or IgM antibodies. Micro-beads pre-coated with antibodies to human C1q are mixed with human serum samples and fluorochrome-labelled B. burgdorferi flagellum antigen. In the presence of serum IgG and/or IgM antibodies to B. burgdorferi, fluorochrome-labelled antigen/antibody complexes are formed. These are then bound by serum C1q and are subsequently captured on the anti-C1q-coated beads. The sample is analysed on a flow cytometer and the presence of fluorescent beads is, thus, indicative of a positive test result. In the present study the sensitivity and specificity of the assay are compared to those of the indirect IDEIA B. burgdorferi IgG and the mu-chain capture IDEIA B. burgdorferi IgM ELISAs for separate determination of IgG and IgM. Detection using a flow cytometer can be performed without separation of the beads from the reaction mixture, which means that in practice, the method is carried out as a one-step assay and it is, thus, very suitable for automation. Other advantages of this kind of assay includes an antibody/antigen reaction which occurs in solution and the potential of using the method for the detection of antibodies against several antigens from the same or different infectious agents (multi-parameter screening).