Gene sequencing for routine verification of pyrazinamide resistance in Mycobacterium tuberculosis: a role for pncA but not rpsA.

Pyrazinamide (PZA) is an important component of first-line therapy for the treatment of tuberculosis. Here, we evaluate targeted gene sequencing as a supplement to phenotypic PZA susceptibility testing of Mycobacterium tuberculosis. Routine sequencing of pncA, but not rpsA, is effective for verification of PZA susceptibility results.

Leprosy-like illness in a patient with Mycobacterium lepromatosis from Ontario, Canada.

Here we present the first case of a patient from Ottawa Canada, presenting with leprosy-like illness associated with Mycobacterium lepromatosis. The patient had no history of travel to leprosy-endemic areas or any obvious risk factors. Clinically, the patient presented with an anesthetic maculopapular rash on the trunk, back, and extremities. A skin biopsy of a lesion revealed a dermal lymphohistiocytic infiltration involving the vessels with an inflammatory process extending to the nerves. A neurological exam also identified a severe sensorimotor polyneuropathy. Concurrently, the patient was diagnosed with non-resectable, non small cell carcinoma of the lung, further complicating his clinical presentation. A Kinyoun stain of nasal blows and a Fite stain of the skin biopsy revealed few to moderate acid fast bacilli respectively. Cultures of the skin biopsy and multiple nasal blows were negative. Molecular studies of a skin biopsy sample including sequence analysis of a 765 bp region of the 16s rRNA gene eventually identified the organism with 100% homology to M. lepromatosis. The patient was treated for leprosy and appeared to improve slightly on therapy but died as a result of his malignancy approximately five months after the initiation of therapy. This represents the first case of a patient with M. lepromatosis like illness outside of Mexico and Singapore.

The relative test performance characteristics of two commercial assays for the detection of Mycobacterium tuberculosis complex in paraffin-fixed human biopsy specimens.

The Seeplex TB Detection-2 assay (Rockville, MD) is a nested endpoint PCR for the Mycobacterium tuberculosis complex (MTBC) targets IS6110 and MPB64 that utilizes dual priming oligonucleotide technology. When used to detect the presence of MTBC DNA in formalin-fixed paraffin-embedded tissue specimens, the sensitivity and specificity of this assay is equivalent to a labor-intensive traditional endpoint PCR assay and is more sensitive than a commercial real-time PCR assay.

False-positive amplified Mycobacterium tuberculosis direct test results for samples containing Mycobacterium leprae.

Nucleic acid amplification tests are widely used in mycobacteriology laboratories to rapidly detect Mycobacterium tuberculosis complex directly in clinical specimens. A positive result provides an early diagnosis of tuberculosis, allowing initiation of appropriate therapy and public health measures.