Multicentre laboratory validation of the colorimetric redox indicator (CRI) assay for the rapid detection of extensively drug-resistant (XDR) Mycobacterium tuberculosis.

OBJECTIVES: To perform a multicentre study to evaluate the performance of the colorimetric redox indicator (CRI) assay and to establish the MICs and critical concentrations of rifampicin, isoniazid, ofloxacin, kanamycin and capreomycin. METHODS: The study was carried out in two phases. Phase I determined the MIC of each drug. Phase II established critical concentrations for the five drugs tested by the CRI assay compared with the conventional proportion method. RESULTS: Phase I: a strain was considered resistant by the CRI assay if the MIC was ≥0.5 mg/L for rifampicin, ≥0.25 mg/L for isoniazid, ≥4.0 mg/L for ofloxacin and ≥5.0 mg/L for kanamycin and capreomycin. Sensitivity was 99.1% for isoniazid and 100% for the other drugs and specificity was 97.9% for capreomycin and 100% for the other drugs. Phase II: the critical concentration was 0.5 mg/L for rifampicin, 0.25 mg/L for isoniazid, 2.0 mg/L for ofloxacin and 2.5 mg/L for kanamycin and capreomycin giving an overall accuracy of 98.4%, 96.6%, 96.7%, 98.3% and 90%, respectively. CONCLUSIONS: Results demonstrate that the CRI assay is an accurate method for the rapid detection of XDR Mycobacterium tuberculosis. The CRI assay is faster than the conventional drug susceptibility testing method using solid medium, has the same turnaround time as the BACTEC MGIT 960 system, but is less expensive, and could be an adequate method for low-income countries.

Micobacteriosis diseminada con compromiso de válvula aórtica protésica: primer caso de Mycobacterium peregrinum de tipo III reportada en Colombia / Disseminated mycobacteriosis affecting a prosthetic aortic valve: first case of Mycobacterium peregrinum type III reported

Las micobacterias de rápido crecimiento son microorganismos pertenecientes a las micobacterias no tuberculosas que tienen amplia distribución ambiental. Aunque usualmente no son patógenas para los humanos, en condiciones desfavorables, pueden causar enfermedad en la población general o en huéspedes inmunocomprometidos, por lo cual se consideran oportunistas. Mycobacterium preregrinum es una micobacteria de rápido crecimiento perteneciente al complejo fortuitum que ha sido reportado como responsable de casos de micobacteriosis en humanos.Se presenta el caso de una micobacteriosis por M. peregrinum de tipo III, el primero reportado en Colombia, en una paciente de 17 años de edad con una endocarditis de una válvula aórtica protésica, implantada inicialmente por estenosis subaórtica congénita con insuficiencia y, posteriormente, por estenosis aórtica relacionada con la válvula inicialmente implantada. Un año después del segundo implante, presentó sintomas respiratorios y pérdida de peso sugestivos de tuberculosis pulmonar.Las coloraciones de Ziehl-Neelsen del esputo fueron positivas aunque la radiografía de tórax no mostró compromiso del parénquima. En el ecocardiograma se encontró una vegetación en la válvula aórtica. En las muestras de sangre y de esputo, se identificó M. peregrinum de tipo III por cultivo, pruebas bioquímicas y análisis molecular del gen hsp65 por PCR-restriction pattern analysis (PRA). La paciente se sometió a cambio de válvula y recibió tratamiento combinado contra la micobacteria, con rápida recuperación. Las muestras tomadas del sistema respiratorio y sanguíneo se tornaron negativas para micobacterias.

Rapidly growing mycobacteria are non-tuberculous mycobacteria amply present in the environment. Although they are not usually pathogenic for humans, they are opportunistic in that they can cause disease in people with disadvantageous conditions or who are immunocompromised. Mycobacterium peregrinum, an opportunistic, rapidly growing mycobacteria, belongs to the M. fortuitum group and has been reported as responsible for human cases of mycobacteriosis. A case of M. peregrinum type III is herein reported as the first in Colombia. It presented as a disseminated disease involving a prosthetic aortic valve (endocarditis) in a seventeen-year-old girl with a well-established diagnosis of prosthetic aortic valve endocarditis who was referred for a surgical replacement. Due to a congenital heart disease (subaortic stenosis with valve insufficiency), she had two previous aortic valve implantation surgeries. One year after the second implantation, the patient presented with respiratory symptoms and weight lost indicative of lung tuberculosis. A chest X-ray did not show parenchymal compromise but several Ziehl-Neelsen stains were positive. An echocardiography showed a vegetation on the prosthetic aortic valve. In blood and sputum samples, M. peregrinum type III was identified through culture, biochemical tests and hsp65 gene molecular analysis (PRA). The patient underwent a valve replacement and received a multidrug antimycobacterial treatment. Progressive recovery ensued and further samples from respiratory tract and blood were negative for mycobacteria.

Disseminated mycobacteriosis affecting a prosthetic aortic valve: first case of Mycobacterium peregrinum type III reported in Colombia.

Rapidly growing mycobacteria are non-tuberculous mycobacteria amply present in the environment. Although they are not usually pathogenic for humans, they are opportunistic in that they can cause disease in people with disadvantageous conditions or who are immunocompromised. Mycobacterium peregrinum, an opportunistic, rapidly growing mycobacteria, belongs to the M. fortuitum group and has been reported as responsible for human cases of mycobacteriosis. A case of M. peregrinum type III is herein reported as the first in Colombia. It presented as a disseminated disease involving a prosthetic aortic valve (endocarditis) in a seventeen-year-old girl with a well-established diagnosis of prosthetic aortic valve endocarditis who was referred for a surgical replacement. Due to a congenital heart disease (subaortic stenosis with valve insufficiency), she had two previous aortic valve implantation surgeries. One year after the second implantation, the patient presented with respiratory symptoms and weight lost indicative of lung tuberculosis. A chest X-ray did not show parenchymal compromise but several Ziehl-Neelsen stains were positive. An echocardiography showed a vegetation on the prosthetic aortic valve. In blood and sputum samples, M. peregrinum type III was identified through culture, biochemical tests and hsp65 gene molecular analysis (PRA). The patient underwent a valve replacement and received a multidrug antimycobacterial treatment. Progressive recovery ensued and further samples from respiratory tract and blood were negative for mycobacteria.