Avaliação do crescimento de poucas colônias de Mycobacterium tuberculosis em meio de cultura sólido como indicador de contaminação cruzada, utilizando técnicas de tipagem molecular

• Autor(a) principal: Ribeiro, Fabíola Karla Corrêa
• Data de Publicação: 2006
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/5893
• topic: Contaminação cruzada; Biologia molecular; Mycobacterium tuberculosis; Tuberculose; Doenças Infecciosas e Parasitárias; 61

For many years, it has been thought that a positive culture of Mycobacterium tuberculosis is a definitive diagnostic evidence of tuberculosis (TB). However, the recent use of molecular tools have resulted in increased recognition of crosscontamination events linked, most of the times, to laboratory procedures. Features of cross-contamination include: culture results not consistent with the clinical course of the patient, isolates with unexpected drug resistance, single culture-positive specimen and low colony count on solid medium. Nonetheless, true-positive cultures of specimens from some groups of patients (with preliminary active pulmonary tuberculosis, HIV infection, or under treatment) can also have some of the characteristics outlined above. The evaluation of low-yield growth cultures as a microbiological marker of cross-contamination would be very helpful in confirming or excluding TB cases. In the present study, we assessed whether or not low-yield growth cultures could be considered a cross-contamination marker, using molecular typing methods (RAPET e RFLP). From January 2003 to January 2005, we evaluated 109 low-yield growth cultures (less than 20 colonies) from 97 patients that were processed in 94 different days. The false-positive rate found in this study was of 1,8% and 2,0% per samples and patients, respectively. These results suggest that low-yield growth cultures do not seem to be a considerable marker for crosscontamination, especially in a clinical trial mycobacteriology laboratory or in laboratories working under the good laboratory and clinical practices (GLCP). It has also been shown that the modified RAPET method is rapid (1 to 2 days), reproducible, and valuable in identifying episodes of possible laboratory crosscontamination.