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A5375 - Correlation Between Zielh-Neelsen, PCR and Culture for Mycobacterium Identification in a Colombian Hospital
Author Block: A. Baldión-Elorza1, G. A. Martínez Salazar2, J. S. Cabrera Silva2, A. F. Delgado Villareal2, P. Rodríguez1, S. A. Turriago Martinez1, F. Soto3, D. Palacios1, J. H. Roa Buitrago2; 1Pathology and Laboratories, Fundacion Santa Fe de Bogotá, Bogota, Colombia, 2Department of Internal Medicine, Fundacion Santa Fe de Bogotá, Bogota, Colombia, 3School of Medicine, Universidad Autónoma de México, Ciudad de México, Mexico.
Mycobacterias, mainly M. tuberculosis, are subject of public health interest. In Colombia according to data published by the National Health Institute, in 2016 there were 13.626 cases of tuberculosis. Meanwhile in Central and South America, Non-tuberculous mycobacterium (NTM) was estimated at 1 per 100,000. We reviewed our database of samples taken to diagnose infection by Mycobacterias. The aim of the study was to characterized the pathogens and compare the different diagnostic methods against gold standard (GS). It is important to know our statistics of Mycobacterium infection in order to create local protocols and guidelines. Type of study: Retrospective and descriptive study. Materials and methods: We reviewed a database recorded from 2010 to 2015 in the laboratory at Fundación Santa Fe de Bogotá. We investigated the local prevalence of Mycobacteria infection and the correlation of the three methods selected for our study (Zielh-Neelsen stain (ZN), Mycobacterium culture or PCR). Results: We reviewed a total of 1071 samples stained with ZN, of these 43 (4%) were positive. 59 samples (93.2% from BAL) were positive for any of the two methods (culture or PCR). From these only 50 had culture and 55 PCR. In the culture group 28 were positive 28/50 (56%) corresponding to 53% M. tuberculosis, 25% NTM and 22% M. tuberculosis complex. In the PCR group 36 were positive (88.8%) and 19 negative (12%). Only 32 (88.8%) and 13 (36%) of the PCR+ samples were also positive for ZN and culture. And 12 (63%) cultures from the 19 negative PCR results. From the 36 positive PCR samples, we obtained 32 (88.8%) ZN positive results and 13 (36%) cultures. From the 19 PCR negative samples, 12 (63%) were culture positive. Conclusions: 1. If we take only positive culture as Gold Standard, only 28 cases were diagnosed by this method. 2. From the 14 cases of negative culture, we found that 5 PCR and 9 ZN were positive. A possible reason could be that the manipulation or dilution of the samples affect the microorganism viability. 3. We found a prevalence of 13 per 1.000 of Mycobacterial infection and 6.5 per 1.000 of NTM isolation, mainly from BAL. The behavior of the NTM isolation were higher than the reported in the medical literature. This show us the importance of the clinical criteria to determine the patients who are really infected.