Non-tuberculous mycobacteria I: one year clinical isolates identification in Tertiary Hospital Aids Reference Center, Rio de Janeiro, Brazil, in pre highly active antiretroviral therapy era

RESUMO

The aim of this study was to determine the prevalence of non-tuberculous mycobacteria (NTM) isolates at University Hospital, Reference Center for Aids in Rio de Janeiro, Brazil, during one year. We used standard biochemical tests for species identification and IS1245 PCR amplification was applied as a Mycobacterium avium specific identification marker. Four hundred and four specimens from 233 patients yielded acid-fast bacilli growth. M. tuberculosis was identified in 85 percent of the patients and NTM in 15 percent. NTM disseminated infection was a common event correlated with human immunodeficiency virus (HIV) infected patients and only in HIV negative patients the source of NTM was non sterile site. M. avium complex (MAC) was biochemically identified in 57.8 percent (49/83) of NTM isolates, most of them from sterile sites (75.5 percent), and in 94 percent (46/49) the IS 1245 marker specific for M. avium was present. Twenty NTM strains showed a MAC biochemical pattern with the exception of a urease-positive (99 percent of MAC are urease-negative), however IS1245 was detected in 96 percent of the strains leading to their identification as M. avium. In this group differences in NTM source was not significant. The second most frequently isolated NTM was identified as M. scrofulaceum (7.2 percent), followed by M. terrae (3.6 percent), M. gordonae (2.4 percent), M. chelonae (1.2 percent), M. fortuitum (1.2 percent) and one strain which could not be identified. All were IS1245 negative except for one strain identified as M. scrofulaceum. It is interesting to note that non-sterile sites were the major source of these isolates (92.8 percent). Our finding indicated that M. avium is still the major atypical species among in the MAC isolates recovered from Brazilian Aids patients without highty active antiretroviral therapy schema. Some discrepancies were seen between the identification methods and further investigations must be done to better characterize NTM isolates using other phenotypic and genotypic methods: