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. 2014 Sep-Oct;56(5):397-401.
doi: 10.1590/s0036-46652014000500005.

Differentiation between Nocardia spp. and Mycobacterium spp.: Critical aspects for bacteriological diagnosis

Edna Cleide Mendes Muricy  1 , Romilda Aparecida Lemes  2 , Sidney Bombarda  3 , Lucilaine Ferrazoli  2 , Erica Chimara  2
Affiliations

Differentiation between Nocardia spp. and Mycobacterium spp.: Critical aspects for bacteriological diagnosis

Edna Cleide Mendes Muricy et al. Rev Inst Med Trop Sao Paulo. 2014 Sep-Oct.

Abstract
in English, Portuguese

New methodologies were developed for the identification of Nocardia but the initial diagnosis still requires a fast and accurate method, mainly due to the similarity to Mycobacterium, both clinical and bacteriologically. Growth on Löwenstein-Jensen (LJ) medium, presence of acid-fast bacilli through Ziehl-Neelsen staining, and colony morphology can be confusing aspects between Nocardia and Mycobacterium. This study describes the occurrence of Nocardia spp. in a mycobacterial-reference laboratory, observing the main difficulties in differentiating Nocardia spp. from Mycobacterium spp., and correlating isolates with nocardiosis cases. Laboratory records for the period between 2008 and 2012 were analyzed, and the isolates identified as Nocardia sp. or as non-acid-fast filamentous bacilli were selected. Epidemiological and bacteriological data were analyzed as well. Thirty-three isolates identified as Nocardia sp. and 22 as non-acid-fast bacilli were selected for this study, and represented 0.12% of isolates during the study period. The presumptive identification was based on macroscopic and microscopic morphology, resistance to lysozyme and restriction profiles using the PRA-hsp65 method. Nocardia spp. can grow on media for mycobacteria isolation (LJ and BBL MGIT™) and microscopy and colony morphology are very similar to some mycobacteria species. Seventeen patients (54.8%) were reported and treated for tuberculosis, but presented signs and symptoms of nocardiosis. It was concluded that the occurrence of Nocardia sp. during the study period was 0.12%. Isolates with characteristics of filamentous bacilli, forming aerial hyphae, with colonies that may be pigmented, rough and without the BstEII digestion pattern in PRA-hsp65 method are suggestive of Nocardia spp. For a mycobacterial routine laboratory, a flow for the presumptive identification of Nocardia is essential, allowing the use of more accurate techniques for the correct identification, proper treatment and better quality of life for patients.

Novas metodologias têm sido desenvolvidas para a identificação de Nocardia spp. mas o diagnóstico inicial ainda necessita de método rápido e preciso, principalmente devido à similaridade com o gênero Mycobacterium, clínica e bacteriologicamente. O crescimento em meio de Löwenstein Jensen (LJ), a presença de bacilos corados pela coloração de Ziehl Neelsen e colônias com características diferentes podem ser fatores de confusão entre nocardias e micobactérias. Este estudo descreve a ocorrência de Nocardia spp. em laboratório de referência em micobacteriologia, observando-se as principais dificuldades em diferenciar Nocardia spp. e Mycobacterium spp., correlacionando isolados com casos de nocardiose. Os registros laboratoriais dos anos 2008 a 2012 foram analisados e os isolados identificados como Nocardia sp. ou como bacilos não álcool - ácido resistentes (NBAAR) foram selecionados. Os dados epidemiológicos e bacteriológicos foram analisados. Trinta e três isolados identificados como Nocardia sp. e 22 como NBAAR foram selecionados para este estudo, perfazendo 0,12% do total de isolados identificados no período estudado. A identificação presuntiva foi baseada na morfologia macroscópica e microscópica, resistência à lisozima e perfis de restrição pelo método PRA-hsp65. Nocardia spp. pode crescer em meios de isolamento para micobactérias (LJ e BBL MGIT™) e microscopia de morfologia e as colônias são muito semelhantes a algumas espécies de micobactérias. Dezessete pacientes (54,8%) foram notificados e tratados para tuberculose, mas apresentaram sinais e sintomas para nocardiose. Concluimos que a ocorrência de Nocardia sp. no período estudado foi de 0,12%. Os isolados com características de bacilos filamentosos, formadores de hifas aéreas, com colônias que podem ter pigmento, rugosas e que não possuem padrão de digestão para BstEII no método PRA-hsp65 são sugestivos de Nocardia spp. Para um laboratório de rotina de Micobactérias, um fluxo de identificação presuntiva para Nocardia spp. é essencial para permitir que esses isolados sejam identificados com técnicas mais precisas, para que seja oferecido o tratamento adequado e qualidade de vida aos pacientes.

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Figures

Fig. 1 -
Fig. 1 -. Macroscopic growth of Nocardia sp. in: A) Lowenstein Jensen medium, B) Agar Sabouraud and C) Bactec MGIT medium.
Fig. 2 -
Fig. 2 -. Microscopic appearance of Nocardia spp. isolates by Ziehl Neelsen staining. 100x increased.
Fig. 3 -
Fig. 3 -. Molecular pattern of Nocardia spp. isolates digested by BstEII restriction enzyme. M: 50 bp molecular size marker.
See this image and copyright information in PMC

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