Isolation, biochemical and molecular identification of Nocardia species among TB suspects in northeastern, Tanzania; a forgotten or neglected threat?

Abstract

BackgroundPulmonary nocardiosis mimic pulmonary tuberculosis in most clinical and radiological manifestations. In Tanzania, where tuberculosis is one of the major public health threat clinical impact of nocardiosis as the cause of the human disease remains unknown. The objective of the present study was to isolate and identify Nocardia isolates recovered from TB suspects in Northeastern, Tanzania by using biochemical and molecular methods.MethodsThe study involved 744 sputum samples collected from 372 TB suspects from four periphery diagnostic centers in Northeastern, Tanzania. Twenty patients were diagnosed as having presumptively Nocardia infections based on microscopic, cultural characteristics and biomèrieux ID 32C Yeast Identification system and confirmed using 16S rRNA and hsp65 gene specific primers for Nocardia species and sequencing.ResultsBiochemically, the majority of the isolates were N. asteroides (n = 8/20, 40%), N. brasiliensis (n = 4/20, 20%), N. farcinica (n = 3/20, 15%), N. nova (n = 1/20, 5%). Other aerobic actinomycetales included Streptomyces cyanescens (n = 2/20, 10%), Streptomyces griseus, Actinomadura madurae each (n = 1/20, 5%). Results of 16S rRNA and hsp65 sequencing were concordant in 15/17 (88. 2%) isolates and discordant in 2/17 (11.8%) isolates. Majority of the isolates belonged to N. cyriacigeorgica and N. farcinica, four (23.5%) each.ConclusionsOur findings suggest that Nocardia species may be an important cause of pulmonary nocardiosis that is underdiagnosed or ignored. This underscores needs to consider pulmonary nocardiosis as a differential diagnosis when there is a failure of anti-TB therapy and as a possible cause of human infections.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-017-2520-8) contains supplementary material, which is available to authorized users.

Nontuberculous mycobacterial and Nocardia infections mimicking pulmonary tuberculosis: a retrospective study of a general hospital patient population in China

“…Our data demonstrated that a quarter of culture-positive ‘suspected TB patients’ are infected with NTM or Nocardia organisms. Notably, nearly all patients with non-TB infections presented with clinical syndromes mimicking those of pulmonary TB, suggesting that the clinical signs are not specific enough to differentiate TB from NTM or Nocardia infections [7, 12]. Therefore, in view of these challenges, the clinical confirmation of patients must still rely mainly on laboratory testing, especially for species identification.…”

“…Unfortunately, clinical manifestations are not specific to TB, leading to delayed treatment or missed diagnoses [6]. Moreover, smear microscopy and mycobacterial culture tests, the laboratory methods universally used for TB diagnosis in general hospitals, do not differentiate between Mycobacterium tuberculosis and other acid-fast bacilli such as non-tuberculous mycobacteria and Nocardia species [6, 7]. In fact, previous studies have demonstrated that patients infected with the latter may be misdiagnosed as TB cases, especially in settings with high TB prevalence where these opportunistic genera are neglected as causes of human disease [7].…”

Assessment of sputum smear-positive but culture-negative results among newly diagnosed pulmonary tuberculosis patients in Tanzania

“…Recently, one study in Tanzania isolated different species of Nocardia among TB suspects, suggesting that Nocardia spp. are an important cause of pulmonary infections that are merely underdiagnosed and/or ignored 27. Furthermore, poor quality of smear microscopy and reading errors may result in either failure to detect active TB or reporting of non-TB cases 28,29.…”

Pathogenic Nocardia: A diverse genus of emerging pathogens or just poorly recognized?

“…Concomitant infections in immunocompromised individuals are common and can include Nocardia co-infecting with other bacterial, fungal, and viral pathogens [11,12]. Tuberculosis (TB) caused by another actinomycete, Mycobacterium tuberculosis, is associated with chronic lung disease, and owing to the similarity in diagnosis and clinical manifestation of nocardiosis and TB, accurate identification of these two acid-fast bacilli can be difficult [13][14][15]. In some cases, concomitant nocardial and TB infections have also been observed and are more likely to occur in HIV-infected individuals [16].…”

“…In some cases, concomitant nocardial and TB infections have also been observed and are more likely to occur in HIV-infected individuals [16]. Treatment of choice for tuberculosis is ineffective for nocardiosis, underscoring the importance of accurate diagnosis for effective treatment [13,14,17].…”