Chronic granulomatous pleuritis caused by nocardia: PCR based diagnosis by nocardial 16S rDNA in pathological specimens

Nocardiosis: A Neglected Disease

Nocardiosis is a neglected tropical disease. It has varied geographical presence and a spectrum of clinical presentations. This review aims to focus on the epidemiology of nocardial infections with a systematic approach to their diagnosis and treatment. Nocardiacauses chronic infections and ailments, and may remain cryptic but progressive in its course. Unless suspected, diagnosis can be easily missed resulting in increased morbidity and mortality. Thorough knowledge of local epidemiology, demography, clinical course and presentation, diagnostic modalities, and antibiotic susceptibility patterns of the prevalent Nocardia species is essential to curb spread of this infection. This is a systematic review in which internet search has been done for citation indices (Embase, PubMed, Ovid, and other individual journals) till March 2020 utilizing the following key words "Nocardia," "taxonomy," "prevalence," "clinical features," "diagnosis," "treatment," and "susceptibility." We selected a total of 87 review articles, case series, and case reports all in English language.

The cytopathology of Actinomyces, Nocardia, and their mimickers

Nocardia species and Actinomyces species are 2 of the most commonly diagnosed filamentous bacteria in routine cytopathology practice. These genera share many overlapping cytomorphologic features, including their thin, beaded, branching, Gram-positive, GMS-positive filamentous structures that fragment at their peripheries into bacillary- and coccoid-appearing forms. Features that help distinguish between these 2 microorganisms include the width of their filamentous structures, the angles at which they branch, and their ability or lack thereof to retain a modified acid-fast stain. In addition to cytomorphologic overlap, overlap in clinical presentation is frequent with pulmonary and mucocutaneous presentations seen in both. Differentiating between Nocardia and Actinomyces is essential because patients with these infections require different approaches to medical management. Both antibiotic susceptibilities and the need for early surgical intervention as part of the treatment plan vary greatly among these 2 groups. This review focuses on the clinical presentation, cytomorphology and staining characteristics that can be useful in identifying and distinguishing between Nocardia and Actinomyces infections, as well as their mimickers.

Nocardia isolation from clinical samples with the paraffin baiting technique

BACKGROUND

The genus Nocardia is a cause of infection in the lungs, skin, brain, cerebrospinal fluid, eyes, joints and kidneys. Nocardia isolation from polymicrobial specimens is difficult due to its slow growth. Several methods have been reported for Nocardia isolation from clinical samples. In the current study, we used three methods: paraffin baiting technique, paraffin agar, and conventional media for Nocardia isolation from various clinical specimens from Iranian patients.

METHODS

In this study, we examined 517 samples from various clinical specimens such as: sputum of patients with suspected tuberculosis, bronchoalveolar lavage, sputum of patients with cystic fibrosis, tracheal aspirate, cutaneous and subcutaneous abscesses, cerebrospinal fluid, dental abscess, mycetoma, wound, bone marrow biopsy, and gastric lavage. All collected specimens were cultured on carbon-free broth tubes (paraffin baiting technique), paraffin agar, Sabouraud dextrose agar, and Sabouraud dextrose agar with cycloheximide and were incubated at 35°C for one month.

RESULTS

Seven Nocardia spp. were isolated with paraffin baiting technique, compared with 5 positive results with the paraffin agar technique and 3 positive results with Sabouraud dextrose agar with and without cycloheximide. The prevalence of nocardial infections in our specimens was 5.28%.

CONCLUSION

In the present study, the use of the paraffin baiting technique appeared to be more effective than other methods for Nocardia isolation from various clinical specimens.

An intrarenal abscess as presenting symptom of an infection with Nocardia farcinica in a patient after renal transplantation

A 52-year-old man presented 8 months after transplantation with an intrarenal mass, which proved to be caused by an infection with Nocardia farcinica. Because of the potential fatal course of nocardiosis, transplantectomy was performed and long-term antibiotic treatment was instituted. Three-and-a-half years later, this patient underwent successful re-transplantation under co-trimoxazole prophylaxis. At present, more than 1 year after his second transplant has been performed, there are no signs of recurrence of Nocardia infection. To our knowledge, this is the first report of a patient with nocardiosis with an intrarenal abscess as presenting symptom.

Clinical and laboratory features of the Nocardia spp. based on current molecular taxonomy

The recent explosion of newly described species of Nocardia results from the impact in the last decade of newer molecular technology, including PCR restriction enzyme analysis and 16S rRNA sequencing. These molecular techniques have revolutionized the identification of the nocardiae by providing rapid and accurate identification of recognized nocardiae and, at the same time, revealing new species and a number of yet-to-be-described species. There are currently more than 30 species of nocardiae of human clinical significance, with the majority of isolates being N. nova complex, N. abscessus, N. transvalensis complex, N. farcinica, N. asteroides type VI (N. cyriacigeorgica), and N. brasiliensis. These species cause a wide variety of diseases and have variable drug susceptibilities. Accurate identification often requires referral to a reference laboratory with molecular capabilities, as many newer species are genetically distinct from established species yet have few or no distinguishing phenotypic characteristics. Correct identification is important in deciding the clinical relevance of a species and in the clinical management and treatment of patients with nocardial disease. This review characterizes the currently known pathogenic species of Nocardia, including clinical disease, drug susceptibility, and methods of identification.