Pulmonary Infections Caused by Emerging Pathogenic Species of Nocardia

Case Report: Nocardia amamiensis Infection Leading to Worsening of Chronic Obstructive Pulmonary Disease Symptoms in an Elderly Man

Nocardiosis is a rare opportunistic infection mostly affecting the lungs, brain, or skin of immunocompromised individuals. Most pulmonary nocardiosis patients present with nonspecific clinical features such as productive cough, exertional dyspnea, and fever. The disease is uncommonly suspected, especially in tuberculosis-endemic regions, and clinical diagnosis is often delayed, resulting in high mortality. Pulmonary nocardiosis in apparently immunocompetent individuals is uncommon. Here, we present the case of an elderly gentleman with a background history of poorly controlled diabetes but no history of systemic steroid use who presented with worsening symptoms of chronic obstructive pulmonary disease in the form of productive cough and dyspnea. The patient had diffuse crepitations in bilateral lung fields and an arterial oxygen saturation of 86% at admission. Sputum microscopy revealed gram-positive filamentous bacteria that could be successfully cultured and identified as Nocardia amamiensis on 16S ribosomal RNA sequencing. Contrast-enhanced computed tomography of the lungs revealed cavitary nodules and consolidation. The patient responded well to treatment with specific antibiotics based on sensitivity patterns. Because of the nonspecific clinical and radiological findings in pulmonary nocardiosis, a high index of suspicion is required, especially in tuberculosis-endemic regions.

Genotypic and phenotypic prevalence of Nocardia species in Iran: First systematic review and meta-analysis of data accumulated over years 1992-2021

Background

Nocardia species belong to the aerobic actinomycetes group of bacteria which are gram-positive and partially acid-fast Bacilli. These bacteria may sometimes be associated with nosocomial infections. Nocardia diseases are not required to be reported to public health authorities in Iran. Hence, the present study was designed to determine the prevalence of human Nocardia spp. in Iran by using a systematic review and meta-analysis according to the preferred reporting items for systematic reviews and meta-Analyses statement.

Methods

The data of the prevalence of Nocardia species were collected from databases such as Embase, PubMed/MEDLINE via Ovid, Web of Science, Scopus and Google Scholar as well as national Iranian databases, including SID, Magiran. Analyses were conducted by STATA 14.0.

Results

The meta-analyses showed that the proportion of Nocardia spp. in Iranian studies varied from 1.71(1.17, 2.24) to 0.46(0.09, 0.83). N. asteroides (21% [95% CI 1.17, 2.24]), N. cyriacigeorgica (17% [95% CI 0.99, 1.77]), N. facanica (10% [95% CI 0.75, 1.00]) were considered to be common causative agents.

Conclusions

Our study presents that despite the fact that Nocardia spp. are normally are saprophytic organisms, are currently accounts as emerging pathogens due to an increase in immunocompromised patients among Iranian populations. Considering our results, the establishment of advanced diagnostic facilities for the rapid detection of Nocardia infections are required for optimal therapeutic strategies of Nocardia spp. in Iran. Our findings could help the programmatic management of the disease within the context of Nocardia control programs.