Abstract
In this study, the aim was to investigate the discriminatory power of molecular diagnostics based on mNGS and traditional 16S ribosomal RNA PCR among Nocardia species. A total of fourteen clinical isolates from patients with positive Nocardia cultures and clinical evidence were included between January 2017 and June 2020 in HeNan Provincial People’s Hospital. DNA extraction and 16S rRNA PCR were performed on positive cultures, and pathogens were detected by mNGS in these same samples directly. Among the 14 Nocardia isolates, four species were identified, and N. cyriacigeorgica (8 cases) is the most common species. Twelve of the 14 Nocardia spp. isolates were identified by the two methods, while two strains of N. cyriacigeorgica were not identified by mNGS. All tested isolates showed susceptibility to trimethoprim-sulfamethoxazole (SXT), amikacin and linezolid. Apart from Nocardia species, other pathogens such as Acinetobacter baumannii, Klebsiella pneumonia, Aspergillus, Enterococcus faecalis, Human herpesvirus, etc., were detected from the same clinical samples by mNGS. However, these different pathogens were considered as colonization or contamination. We found that it is essential to accurately identify species for determining antibiotic sensitivity and, consequently, choosing antibiotic treatment. 16S rRNA PCR was useful for identification of nocardial infection among species, while this technique needs the clinicians to make the pre-considerations of nocardiosis. However, mNGS may be a putative tool for rapid and accurate detection and identification of Nocardia, beneficial for applications of antimicrobial drugs and timely adjustments of medication.
Highlights
Nocardia is a genus of aerobic, Gram-positive, branching, filamentous, weakly acid-fast bacteria (Wang et al, 2015)
A study by Yang et al that analyzed 13 patients infected by nocardiosis showed that twelve cases were diagnosed with pulmonary nocardiosis and bronchiectasis in 6 patients (Yang et al, 2017)
Bronchiectasis and chronic obstructive pulmonary disease (COPD) were deemed as risk factors for pulmonary nocardiosis (Kancherla et al, 2019)
Summary
Nocardia is a genus of aerobic, Gram-positive, branching, filamentous, weakly acid-fast bacteria (Wang et al, 2015). The organisms are saprophytic and are found in water, soil, dust, and vegetable matter. Upon exposure to dust particles, Nocardia may become airborne, causing infection by inhalation (Chen et al, 2014). Individuals with poor immune system, for example, patients with lung disorders, diabetes, cancers, HIV/AIDS, chronic alcoholism, connective tissue disorders, organ transplantation, and those undergoing corticosteroid therapy are prone to infections with Nocardia spp. The major clinical symptoms of human nocardiosis include lymphadenitis, lymphangitis, encephalitis, pneumonia, and cutaneous tissue lesions (Condas et al, 2015). Pulmonary nocardiosis is clinically severe (Sadamatsu et al, 2017). Nocardiosis has been described as isolated cases and case series in lungs and other sites of immunocompetent patients, representing 33%-56% of total cases. Bronchiectasis, chronic obstructive pulmonary disease (COPD), pulmonary alveolar proteinosis, and asthma are predisposing factors among patients with chronic respiratory diseases (Sadamatsu et al, 2017)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
