Search Results (51)

Background and Clinical Significance: Disseminated nocardiosis is a rare, life-threatening infection, often misdiagnosed due to its resemblance to other conditions. Case Presentation: A 62-year-old post-renal transplant patient presented with pulmonary, hepatic, and pancreatic lesions. Despite multiple negative bacterial cultures, a histopathological examination of the liver revealed necrotizing granulomas with filamentous microorganisms, ultimately identified as Nocardia. Conclusions: This case highlights diagnostic challenges and the importance of integrating microbiological, pathological, and radiographical findings to manage and diagnose disseminated nocardiosis infections in immunocompromised individuals. Full article

Nocardia spp. are opportunistic pathogens of humans, domestic animals, and wildlife that can cause high levels of morbidity and mortality. Here, we present a unique case of nocardial airsacculitis in a free-ranging mallard (Anas platyrhynchos) from Arizona, USA, and compare it to the hosts, geographic distribution, diagnostic methodology, and infection site of known nocardiosis cases in birds. A gross necropsy, histopathology, and bacterial culture were performed. There were no gross findings associated with the nocardiosis. Histopathology showed multiple granulomas expanding the air sac with intralesional filamentous bacteria that were Grocott’s methenamine silver-positive, Fite–Faraco and Ziehl–Neelsen acid-fast, positive with the Periodic acid–Schiff reaction, and variably Gram-positive. The organism was isolated in culture and identified as Nocardia cyriacigeorgica based on the sequencing of a 463 bp portion of the 16S rRNA gene. While reports of nocardiosis in the class Aves are rare and some are possibly misdiagnosed due to limited diagnostics, cases are reported globally, sometimes resulting in epizootics. More information is needed to understand whether immunosuppression plays a role in disease development in birds. Known to be an emerging pathogen in humans, N. cyriacigeorgica can be considered as a differential diagnosis for pulmonary and potentially cutaneous or disseminated infections in birds. Full article

Respiratory syncytial virus (RSV) represents one of the main respiratory infections found among immunocompromised patients. Objective: The study analyzes the incidence of RSV infection in different populations of immunocompromised patients as organ transplant recipients (lung, other solid organs, hematopoietic stem cells) and oncologic patients (solid organ malignancy and hematological malignancy) compared to a group of non-immunocompromised patients. We also assessed the prevalence of viral, bacterial, and mycotic coinfection. Moreover, we aimed at evaluating the efficacy of ribavirin treatment in terms of mortality reduction. Methods: We conducted a retrospective analysis on a total of 466 transplant patients undergoing bronchoscopy with bronchoalveolar lavage for suspected viral disease or surveillance between 2016 and 2023, compared to 460 controls. Results: The incidence of RSV was significantly higher in immunocompromised patients, particularly in those with lung and bone marrow transplants. Among RSV+ patients, a higher prevalence of viral (influenza virus), bacterial (S. pneumoniae, M. pneumoniae, Nocardia spp.), and fungal (Aspergillus spp.) coinfections were observed. The efficacy of ribavirin in reducing mortality did not show significant differences compared to supportive therapy alone. Conclusions: The results of our exploratory study suggest that immunocompromised patients are particularly vulnerable to RSV infection and coinfections. Our hypothesis-generating data warrant the need for future studies aimed at exploring preventive and therapeutic strategies for RSV infection in these high-risk patient groups. Full article

Pulmonary nocardiosis (PN) is a rare, opportunistic, and potentially life-threatening infection, especially in disseminated cases. This retrospective study aimed to characterize the clinical features of PN and assess the diagnostic utility of metagenomic next-generation sequencing (mNGS). We reviewed data from 19 patients diagnosed with PN between September 2019 and August 2022, including 3 with disseminated disease. Common symptoms included fever, cough, and sputum production, while chest imaging frequently revealed nodules, consolidations, exudates, cavities, and pleural effusions. The sensitivity of mNGS for detecting Nocardia was significantly higher than that of culture (100% vs. 36.84%, p < 0.001). mNGS successfully identified Nocardia species and co-infected pathogens. The most common species was Nocardia farcinica. Four PN cases were co-infected with Rhizomucor pusillus, Cryptococcus neoformans, Lichtheimia ramosa, and Aspergillus spp. Eighteen patients (94.7%) received trimethoprim-sulfamethoxazole (TMP-SMZ). Sixteen cases (84.2%) were improved or cured. Misdiagnosis is common due to the nonspecificity of clinical and imaging presentations of pulmonary nocardiosis. The timely combination of mNGS represents a promising approach to enhance the diagnosis of pulmonary nocardiosis and inform targeted antimicrobial therapy. TMP-SMZ is the first line of treatment. Full article

Nocardia, an easily missed but potentially fatal opportunistic pathogen, can lead to serious infections like lung and brain abscesses. Intranasal inoculation (IN) is the traditional approach for constructing a Nocardia-induced pneumonia mice model, while it usually only results in limited local bacterial infection in the lungs. To comprehensively assess infection dynamics across distinct pulmonary inoculation routes in mice models, this study compared the pathogenicity of three different Nocardia farcinica pneumonia models established via IN, intratracheal aerosolization (ITA), and intratracheal instillation (ITI). C57BL/6J mice were infected with N. farcinica through IN, ITA and ITI with comparative analyses of bacterial distribution in lungs, survival rate, weight, bacterial load, inflammatory cytokines, histopathological characteristics and transcriptome differences. The findings suggest that ITA N. farcinica infections caused severer clinical symptoms, higher mortality, pulmonary bacterial load, levels of inflammatory cytokines in bronchoalveolar lavage fluid, and more significant histopathological damage to lungs than IN and ITI. Furthermore, ITA resulted in better lung bacterial distribution and delivery efficiency than ITI and IN. Transcriptome analysis of lungs from N. farcinica infected mice via IN, ITA and ITI revealed significant differential gene expression, whereas ITA route resulted in a larger fold change. ITA provides a more consistent and severe model of N. farcinica pneumonia in mice than IN and ITI, which can make the bacteria more evenly distributed in the lungs, leading to more severe pathological damage and higher mortality rates. In conclusion, ITA is an optimal route for developing animal models of N. farcinica pneumonia infections. Full article

Nocardia spp. is an environmental Gram-positive bacterium able to cause infections in humans, predominantly of an opportunistic nature. Nocardial brain abscesses are rare and result from dissemination from another primary lesion, mainly observed in immunocompromised hosts. The diagnosis of nocardiosis relies on direct examination and bacterial culture, but antimicrobial susceptibility testing (AST) remains controversial due to technical challenges, limited standardization, and a paucity of studies correlating in vitro susceptibility with clinical efficacy. Management is challenging and usually based on expert opinion, as robust evidence is limited. In this case report, we describe an immunocompromised patient with a Nocardia farcinica brain abscess who achieved clinical resolution following combination therapy that included ceftriaxone, despite in vitro resistance, illustrating the complexities in interpreting AST and guiding treatment decisions in rare infections. Full article

The liver of fish is an essential metabolic organ that also serves an immune regulatory role. In this study, we constructed a model of largemouth bass (Micropterus salmoides) infected with Nocardia seriolae by injection to explore the immune and antioxidant functions of the liver. The results showed that N. seriolae infection caused severe pathological changes in the liver, including cell necrosis, granuloma formation, and leukocyte infiltration. The level of mRNA expression of immune-related genes in the liver was significantly increased 2 days post-infection. Moreover, the combined analysis of transcriptome and metabolome showed that N. seriolae infection markedly affected liver metabolism, including glutathione metabolism, arginine and proline metabolism, arachidonic acid metabolism, as well as starch and sucrose metabolism. Additionally, multiple key biomarkers were identified as involved in regulating responses to N. seriolae infection, including arginine, glutathione, gpx, GST, PLA2G, GAA, and PYG. To further elucidate the regulatory effects of arginine on the immune and antioxidant processes in the liver, primary hepatocytes were isolated and cultured. The results demonstrated that arginine supplementation significantly reduced the expression of LPS-induced apoptosis-related genes (bax, cas3, cas8, and cas9) by up to 50% while increasing the expression of antioxidant genes (gpx, GST) by up to 700% at 24 h. Through the analysis of metabolic changes and immune responses in the liver following N. seriolae infection, combined with in-vitro experiments, this study elucidated the anti-apoptotic and antioxidant effects of arginine, revealing the immune response mechanisms in fish liver and laying the groundwork for using nutritional strategies to improve fish health. Full article

Cutaneous nocardiosis is an uncommon bacterial infection caused by Nocardia spp.; Nocardia brasiliensis is the agent involved in most cases. This infection is acquired through the direct traumatic inoculation of soil, plants, or other substrates where the bacteria are found. Clinically, it usually manifests as an erythematous ulcerated nodule. In one-third of cases, nodules or gummas are distributed over the lymphatic pathways that resemble lymphocutaneous sporotrichosis. Its manifestations vary and can present acutely or more frequently with a latent clinical picture over time. Diagnosis is established mainly by Gram staining, biopsy, exudate culture, and molecular biology. Nocardia infections can recur, implying that antimicrobial therapy must be prolonged (between 6 and 12 months) and involve monitoring patients for at least 6 months after the end of treatment. Early diagnosis and targeted treatment may reduce patient mortality rates. We report the case of an 82-year-old woman who presented with four nodules with a lymphangitic spread on her left hand and forearm, one week after the trauma. Molecular identification was performed using 16S rDNA gene sequencing, and Nocardia brasiliensis was identified. Full article

The large yellow croaker (Larimichthys crocea), one of the most economically valuable marine fish species in China, suffers significant economic losses in aquaculture due to infectious diseases caused by marine pathogens, such as Nocardia seriolae. The pathogenic mechanisms underlying N. seriolae infection in L. crocea and the host immune responses remain inadequately characterized. To investigate the molecular mechanisms of this infection, we conducted transcriptome sequencing on the head kidney tissues of L. crocea at 1, 3, 7, and 14 days post-infection with N. seriolae. In total, 421, 1052, 3215, and 2459 upregulated genes, along with 1853, 1777, 3718, and 3134 downregulated genes were identified, respectively. KEGG enrichment analysis revealed that differentially expressed genes were predominantly associated with immune and metabolic pathways. Notably, pathways involved in Toll-like receptor signaling, ECM–receptor interaction, cytokine–cytokine receptor interaction, and focal adhesion were significantly enriched, highlighting an immune response to N. seriolae infection in L. crocea. In addition, significant enrichment of the citrate cycle (TCA cycle) and oxidative phosphorylation pathways in metabolic processes suggests an upregulated ATP synthesis to meet the heightened energy demand associated with the immune response to infection. These findings contribute to a deeper understanding of the immune defense mechanisms in the head kidney of L. crocea against N. seriolae infection and elucidate aspects of N. seriolae pathogenicity. Full article

Background/Objectives: The interleukin 17 (IL-17) family, known for its proinflammatory properties, is important in immune responses against bacterial and fungal infections. To exert its immune function, the IL-17 family typically binds to IL-17 receptor (IL-17R) to facilitate signal transduction. Methods: This study identified, cloned and analyzed seven IL-17 and nine IL-17R family members in snakeheads. Results: A duplication event occurred in snakehead IL-17s and IL-17Rs, but bioinformatics analyses indicated that these genes were conserved in both protein domains and evolutionary processes. Tissue distribution analysis revealed that IL-17s/IL-17Rs were widely distributed in the detected tissues, with relatively high expression levels in immune tissues. Upon Nocardia seriolae stimulation, most members were expressed, particularly IL-17C2, IL-17D, IL-17N, IL-17RA1, IL-17RA2, IL-17RC1, and IL-17RE1, which were significantly upregulated in gill and intestine. Conclusions: These results suggested that IL-17s and IL-17Rs played a crucial role in mucosal immunity against bacterial infection, providing insights into immunoprophylactic strategies for bacterial diseases in aquaculture. Full article

The aim of this study was to reveal diagnostic biomarkers of considerable importance for common pathogenic Nocardia, utilizing pan-genomic and comparative genome analysis to accurately characterize clinical Nocardia infections. In this study, complete or assembled genome sequences of common pathogenic Nocardia and closely related species were obtained from NCBI as discovery and validation sets, respectively. Genome annotation was performed using Prokka software, and pan-genomic analysis and extraction of Nocardia core genes were performed using BPGA software. Comparative genome analysis of these core genes with the validation-set gene sequences was then performed using BLAT, with a threshold of 30% amino acid coverage and identity, in order to distinguish specific core genes. Finally, candidate gene-specific primers were designed using Snapgene software and DNA samples were obtained from clinical Nocardia strains and closely related species for validation. The analysis identified eighteen core genes specific to Nocardia spp., four core genes specific to N. farcinica, and forty-six core genes specific to N. cyriacigeorgica. After rigorous clinical validation, one gene from Nocardia spp. and five genes from N. cyriacigeorgica were confirmed to have high specificity and therefore can be used as reliable biomarkers for accurate diagnosis of Nocardia infection. This pioneering research reveals diagnostic biomarkers of considerable significance, with the potential to substantially enhance the precise diagnosis of common pathogenic Nocardia infections, thereby laying the groundwork for innovative diagnostic methodologies in subsequent studies. Full article

The typical clinical signs of Nocardia seriolae infection include white nodules, ranging from 0.1 to 10 mm in diameter, distributed across various internal organs. However, the structural composition of nodules of different sizes remains unexplored. In this study, natural cases of largemouth bass (Micropterus salmoides) were collected, and pathogenic bacteria were isolated and confirmed through a re-infection experiment. The isolated bacteria were identified as N. seriolae through 16S rRNA and gyrB gene sequencing. Healthy largemouth bass were infected with the isolate using an immersion infection and observed continuously over 56 days. Samples were successfully obtained from the incubation, prodromal, symptomatic, and convalescent phases, allowing for gross, histological, and ultrastructural observations of nodular lesion progression. Results demonstrated two types of nodular lesions: necrotic foci and granulomas. Macroscopically visible nodules larger than 1 mm, observed primarily in the liver, spleen, kidney, and muscle tissues of moribund fish, exhibited coagulative necrosis and were identified as the principal cause of mortality. Conversely, granulomas, with diameters less than 1 mm, were consistently present in the spleen, kidney, and liver during the symptomatic and convalescent phases. Full article

Infections caused by nontuberculous mycobacteria (NTM) are rising globally throughout the world. The number of species isolated from clinical samples is steadily growing, which demands the implementation of a robust diagnostic method with wide specificity. This study was carried out in in 2022–2024 in three clinical antituberculosis centers in the biggest cities of Russia: Moscow, Saint Petersburg, and Novosibirsk. We developed the DNA hybridization assay ‘Myco-biochip’ that allows the identification of 79 mycobacterial species and analyzed 3119 samples from 2221 patients. Sixty-eight mycobacterial species were identified in clinics, including the three novel species phylogenetically related to M. duvalii, M. lentiflavum, and M. talmoniae. The identification of a close relative of M. talmoniae adds to the existence of separate clade between M. terrae, M. triviale complexes and other slow-growing Mycobacteria, which supports the thesis against the splitting of Mycobacteria into five separate genera. Adding to the list of potentially pathogenic species, we identified M. adipatum and M. terramassiliense, which were previously described as natural habitats. The diversity of acid-fast bacilli identified in TB-suspected persons was not limited to the Mycobacteria genus and also includes species from genera Nocardia, Gordonia, Corynebacterium, Tsukamurella, and Rhodococcus of the order Mycobacteriales. The revealed bacterial diversity in patients with suspected NTM-diseases requires the implementation of relevant species identification assays as the first step in the laboratory diagnostic pipeline. Full article

Nocardia is an emerging bacterial disease that often affects patients with compromised immune systems. As the number of patients undergoing solid organ transplants continues to rise, and as more cancer survivors are treated with long-term immune-modifying agents, corticosteroids, and immunosuppressive medications, organisms that typically pose no harm are becoming a public health concern. Carbapenems are usually a second-line therapy in the setting of Nocardia infections. We present the case of a patient who had an immunocompromised status and was diagnosed with Nocardia farcinica, which showed in vitro resistance to carbapenems. The symptoms were non-specific and had a common presentation with headache, fatigue, and a nonresponsive cough to usual cough drugs, although the infection was disseminated and had severe CNS and ocular involvement. The clinical course worsened when the carbapenem was withdrawn and markedly improved when it was re-administered, although the initial antibiogram showed resistance to carbapenems. Despite the observed in vitro resistance in the laboratory, the re-administration of carbapenems was beneficial, as both inflammatory markers and clinical status showed improvement. This was based on clinical judgment, which carefully evaluated the associated risks and benefits. Also, this raises the question of potential risks to develop real resistance to carbapenems of some Nocardia species, which could pose a significant challenge to healthcare. It could become a serious healthcare problem in the future and should prompt active environmental testing. Full article

To gain insights into the prevalence and antimicrobial resistance patterns of major bacterial pathogens affecting largemouth bass (Micropterus salmoides) in the Pearl River Delta (PRD) region, Guangdong, China, a study was conducted from August 2021 to July 2022. During this period, bacteria were isolated and identified from the internal organs of diseased largemouth bass within the PRD region. The antimicrobial resistance patterns of 11 antibiotics approved for use in aquaculture in China were analyzed in 80 strains of Edwardsiella piscicida using the microbroth dilution method. The results showed that 151 bacterial isolates were obtained from 532 samples, with E. piscicida (17.29%, 92/532), Aeromonas veronii (4.70%, 25/532), and Nocardia seriolae (2.26%, 12/532) being the main pathogens. Notably, E. piscicida accounted for the highest proportion of all isolated bacteria, reaching 60.92% (92/151), and mainly occurred from November to April, accounting for 68.48% (63/92) of the cases. The symptoms in largemouth bass infected with E. piscicida included ascites, enteritis, and hemorrhaging of tissues and organs. The drug sensitivity results showed that the resistance rates of all E. piscicida strains to ciprofloxacin, all sulfonamides, thiamphenicol, florfenicol, enrofloxacin, doxycycline, flumequine, and neomycin were 96.25%, 60–63%, 56.25%, 43.75%, 40%, 32.5%, 16.25%, and 1.25%, respectively. In addition, 76.25% (61/80) of these strains demonstrated resistance to more than two types of antibiotics. Cluster analysis revealed 23 antibiotic types (A–W) among the 80 isolates, which were clustered into two groups. Therefore, tailored antibiotic treatment based on regional antimicrobial resistance patterns is essential for effective disease management. The findings indicate that in the event of an Edwardsiella infection in largemouth bass, neomycin, doxycycline, and flumequine are viable treatment options. Alternatively, one may choose drugs that are effective as determined by clinical drug sensitivity testing. Full article