Ten Year Review of Pulmonary Nocardiosis: A Series of 55 Cases

Clinical screening of Nocardia in sputum smears based on neural networks

Objective

Nocardia is clinically rare but highly pathogenic in clinical practice. Due to the lack of Nocardia screening methods, Nocardia is often missed in diagnosis, leading to worsening the condition. Therefore, this paper proposes a Nocardia screening method based on neural networks, aiming at quick Nocardia detection in sputum specimens with low costs and thereby reducing the missed diagnosis rate.

Methods

Firstly, sputum specimens were collected from patients who were infected with Nocardia, and a part of the specimens were mixed with new sputum specimens from patients without Nocardia infection to enhance the data diversity. Secondly, the specimens were converted into smears with Gram staining. Images were captured under a microscope and subsequently annotated by experts, creating two datasets. Thirdly, each dataset was divided into three subsets: the training set, the validation set and the test set. The training and validation sets were used for training networks, while the test set was used for evaluating the effeteness of the trained networks. Finally, a neural network model was trained on this dataset, with an image of Gram-stained sputum smear as input, this model determines the presence and locations of Nocardia instances within the image.

Results

After training, the detection network was evaluated on two datasets, resulting in classification accuracies of 97.3% and 98.3%, respectively. This network can identify Nocardia instances in about 24 milliseconds per image on a personal computer. The detection metrics of mAP50 on both datasets were 0.780 and 0.841, respectively.

Conclusion

The Nocardia screening method can accurately and efficiently determine whether Nocardia exists in the images of Gram-stained sputum smears. Additionally, it can precisely locate the Nocardia instances, assisting doctors in confirming the presence of Nocardia.

Impact of immune status on the clinical characteristics, treatment outcomes and mortality of pulmonary nocardiosis: a retrospective analysis in a tertiary care hospital from a low to middle-income country

Nocardiosis is an opportunistic infection that primarily targets the immunosuppressed. We investigate the differences in demographics and characteristics between immunosuppressed and immunocompetent patients with nocardiosis in a tertiary care hospital in Pakistan. Retrospective records were reviewed for patients diagnosed with pulmonary nocardiosis between 2010 and 2020. Immunosuppressed individuals were identified as those with autoimmune diseases, hematologic diseases and malignancies, HIV, immunosuppressant therapy, etc. Data collected included basic demographics, comorbid conditions, medication history, clinical presentation, radiological and microbiological data, and nocardiosis outcomes and complications. A total of 66 patients with nocardiosis were included in this study out of which 48 were immunosuppressed while 18 were immunocompetent. Both groups were compared for a number of variables including patient characteristics, underlying conditions, radiological findings, treatment regimen and outcomes. Immunosuppressed individuals were younger, and had higher rates of diabetes, chronic renal disease, chronic liver disease, higher platelet counts, surgical intervention, and longer hospital stays. Fever, dyspnea, and sputum production were the most common presentations. Nocardia asteroides was found to be the most common species of Nocardia overall. Nocardiosis presents differently in patients with immunosuppressed and immunocompetent patients consistent with previous studies. Nocardiosis should be considered in any patient presenting with treatment-resistant pulmonary or neurological symptoms.

Molecular detection of Nocardia: development and application of a real-time PCR assay in sputum and bronchoalveolar lavage fluid samples

The diagnosis of pulmonary nocardiosis remains challenging. Rapid detection of Nocardia is of primary importance for early diagnosis and precise treatment of nocardiosis. In this study, our objective was to develop and validate a new TaqMan real-time PCR (qPCR) assay for rapidly detecting Nocardia spp. in respiratory samples. Based on published sequence data, primers in a conserved region of the 16S rRNA gene and a probe within that region that was specific for Nocardia were designed. The distinction effect of the qPCR assay was assessed between Nocardia and other respiratory-associated bacteria. Furthermore, the specificity and sensitivity of the assay were evaluated in respiratory clinical samples (n = 205), compared to the results of 16S rRNA gene amplicon sequencing and clinical diagnosis. The qPCR assay exhibited high specificity, sensitivity, repeatability, and reproducibility. The limit of detection of standard plasmid DNA was 3 × 10² copies/mL. Additionally, the qPCR assay was applied to the direct detection of 205 clinical respiratory samples. The specificity and sensitivity of the qPCR were all 100% compared to 16S rRNA gene amplicon sequencing, as well as 98.4% and 100% compared to clinical diagnosis respectively. The qPCR yielded results within 3 h of sample processing, compared to several days for culture, significantly reducing turnaround time. The results suggest that the new qPCR assay developed in this study provides reliable and rapid detection of Nocardia spp. in the respiratory tracts and is expected to reduce the time required for diagnosing and treating nocardiosis.

A Rare Case of Chest Wall Abscess by Nocardia in a Patient With Sarcoidosis

Nocardia is a rare gram-positive pathogen reported to cause infections in immunocompromised individuals. It usually involves the lungs but may also lead to abscess formation; cases of disseminated nocardiosis have also been reported. We are presenting a case of an Asian male who had sarcoidosis with pulmonary and skin involvement. The patient was on long-term immunosuppressive therapy with corticosteroids with good control of the disease. He developed a fever, weight loss, and right-sided chest pain. CT of the chest showed new nodular infiltrates. Worsening of sarcoidosis was suspected; the corticosteroid dose was increased and methotrexate was started. There was no favorable response to the increase in immunosuppressive therapy. Weight loss was followed by worsening shortness of breath and fluctuant swelling in the right lateral half of the chest. Bronchoalveolar lavage was done to rule out tuberculosis but it did not show any organism’s growth. Ultrasound-guided needle aspiration from the abscess was done that showed growth of Nocardia species. Therapeutic dose co-trimoxazole (trimethoprim-sulphamethoxazole) was started as first-line therapy after confirming the organism’s drug susceptibility pattern along with needle aspiration of the collection on the chest wall. Immunosuppressive agents were stopped. There was a good response to treatment with resolution of symptoms within two months. However, complete radiological recovery took 10 months. Co-trimoxazole (trimethoprim-sulphamethoxazole) therapy continued for two months after radiological recovery. Physicians, therefore, should keep Nocardia as an important differential diagnosis while treating the immunosuppressed population.

Prognosis and factors associated with disseminated nocardiosis: a ten-year retrospective multicenter study

OBJECTIVES

Nocardiosis is a rare opportunistic infection that is frequently associated with dissemination (i.e. involvement of several body sites). Identifying the factors associated with Nocardia spp. dissemination may help improving the management of patients with nocardiosis.

METHODS

This 10-year (2010-2020) retrospective multicenter cohort study included adult patients with Nocardia-confirmed infections. The first objective was to determine the factors associated with disseminated nocardiosis. The secondary endpoints were to determine and compare the management and the 12-month overall mortality in patients with localized and disseminated nocardiosis. Univariate and multivariate logistic regression analyses were used.

RESULTS

Nocardia spp. infection was confirmed in 110 patients, of whom 38 (34.5%) had disseminated nocardiosis. In univariate analysis, the factors associated with dissemination were immunosuppressive conditions: having an auto-immune disease and receiving high-dose corticosteroid (31.5% vs 8.3%, P=0.003 and 52.6% vs 26.3%, P=0.007, respectively). Absolute lymphocyte count <1G/L at diagnosis was the only biomarker associated with dissemination (57.2% vs 26.3%, P=0.007). Nocardia farcinica was not only the most frequent species identified in patient specimens (n=22, 20%) but was also associated with a higher rate of dissemination (36.8% vs 11.1%, P=0.002). Multivariate analysis confirmed the association between auto-immune diseases, lymphopenia, N. farcinica species and the higher rate of dissemination. Even though patients with disseminated nocardiosis were treated longer and more often with an antibiotic combination therapy, their 12-month overall mortality was significantly higher than that of patients with localized nocardiosis (36.8% vs 18%).

CONCLUSIONS

Dissemination of Nocardia spp. is favoured by auto-immune diseases, lymphopenia, and infection with N. farcinica.

A Case of Asymptomatic Pulmonary Nocardia cyriacigeorgica Infection With Mild Diabetes Mellitus

Nocardiosis is a relatively rare opportunistic infection, ranging from localized to systemic diseases, commonly occurring in immunocompromised patients with high mortality rates. We present a case of a 61-year-old man who received medical treatment for type 2 diabetes mellitus and underwent a physical examination that showed abnormal chest shadows on radiography. Chest computed tomography revealed bronchiectasis and infiltration in the left lower lobe. Nocardia spp. was detected in the bronchial washes, and he was started on sulfamethoxazole-trimethoprim under the diagnosis of pulmonary nocardiosis. 16S ribosomal RNA gene sequencing analysis identified the species as Nocardia cyriacigeorgica. His pulmonary lesions successfully improved after treatment for six months. Pulmonary nocardiosis often presents with symptoms such as hemoptysis and blood-tinged sputum, and bronchiectasis has been identified as an underlying condition. Even in hosts without underlying immunocompromising conditions, Nocardia spp. can be a causative microorganism of pulmonary infections, and it should be considered in the differential diagnoses.

Nocardia Infection in Nephrotic Syndrome Patients: Three Case Studies and A Systematic Literature Review

Objective

The multicenter literature review and case studies of 3 patients were undertaken to provide an updated understanding of nocardiosis, an opportunistic bacterial infection affecting immunosuppressed nephrotic syndrome (NS) patients receiving long-term glucocorticoid and immunosuppressant treatment. The results provided clinical and microbiological data to assist physicians in managing nocardiosis patients.

Methods

Three cases between 2017 and 2018 from a single center were reported. Additionally, a systematic review of multicenter cases described in the NCBI PubMed, Web of Science, and Embase in English between January 1, 2001 and May 10, 2021 was conducted.

Results

This study described three cases of Nocardia infection in NS patients. The systematic literature review identified 24 cases with sufficient individual patient data. A total of 27 cases extracted from the literature review showed that most patients were > 50 years of age and 70.4% were male. Furthermore, the glucocorticoid or corticosteroid mean dose was 30.9 ± 13.7 mg per day. The average time between hormone therapy and Nocardia infection was 8.5 ± 9.7 months. Pulmonary (85.2%) and skin (44.4%) infections were the most common manifestations in NS patients, with disseminated infections in 77.8% of patients. Nodule/masses and consolidations were the major radiological manifestations. Most patients showed elevated inflammatory biomarkers levels, including white blood cell counts, neutrophils percentage, and C-reactive protein. Twenty-five patients received trimethoprim-sulfamethoxazole monotherapy (18.5%) or trimethoprim-sulfamethoxazole-based multidrug therapy (74.1%), and the remaining two patients (7.4%) received biapenem monotherapy. All patients, except the two who were lost to follow-up, survived without relapse after antibiotic therapy.

Conclusions

Nephrotic syndrome patients are at high risk of Nocardia infection even if receiving low-dose glucocorticoid during the maintenance therapy. The most common manifestations of nocardiosis in NS patients include abnormal lungs revealing nodules and consolidations, skin and subcutaneous abscesses. The NS patients have a high rate of disseminated and cutaneous infections but a low mortality rate. Accurate and prompt microbiological diagnosis is critical for early treatment, besides the combination of appropriate antibiotic therapy and surgical drainage when needed for an improved prognosis.

Clinical Features, Radiological Findings, and Treatment Outcomes in Patients with Pulmonary Nocardiosis: A Retrospective Analysis

Introduction Lack of specific clinical features makes the diagnosis of pulmonary nocardiosis difficult. A high index of suspicion is required for diagnosis especially in cohorts with pre-existing risk factors. This study aimed to study the clinical and radiological characteristics and outcomes in patients with pulmonary nocardiosis. Methods This was a retrospective observational study. Data of confirmed cases with pulmonary nocardiosis were collected from a digital patient management system. Results A total of eight cases of pulmonary nocardiosis were included. The mean age of patients was 50 ± 14.3 years with a female preponderance (62.5%). The most common co-morbidity was chronic lung disease (37.5%). The common clinical feature of pulmonary nocardiosis was cough with expectoration (50%) and the mean duration of symptoms was 18 days. The common radiological (CT thorax) findings were consolidation, bronchiectasis, mediastinal lymphadenopathy, and nodularity (50% each). One patient had an extension of pulmonary disease in the chest wall. Microbiological detection of Nocardia spp. was done in sputum samples (50%) and in bronchoalveolar lavage (BAL) samples (50%). Culture was positive in two BAL samples. Intravenous empirical antibiotics in combination with oral trimethoprim-sulfamethoxazole double standard (15 mg/kg trimethoprim) were started at the time of diagnosis. Ceftriaxone and amikacin were commonly used antimicrobials. Conclusion Nocardia spp. commonly causes disease in patients with pre-existing chronic disease. A high index of suspicion is required in patients with subacute to chronic respiratory symptoms, raised inflammatory markers, and the absence of common respiratory pathogens in evaluation.

Isolation and Characterization of Nocardia Species from Pulmonary Nocardiosis in a tertiary hospital in China

The aim of this study was to investigate the clinical features, distribution and antimicrobial susceptibility of Nocardia species isolated from pulmonary nocardiosis cases in tertiary hospital in China. The species were collected from January 1, 2018 to May 31, 2019 and identified using MALDI-TOF MS or PCR. Antimicrobial susceptibility testing was performed using the broth microdilution method. Within the 44 Nocardia species, N. farcinica was the most frequently identified species (n = 36), followed by N. nova (n = 5), N. otitidiscaviarum (n = 1), N. cyriacigeorgica (n = 1), and N. transvalensis (n = 1). The top three predisposing factors of pulmonary nocardiosis were chronic obstructive pulmonary disease (45.5%), hypertension (34.1%), and tuberculosis (31.8%). All 44 Nocardia strains were susceptible to amikacin, trimethoprim / sulfamethoxazole, and linezolid. The resistance rates of Nocardia to amoxicillin-clavulanic acid, ciprofloxacin, clarithromycin, ceftriaxone, tobramycin, and imipenem were 4.5%, 9.1%, 79.5%, 72.7%, 63.6%, and 38.6%, respectively. Two Nocardia strains had decreased sensitivity to trimethoprim / sulfamethoxazole. In conclusion, N. farcinica was the most frequently isolated Nocardia species in the First Hospital of Changsha. All isolated clinical Nocardia strains showed susceptible to amikacin, trimethoprim / sulfamethoxazole, and linezolid, suggesting that these drugs can be primary therapeutic choices for treating Nocardia infections.

Cushing's Syndrome With Nocardiosis: A Case Report and a Systematic Review of the Literature

OBJECTIVE

To analyze and summarize the clinical characteristics, treatments, and prognosis of Cushing's syndrome (CS) with nocardiosis.

METHODS

A patient in our hospital and additional 17 patients of CS with nocardiosis in the English literature were included in this study. Clinical characteristics, laboratory data, imaging studies, treatments, and prognosis were evaluated.

RESULTS

A 41-year-old man with CS was diagnosed and treated in our hospital. He had co-infections of nocardiosis and aspergillosis. Together with 17 patients of CS with nocardiosis in the English literature, 2 patients (11.1%) were diagnosed as Cushing's disease (CD) while 16 (88.9%) were diagnosed or suspected as ectopic ACTH syndrome (EAS). The average 24hrUFC was 7,587.1 ± 2,772.0 μg/d. The average serum total cortisol and ACTH (8 AM) was 80.2 ± 18.7 μg/dl and 441.8 ± 131.8 pg/ml, respectively. The most common pulmonary radiologic findings in CT scan were cavitary lesions (10/18) and nodules (8/18). Co-infections were found in 33.3% (6/18) patients. The CS patients with co-infections had higher levels of ACTH (671.5 ± 398.2 vs 245.5 ± 217.1 pg/ml, P = 0.047), and 38.9% (7/18) patients survived through the antibiotic therapy and the treatment of CS. Patients with lower level of ACTH (survival vs mortality: 213.1 ± 159.0 vs 554.7 ± 401.0 pg/ml, P = 0.04), no co-infection, underwent CS surgery, and received antibiotic therapy for more than 6 months, had more possibilities to survive.

CONCLUSIONS

Nocardia infection should be cautioned when a patient of CS presented with abnormal chest radiographs. The mortality risk factors for CS with nocardiosis are high level of ACTH and co-infections. We should endeavor to make early etiological diagnosis, apply long-term sensitive antibiotics and aggressive treatments of CS.

Clinical Nocardia species: Identification, clinical characteristics, and antimicrobial susceptibility in Shandong, China

Nocardia is a pathogen responsible for a variety of clinical infections. Here, we aimed to investigate the species distribution, clinical manifestations, and antimicrobial susceptibility of Nocardia species over 3 years in two tertiary general hospitals in China. In this retrospective study, a total of 27 Nocardia species were isolated from 27 individuals between January 2017 and December 2019. Nocardia isolates were identified to species level by mass spectrometry and 16S rRNA PCR sequencing. Clinical data were collected from medical records. Antimicrobial susceptibility was determined by the standard Broth microdilution method. The 27 patients with Nocardia infection included 12 males and 15 females with a mean age of 60.11 years. Among 27 Nocardia isolates, 7 species were identified, with the most common species being Nocardia otitidiscaviarum (40.7%). The antimicrobial susceptibility profiles varied between different Nocardia species. Notably, all Nocardia isolates were linezolid susceptible. The majority of Nocardia isolates were collected from a department of respiratory medicine (55.56%) and sputum specimen (44.44%). Pulmonary region was the most involved body site (70.37%) followed by skin (7.4%) and pleural cavity (7.4%). Most patients with Nocardia infection needed combination antibiotic therapy. Two deaths were reported during the treatment period and 24 patients achieved improvement after antibiotic therapy. The clinical manifestations of Nocardia infection and antimicrobial susceptibility profiles varied with diverse Nocardia species. Thus, the accurate identification of these species is crucial for the diagnosis and the selection of antibiotic treatment.

Genomic Virulence Features of Two Novel Species Nocardia barduliensis sp. nov. and Nocardia gipuzkoensis sp. nov., Isolated from Patients with Chronic Pulmonary Diseases

Strains 335427^T and 234509^T, isolated from two 76-year-old patients with chronic pulmonary diseases, were the subject of polyphasic taxonomic studies and comparative genomic analyses for virulence factors. The 16 rRNA gene sequence similarity between strains 335427^T and 234509^T and their closest phylogenetic neighbors Nocardia asiatica NBRC 100129^T and Nocardia abscessus NBRC 100374^T were 99.5% and 100%, respectively. Digital DNA-DNA hybridization values between the aforementioned studied strains were well below the 70% threshold for assigning prokaryotic strains to a novel species. Strains 335427^T and 234509^T have genome sizes of 8.49 Mpb and 8.07 Mpb, respectively, with G + C content of 68.5%. Isolate 335427^T has C_16:0, C_18:1 ω₉c, C_18:0 and C_18:0 10 methyl as major fatty acids (>15%) and mycolic acids formed of 52-54 carbon atoms. However, only C_18:1 ω₉c was detected for isolate 234509^T, which had mycolic acids with 44-56 carbon. Based on phenotypic and genetic data, strains 335427^T (DSM 109819^T = CECT 9924^T) and 234509^T (DSM 111366^T = CECT 30129^T) merit recognition as novel species, which are named Nocardia barduliensis sp. nov. and Nocardia gipuzkoensis sp. nov., respectively. All the strains studied had homologous VF-associated genes to those described in M. tuberculosis, including experimentally verified virulence genes in humans related to tuberculosis. The narGHIJ (nitrate reduction pathway) and gvpAFGOJLMK (gas vesicles) genetic maps of strains 335427^T, 234509^T, NBRC 100129^T and NBRC 100374^T showed the same syntenic block and raise the question of whether their functions are interlinked during the infection of the human host. However, further research is required to decipher the role of the gas vesicle in the pathogenicity mechanism of Nocardia spp.

Nocardiosis mimicking lung cancer in a heart transplant patient with end-stage renal disease

Nocardiosis is a rare bacterial opportunistic infection that most commonly manifests as lung disease. However, disseminated infection and abscess formation can occur. Due to diverse radiographic findings and difficult cultivation it is not an easy diagnosis to make. Antibiotics such as Trimethoprimsulfamethoxazole alone or in combination with imipenem or imipenem in combination with amikacin need to be administered over a period of at least six to twelve weeks.

We report a case of a 64-year old female heart transplant recipient requiring dialysis who suffered from dyspnea and a productive cough among other symptoms. Computed tomography revealed a tumor in the left upper lobe suggesting lung cancer. Both transbronchial and transthoracic biopsy could not confirm a malignant disease. Finally, Nocardia nova was isolated from a bronchoalveolar lavage and specific antibiotic treatment was initiated. As a result, the mass in the left upper lobe significantly regressed after a few weeks.