Pulmonary nocardiosis in Western Europe—Clinical evaluation of 43 patients and population-based estimates of hospitalization rates

Metagenome next-generation sequencing plays a key role in the diagnosis and selection of effective antibiotics on the treatment of Nocardia pneumonia: a case report

Nocardia disease is an opportunistic infection, the occurrence is rare and mostly occurs in patients with immune deficiency. Even if the patient is immunocompetent, it can still be life-threatening. This case report describes a previously healthy 78-year-old male farmer with lung lesions discovered on a computerized tomography scan. Combined with the patient's history of fever and the results of elevated laboratory markers associated with inflammation, the patient was diagnosed with a lung infection. After escalating empirical broad-spectrum antibiotics, antiviral and antifungal therapy, the patient continued to deteriorate to septic shock. In the meanwhile, the patient's sputum was cultured repeatedly, and no obvious positive pathogenic bacteria were found. Considering the patient was elderly and that these lesions were solid with burr signs, as well as the progression after antimicrobial therapy cancer was considered in the differential diagnosis. Artificial intelligence (YITU, Hangzhou Yitu Medical Technology Limited Company) was also applied, and it also calculated that these lesions were cancerous. The patient received a puncture biopsy of the largest lung lesion. During the puncture pus was withdrawn from largest lung lesion. Culture and metagenome next-generation sequencing (mNGS) detection performed on pus indicated Nocardia otitidiscaviarum. The test report of the mNGS is also attached with a susceptibility report of commonly used clinical antibiotics to this Nocardia spp. Using this result, the patient's disease was quickly controlled after selecting the targeted drug compound sulfamethoxazole and intravenous meropenem for treatment. In view of the high misdiagnosis rate and poor sensitivity of culture for Nocardia spp., this case emphasized mNGS playing a key role in the diagnosis and selection of effective antibiotics for the treatment of Nocardia spp. lung infections.

A Rare Case Report of Disseminated Nocardia Farcinica Granulomatous Hepatitis and Clinical Management Experience

Background

Nocardiosis is primarily an opportunistic infection affecting immunocompromised individuals, with a predilection for the lungs, brain, or skin in those with compromised immune function. Granulomatous hepatitis caused by Nocardia is a rare clinical manifestation. This study aims to provide a systematic overview of the clinical features of Nocardiosis caused by Nocardia farcinica, enhancing our understanding of this disease.

Methods

We report a case of a 75-year-old male with no underlying diseases presenting with a history of "recurrent fever for more than 4 months", along with fatigue, poor appetite, and pleural and abdominal effusion. Despite treatment at multiple hospitals, the patient showed little improvement. Chest CT revealed chronic inflammation, small nodules, bilateral pleural effusion, and pleural thickening. Abdominal CT indicated multiple low-density lesions in the liver, multiple small calcifications, and abdominal effusion.

Results

Liver biopsy suggested inflammatory changes, with focal granuloma formation. Metagenomic next-generation sequencing (mNGS) of liver tissue indicated Nocardia farcinica, leading to the final diagnosis of disseminated Nocardia farcinica granulomatous hepatitis.

Conclusion

Nocardia infection is a rare disease primarily observed in immunocompromised patients but can also occur in those with normal immune function. The clinical and radiological features lack specificity; however, the utilization of mNGS technology enables rapid identification of the pathogenic microorganism. Nocardia farcinica is generally susceptible to sulfonamide drugs and amikacin, offering viable treatment options.

Clinical characteristics and drug resistance of Nocardia in Henan, China, 2017-2023

BACKGROUND

The aim of this study was to investigate the clinical features of Nocardia infections, antibiotic resistance profile, choice of antibiotics and treatment outcome, among others. In addition, the study compared the clinical and microbiological characteristics of nocardiosis in bronchiectasis patients and non-bronchiectasis patients.

METHODS

Detailed clinical data were collected from the medical records of 71 non-duplicate nocardiosis patients from 2017 to 2023 at a tertiary hospital in Zhengzhou, China. Nocardia isolates were identified to the species level using MALDI-TOF MS and 16S rRNA PCR sequencing. Clinical data were collected from medical records, and drug susceptibility was determined using the broth microdilution method.

RESULTS

Of the 71 cases of nocardiosis, 70 (98.6%) were diagnosed as pulmonary infections with common underlying diseases including bronchiectasis, tuberculosis, diabetes mellitus and chronic obstructive pulmonary disease (COPD). Thirteen different strains were found in 71 isolates, the most common of which were N. farcinica (26.8%) and N. cyriacigeorgica (18.3%). All Nocardia strains were 100% susceptible to both TMP-SMX and linezolid, and different Nocardia species showed different patterns of drug susceptibility in vitro. Pulmonary nocardiosis is prone to comorbidities such as bronchiectasis, diabetes mellitus, COPD, etc., and Nocardia is also frequently accompanied by co-infection of the body with pathogens such as Mycobacterium and Aspergillus spp. Sixty-one patients underwent a detailed treatment regimen, of whom 32 (52.5%) received single or multi-drug therapy based on TMP-SMX. Bronchiectasis was associated with a higher frequency of Nocardia infections, and there were significant differences between the bronchiectasis and non-bronchiectasis groups in terms of age distribution, clinical characteristics, identification of Nocardia species, and antibiotic susceptibility (P < 0.05).

CONCLUSIONS

Our study contributes to the understanding of the species diversity of Nocardia isolates in Henan, China, and the clinical characteristics of patients with pulmonary nocardiosis infections. Clinical and microbiologic differences between patients with and without bronchiectasis. These findings will contribute to the early diagnosis and treatment of patients.

A rare case of a hard-to-heal ulcer caused by pulmonary Nocardia infection

DECLARATION OF INTEREST

The authors have no conflicts of interest.

Effects of sputum bacillary load and age on GeneXpert and traditional methods in pulmonary tuberculosis: a 4-year retrospective comparative study

BACKGROUND

The purpose of this study was to evaluate the diagnostic value of the GeneXpert® MTB/RIF (Xpert®), Auramine O staining method, and Lowenstein-Jensen medium for bacteriologically confirmed pulmonary tuberculosis and explore the effects of the sputum bacillary load (SBL) and qRT‒PCR threshold cycle (Ct) value on the detection methods.

METHODS

We retrospectively analysed the results in the Department of Infectious Disease for 49 months. The χ2 test was used to compare the performances of each method, receiver operating characteristic curve analysis was used to determine the optimal cut-off values, and the factors associated with a false-negative result from Xpert® were analysed by logistic regression.

RESULTS

Simultaneous analysis of 980 sputum specimens showed that the positive detection rate of Xpert® did not increase with increasing SBL, and there were differences between the three when SBL ≤ 1 + (all P < 0.05). There was a good negative correlation between the Ct value and the SBL (P < 0.0001). Age was an independent risk factor for false-negative Xpert® results (P = 0.029), and when Ct < 16, the diagnostic sensitivity and specificity were both 100.00%. The optimal cut-off Ct values for resegmentation based on the drug resistance classification were < 18.6, 18.6-34.1, and > 34.1 cycles.

CONCLUSIONS

Xpert® was not affected by SBL but it was by age, and it is more advantageous when SBL ≤ 1 + . The results regarding rifampicin resistance were reliable, and the novel Ct segmentation was a practical and more clinically meaningful classification method for diagnosing rifampicin resistance. These findings will help improve physicians' ability to accurately diagnose TB.

Mild Pulmonary Nocardiosis Caused by Nocardia terpenica in an Immunocompetent Patient

A 53-year-old immunocompetent man was admitted to our hospital because of paroxysmal cough with a low fever for more than 5 months. On admission, chest computed tomography showed multiple plaques and nodules, some with small central cavities, in both lungs and cystic and columnar bronchiectasis of the right middle bronchus. Treatment with various antibiotics was ineffective. Metagenomic next-generation sequencing of the bronchoalveolar lavage fluid showed Nocardia terpenica, and this organism was cultured from bronchoalveolar lavage fluid, resulting in a diagnosis of pulmonary nocardiosis. After administration of trimethoprim-sulfamethoxazole for 5 weeks, chest computed tomography showed a significant reduction in the lung lesions that had been detected on admission. Immunosuppressed patients are particularly prone to nocardiosis infection, which is usually severe. N. terpenica has rarely been detected in clinical samples, and its characteristics require further study with the accumulation of more clinical cases.

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.

Clinical characteristics, outcomes, and factors associated with mortality in Nocardia pneumonia: 18 years' real-world data from a tertiary care hospital in Karachi, Pakistan

BACKGROUND

Pulmonary nocardiosis is a rare pulmonary infection with high morbidity and mortality. Limited real-world data on pulmonary nocardiosis patients are available from developing countries like Pakistan.

METHODS

This retrospective observational study was conducted at the Aga Khan University Hospital, Karachi, Pakistan, from August 2003 to June 2020. Demographics, immune status, underlying diseases, laboratory data, treatment, and outcomes of all nocardiosis patients were recorded in predesigned proforma.

RESULTS

Sixty-six patients with smear/culture-proven pulmonary nocardiosis were identified. Most patients (83.3%) were treated with trimethoprim-sulfamethoxazole alone or in combination with other medicines. The overall mortality rate in our study was 33.3% (n = 22/66). Factors significantly associated with mortality were respiratory failure (p < 0.001), raised procalcitonin levels (p = 0.01), concomitant fungal infections (p = 0.01), concomitant TB (p = 0.03), and patients on combination therapy (p < 0.001). Respiratory failure (odds ratio [OR] 46.94 [95% confidence intervals [CI]: 5.01-439.03] p < 0.001), concomitant fungal infection (OR 17.09 [95% CI: 1.47-197.88] p- = 0.02) and patients on combination therapy (OR 6.90 [95% CI: 1.23-38.61] p = 0.02) were also identified as independent risk factors for mortality on multivariate analysis.

CONCLUSIONS

This study provides essential information on the clinical characteristics and risk factors, outcomes, and factors associated with mortality for pulmonary nocardial infections.

Rapid detection of pulmonary nocardiosis by metagenomic next generation sequencing

We retrospectively analyzed 3 cases of pulmonary nocardiosis. Patients were identified by metagenomic next generation sequencing (mNGS) in the First Affiliated Hospital of Soochow University, from January 2019 to April 2022. All patients had underlying diseases, and were in immunocompromised state, with membranous nephropathy, acute lymphoblastic leukemia (ALL), and systemic lupus erythematosus (SLE), respectively. Symptoms common to all cases included fever, cough and expectoration. Chest computed tomography (CT) presented patchy shadows or nodules, with or without cavitation lesions, or pleural effusion. mNGS detected Nocardia spp. via bronchoalveolar lavage fluid (BALF) or blood samples from patients. All the patients were discharged with recovery after using the trimethoprim-sulfamethoxazole (TMP-SMX) and remained without evidence of disease during regular follow-ups. mNGS may be a tool for rapid and accurate detection and identification of pulmonary nocardiosis, but interpreting the mNGS results should be more cautious because the mNGS assay can also detect colonization.

Case report: Nocardia gipuzkoensis infection in an immunocompetent patient diagnosed by metagenomic next-generation sequencing and whole genome sequencing

The infection of Nocardia gipuzkoensis is a relatively uncommon form of pulmonary nocardiosis seen in clinical patients. In general, nocardiosis tends to occur in patients with immune deficiency. Here, we report a 23-year-old female who was admitted to the hospital due to cough and sputum production over 10 years, diagnosed with bronchiectasis. The N. gipuzkoensis infection was identified by metagenomic next-generation sequencing and whole genome sequencing. Imipenem/cilastatin and compound sulfamethoxazole tablets were used to control the infection and the pulmonary inflammation subsided gradually.

Case report: Nocardia farcinica pneumonia in early-stage post liver transplantation

Background

Liver transplantation is a well-established treatment for end-stage liver disease. The evolution of immunosuppressants has supported the recent advances in this field. However, this leads to immunosuppression and increases the risk for infections. Nocardia is an aerobic gram-positive bacillus, which can cause multi-systemic or multi-organ infections. Nocardia is an opportunistic pathogen that principally affects immunosuppressed patients.

Case presentation

Herein, we present a case of Nocardia farcinica pneumonia in a patient at early-stage post-liver transplantation. Following appropriate microbiological tests and imaging, the diagnosis was finally confirmed. A full recovery was achieved after optimal antibiotic therapy of sulfamethoxazole, minocycline, and amikacin.

Conclusions

Nocardia farcinica pneumonia is a rare and life-threatening disease, especially in patients after liver transplantation. Imaging and microbiological tests are helpful for the early diagnosis of the disease. Trimethoprim-sulfamethoxazole (TMP-SMX) as part of first-line therapy for nocardiosis is recommended.

A Case of Pulmonary Nocardiosis Presenting with Multiple Cavitary Nodules in a Patient with Thrombocytopenia

Nocardiosis is an infrequent opportunistic infection that deserves more attention because of its increasing morbidity and high rate of misdiagnosis. Clinical and radiological manifestations as well as antibiograms of pulmonary nocardiosis are diverse. Herein, we report a patient with idiopathic thrombocytopenia treated with glucocorticoids, which later presented with severe pulmonary infection with widely distributed nodules on chest computed tomography. Fungal infection or tuberculosis was under initial suspicion and microbiological tests of bronchoalveolar lavage fluid eventually yielded an affirmative result of Nocardia cyriacigeorgica. The patient responded in the beginning; however, therapeutic strategies had to be altered several times due to adverse events. The patient eventually ended up with radiographic resolution at the end of six months. We wish to share some experience in dealing with this disease especially recognizing pulmonary nocardiosis in computed tomography imaging.

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.

Clinical Features of Pulmonary Nocardiosis in Patients with Different Underlying Diseases: A Case Series Study

Objective

To investigate the clinical features of pulmonary nocardiosis (PN) in patients with different underlying diseases.

Methods

Clinical, imaging, treatment and prognosis data from patients diagnosed with PN from July 2011 to June 2021 at the First Affiliated Hospital, Zhejiang University School of Medicine were collected and analyzed. According to different underlying diseases, patients were grouped into immunocompromised host (ICH) group and immunocompetent host (ICO) group, and clinical characteristics were compared between the two groups.

Results

There were 64 patients with PN, including 42 males, aged from 21 to 86 (57.1 ± 15.7) years. The most common clinical manifestations were cough, expectoration, fever. There were 41 cases in the ICH group and 23 cases in the ICO group. There were 11 cases with underlying pulmonary diseases in the ICH group, including 2 cases of bronchiectasis, 4 cases of chronic obstructive pulmonary disease (COPD), etc. There were 11 cases of underlying pulmonary basic diseases in ICO group, including 7 cases of bronchiectasis and COPD, 1 case of bronchiectasis, 1 case of COPD, etc. The proportion of patients with bronchiectasis and COPD in the ICO group was significantly higher (P < 0.05). Extrapulmonary nocardiosis infection occurred in 6 patients of the ICH group. During the period of hospitalization, 87.0% patients in ICO group received SMZ/TMP therapy, 73.2% of patients in ICH group received two drug combination therapy. In the ICH group, mortality at 28 days was 14.6% and 8.7% in the ICO group.

Conclusion

PN mainly occurred in ICH patients, but also occurred in the ICO cases to a lesser extent, especially in patients with bronchiectasis and/or COPD. Complicated with extrapulmonary infections mainly occurred in ICH population and combination of two antibiotics was often used in ICH group. The case fatality rates were 14.6% in ICH and 8.7% in ICO cases, respectively.

Chest Infections after Lung Transplantation

Despite substantial progress in the long-term follow-up strategies for lung transplant recipients, morbidity and mortality remain high mostly due to the elevated infectious risk and to the development of chronic lung allograft dysfunction. The high immunosuppressive levels necessary to prevent acute rejection and the graft's constant exposure to the environment come at the high price of frequent infectious complications. Moreover, some infectious agents have been shown to trigger acute rejection or chronic allograft dysfunction. A rapid diagnostic approach followed by an early treatment and follow-up strategy are of paramount importance. They are, however, challenging endeavors due to the vast spectrum of possible pathogens and to the discrete clinical features as a consequence of transplant recipients' impaired immune response. This review proposes a stratified diagnostic strategy, discusses the most relevant pathogens and the corresponding therapeutic approaches while also offering an insight in the infection prevention strategies: vaccination, prophylaxis, preemptive therapy, antibiotic stewardship.

Treatment of disseminated nocardiosis: a host-pathogen approach with adjuvant interferon gamma

Disseminated nocardiosis is a rare, life-threatening disease. Particularly at risk are immunocompromised patients, highlighting the crucial role of host factors. Conventional intensive antibiotic treatment has improved survival rates, but the overall prognosis of patients with disseminated nocardiosis remains unsatisfactory. In this Grand Round, we present a case of severe nocardiosis that did not respond to standard therapy. The patient's condition deteriorated when antibiotic therapy was given alone and improved substantially only after coadministration of interferon gamma. We review the literature relevant to adjuvant interferon gamma therapy of nocardiosis and discuss its potential harms and benefits. Overall, we consider such treatment as beneficial and low risk if the patient is followed-up closely. We conclude that clinicians should consider this regimen in refractory cases of severe Nocardia infection.

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.

Molecular characterization and improved diagnostics of Nocardia strains isolated over the last two decades at a German tertiary care center

Nocardiosis is a rare but life-threatening infection caused by aerobic Actinomycetes of the genus Nocardia particularly affecting immunocompromised hosts. The identification of Nocardia ssp. and antibiotic susceptibility testing by standard microbiological methods are incomplete and molecular techniques may improve diagnostics. We studied 39 Nocardia strains isolated from 33 patients between 2000 and 2018. Twenty-four patients (72.7 %) were immunocompromised. Whole genome sequencing (WGS) revealed a broad taxonomic range of those isolates spanning 13 different species, including four strains that belonged to three novel species based on average nucleotide identity (ANI < 95 % with currently available genome sequences). 16S rRNA gene analyses mirrored WGS results. Conventional MALDI-TOF analysis correctly identified 29 isolates at the species level (74.4 %). Our advanced protocol with formic acid and acetonitrile treatment increased identification to 35 isolates (89.7 %). Antibiotic resistance was tested using both a microdilution method and MIC strip testing. Results were in good concordance with an overall trimethoprim-sulfamethoxazole (SXT) resistance rate of 13.5 %. WGS of a SXT resistant N. farcinica isolate showed a deletion of several amino acids in a homolog of dihydropteroate synthase (FolP2) that was not seen in sensitive members of this species. Diversity of Nocardia isolates was high and involved many different species, suggesting that this taxon has broadly distributed mechanisms for infecting individuals. Widely applicable diagnostic methods including MALDI-TOF and 16S rRNA gene analyses correctly identified most strains. WGS additionally revealed molecular insights into SXT resistance mechanisms of clinical Nocardia isolates highlighting the potential application of (meta)genomic-based diagnostics in the future.

Clinical analysis of 11 cases of nocardiosis

Nocardiosis is a rare, life-threatening, opportunistic, and suppurative infection. Its clinical manifestation lacks specificity, which makes early diagnosis difficult. A retrospective analysis of the clinical records of 11 patients with nocardiosis admitted to our hospital from January 2013 to November 2018 was conducted. All patients had at least one underlying disorder, such as an autoimmune disease (6/11), a blood malignancy (2/11), avascular necrosis of the femoral head (1/11), bronchiectasis (1/11), or pneumonia (1/11). The first-line treatment was trimethoprim-sulfamethoxazole (TMP-SMX); one or two additional antibiotics were given according to the drug-sensitive test. The median time from onset to treatment was 3 weeks (ranging from 1 to 9 weeks). The median duration of treatment after diagnosis was 20.5 weeks (ranging from 7 to 47 weeks). Eight patients were discharged and survived, and three patients died. This indicates that early use of TMP-SMX combined with sensitive antibiotics could improve the condition of patients and improve the cure rate (8/11). Clinically, it is necessary to consider the possibility of nocardiosis in patients with long-term use of immunosuppressants and poor response to treatment of common bacterial infections. Early diagnosis, timely treatment, and combination drug therapy are keys to improving the outcomes of patients with nocardiosis.

Nocardiosis at an Organ Transplant Center in Saudi Arabia: 15 years' experience

Background:

Nocardiosis is a rare infection that affects immunocompromised patients on immunosuppressive medications used for transplantation and cancer therapy. Such therapies are becoming more widely available in the Middle East region. Yet, reports on nocardiosis are scarce.

Materials and Methods:

This was a retrospective analysis of patients who were diagnosed with nocardiosis from 2004 to 2018 at a transplantation and cancer center. Nocardiosis were defined per the European Organization for Research and Treatment of Cancer criteria.

Results:

During the study period, 35 patients with nocardiosis (male: 68.5%) were identified. The most common underlying associated condition was transplantation 11 (31.4%), followed by malignancy 7 (20%), connective tissue disease and sarcoidosis 7 (20%), chronic lung disease 5 (14%), miscellaneous conditions 4 (11%), and one patient with human immunodeficiency virus. Nocardia was disseminated in 8 patients (22.9%) and isolated in 27 (77.1%); the latter included 13 patients (37.1%) with bronchial form, 11 (31.4%) with isolated visceral form, and 3 (8.6%) with cutaneous form. Pulmonary involvement occurred in 90% of the cases with cough, fever, and dyspnea being the most common symptoms. The main strain isolate was Nocardia asteroides, and the cure rate was 90%. Mortality related to nocardiosis occurred in 3 transplant patients (8.6%).

Conclusion:

Wider use of immunosuppressive therapy warrants vigilance to nocardiosis, which can present in a myriad of clinical forms. In our series, mortality was confined to the transplantation group, probably because of the relatively heavy immunosuppression. Nonetheless, prognosis is favorable if the infection is recognized and treated early.

How do I manage nocardiosis?

BACKGROUND

Nocardiosis is a rare infection that is often difficult to treat and may be life-threatening. There is no consensus on its management.

OBJECTIVES

Our aim was to provide the current evidence for the diagnosis and management of individuals with nocardiosis, and to propose a management approach for this uncommon infection.

SOURCES

We systematically searched the medical literature on nocardiosis for studies published between 2010 and 2020 and describing ten or more individuals.

CONTENT

Nocardiosis, a primarily opportunistic infection which may occur in immunocompetent persons, most commonly involves the lungs and frequently disseminates to other sites including the central nervous system. The reference standard for Nocardia species identification is molecular biology, and the preferred method for antibiotic susceptibility testing (AST) is broth microdilution. Monotherapy seems appropriate for patients with primary skin nocardiosis or non-severe pulmonary disease; we reserve a multidrug regimen for more severe infections. Species identification and AST results are often missing at initiation of antibiotics. Trimethoprim-sulfamethoxazole is the preferred agent for initial therapy, because Nocardia is very often susceptible to this agent, and because it has been the keystone of nocardiosis treatment for years. Linezolid, to which Nocardia is almost always susceptible, may be an alternative. When combination therapy is required, the repertoire of companion drugs includes third-generation cephalosporins, amikacin and imipenem. Therapeutic modifications should take into account clinical response to initial therapy and AST results. Treatment duration of 6 months is appropriate for most situations, but longer durations are preferred for disseminated nocardiosis and shorter durations are reasonable in low-risk situations. Secondary prophylaxis may be considered in selected individuals with permanent immunosuppression.

IMPLICATIONS

We hereby provide the clinician with an easy-to-use algorithm for the management of individuals with nocardiosis. We also illuminate gaps in evidence and suggest future research directions.

Nocardia Infections: Ten Years Experience from a Tertiary Health Care Center in North India (2007-2016)

BACKGROUND

Nocardia species are important cause of infections in humans but are underreported due to missed diagnosis as well as misdiagnosis. Majority of the literature on these infections consists of case reports or series with few articles describing high number of cases.

OBJECTIVE

To study the epidemiology of Nocardia infections in a tertiary care center.

MATERIALS AND METHODS

This retrospective observational study was done in a tertiary care centre of North India over a period of 10 years (2007-2016). The detection of Nocardia spp. from clinical specimens was done by conventional methods viz. direct microscopy (Gram's stain, modified Ziehl -Neelsen stain [1%], KOH examination) and culture.

RESULTS

A total of 25 cases of nocardiosis were diagnosed during the study period. The mean age of the patients was 50.9 years (range 30-72 years) with a male:female ratio of 3:2. The site of disease in these patients included pulmonary (n=18), cutaneous (n=4), perinephric abscess (n=1), ocular (n=1) and bone (n=1). Risk factors associated were underlying lung disease (n=11), smoking (n=7), diabetes (n=5) and steroid therapy (n=4) in pulmonary nocardiosis, iatrogenic (n=1) and leprosy (n=1) in cutaneous nocardiosis, diabetes in perinephric abscess and cataract surgery in ocular nocardiosis. Culture was positive in 12/25 (48%) patients for Nocardia spp. Direct microscopy was positive in 22 patients. We wish to highlight that meticulous observation of KOH wet mount examination helped in clinching the diagnosis of Nocardiosis in 3 cases which were earlier missed by other methods.

CONCLUSION

Good communication with the clinician alongside a meticulous effort in the laboratory is essential for appropriate diagnosis and management of these cases.

Disseminated nocardiosis in an immunosuppressed patient with systemic lupus erythematosus and neuromyelitis optica spectrum disorder

Opportunistic infections are an ongoing concern in patients with autoimmune disease who are being treated with immunosuppressive agents. Nocardiosis is an uncommon opportunistic infection which has been reported in association with immunosuppressed patients and autoimmune disease. It is challenging to diagnose and can have multisystem manifestations. Failure to diagnose and appropriately treat can result in significant mortality. We present a 49 year old woman with systemic lupus erythematosus and neuromyelitis optica spectrum disorder who was treated with mycophenolate mofetil, prednisone and recent plasmapheresis. She developed acute onset of shortness of breath and fevers and was ultimately diagnosed with disseminated nocardiosis with lung, brain and muscle abscesses.

Molecular Characterization and Antimicrobial Susceptibilities of Nocardia Species Isolated from the Soil; A Comparison with Species Isolated from Humans

Nocardia species, one of the most predominant Actinobacteria of the soil microbiota, cause infection in humans following traumatic inoculation or inhalation. The identification, typing, phylogenetic relationship and antimicrobial susceptibilities of 38 soil Nocardia strains from Lara State, Venezuela, were studied by 16S rRNA and gyrB (subunit B of topoisomerase II) genes, multilocus sequence analysis (MLSA), whole-genome sequencing (WGS), and microdilution. The results were compared with those for human strains. Just seven Nocardia species with one or two strains each, except for Nocardia cyriacigeorgica with 29, were identified. MLSA confirmed the species assignments made by 16S rRNA and gyrB analyses (89.5% and 71.0% respectively), and grouped each soil strain with its corresponding reference and clinical strains, except for 19 N. cyriacigeorgica strains found at five locations which grouped into a soil-only cluster. The soil strains of N. cyriacigeorgica showed fewer gyrB haplotypes than the examined human strains (13 vs. 17) but did show a larger number of gyrB SNPs (212 vs. 77). Their susceptibilities to antimicrobials were similar except for beta-lactams, fluoroquinolones, minocycline, and clarithromycin, with the soil strains more susceptible to the first three (p ≤ 0.05). WGS was performed on four strains belonging to the soil-only cluster and on two outside it, and the results compared with public N. cyriacigeorgica genomes. The average nucleotide/amino acid identity, in silico genome-to-genome hybridization similarity, and the difference in the genomic GC content, suggest that some strains of the soil-only cluster may belong to a novel subspecies or even a new species (proposed name Nocardia venezuelensis).

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.

Comparative Genomics and Metabolomics in the Genus Nocardia

Using automated genome analysis tools, it is often unclear to what degree genetic variability in homologous biosynthetic pathways relates to structural variation. This hampers strain prioritization and compound identification and can lead to overinterpretation of chemical diversity. Here, we assessed the metabolic potential of Nocardia, an underinvestigated actinobacterial genus that is known to comprise opportunistic human pathogens. Our analysis revealed a plethora of putative biosynthetic gene clusters of various classes, including polyketide, nonribosomal peptide, and terpenoid pathways. Furthermore, we used the highly conserved biosynthetic pathway for nocobactin-like siderophores to investigate how gene cluster differences correlate to structural differences in the produced compounds. Sequence similarity networks generated by BiG-SCAPE (Biosynthetic Gene Similarity Clustering and Prospecting Engine) showed the presence of several distinct gene cluster families. Metabolic profiling of selected Nocardia strains using liquid chromatography-mass spectrometry (LC-MS) metabolomics data, nuclear magnetic resonance (NMR) spectroscopy, and GNPS (Global Natural Product Social molecular networking) revealed that nocobactin-like biosynthetic gene cluster (BGC) families above a BiG-SCAPE threshold of 70% can be assigned to distinct structural types of nocobactin-like siderophores.IMPORTANCE Our work emphasizes that Nocardia represent a prolific source for natural products rivaling better-characterized genera such as Streptomyces or Amycolatopsis Furthermore, we showed that large-scale analysis of biosynthetic gene clusters using similarity networks with high stringency allows the distinction and prediction of natural product structural variations. This will facilitate future genomics-driven drug discovery campaigns.

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.

A multicentre analysis of Nocardia pneumonia in Spain: 2010-2016

OBJECTIVE

To analyse all cases of Nocardia pneumonia occurring between 2010 and 2016 in five Spanish hospitals.

METHODS

This was a retrospective observational analysis of clinical and microbiological data collected from 55 cases of Nocardia pneumonia.

RESULTS

There were one to 20 cases per hospital and six to nine cases per year. Chronic obstructive pulmonary disease, bronchiectasis, and asthma were the main predisposing underlying respiratory conditions. Thirty-four patients were receiving systemic and/or inhaled corticosteroids prior to infection, eight had neoplasia, and six had haematological malignancies. Clinical and radiological findings were common to pneumonia of other infectious aetiologies, except for the frequent presence of nodules and cavitation. Overall, the 1-year mortality was high (38.2%), and mortality was directly related to the pulmonary disease in 15 patients (27.3%). The most frequently identified species were N. cyriacigeorgica (n=21), N. abscessus (n=8), and N. farcinica (n=5). All Nocardia isolates were susceptible to linezolid and all but two were susceptible to amikacin and trimethoprim-sulfamethoxazole.

CONCLUSIONS

Nocardia pneumonia-associated mortality remains high, probably because of the debilitated status of patients in whom this pathogen is able to cause pulmonary infection.