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

Genomic characteristics, virulence potential, antimicrobial resistance profiles, and phylogenetic insights into Nocardia cyriacigeorgica

BACKGROUND

Nocardia cyriacigeorgica, an opportunistic pathogen, is increasingly implicated in human infections. This pathogen predominantly causes pulmonary infections, leading to acute, subacute, or chronic necrotizing suppurative lesions, in severe cases, may progress to disseminated infections. Effective clinical diagnosis, prevention, and treatment strategies require a thorough understanding of its biological characteristics and pathogenic mechanisms. However, despite the rising incidence of nocardial diseases, research on the pathogenicity of N. cyriacigeorgica remains limited, primarily focusing on case reports and epidemiological studies. This study aimed to provide a comprehensive analysis of the genomic features, phylogenetic relationships, antimicrobial resistance profiles, and candidate virulence factors of N. cyriacigeorgica strains to inform future investigations into its pathogenesis.

METHODS

Whole-genome sequencing was conducted on five N. cyriacigeorgica strains isolated from patients with pulmonary infection at our hospital. This analysis utilized a combination of second-generation Illumina HiSeq and third-generation PacBio sequencing technologies. Additionally, publicly available genomic data from 58 strains in the National Center Biotechnology Information database were integrated, resulting in a dataset of 63 genomes. These genomes were subjected to comparative genomic analyses, including phylogenetic reconstruction, pan-genome evaluation, and gene distribution assessments.

RESULTS

Phylogenetic analysis identified five major clades within N. cyriacigeorgica. ANI analysis further subdivided clade B into five distinct subgroups. Pan-genome analysis revealed clade-specific orthogroups in the distribution of genes assigned to Clusters of Orthologous Groups, with clade A containing the highest number of clade-specific gene families. Comparative genomic analysis uncovered several potential pathogenic genes implicated in host cell invasion, phagosomal maturation arrest, and intracellular survival within macrophages, which were conserved across all analyzed strains. Notable differences in the distribution of enterobactin-encoding genes were observed among the clades. The mce3C gene also displayed variable distributions across clades; however, no correlation was established between its presence and strain source. Among the 63 strains, 27 were found to harbor both mce3C and mce4F genes, which were categorized into five distinct patterns. Furthermore, antibiotic resistance genes, including VanSO, VanRO, erm(O)-Irm, srmB, ermH, bcl, bla1, and cmIR, demonstrated clade-specific distribution patterns. Notably, the genes erm(O)-Irm, srmB, and ermH were associated with the isolation origin of the strains.

CONCLUSIONS

This study provides a comprehensive evaluation of the genomic characteristics, potential virulence factors, antimicrobial resistance genes, and phylogenetic relationships of N. cyriacigeorgica. The findings offer valuable insights into the mechanisms underlying intracellular survival, replication within macrophages, and pathogen-host interactions in N. cyriacigeorgica infections. These results establish a foundation for future research into the pathogenesis and clinical management of N. cyriacigeorgica.

Successful maintenance therapy with moxifloxacin for disseminated nocardiosis caused by Nocardia farcinica in a patient with Cushing's syndrome

Nocardia species are aerobic, Gram-positive actinomycetes often causing opportunistic infections, particularly in immunocompromised hosts. Nocardia farcinica is notable for disseminated nocardiosis (DN), frequently involving the lungs and central nervous system (CNS). Cushing's syndrome (CS), characterized by hypercortisolemia, further predisposes patients to severe infections. We report a 73-year-old woman with ACTH-dependent CS due to a pituitary adenoma who developed DN with pleuropulmonary, CNS, and gluteal abscesses. Diagnosis was confirmed through cultures and MALDI-TOF MS, identifying N. farcinica. Resistance to standard antibiotics required a tailored regimen, including imipenem, amikacin, and moxifloxacin, alongside surgical management of abscesses and the adenoma. This case emphasizes the importance of rapid diagnostic methods and individualized therapies in managing DN with CS, a rare but severe combination. It highlights the need for vigilance in high-risk patients and contributes valuable insights for optimizing outcomes in such complex cases.

A case of disseminated nocardia infection with initial symptoms manifesting as cognitive impairment: Case report and literature review

RATIONALE

Nocardia infections, although rare, pose significant challenges in diagnosis and treatment, especially when involving the central nervous system (CNS). Mortality rates in such cases can be high, highlighting the need for early recognition and tailored antimicrobial therapy.

PATIENT CONCERNS

A 58-year-old male with a history of chronic obstructive pulmonary disease, antineutrophil cytoplasmic antibody-associated glomerulonephritis, and steroid-induced diabetes mellitus presented with disorganized speech, fever, cough, dyspnea, and psychiatric symptoms.

DIAGNOSES

The patient was diagnosed with severe pneumonia, left pneumothorax, bilateral pulmonary bullae, and CNS involvement. Next-generation sequencing (NGS) identified Nocardia farcinica as the causative agent.

INTERVENTIONS

Initial treatment with ceftriaxone was ineffective. Upon identification of N. farcinica via NGS, the patient was started on a tailored antimicrobial regimen consisting of sulfamethoxazole, linezolid, and meropenem.

OUTCOMES

Despite initial clinical improvement, the patient was discharged early due to financial constraints. Unfortunately, he later succumbed to the infection.

LESSONS

This case underscores the difficulty of diagnosing Nocardia infections, particularly when they involve the CNS. The use of advanced diagnostic tools such as NGS, along with early and appropriate antimicrobial therapy, is crucial for improving patient outcomes. Financial and healthcare access challenges may impact the success of treatment, emphasizing the importance of comprehensive follow-up and patient support.

Nocardia in an Immunocompetent Patient Simulating Pulmonary Carcinoma: A Case Report and Literature Review

Nocardiosis is an opportunistic infectious pathology of low incidence that usually affects the lungs, skin, and brain. It has been implicated in causing serious and potentially fatal infections without treatment. It affects immunocompetent and immunocompromised patients. In immunocompetent patients, it is presented with local conditions, and in immunocompromised patients, it is seen in disseminated forms. We present the case of a 61-year-old male immunocompetent patient with a high suspicion of pulmonary carcinoma, in whom pathology showed infection by Nocardia spp.

Comparison of Clinical Characteristics and Treatment Outcome Between Localized and Disseminated Nocardiosis in a Tertiary Hospital in China

Background

In China, due to the large population, infections caused by Nocardia may not be as rare. Unfortunately, there is still inadequate knowledge of the clinical impact caused by Nocardia. This study aimed to compare the clinical characteristics and treatment of localized and disseminated nocardiosis.

Methods

The clinical and microbiological data of patients diagnosed with nocardiosis in a tertiary hospital in Beijing from July 2011 to July 2021 were collected and retrospectively analyzed.

Results

Among the 54 nocardiosis cases, 34 cases were in the localized infection group, while 20 cases in the disseminated infection group. The proportion of patients with chronic structural lung disease was higher in the localized group (P=0.010). In contrast, patients with disseminated infections were more prone to receive long-term glucocorticoids and/or immunosuppressants (P=0.027). Pulmonary nodules were prominent features of imaging changes in patients with disseminated infections (P=0.027) whereas bronchial dilatation was more common in patients with localized infections (P=0.025). In addition, the disseminated group had longer average hospitalization days relative to the localized group (P=0.016), but there was no significant difference in mortality between them (P=0.942).

Conclusion

There were differences in the clinical profiles between patients with localized and disseminated nocardiosis in terms of clinical presentation, infection site, radiological features, treatment, and prognosis. These findings may provide references for the management and treatment of patients with nocardiosis.

Pancytopenia following adjuvant therapy with interferon-gamma in a patient with disseminated nocardiosis

A patient with disseminated nocardiosis developed pancytopenia after treatment with recombinant interferon-gamma (IFN-γ). While no previous clinical reports link pancytopenia to IFN-γ, our observations align with basic research on myelosuppressive effects of IFN-γ. Adjunctive IFN-γ may improve standard nocardiosis therapy, but vigilant monitoring of its hematologic effects is necessary.

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.

Brucella infection combined with Nocardia infection: A case report and literature review

Human brucellosis is an infectious disease caused by Brucella and is often misdiagnosed for atypical manifestations including fever of unknown origin, headache, weakness, among else. Nocardiosis is a zoonotic disease caused by the genus Nocardia, which usually spreads through the respiratory tract, skin, and digestive tract. Limited research has documented cases of co-infection involving both Brucella and Nocardia pathogens in patients. A 55-year-old male was admitted to our hospital with intermittent high-grade fever. Following sputum and blood cultures, as well as other laboratory examinations, the patient was diagnosed with concurrent brucellosis and nocardiosis. According to recommendations of previous studies and reports, the patient was successively treated with levofloxacin, doxycycline, piperacillin sodium and sulbactam sodium, trimethoprim-sulfamethoxazole, rifampicin, and tigecycline, after which the patient recovered and was discharged. Brucella and Nocardia are both opportunistic pathogens and simultaneous infection of Brucella and Nocardia is relatively rare. If patients continue to experience persistent fever despite receiving empirical antibiotic therapy, it becomes necessary to conduct examinations to identify potential atypical pathogens, including Brucella and Nocardia. Sputum staining, sputum culture, and blood culture are critical auxiliary examinations during clinical practice. The treatment plan should be selected based on guidelines and the individual patient's condition. Regular reevaluation should be conducted, and antimicrobial agents should be adjusted accordingly.

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.

Interstitial pneumonia combined with nocardia cyriacigeorgica infection: A case report

BACKGROUND

Nocardia infection is a relatively uncommon disease, with no reports among patients with interstitial pneumonia. Due to its atypical clinical symptoms and chest computed tomography (CT) findings and the frequent yielding of negative results by conventional cultures, it poses challenges for timely diagnosis and treatment.

CASE SUMMARY

A 63-year-old female patient presented to our hospital in July 2022 with a 3-mo history of intermittent cough and poor appetite, accompanied by a 2-wk long duration of headaches. She had a previous medical history of interstitial pneumonia and was on oral prednisone and cyclosporine. Chest CT revealed the presence of newly developed round nodules. The diagnosis of Nocardia cyriacigeorgica infection was confirmed through metagenomic next-generation sequencing (mNGS) performed on bronchoalveolar lavage fluid. Targeted anti-infection therapy was initiated, resulting in symptom improvement and radiological resolution, further validating the mNGS results.

CONCLUSION

Nocardia cyriacigeorgica infection is a clinically rare condition that is primarily observed in immunocompromised patients. Its clinical and radiological manifestations lack specificity, but mNGS can aid in rapidly obtaining pathogenic information. Early initiation of targeted antimicrobial therapy based on mNGS results can improve patient prognosis.

Skin lesions by Scedosporium apiospermum and Nocardia pulmonary infection in an oncologic patient: a case report

BACKGROUND

Fungal infections, other than candidiasis and aspergillosis, are an uncommon entity. Despite this, emerging pathogens are a growing threat. In the following case report, we present the case of an immunocompromised patient suffering from two serious opportunistic infections in the same episode: the first of these, Nocardia multilobar pneumonia; and the second, skin infection by Scedosporium apiospermum. These required prolonged antibacterial and antifungal treatment.

CASE PRESENTATION

This case is a 71-year-old oncological patient admitted for recurrent pneumonias that was diagnosed for Nocardia pulmonary infection. Nervous system involvement was discarded and cotrimoxazole was started. Haemorrhagic skin ulcers in the lower limbs appeared after two weeks of hospital admission. We collected samples which were positive for Scedosporium apiospermum and we added voriconazole to the treatment. As a local complication, the patient presented a deep bruise that needed debridement. We completed 4 weeks of intravenous treatment with slow improvement and continued with oral treatment until the disappearance of the lesions occurs.

CONCLUSIONS

Opportunistic infections are a rising entity as the number of immunocompromised patients is growing due to more use of immunosuppressive therapies and transplants. Clinicians must have a high suspicion to diagnose and treat them. A fluid collaboration with Microbiology is necessary as antimicrobial resistance is frequent.

Pulmonary and central nervous system nocardiosis: Alcoholism as an immunocompromising factor

Nocardiosis is a disease with worldwide distribution. It is usually found in tropical areas and mainly affects immunocompromised patients, however, there are also cases where its infection has been reported in immunocompetent patients. This pathology is caused by bacteria known as Nocardia spp., which are gram-positive microorganisms and environmental saprophytes, and although exposure to Nocardia spp. is almost universal, only a small fraction of exposed people develops the disease. We present the case of a 47-year-old man, with no evidence of immunosuppression, from a rural area of Boyacá, who was admitted due to intense and intermittent headache accompanied by paresthesia and, finally, a decrease in consciousness. A brain magnetic resonance was performed and evidenced a fronto-temporo- occipital space-occupying lesion in the cortico-subcortical region with a compressive effect and displacement of the ventricular system cavities. It was suspected at first a neoplastic lesion or a brain abscess. The lesion was surgically resected, and its culture showed Nocardia africana/nova. In later studies a possible primary pulmonary focus was evidenced. Alcoholism was the only risk factor documented. The patient completed 6 weeks of hospital antibiotic treatment with favorable clinical and radiological evolution and was discharged with a 1-year plan of outpatient antibiotic therapy. Although Nocardia spp. mainly affects immunocompromised patients, evidence shows that this microorganism can also be a threat to individuals without traditional immunosuppression risk factors.

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.

Identification and antimicrobial susceptibility of referred Nocardia isolates in Victoria, Australia 2009-2019

Introduction. Nocardia is an opportunistic pathogen that can cause significant morbidity and mortality, particularly in the immunocompromised host. Antimicrobial susceptibility profiles vary across Nocardia spp. and vary within Australia as well as worldwide. Knowledge of local susceptibility patterns is important in informing appropriate empiric antimicrobial therapy.Gap Statement. This is the largest study to date in Australia that correlates antimicrobial susceptibility profiles with molecular identification of Nocardia species. It is the first study that examines isolates from multiple institutions across the state of Victoria, Australia.Aim. To investigate the species distribution and antibiotic susceptibility of Nocardia spp. isolates referred to the Mycobacterial Reference Laboratory (MRL) in Victoria, Australia from 2009 to 2019.Methodology. We conducted a retrospective review of Nocardia spp. isolates which were identified using molecular sequencing. Antimicrobial susceptibility testing was performed using standardized broth microdilution method with Sensititre RAPMYCO1 plates. Species distribution and antibiotic susceptibility profiles were analysed.Results. In total, 414 Nocardia isolates were identified to 27 species levels, the majority originating from the respiratory tract (n=336, 81.2 %). N. nova (n=147, 35.5 %) was the most frequently isolated, followed by N. cyriacigeorgica (n=75, 18.1 %). Species distribution varied by isolate source, with N. farcinica and N. paucivorans found more commonly from sterile sites. Linezolid and amikacin had the highest proportion of susceptible isolates (100 and 99% respectively), while low susceptibility rates were detected for ceftriaxone (59 %) and imipenem (41 %). Susceptibility to trimethoprim sulfamethoxazole varied by species (0-100 %).Conclusion. This is the largest study to date in Australia of Nocardia species distribution and antimicrobial susceptibility patterns. N. farcinica and N. paucivorans were more likely to be isolated from sterile sites, while N. brasiliensis and N. otitidiscvarium were more likely to be isolated from skin and soft tissue. First line therapeutic antimicrobial recommendations by local guidelines were not necessarily reflective of the in vitro susceptibility of Nocardia isolates in this study, with high susceptibility detected for linezolid and amikacin, but poor susceptibility demonstrated for ceftriaxone and imipenem. Profiles for trimethoprim-sulfamethoxazole varied across different Nocardia species, warranting ongoing susceptibility testing for targeted clinical use.

Comprehensive Analysis of the Nocardia cyriacigeorgica Complex Reveals Five Species-Level Clades with Different Evolutionary and Pathogenicity Characteristics

Nocardia cyriacigeorgica is a common etiological agent of nocardiosis that has increasingly been implicated in serious pulmonary infections, especially in immunocompromised individuals. However, the evolution, diversity, and pathogenesis of N. cyriacigeorgica have remained unclear. Here, we performed a comparative genomic analysis using 91 N. cyriacigeorgica strains, 45 of which were newly sequenced in this study. Phylogenetic and average nucleotide identity (ANI) analyses revealed that N. cyriacigeorgica contained five species-level clades (8.6 to 14.6% interclade genetic divergence), namely, the N. cyriacigeorgica complex (NCC). Further pan-genome analysis revealed extensive differences among the five clades in nine functional categories, such as energy production, lipid metabolism, secondary metabolites, and signal transduction mechanisms. All 2,935 single-copy core genes undergoing purifying selection were highly conserved across NCC. However, clades D and E exhibited reduced selective constraints, compared to clades A to C. Horizontal gene transfer (HGT) and mobile genetic elements contributed to genomic plasticity, and clades A and B had experienced a higher level of HGT events than other clades. A total of 129 virulence factors were ubiquitous across NCC, such as the mce operon, hemolysin, and type VII secretion system (T7SS). However, different distributions of three toxin-coding genes and two new types of mce operons were detected, which might contribute to pathogenicity differences among the members of the NCC. Overall, our study provides comprehensive insights into the evolution, genetic diversity, and pathogenicity of NCC, facilitating the prevention of infections.

IMPORTANCENocardia species are opportunistic bacterial pathogens that can affect all organ systems, primarily the skin, lungs, and brain. N. cyriacigeorgica is the most prevalent species within the genus, exhibits clinical significance, and can cause severe infections when disseminated throughout the body. However, the evolution, diversity, and pathogenicity of N. cyriacigeorgica remain unclear. Here, we have conducted a comparative genomic analysis of 91 N. cyriacigeorgica strains and revealed that N. cyriacigeorgica is not a single species but is composed of five closely related species. In addition, we discovered that these five species differ in many ways, involving selection pressure, horizontal gene transfer, functional capacity, pathogenicity, and antibiotic resistance. Overall, our work provides important clues in dissecting the evolution, genetic diversity, and pathogenicity of NCC, thereby advancing prevention measures against these infections.

Pneumococcal Pneumonia Co-infection with Mycobacterium avium and Nocardia cyriacigeorgica in an Immunocompetent Patient

A 61-year-old woman was transferred with a complaint of a fever and productive cough. She had tested positive for Mycobacterium avium and Nocardia cyriacigeorgica at least twice, and Streptococcus pneumonia (PISP) was isolated (3+) from her purulent sputum. As radiological findings, a lower lung field-dominant infiltration shadow and nodular shadow with cavity were recognized in the bilateral lung fields. We diagnosed her with pneumococcal pneumonia co-infection with M. avium and N. cyriacigeorgica. She was treated with MEPM for pneumococcal pneumonia, a standard regimen containing clarithromycin for pulmonary M. avium complex (MAC) disease, and sulfamethoxazole/trimethoprim for pulmonary nocardiosis. She improved with appropriate treatment.

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.

Nocardiosis in Japan: a multicentric retrospective cohort study

Background Nocardia species cause a broad spectrum of infections, especially in immunocompromised patients. Given its relative rarity, data on the prognosis and distribution of nocardiosis from a large cohort are scarce. The present study aimed to scrutinize the clinical features and outcomes of nocardiosis in Japan, including one-year mortality and microbiological data. Methods The present, multicentric, retrospective cohort study enrolled patients aged ≥ 18 years with nocardiosis diagnosed between January 2010 and December 2017 and recorded their clinical and microbiological characteristics. Factors associated with one-year mortality were also determined using Cox proportional hazard analysis. Results In total, 317 patients were identified at 89 hospitals. Almost half (155/317, 48.9%) were receiving immunosuppressive agents, and 51 had disseminated nocardiosis (51/317, 16.1%). The one-year, all-cause mortality rate was 29.4% (80/272; lost to follow-up, n = 45). The most frequently isolated species was Nocardia farcinica (79/317, 24.9%) followed by the N. nova complex (61/317, 19.2%). Selected antimicrobial agents were generally effective, with linezolid (100% susceptibility [S]) and amikacin (94% S) having the most activity against Nocardia species. In Cox proportional hazard analysis, factors independently associated with one-year mortality were a Charlson Comorbidity Index score ≥ 5 (adjusted hazard ratio [aHR], 3.61; 95% confidence interval [CI], 1.95-6.71, P < 0.001) and disseminated nocardiosis (aHR, 1.79; 95%CI, 1.01-3.18, P = 0.047). Conclusions The presence of advanced comorbidities and disseminated infection, rather than variations in antimicrobial therapy or Nocardia species, were independently associated with one-year mortality.

Management dilemmas in Nocardia brain infection

PURPOSE OF REVIEW

Brain nocardiosis is a rare but severe infection mostly occurring among immunocompromised patients. In this review, we present recent data on this infection and address some of the common clinical dilemmas encountered in patients with brain nocardiosis.

RECENT FINDINGS

Strategies used to approach a patient with suspected brain nocardiosis include the 'conservative strategy' (without early neurosurgery) and the 'neurosurgical strategy' (with early aspiration or excision of brain abscess[es]). The advantages and disadvantages of both strategies are summarised. Our opinion is that the use of the 'conservative strategy' should be limited to well-selected patients presenting with an easily accessible extra-neurological lesion(s) and have brain abscesses at low risk of treatment failure. In terms of antimicrobial therapy, we summarise the data supporting the use of a multidrug regimen in patients with brain nocardiosis.Last, we list possible reasons for treatment failure in patients with brain nocardiosis and suggest interventions to overcome them.

SUMMARY

Literature is scarce regarding brain nocardiosis, as a consequence of the rarity of this disease. A multidisciplinary and individualised management is required to optimise the outcome of patients with brain nocardiosis.

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.

Trimethoprim/sulfamethoxazole for nocardiosis in solid organ transplant recipients: Real-life data from a multicentre retrospective study

BACKGROUND

Little is known regarding the optimal management of nocardiosis among solid organ transplant (SOT) recipients. It is often suggested to avoid trimethoprim/sulfamethoxazole (TMP-SMX) monotherapy in heavily immunocompromised patients (such as SOT recipients) and/or in case of severe or disseminated nocardiosis. Our aim was to report our experience with TMP-SMX monotherapy in SOT recipients with nocardiosis.

METHODS

Using data from a previously published European study, we assessed the incidence of adverse events in SOT recipients receiving TMP-SMX monotherapy and assessed its effectiveness.

RESULTS

Thirty-one SOT recipients with nocardiosis were included, mostly kidney transplant recipients (20/31, 65%). Eleven (36%) had disseminated infection, and four (13%) had brain nocardiosis. Most patients had lung and/or pleural involvement (26/31, 84%). Daily dose of trimethoprim at initiation was 10 [6.4-14.8] mg/kg. The median estimated glomerular filtration rate at time of diagnosis of nocardiosis was 44 [30-62] ml/min/1.73 m². TMP-SMX was discontinued prematurely in one third of the patients (10/31, 32%, mostly for hematological toxicity [n = 3] or increased serum creatinine [n = 3]). Focusing on the 24 (77%) patients who completed at least 30 days of TMP-SMX monotherapy, 4 had late (>30 days) drug discontinuation, 1 experienced treatment failure, and 19 completed planned TMP-SMX monotherapy. Clinical outcome was favorable in these 19 patients, despite the fact that 8 (42%) had disseminated infection and 2 (11%) brain nocardiosis. Overall, all-cause 1-year mortality was 10% (3/31).

CONCLUSIONS

TMP-SMX monotherapy appears to be effective for the treatment of most nocardiosis among SOT recipients. Interventional studies are needed to compare its safety and effectiveness with those of other regimens used to treat posttransplant nocardiosis.

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.

Nocardia cyriacigeorgica infection in a patient with pulmonary sequestration: A case report

BACKGROUND

Nocardia cyriacigeorgica (N. cyriacigeorgica) infection is uncommon in clinical practice. Pulmonary sequestration complicated with N. cyriacigeorgica has not been reported in the literature. Here, we present a case of pulmonary se-questration complicated with N. cyriacigeorgica infection in an immunocom-petent woman.

CASE SUMMARY

A 37-year-old woman complaining of a recurrent cough was admitted to our hospital. Pulmonary sequestration in the lower lobe of the left lung was diagnosed by enhanced computed tomography. Bronchoalveolar lavage fluid was then collected, which showed gram positive bacilli with weakly positive modified acid-fast staining. The pathogen was identified as N. cyriacigeorgica after bacterial culture and mass spectrometry analysis. The patient was diagnosed with pulmonary sequestration complicated with N. cyriacigeorgica infection, and her symptoms quickly improved following anti-infective therapy.

CONCLUSION

Nocardiosis is considered to be an opportunistic infection. This is the first report of pulmonary sequestration complicated with N. cyriacigeorgica infection in a patient with normal immunity.

Role of Williamsia and Segniliparus in human infections with the approach taxonomy, cultivation, and identification methods

The genera Williamsia and Segniliparus are of aerobic actinomycetes and at the time of writing, they have 12 and 2 species, respectively. These genera cause various infections in humans. In this review, we surveyed their taxonomy, isolation, identification, as well as their role to cause human infections.

Invasive Nocardiosis in Transplant and Nontransplant Patients: 20-Year Experience in a Tertiary Care Center

Objective

To present the clinical characteristics and outcome of transplant and nontransplant patients with invasive nocardiosis.

Patients and Methods

We conducted a retrospective chart review of 110 patients 18 years and older diagnosed with culture-proven invasive nocardiosis (defined as the presence of clinical signs and/or radiographic abnormalities) between August 1, 1998, and November 30, 2018. Information on demographic, clinical, radiographic, and microbiological characteristics as well as mortality was collected.

Results

One hundred ten individuals with invasive nocardiosis were identified, of whom 54 (49%) were transplant and 56 nontransplant (51%) patients. Most transplant patients were kidney and lung recipients. The overall mean age was 64.9 years, and transplant patients had a higher prevalence of diabetes and chronic kidney disease. A substantial proportion of nontransplant patients were receiving corticosteroids (39%), immunosuppressive medications (16%), and chemotherapy (9%) and had chronic obstructive pulmonary disease (20%), rheumatologic conditions (18%), and malignant neoplasia (18%). A higher proportion of transplant patients (28%) than nontransplant patients (4%) received trimethoprim-sulfamethoxazole prophylaxis. In both groups, the lung was the most common site of infection. Seventy percent of all Nocardia species isolated were present in almost equal proportion: N brasiliensis (16%), N farcinica (16%), N nova (15%), N cyriacigeorgia (13%), and N asteroides (11%). More than 90% of isolates were susceptible to trimethoprim-sulfamethoxazole, linezolid, and amikacin. There was no significant difference in mortality between the 2 groups at 1, 6, and 12 months after the initial diagnosis.

Conclusion

The frequency of invasive Nocardia infection was similar in transplant and nontransplant patients and mortality at 1, 6, and 12 months was similar in both groups. Trimethoprim-sulfamethoxazole prophylaxis failed to prevent Nocardia infection.

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.

Invasive Nocardiosis: Disease Presentation, Diagnosis and Treatment - Old Questions, New Answers?

Nocardia spp. is an environmental filamentous Gram-positive bacterium that may cause infections in humans and, despite recent progress, many challenges remain regarding the management of nocardiosis. This review aims at describing most recently published data regarding the diagnosis, treatment and follow-up of patients with invasive nocardiosis. As nocardiosis mainly affects patients with cell-mediated immunity defects, a comprehensive workup is mandatory in case of invasive nocardiosis occurring in ”apparently healthy patients”. Indeed, invasive nocardiosis might reveal an unknown primary immunodeficiency or the presence of anti-GM-CSF autoantibodies. Even if the diagnosis of nocardiosis mostly relies on direct examination and bacterial culture, a genus-specific PCR may be used for the detection of Nocardia, when directly performed on a clinical sample. Brain imaging should always be performed, even in the absence of neurological symptoms. Cotrimoxazole (trimethoprim/sulfamethoxazole), linezolid, parenteral cephalosporins, carbapenems and amikacin may be used as initial antibiotics to treat nocardiosis. Cotrimoxazole or linezolid can be used as monotherapy in selected patients without brain involvement. Although treatment duration has historically been set to at least 6 months in the absence of central nervous system involvement, shorter durations (<120 days) seem to be associated with a favourable outcome.

Severe Nocardia pneumonia in an immunocompromised patient with alpha-1 antitrypsin deficiency

Pulmonary nocardiosis is an uncommon pulmonary infection that is more likely found in immunocompromised patients with underlying chronic lung disease. The presentation of pulmonary nocardiosis is widely variable and shares features with other types of pulmonary infections. Nocardia is also not as easily isolated on standard culture mediums and hence more difficult to identify. We describe the case of a patient with a severe necrotising pneumonia who was chronically immunosuppressed with steroids and has alpha-1 antitrypsin deficiency.

Isolated Nocardiosis, an Unrecognized Primary Immunodeficiency?

Nocardiosis is an infectious disease caused by the gram-positive bacterium Nocardia spp. Although it is commonly accepted that exposure to Nocardia is almost universal, only a small fraction of exposed individuals develop the disease, while the vast majority remain healthy. Nocardiosis has been described as an "opportunistic" disease of immunocompromised patients, suggesting that exposure to the pathogen is necessary, but a host predisposition is also required. Interestingly, increasing numbers of nocardiosis cases in individuals without any detected risk factors, i.e., without overt immunodeficiency, are being reported. Furthermore, a growing body of evidence have shown that selective susceptibility to a specific pathogen can be caused by a primary immunodeficiency (PID). This raises the question of whether an undiagnosed PID may cause nocardiosis affecting otherwise healthy individuals. This review summarizes the specific clinical and microbiological characteristics of patients with isolated nocardiosis published during the past 30 years. Furthermore, it gives an overview of the known human immune mechanisms to fend off Nocardia spp. obtained from the study of PIDs and patients under immunomodulatory therapies.

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.