Disseminated Nocardia infection-A rare presentation

Nocardia infection is rare and requires early diagnosis, extended use of sulfonamides for good prognosis, and prevention of recurrence. It is crucial to suspect nocardiosis in cases of atypical pneumonias or unexplained visceral organ dysfunction.

A case of triple infection including strongyloides stercoralis in a microscopic polyangiitis patient

We present the case of a microscopic polyangiitis (MPA) patient who developed strongyloidiasis, nocardia and citrobacter freundii (CF) infection after corticosteroides and immunosuppressant therapy. When digestive, respiratory or other system symptoms consecutively occur in a immunocompromised host who lives in tropical or temperate zone and have close contact with soil, we should take strongyloidiasis into consideration despite absence of eosinophilia. Mixed infection with nocardia cannot be easily excluded. It is essential to search for the etiology proof with multiple approaches positively and repeatedly.

Primary Nocardia brain abscesses and role of intraventricular antibiotic therapy

Intracranial infections caused by Nocardia Farcinica are challenging to treat and potentially lethal because of the organism's tendency to resist antibiotics and high relapse rates. Such infections usually occur in immunocompromised patients who have predisposing factors. Nocardia brain abscesses carry a higher morbidity and mortality rate than other bacterial brain abscesses, with reported mortality rates of 55% (even up to 90% in cases of late diagnosis) in immunocompromised patients. An aggressive therapeutic approach is required and an early identification of the microorganism is paramount. Given the high microbial resistance, it is usually an infection with a low cure rate. We present the case of a patient with primary brain abscesses due to Nocardia Farcinica, successfully treated with intrathecal Amikacin administration through ventricular drain, in addition to surgical evacuation and intravenous antibiotic therapy. In this case, clinical and radiological improvement were observed once the intrathecal treatment was started. To our best knowledge, no cases of intraventricular use of Amikacin have been previously reported to treat this type of infection and we believe that it may be useful in properly selected patients.

Nocardia infection causing non-healing surgical wounds: A case series from Bangladesh

OBJECTIVE

Nocardia can be introduced accidentally causing non-healing surgical wounds.

METHOD

From February 2017 to January 2021 samples from wounds were collected. Nocardia identification and susceptibility testing were carried out by standard procedure.

RESULTS

Seventeen (35.4 %) Nocardia spp. and 20 other pathogens (41.7%) were recovered by culture. Drug susceptibility among Nocardia was >70% to amikacin, amoxicillin-clavulanic acid, levofloxacin, linezolid, and imipenem, 47% to cephalosporins and 41% to trimethoprim/sulfamethoxazole.

CONCLUSIONS

Infections with Nocardia spp. should be considered in non-healing surgical wounds.

Stroke like presentation of disseminated CNS Nocardia beijingensis infection in an immunocompetent patient: Case report and review of the literature

We describe a rare case of pulmonary and central nervous system (CNS) Nocardia beijingensis infection in an immunocompetent patient presenting with stroke like symptoms and newly discovered pulmonary and brain mass. Initial work up suggested lung cancer with metastasis to the brain. However, further evaluation revealed disseminated N. beijingensis. A literature review of N. beijingensis infections in immunocompetent host is also presented.

Evaluation of anti-biofilm potential of biosurfactant extracted from Nocardia species

INTRODUCTION

Bacterial natural products such as biosurfactants and surface-active agents are important compounds which exhibit many applications in the fields of medicine.

AIM

The aim of the present study was to isolate and identify Nocardia strains with high biosurfactant production and antibiofilm ability.

MATERIALS AND METHODS

In the present study, a biosurfactant producing Nocardia species was isolated and identified by a laboratory method. Nocardia species were initially screened and then tested for their ability to produce biosurfactant. The oil spreading test and the surface tension measurements showed that one strain was a biosurfactant producer. The strain with the best surface activity results was selected for further studies and identified by 16S rRNA gene sequencing method. Fourier transform infrared spectroscopy (FTIR) and compositional analysis proved a biosurfactant structure.

RESULTS

Oil spreading test and blue agar plate test confirmed biosurfactants and extracellular anionic glycolipids. E24% assay using olive oil revealed strong emulsifying characteristic of the extracted biosurfactant with 100% emulsifying strength. FTIR spectrum indicated the presence of aliphatic hydrocarbon chain (lipid) along with the polysaccharide portion, confirming the glycolipid nature of the biosurfactant. The stability of the biosurfactant produced in different conditions was significant. Increasing concentration of BS significantly inhibited Pseudomonas aeruginosa biofilm.

CONCLUSIONS

N. coubleae can be a representative of the genus Nocardia for the production of biosurfactants with beneficial physicochemical properties.

Natural Products from Nocardia and Their Role in Pathogenicity

Nocardia spp. are filamentous Actinobacteria of the order Corynebacteriales and mostly known for their ability to cause localized and systemic infections in humans. However, the onset and progression of nocardiosis is only poorly understood, in particular the mechanisms of strain-specific presentations. Recent genome sequencing has revealed an extraordinary capacity for the production of specialized small molecules. Such secondary metabolites are often crucial for the producing microbe to survive the challenges of different environmental conditions. An interesting question thus concerns the role of these natural products in Nocardia-associated pathogenicity and immune evasion in a human host. In this review, a summary and discussion of Nocardia metabolites is presented, which may play a part in nocardiosis because of their cytotoxic, immunosuppressive and metal-chelating properties or otherwise vitally important functions. This review also contains so far unpublished data concerning the biosynthesis of these molecules that were obtained by detailed bioinformatic analyses.

Cladophialophora bantiana and Nocardia farcinica infection simultaneously occurring in a kidney transplant recipient: Case report and literature review

Solid organ transplant recipients are at increased risk of acquiring devastating infections with unusual pathogens. Nocardia are aerobic actinomycetes that affect the lungs, brain, skin and soft tissue. Cladophialophora species are dematiaceous fungi that overwhelmingly cause infections in the brain. Both organisms carry a high mortality rate. We present the first reported renal transplant case with Cladophialophora bantiana involving the renal allograft with concurrent invasive nocardiosis involving the lungs and brain.

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.

Pulmonary Nocardia infection in a child with idiopathic pulmonary hemosiderosis

BACKGROUND

Idiopathic pulmonary hemosiderosis (IPH) encompasses a rare and agnogenic group of diffuse alveolar capillary hemorrhagic diseases. Corticosteroid treatment is the globally preferred therapeutic strategy for IPH; however, it can cause immunodeficiency. Nocardia infection often occurs in immunocompromised patients and primarily involves the pleura and lungs. Herein, we describe a case of pediatric pulmonary Nocardia infection after the corticosteroid treatment of IPH.

CASE PRESENTATION

A 7-year-old girl presented with chief complaints of pale complexion persisting for 1 year and a cough for 20 days. Abundant hemosiderin-laden macrophages were detected in the gastric juice, which supported the diagnosis of IPH. Uninterrupted doses of corticosteroids were administered during the last hospitalization. After nearly 2 months of corticosteroids therapy, the patient began to cough and produce a purulent sputum. Next-generation sequencing of the bronchoalveolar lavage fluid revealed Nocardia abscessus (N. abscessus) DNA. Linezolid was administered with good response, and the patient was discharged after 18 days of hospitalization. Her symptoms and pulmonary lesions had recovered, and the IPH appeared to be well-controlled with low dose of corticosteroids in follow-up.

CONCLUSIONS

Nocardia infection should be considered in the differential diagnoses for IPH patients receiving corticosteroid therapy, especially in patients with poor response to conventional empirical antibiotic therapy. Next-generation sequencing of bronchoalveolar lavage fluid may be used to quickly identify the Nocardia. Sulfonamides or linezolid are effective for pediatric pulmonary Nocardia infection.

Case Report: A Severe and Multi-Site Nocardia farcinica Infection Rapidly and Precisely Identified by Metagenomic Next-Generation Sequencing

Nocardia genus is an aerobic, gram-positive, and opportunistic pathogen, which mainly affects cell-mediated immunosuppressed patients. Early diagnosis and treatment greatly improve prognosis. However, the limitation of golden standard-bacterial culture exists. Here, we report a 61-year-old male with pneumonia, sepsis and intermuscular abscesses induced by Nocardia farcinica. Venous blood culture reported negative results. Former improper diagnosis and treatment did not improve his condition. With the assistant of metagenomic next-generation sequencing, the pathogen was identified as Nocardia farcinica. He was then applied with accurate treatment and had a remarkable clinical and radiological improvement.

Isolation and Characterization of Nocardiae Associated with Foaming Coastal Marine Waters

Nocardiosis is an infectious disease caused by Nocardia species that occurs worldwide, albeit more prevalently in tropical/subtropical regions. It can appear as either acute, subacute or as a chronic infection mostly with those with a compromised/weakened immune system. Inhalation of spores and or mycelium fragments is the main transmission route for developing pulmonary nocardiosis. In contrast, cutaneous nocardiosis usually occurs via direct contact. In the subtropical region of the Sunshine Coast in Australia foaming events with thick and persistent and orange-brown color foam have been observed during summer seasons in the near shore marine environments. This study reports the existence of nocardiae in these near shore marine environments by the use of a novel isolation method which used the gas requirements of nocardiae as a selective battery. A total of 32 nocardiae were isolated with the use of this novel method and subsequently conducted molecular identification methods confirmed that the isolates belonged to the genus Nocardia. Twenty-one isolates out of the 32 were closely related to N. nova strains MGA115 and one was related to CBU 09/875, in addition when compared with human pathogenic nocardiae twenty of the isolates were found to be related to N. nova strain JCM 6044. Isolates displayed varied resistance against some of the antibiotics tested when interpretation threshold recommended the Comite de L'Antibiogramme de la Societe Francaise de Microbiologie were used. The highest level of resistance against cefotaxime (n = 27) and ceftriaxone (n = 24). Some of the isolates (n = 6) that displayed resistance to selected antibiotics also possessed potential human pathogenic characteristics such as adherence and translocation through human long epithelial cells as well as displaying phage resistance (n = 26). They might thus present a potential public health risk if frequently encountered through exposure to aerosols generated by the foam as well as direct contact through a wound. Preventative measures to control the growth of nocardiae in such environments such as the control of pollutants, might prevent potential infections that might be caused by these bacteria in humans as well as in marine animals.

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.

Evaluation of pathogenicity and therapeutic effectiveness of antibiotics using silkworm Nocardia infection model

Nocardia is a ubiquitous environmental microbe that causes nocardiosis against immunosuppressed and immunocompromised hosts. The assay system for the quantitative evaluation of virulence of Nocardia sp. or therapeutic effectiveness of antimicrobials for treatment of nocardiosis is not established so far. In this study, we established an infection model of Nocardia sp. using silkworm as an alternative animal model. We found that all tested Nocardia sp. such as Nocardia asiatica, Nocardia elegans, Nocardia exalbida, Nocardia farcinica, and Nocardia nova killed silkworm and their killing ability were different by species. N. farcinica showed higher pathogenicity among tested strain, similar to the mouse model as previously reported. In addition, we found that antimicrobials such as amikacin and minocycline showed therapeutic effectiveness in silkworms infected with N. farcinica, and we could determine effective doses 50 (ED₅₀) values. These results suggest that silkworm is a useful alternative animal to evaluate the pathogenicity of Nocardia pathogen and the therapeutic effects of antimicrobials against Nocardia sp. in a quantitative manner.

Clinical Presentation, Management, and Outcomes of Patients With Brain Abscess due to Nocardia Species

Background

Nocardial brain abscesses are rare, and published literature describing brain abscesses due to Nocardia species is limited to individual case reports or small series. We report one of the largest contemporary retrospective studies describing risk factors, diagnostic evaluation, management, and outcomes of nocardial brain abscess.

Methods

Retrospective review of all adults with brain abscess due to culture-confirmed Nocardia species at our institution between January 1, 2009, and June 30, 2020.

Results

Overall, 24 patients had nocardial brain abscesses during the study period. The median age at presentation was 64 years, and 62.5% were immunocompromised. Pulmonary and cutaneous infections were the most common primary sites of nocardial infection. All 24 patients had magnetic resonance imaging performed, and the frontal lobe was the most commonly involved. The most common organism isolated was Nocardia farcinica, followed by Nocardia wallacei and Nocardia cyriacigeorgica. Thirteen patients were managed with antimicrobial therapy alone, while 11 had both medical and surgical management. In all patients, dual therapy was recommended for the initial 6 weeks of treatment, and 22 patients received at least 1 oral agent as part of their final antibiotic regimen, predominantly trimethoprim-sulfamethoxazole and linezolid. Fourteen patients achieved complete clinical and radiographic resolution of infection.

Conclusions

Nocardia is an important cause of brain abscess in the immunocompromised host. Early diagnostic and therapeutic aspiration may help health care providers confirm the diagnosis, choose an appropriate antimicrobial regimen, and achieve source control.

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.

Epidemiology and in vitro antimicrobial susceptibility of aerobic Actinomycetales in a clinical setting

INTRODUCTION

The incidence of infections caused by aerobic actinomycetes is increasing. Recent changes in taxonomy and the variability in susceptibility patterns among species make necessary a proper identification and antibiotic susceptibility testing.

MATERIAL AND METHODS

Fifty-three strains of aerobic actinomycetes were identified by MALDI-TOF MS using the VITEK MS Mycobacterium/Nocardia kit (bioMérieux, France) in a tertiary hospital in Spain during a six-year period. Antimicrobial susceptibility testing of the isolates was performed using the Sensititre Rapmycoi microdilution panel (Thermo Fisher Scientific, Massachusetts, USA).

RESULTS

Forty strains of Nocardia spp. were identified in the study, being N. farcinica and N. cyriacigeorgica the most prevalent ones. All isolates were susceptible to linezolid and the resistance to amikacin was only observed in one isolate of Gordonia sputi. Resistance to cotrimoxazole was only found in five isolates.

CONCLUSIONS

Routine identification and antimicrobial susceptibility testing of aerobic actinomycetes is advisable for an efficient identification of species and effective treatment.

Comparative Genomics Reveals Prophylactic and Catabolic Capabilities of Actinobacteria within the Fungus-Farming Termite Symbiosis

Actinobacteria, one of the largest bacterial phyla, are ubiquitous in many of Earth's ecosystems and often act as defensive symbionts with animal hosts. Members of the phylum have repeatedly been isolated from basidiomycete-cultivating fungus-farming termites that maintain a monoculture fungus crop on macerated dead plant substrate. The proclivity for antimicrobial and enzyme production of Actinobacteria make them likely contributors to plant decomposition and defense in the symbiosis. To test this, we analyzed the prophylactic (biosynthetic gene cluster [BGC]) and metabolic (carbohydrate-active enzyme [CAZy]) potential in 16 (10 existing and six new genomes) termite-associated Actinobacteria and compared these to the soil-dwelling close relatives. Using antiSMASH, we identified 435 BGCs, of which 329 (65 unique) were similar to known compound gene clusters, while 106 were putatively novel, suggesting ample prospects for novel compound discovery. BGCs were identified among all major compound categories, including 26 encoding the production of known antimicrobial compounds, which ranged in activity (antibacterial being most prevalent) and modes of action that might suggest broad defensive potential. Peptide pattern recognition analysis revealed 823 (43 unique) CAZymes coding for enzymes that target key plant and fungal cell wall components (predominantly chitin, cellulose, and hemicellulose), confirming a substantial degradative potential of these bacteria. Comparison of termite-associated and soil-dwelling bacteria indicated no significant difference in either BGC or CAZy potential, suggesting that the farming termite hosts may have coopted these soil-dwelling bacteria due to their metabolic potential but that they have not been subject to genome change associated with symbiosis.IMPORTANCEActinobacteria have repeatedly been isolated in fungus-farming termites, and our genome analyses provide insights into the potential roles they may serve in defense and for plant biomass breakdown. These insights, combined with their relatively higher abundances in fungus combs than in termite gut, suggest that they are more likely to play roles in fungus combs than in termite guts. Up to 25% of the BGCs we identify have no similarity to known clusters, indicating a large potential for novel chemistry to be discovered. Similarities in metabolic potential of soil-dwelling and termite-associated bacteria suggest that they have environmental origins, but their consistent presence with the termite system suggests their importance for the symbiosis.

Nocardia keratitis mimicking superior limbic keratoconjunctivitis and herpes simplex virus

Purpose

Nocardia keratitis is a rare type of infectious keratitis and may mimic other corneal diseases and lead to delay in diagnosis. This case illustrates how Nocardia often escapes accurate diagnosis due to its insidious onset, variable clinical manifestations, and unusual characteristics on cultures.

Observation

The patient presented with an epithelial defect and superior pannus and scarring, which was misdiagnosed as superior limbic keratoconjunctivitis (SLK) and herpes simplex virus (HSV) keratitis. Repeat corneal scraping cultures, smears, and conjunctival biopsy were necessary to elucidate the diagnosis. It can be effectively treated with the intravenous preparation of trimethoprim-sulfamethoxazole 80 mg/mL (brand name SEPTRA) used topically as eye drops.

Conclusion

The diagnosis of Nocardia keratitis relies on a high clinical suspicion and a prompt corneal scraping with culture. Due to its potential for rapid resolution with early therapy, it is important to isolate Nocardia early in its disease course.

Importance

Topical amikacin had been the standard of care for Nocardia keratitis for many years. However, recently there is increasing resistance of Nocardia to amikacin. SEPTRA offers an alternative therapy. Nocardia keratitis mimics other infectious and inflammatory etiologies so rapid diagnosis and treatment is critical in the prevention of long-term complications.

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.

Microbial risk assessment of Nocardia cyriacigeorgica in polluted environments, case of urban rainfall water

•

Urban infiltration basins are a reservoir of a high diversity of Nocardia encompassing both pathogenic and not-pathogenic species.

•

Relative abundance of pathogenic Nocardia species presents a positive correlation with metal trace elements.

•

High infraspecific variability within N. cyriacigeorgica, forming three phylogroups.

•

Environmental N. cyriacigeorgica strains may be as virulent as clinical GUH-2 strain.

•

hsp65 marker can be used by metabarcoding approach for assessment of environmental Nocardia biodiversity.

Urban Infiltration Basins (UIBs) are used to manage urban runoff transfers and feed aquifers. These UIBs can accumulate urban pollutants and favor the growth of potentially pathogenic biological agents as Nocardia.

Objectives

To assess the spatio-temporal dynamics of pathogenic Nocardia in UIBs and to stablish phylogenetic relationships between clinical and UIB N. cyriacigeorgica strains. To assess pathogenicity associated with environmental N. cyriacigeorgica using an animal model, and to identify genetic elements that may be associated to its virulence.

Methods

A well-characterized UIB in terms of chemical pollutants from Lyon area was used in this study during a whole year. Cultural and Next-Generation-Sequencing methods were used for Nocardia detection and typing. Clinical and environmental isolates phylogenetic relationships and virulences were compared with Multilocus-Sequence-Analysis study together with a murine model.

Results

In autumn, N. cyriacigeorgica and N. nova were the pathogenic most prevalent species in the UIB. The complex N. abscessus/asiatica was also detected together with some other non-pathogenic species. The presence of pathogenic Nocardia was positively correlated to metallic trace elements. Up to 1.0 × 10³ CFU/g sediment of N. cyriacigeorgica and 6 OTUs splited in two different phylogroups were retrieved and were close to clinical strains. The EML446 tested UIB isolate showed significant infectivity in mice with pulmonary damages similar to clinical clone (GUH-2).

Conclusion

Hsp65 marker-based metabarcoding approach allowed detecting N. cyriacigeogica as the most abundant Nocardia pathogenic species in a UIB. Metal trace elements-polluted environments can be reservoirs of pathogenic Nocardia which may have a similar virulence to clinical strains.

Granulocyte Macrophage Colony-Stimulating Factor-Specific Autoantibodies and Cerebral Nocardia With Pulmonary Alveolar Proteinosis

In this study, we report the history of a 40-year-old man with a primary cerebral abscess caused by Nocardia abscessus that led to the discovery of autoimmune pulmonary alveolar lipoproteinosis (anti-granulocyte-macrophage colony-stimulating factor [GM-CSF] autoantibodies). Anti-GM-CSF autoantibodies promote immunodeficiency and should be monitored to prevent opportunistic and disseminated infections and to diagnose asymptomatic pulmonary alveolar lipoproteinosis.

Current diagnostic tools and management modalities of Nocardia keratitis

Nocardia species are an uncommon but important cause of keratitis. The purpose of this review is to discus previous published papers relation to the epidemiology, etiology, diagnosis and management of Nocardia keratitis. Nocardia asteroides is the most frequently reported from Nocardia keratitis. Pain, photophobia, blepharospasm and lid swelling are mainly clinical manifestations. Usual risk factors for Nocardia keratitis are trauma, surgery, corticosteroids, and contact lens wear. Several antibiotics were used for treatment of Nocardia infection but according to studies, topical amikacin is the drug of choice for Nocardia keratitis. Topical steroid should not prescribe in these patients. In conclusion, although Nocardia keratitis is rare, early diagnosis and treatment are essential to prevent any scar formation and preserve a good visual acuity.

Endogenous Nocardial Endophthalmitis Misdiagnosed as Giant Cell Arteritis

Purpose

Endogenous endophthalmitis is uncommon but potentially dangerous. We present a fatal presentation of endogenous Nocardial endophthalmitis in the context of steroid use for treatment of giant cell arteritis.

Case Presentation

An 84-year-old Caucasian female presented to the local emergency room with severe headaches, myalgia and shoulder and calf muscle pain. She was treated for a presumed diagnosis of giant-cell arteritis with corticosteroids and subsequently developed an intense retro-orbital pain in the right eye. Fundus examination revealed a white, vascularized chorioretinal mass at the equator of the eye in the inferotemporal quadrant. Antibiotics were given and a vitrectomy was performed. The culture of the vitreous showed Nocardia nova and a diagnosis of disseminated Nocardiosis was made.

Conclusion and Significance

Although uncommon, it is important that ophthalmologists are aware of Nocardial infections as a differential diagnosis of retinal mass, particularly in immunocompromised patients.

Revisiting nocardiosis at a tertiary care institution: Any change in recent years?

OBJECTIVE

To analyse relevant changes in incidence, clinical and microbiological characteristics of nocardiosis over the last 24 years at the current institution.

MATERIALS AND METHODS

The clinical records of patients with nocardiosis (2006-2018) were reviewed and then compared with a previous cohort (1995-2006). Nocardia isolates were identified by 5'-end-16S-rRNA-gene-PCR targeting the first 500 bp of the gene and sequencing. Susceptibility tests were determined by broth microdilution (CLSI guidelines).

RESULTS

Forty-two patients (64.3% male) with nocardiosis were evaluated in the recent cohort: 51.2% had COPD, 43.9% were on corticosteroid therapy and 31.7% had cancer. The incidence of nocardiosis varied from 6.3 to 7.1/100,000 admissions (p = 0.62). There was a decrease in HIV patients (27% vs. 4.9%, p = 0.01) and solid organ transplantation (SOT) recipients (18.9% vs. 2 .4%, p = 0.01). Cases with pulmonary involvement had increased (70.3% vs. 90.5%, p = 0.04). Nocardia species were similar but the most common were N. cyriacigeorgica (32.4% vs. 40.5%, p = 0.49) and N. farcinica (24.3% vs. 14.3%, p = 0.39). Antibiotic resistance remained stable: cotrimoxazole (10.8% vs. 5.7%, p = 0.68), imipenem (5.4% vs. 5.6%, p = 1.0); amikacin and linezolid were 100% active. No differences were found in breakthrough nocardiosis (21.6% vs. 9.8%, p = 0.21) or related mortality (21.6% vs. 21.4%, p = 1.0). The multivariate analysis confirmed that nocardiosis caused by N. farcinica is a risk factor for poor outcome (p = 0.045).

CONCLUSIONS

Nocardiosis incidence has remained stable. It mainly affected elderly patients with chronic respiratory conditions and those on corticosteroid treatment. Infections in HIV and SOT patients have practically disappeared. Pulmonary involvement remains the most common area to be affected. Nocardiosis caused by N. farcinica is apparently a risk factor for poor clinical 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.

Clinical features and prognosis of nocardiosis in patients with connective tissue diseases

OBJECTIVES

To investigate the clinical features and prognosis of nocardiosis complicated by connective tissue diseases (CTDs).

METHODS

We examined patients with CTDs who were diagnosed with nocardiosis from October 2004 to 2019. We retrospectively investigated patient characteristics and therapeutic outcomes. We then performed a comparison between survivors and non-survivors.

RESULTS

Fourteen patients were examined. Underlying CTDs were systemic lupus erythematosus (28.6%), vasculitis syndrome (28.6%), rheumatoid arthritis (21.4%), adult Still disease (14.3%) and dermatomyositis (7.1%). Infected organs were lung (85.7%), brain (42.9%), skin/cutaneous lesions (28.6%) and muscle (7.1%). Disseminated infections were seen in nine patients (64.3%). At the onset of nocardiosis, all patients were given prednisolone (23.2 ± 11.9 mg/day). Only two patients (14.3%) were given TMP-SMX for prophylaxis of pneumocystis pneumonia. Relapse occurred in one patient (7.1%) and four patients (28.6%) died from nocardiosis for a cumulative survival rate at 52 weeks of 76.9%. In a comparison of survivors (71.4%) and non-survivors (28.6%), cutaneous lesions were significantly more frequent in the latter (10 vs 75%, p = .04) with an odds ratio of 27.0 (95% CI: 1.7-453.4).

CONCLUSION

Cutaneous lesions as a result of dissemination might be a risk factor for nocardiosis mortality in patients with CTDs.

Nocardia macrotermitis sp. nov. and Nocardia aurantia sp. nov., isolated from the gut of the fungus-growing termite Macrotermes natalensis

The taxonomic positions of two novel aerobic, Gram-stain-positive Actinobacteria, designated RB20T and RB56T, were determined using a polyphasic approach. Both were isolated from the fungus-farming termite Macrotermes natalensis. Results of 16S rRNA gene sequence analysis revealed that both strains are members of the genus Nocardia with the closest phylogenetic neighbours Nocardia miyunensis JCM12860T (98.9 %) and Nocardia nova DSM44481T (98.5 %) for RB20T and Nocardia takedensis DSM 44801T (98.3 %), Nocardia pseudobrasiliensis DSM 44290T (98.3 %) and Nocardia rayongensis JCM 19832T (98.2 %) for RB56T. Digital DNA-DNA hybridization (DDH) between RB20T and N. miyunensis JCM12860T and N. nova DSM 44481T resulted in similarity values of 33.9 and 22.0 %, respectively. DDH between RB56T and N. takedensis DSM44801T and N. pseudobrasiliensis DSM44290T showed similarity values of 20.7 and 22.3 %, respectively. In addition, wet-lab DDH between RB56T and N. rayongensis JCM19832T resulted in 10.2 % (14.5 %) similarity. Both strains showed morphological and chemotaxonomic features typical for the genus Nocardia, such as the presence of meso-diaminopimelic acid (A2pm) within the cell wall, arabinose and galactose as major sugar components within whole cell-wall hydrolysates, the presence of mycolic acids and major phospholipids (diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol), and the predominant menaquinone MK-8 (H4, ω-cyclo). The main fatty acids for both strains were hexadecanoic acid (C16 : 0), 10-methyloctadecanoic acid (10-methyl C18 : 0) and cis-9-octadecenoic acid (C18 : 1 ω9c). We propose two novel species within the genus Nocardia: Nocardia macrotermitis sp. nov. with the type strain RB20T (=VKM Ac-2841T=NRRL B65541T) and Nocardia aurantia sp. nov. with the type strain RB56T (=VKM Ac-2842T=NRRL B65542T).

Sulfonamides without trimethoprim in the treatment of Nocardia infections: A case report and literature review

Sulfonamides are recommended as part of first-line therapy for most Nocardia infections, with trimethoprim-sulfamethoxazole (TMP-SMX) considered the drug of choice for susceptible isolates. However, in the case of central nervous system, disseminated disease, and other serious Nocardia infections, TMP-SMX should not be used as monotherapy. The preferred treatment for a patient unable to take TMP-SMX because of allergy or intolerance remains uncertain. Prior to the availability of TMP-SMX in 1973, other sulfonamides were mainstays of treatment. We describe a Nocardia infection successfully treated with sulfadiazine in a lung transplant recipient who could not tolerate TMP-SMX. A review of similar cases reported in the literature provides insight into the successful treatment of Nocardia infections with sulfonamide regimens not containing trimethoprim in transplant recipients and other immunocompromised hosts.

Global analysis of adenylate-forming enzymes reveals β-lactone biosynthesis pathway in pathogenic Nocardia

Enzymes that cleave ATP to activate carboxylic acids play essential roles in primary and secondary metabolism in all domains of life. Class I adenylate-forming enzymes share a conserved structural fold but act on a wide range of substrates to catalyze reactions involved in bioluminescence, nonribosomal peptide biosynthesis, fatty acid activation, and β-lactone formation. Despite their metabolic importance, the substrates and functions of the vast majority of adenylate-forming enzymes are unknown without tools available to accurately predict them. Given the crucial roles of adenylate-forming enzymes in biosynthesis, this also severely limits our ability to predict natural product structures from biosynthetic gene clusters. Here we used machine learning to predict adenylate-forming enzyme function and substrate specificity from protein sequences. We built a web-based predictive tool and used it to comprehensively map the biochemical diversity of adenylate-forming enzymes across >50,000 candidate biosynthetic gene clusters in bacterial, fungal, and plant genomes. Ancestral phylogenetic reconstruction and sequence similarity networking of enzymes from these clusters suggested divergent evolution of the adenylate-forming superfamily from a core enzyme scaffold most related to contemporary CoA ligases toward more specialized functions including β-lactone synthetases. Our classifier predicted β-lactone synthetases in uncharacterized biosynthetic gene clusters conserved in >90 different strains of Nocardia. To test our prediction, we purified a candidate β-lactone synthetase from Nocardia brasiliensis and reconstituted the biosynthetic pathway in vitro to link the gene cluster to the β-lactone natural product, nocardiolactone. We anticipate that our machine learning approach will aid in functional classification of enzymes and advance natural product discovery.

Pulmonary nocardiosis: A Single Center Study

Objectives

Nocardiosis is a rare infection caused by Nocardia spp., a gram-positive bacteria non-commensal of the human flora. Nocardiosis usually presents with lung infection but may disseminate to other organs, most frequently the brain. The major risk factor is immunosuppression, but lung diseases also increase the risk of infection. Treatment with antibiotics is usually prolonged. In this study, we made a retrospective analysis of pulmonary nocardiosis cases and a review of the available literature.

Methods

We made a retrospective analysis of all pulmonary nocardiosis cases from 13 years (January 2005 to December 2017) in our institution, selecting patients from pulmonology and infectious diseases consultation.

Results

We found four patients diagnosed with pulmonary nocardiosis, three males (patients 1, 2 and 3) and one female (patient 4). Median age was 71 ± 15 years old. Different specimens were identified (N. cyriacigeorgica, Nocardia spp., N. nova, and N. wallacei/transvalensis). Bronchofibroscopy with bronchoalveolar lavage culture was the most frequent diagnostic procedure (patients 1 and 4). Only patient 2 presented an unfavorable response to treatment and died from septic shock.

Conclusions

Pulmonary nocardiosis has a good prognosis if diagnosed early and treated adequately. It should always be considered in the differential diagnosis of pulmonary infections concomitant with brain or other soft tissue lesion, especially in immunocompromised patients.

A rare case of isolated cauda equina Nocardia farcinica infection

Nocardia is a Gram-positive, partially acid-fast, catalase-positive, and urease-positive bacterium that grows aerobically. We present an extremely rare case of cauda equina syndrome due to isolated intramedullary Nocardia farcinica infection. A 44-year-old male presented with low backache and gradually progressive weakness in bilateral lower limbs followed by paraplegia. He was found to have a well-defined, sharply demarcated ring-enhancing lesion located from T11-T12 to L3 vertebral body. He underwent laminectomy and decompression. The histopathological examination revealed a Gram-positive filamentous organism that looks like Nocardia. The culture report was suggestive of Nocardia farcinica. He was then treated with antibiotics and had a remarkable clinical and radiological improvement.

Actinomycetes from the Red Sea Sponge Coscinoderma mathewsi: Isolation, Diversity, and Potential for Bioactive Compounds Discovery

The diversity of actinomycetes associated with the marine sponge Coscinoderma mathewsi collected from Hurghada (Egypt) was studied. Twenty-three actinomycetes were separated and identified based on the 16S rDNA gene sequence analysis. Out of them, three isolates were classified as novel species of the genera Micromonospora, Nocardia, and Gordonia. Genome sequencing of actinomycete strains has revealed many silent biosynthetic gene clusters and has shown their exceptional capacity for the production of secondary metabolites, not observed under classical cultivation conditions. Therefore, the effect of mycolic-acid-containing bacteria or mycolic acid on the biosynthesis of cryptic natural products was investigated. Sponge-derived actinomycete Micromonospora sp. UA17 was co-cultured using liquid fermentation with two mycolic acid-containing actinomycetes (Gordonia sp. UA19 and Nocardia sp. UA 23), or supplemented with pure mycolic acid. LC-HRESIMS data were analyzed to compare natural production across all crude extracts. Micromonospora sp. UA17 was rich with isotetracenone, indolocarbazole, and anthracycline analogs. Some co-culture extracts showed metabolites such as a chlorocardicin, neocopiamycin A, and chicamycin B that were not found in the respective monocultures, suggesting a mycolic acid effect on the induction of cryptic natural product biosynthetic pathways. The antibacterial, antifungal, and antiparasitic activities for the different cultures extracts were also tested.

A rare disease mimicking lung cancer

We present an interesting case of a 34 year old gentleman with bilateral FDG avid lesions in the apex of the lung. He presented with a two month history of cough, fever and hemoptysis. A contrast enhanced CT scan showed a spiculated lesion in the right upper lobe. A CT guided biopsy was done which was suggestive of an inflammatory lesion. He was started empirically on anti tubercular therapy, but his symptoms did not subside. A PET CT scan was done, which showed the lesion to be FDG avid. A repeat biopsy was done and again it was reported as an inflammatory infiltrate. He was then referred to our center for a surgical biopsy. We repeated a PET scan and were surprised to find another lesion in the apex of the opposite lung. The case was discussed with our interventional pulmonogy team and an EBUS guided biopsy of the lesion was done. On microbiological analysis the specimen was found to be positive for Nocardia.

Opportunistic bacterial, viral and fungal infections of the lung

Opportunistic infections are a major cause of morbidity and mortality in severely immunocompromised patients, such as those given chemotherapy or biological therapies, and those with haematological malignancy, aplastic anaemia or HIV infection, or recipients of solid organ or stem cell transplants. The type and degree of immune defect dictates the profile of potential opportunistic pathogens; T-cell-mediated defects increase the risk of viral (cytomegalovirus, respiratory viruses) and Pneumocystis jirovecii infections, whereas neutrophil defects are associated with bacterial pneumonia and invasive aspergillosis. However, patients often have combinations of immune defects, and a wide range of other opportunistic infections can cause pneumonia. Importantly, conventional non-opportunistic pathogens are frequently encountered in immunocompromised hosts and should not be overlooked The radiological pattern of disease (best assessed by computed tomography) and speed of onset help identify the likely pathogen(s); this can then be supported by targeted investigation including early use of bronchoscopy in selected patients. Rapid and expert clinical assessment can identify the most likely pathogens, allowing timely appropriate therapy.

Cutaneous nocardiosis in a liver transplant recipient - case report

Solid organ transplant recipients are specific group due to taken immunosuppressive agents. This can result in side effects including infections caused by rare opportunistic pathogens.

A CASE REPORT

A 64-year old woman after orthotopic liver transplantation due to primary biliary cirrhosis and autoimmune hepatitis was admitted to hospital because of several infections. A painful lesion on left lower leg was noticed 3 months after surgery, while the patient was hospitalized with pneumonia. The Doppler ultrasound showed no signs of deep vein thrombosis. In the course of next month, the inflammatory infiltration has increased and the patient was readmitted to the hospital. After another ultrasound and MRI, which revealed solid-cystic character of the lesion, erythema nodosum was suspected. However, no pathogens were detected in blood and tissue cultures. After empiric antibiotic therapy regression of the lesion were observed. Recurrence of inflammation of the skin, the subcutaneous tissue and the knee joint resulted in readmission to the hospital after 3 months. Empiric antimicrobial therapy was administrated again and the dose of immunosuppressive agent was reduced. Since there was no bacterial growth in another routine culture of blood and synovial fluid, samples were cultured for opportunistic bacteria - Nocardia spp, Cryptococcus spp, Nontuberculous mycobacteria. Nocardia abscessus has grown after few weeks. Ceftriaxone, then trimethoprim-sulfamethoxazole (3x960 mg for 6 months) was administered according to antibiogram. Treatment resulted in regression of the lesion, pain alleviation and simultaneous liver function tests elevation.

CONCLUSIONS

Cutaneous and subcutaneous nocardiosis is a rare infection. Solid organ transplant recipients are at risk of nocardiosis so it should be considered in differential diagnosis, especially when infections are hard to treat.

Pulmonary Nocardiosis with Aspergillosis in a patient with COPD: A rare co-infection

Pulmonary Nocardiosis and invasive Aspergillosis are well documented in immunocompromised patients. The coexistence of both infections is a diagnostic rarity, especially in patients with underlying structural lung diseases. We describe this rare association in a 46-year-old female with a history of pulmonary tuberculosis and COPD. The diagnosis of pulmonary Nocardiosis is challenging due to non-specific clinical features, inherent ability to mimic malignancy, tuberculosis and difficulty in the cultivation of the organism. The treating physicians should aware of the rare occurrence of such co-infections in order to prevent misdiagnosis and prompt treatment.

Detection of Nocardia, Streptomyces and Rhodococcus from bronchoalveolar lavage specimens of patients with HIV by Multiplex PCR Assay

Background

Nocardia, Streptomyces and Rhodococcus are life threatening opportunistic pathogens under immunodeficiency conditions, particularly among patients infected with HIV. Rapid and accurate detection of these infections can improve immune health quality, patient management and appropriate treatment. The aim of this study was to design a novel multiplex-PCR assay for rapid diagnosis of these three organisms directly from bronchoalveolar lavage (BAL) specimens of patients infected with HIV.

Methods

The genus specific primers were designed for direct-detection of Nocardia, Streptomyces and Rhodococcus in a single tube multiplex PCR. This PCR specifically amplified the target genes from pure cultures. It subsequently was applied on BAL specimens of 29 HIV positive patients that had previously been culture negative for actinomycete bacteria, of which Nocardia, Streptomyces and Rhodococcus are members.

Results

Of 29 respiratory clinical specimens, there were positive for Nocardia spp. and one was positive for Streptomyces spp using the multiplex PCR assay. The sequencing of the PCR products identified the species as Nocardia cyriacigeorgica (n=2), Nocardia farcinica and Streptomyces albus.

Conclusion

This novel multiplex PCR assay yielded reliable results for accurate identification of Nocardia, Streptomyces and Rhodococcus from BAL while the results of bacterial culture were negative.

Targeting novel genes for simultaneous detection of five fungal and bacterial agents from BAL samples using multiplex PCR assay

The main purpose of our study was to evaluate multiplex PCR assay targeting novel genes for detection of five fungal and bacterial agents in BAL samples; because many fungi and bacteria that cause respiratory infections have similar clinical symptoms, diagnosing and differentiating them are therefore essential to controlling and treating them. A total of 100 BAL specimens from a mycobacterium and mycology laboratory were collected from patients suspected of having TB or other respiratory diseases. Novel DNA targets for Aspergillus, Nocardia, Cryptococcus, and Streptomyces were found using modified comparative genomic analysis. Afterward, the primers were designed based on novel targets, and the sensitivity and specificity of the newly designed primers were evaluated. These primers, along with specific primers for M. tuberculosis (SDR), were used in a multiplex PCR assay. The results showed the culture test to be more sensitive than the PCR assay in detecting M. tuberculosis. However, in the detection of Aspergillus, the PCR assay was more sensitive than the culture test. We also found one positive culture and two positive PCR assays for Nocardiosis. Cryptococcal infections and Streptomyces associated with lung diseases were not identified by the culture test nor by the PCR assay. The multiplex PCR is one of the cheapest molecular diagnostic tests readily available for BAL samples in clinical laboratories. This assay can be used for early reports of the causative agents and for treating patients with appropriate drugs at an early stage.

Opportunistic Infections in Transplant Patients

Transplants have become common with excellent patient and graft outcomes owing to advances in surgical technique, immunosuppression, and antimicrobial prophylaxis. In 2017, 34,770 solid organ transplants were performed in the United States. For solid organ transplant recipients, infection remains a common complication owing to the regimens required to prevent rejection. Opportunistic infections, which are infections that are generally of lower virulence within a healthy host but cause more severe and frequent disease in immunosuppressed individuals, typically occur in the period 1 month to 1 year after transplantation. This article focuses on opportunistic infections in the solid organ transplant recipient.

Safety and Outcomes of Linezolid Use for Nocardiosis

Background

Tropical Australia has a high incidence of nocardiosis, with high rates of intrinsic antimicrobial resistance. Linezolid, the only antimicrobial to which all local Nocardia species are susceptible, has been recommended in empirical combination treatment regimens for moderate-severe Nocardia infections at Royal Darwin Hospital (RDH) since 2014. We report the safety and efficacy of linezolid use for nocardiosis in this setting.

Methods

We identified cases through a retrospective review of all RDH Nocardia isolates from December 2014 to August 2018 and included 5 linezolid-treated cases from a previous cohort. Laboratory, demographic, and clinical data were included in the primary analysis of safety and treatment outcomes.

Results

Between 2014 and 2018, Nocardia was isolated from 35 individuals; 28 (80%) had clinically significant infection and 23 (82%) received treatment. All isolates were linezolid-susceptible. Safety and efficacy were assessed for 20 patients receiving linezolid-containing regimens and 8 receiving nonlinezolid regimens. Median linezolid induction therapy duration was 28 days. Common adverse effects in those receiving linezolid were thrombocytopenia (45%) and anemia (40%). Adverse events prompted discontinuation of trimethoprim-sulfamethoxazole more often than linezolid (40% vs 20%). Linezolid therapeutic drug monitoring was used in 1 patient, with successful dose reduction and outcome. There was no difference in 30-day survival between those treated with linezolid (90%) vs no linezolid (87%). One Nocardia-attributed death occurred during linezolid therapy.

Conclusions

Linezolid is safe and efficacious in empirical treatment for moderate to severe nocardiosis in a monitored hospital setting, with 100% drug susceptibility and no difference in adverse events or outcomes compared with nonlinezolid regimens.

A Rare Case of Drug-Resistant Nocardia transvalensis Infection in a Renal Transplant Patient

Nocardia transvalensis is a rare species of Nocardia and is known to be a drug-resistant organism. Multiple cases have been reported of Nocardia species causing opportunistic infections in immunocompromised hosts. To our knowledge, we report the first case of successfully treated drug-resistant Nocardia transvalensis causing pulmonary nocardiosis in a renal transplant patient. Our case validates the importance of prompt identification of Nocardia species and their drug sensitivities to improve clinical outcomes and reduce mortality.

Retrospective Analysis of Antimicrobial Susceptibility Profiles of Nocardia Species from a Tertiary Hospital and Reference Laboratory, 2011 to 2017

Nocardia species are found worldwide and are opportunistic pathogens of both immunocompromised and immunocompetent hosts. Recent updates to the taxonomy of this genus have indicated that there are more than 90 recognized species of Nocardia with 54 species reported to be clinically relevant. In this paper, we report the species distribution, specimen source distribution, and antimicrobial susceptibility profiles of 2,091 clinical isolates recovered for the years 2011 to 2017 using the updated taxonomy. The most commonly isolated species included Nocardia nova complex, Nocardia cyriacigeorgica, and Nocardia farcinica complex, with an additional 25 species or species complexes recovered from clinical specimens. The antimicrobial susceptibility profile was highly variable between the species, but in general, amikacin, linezolid, and trimethoprim-sulfamethoxazole demonstrated good in vitro activity against most species.

Inhibition Activity of Avibactam against Nocardia farcinica β-Lactamase FARIFM10152

Nocardia farcinica, one of the most frequent pathogenic species responsible for nocardiosis, is characterized by frequent brain involvement and resistance to β-lactams mediated by a class A β-lactamase. Kinetic parameters for hydrolysis of various β-lactams by FAR_IFM10152 from strain IFM 10152 were determined by spectrophotometry revealing a high catalytic activity (k _cat/K_m ) for amoxicillin, aztreonam, and nitrocefin. For cephems, k _cat/K_m was lower but remained greater than 10⁴ M^-1 s^-1 A low catalytic activity was observed for meropenem, imipenem, and ceftazidime hydrolysis. FAR_IFM10152 inhibition by avibactam and clavulanate was compared using nitrocefin as a reporter substrate. FAR_IFM10152 was efficaciously inhibited by avibactam with a carbamoylation rate constant (k ₂/K_i ) of (1.7 ± 0.3) × 10⁴ M^-1 s^-1 The 50% effective concentrations (EC₅₀s) of avibactam and clavulanate were 0.060 ± 0.007 μM and 0.28 ± 0.06 μM, respectively. Amoxicillin, cefotaxime, imipenem, and meropenem MICs were measured for ten clinical strains in the presence of avibactam and clavulanate. At 4 μg/ml, avibactam and clavulanate restored amoxicillin susceptibility in all but one of the tested strains but had no effect on the MICs of cefotaxime, imipenem, and meropenem. At 0.4 μg/ml, amoxicillin susceptibility (MIC ≤ 8 μg/ml) was restored for 9 out of 10 strains by avibactam but only for 4 out of 10 strains by clavulanate. Together, these results indicate that avibactam was at least as potent as clavulanate, suggesting that the amoxicillin-avibactam combination could be considered as an option for the rescue treatment of N. farcinica infections if clavulanate cannot be used.

Nocardia bacteremia: A single-center retrospective review and a systematic review of the literature

OBJECTIVES

Nocardia bacteremia is a rare but severe disease associated with high mortality. This systematic review is the largest and most comprehensive review performed over the past 20 years.

METHODS

A single-center retrospective review of Nocardia bacteremia was performed using hospital microbiology records from January 1, 2010 to December 31, 2017. A systematic literature review was also performed to identify cases of Nocardia bacteremia described in the NCBI PubMed database in English between January 1, 1999 and December 31, 2018.

RESULTS

Four new cases of Nocardia bacteremia are described. The systematic review identified 134 cases with sufficient information available for analysis. Of the total 138 cases, the median age was 58 years (interquartile range (IQR) 44-69 years) and 70% were male. Eighty-one percent were immunocompromised (corticosteroid use (49%), hematological malignancy (20%), solid organ transplant (20%), solid organ malignancy (19%), and hematopoietic stem cell transplantation (15%)) and 29% had endovascular devices. Pulmonary infection was the most common concurrent site of clinical disease (67%). The median incubation time to the detection of Nocardia bacteremia was 4 days (IQR 3-6 days). Blood cultures were the only positive microbiological specimen in 38% of cases. The median total duration of treatment was 75 days (IQR 25-182 days). Thirty-day all-cause mortality was 28% and overall all-cause mortality was 40%.

CONCLUSIONS

Nocardia bacteremia is most frequently identified in immunocompromised patients and those with intravascular devices. Although rare, it represents a serious infection with high associated overall mortality.

Nocardia colonization in contrast to nocardiosis: a comparison of patients' clinical characteristics

Information on Nocardia colonization of the lower respiratory tract is scarce. The current study is aimed at comparing clinical characteristics between individuals with Nocardia colonization and those with nocardiosis. All patients with Nocardia isolation between 2007 and 2018 at a tertiary hospital in Israel were included. Nocardia isolation was based on biochemical tests together with phenotypic susceptibility and resistance patterns until 2011 and on matrix-assisted laser desorption/ionization time-of-flight mass spectrometer from 2012. We defined nocardiosis as a clinically evident infection related to the isolation of the bacteria, which required antibiotic therapy. We defined colonization as Nocardia isolation with no clinical evidence of disease. The medical charts of all included individuals were independently reviewed by an infectious disease specialist to ensure adequate classification. Logistic regression models were fitted to compare clinical characteristics between the groups. Fifteen (20%) of the 75 Nocardia isolations met the criteria for colonization. Of those, 13 (87%) had background illnesses. Having a chronic pulmonary disease was associated with increased likelihood of Nocardia colonization, in contrast to nocardiosis (adjusted odds ratio [OR] 4.06, 95% confidence interval [CI] 1.06-15.48, p = 0.040), while an inverse association was found with corticosteroid therapy (adjusted OR 0.21, 95% CI 0.06-0.74, p = 0.015). Nocardia colonization of the lower respiratory tract accounts for a substantial proportion of all Nocardia isolations. Individuals colonized with Nocardia typically have chronic pulmonary disease and are less frequently treated with corticosteroid than patients with nocardiosis.

Nocardiosis: 7-year experience at an Australian tertiary hospital

BACKGROUND

Nocardiosis has historically been reported in immunocompromised patients, but Australian epidemiological and antimicrobial susceptibility data are limited.

AIM

To describe the epidemiology, diagnosis and initial treatment of nocardiosis in an Australian tertiary hospital over 7 years.

METHODS

In this retrospective study, all positive cultures for Nocardia species from any site isolated at the Alfred Hospital, Melbourne, between 1 January 2010 and 31 December 2016 were identified, and corresponding laboratory data and medical records reviewed.

RESULTS

Sixty-eight non-duplicate isolates were identified from 67 patients. Common predisposing factors were chronic lung disease (38/67; 57%), organ, particularly lung, transplantation (13/67; 19%) and solid organ malignancy (6/67; 9%); 12% (8/67) of patients had no identifiable systemic risk factors. Seventy-nine percent (53/67) of patients had pulmonary nocardiosis only. Nocardia nova was the most commonly isolated species (20/68; 29%). In 48% (32/67) of patients, Nocardia species were isolated only on specific mycobacterial media. All tested species were susceptible to sulfamethoxazole-trimethoprim and amikacin, with the majority (58/63; 92%) susceptible to imipenem. All-cause mortality rates at 6 and 12 months where data were available were 15% (10/66 patients) and 22% (14/64 patients) respectively.

CONCLUSION

In the largest Australian series in 25 years, nocardiosis predominantly affected patients with chronic lung disease or impaired cell-mediated immunity. A significant proportion of organisms from pulmonary sites were isolated on mycobacterial culture media only, suggesting that its use may improve yield. Isolates remain highly susceptible to sulfamethoxazole-trimethoprim, amikacin and imipenem, while other agents should be used only after confirmation of in vitro susceptibility.