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Nocardia is a genus of gram-positive, filamentous, aerobic bacteria that belongs to the Actinomycetales order. With over 50 species, it is ubiquitous in dust, soil, decaying organic matter, and stagnant water. Inhalation of the pathogen often leads to pulmonary nocardiosis, while extrapulmonary nocardiosis can affect the central nervous system, skin, and subcutaneous tissues. Primary cutaneous nocardiosis occurs when the pathogen is introduced through a skin lesion or insect bite, for example, this report presents a case of primary cutaneous nocardiosis in a patient with Minimal Change Glomerulonephritis and iatrogenic immunosuppression. Magnetic resonance imaging revealed extensive involvement of the skin, subcutaneous tissue, and lower limb muscles.

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 (bioMerieux, 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.

The objective of this study is to explore the molecular basis of trimethoprim-sulfamethoxazole (SXT) resistance in Nocardia, an SXT-resistant N. farcinica strain, named SZ 1509, by whole-genome sequencing.Antimicrobial susceptibility testing of SZ 1509 was performed by broth microdilution, Etest, and disk diffusion arrays. Genome sequencing and analysis were performed to discover the SXT resistance determinant and its genetic context. Inverse PCR was conducted to confirm the circular form of the composite transposon. PCR for the sul1 gene was performed among SXT-susceptible isolates.SZ 1509 is resistant to many drugs, especially SXT, with a minimum inhibitory concentration (MIC) of up to 32/608 µg/mL (ratio of 1:19 for trimethoprim: sulfamethoxazole). Its assembled genome consists of one chromosome and four plasmids with a total size of 6 613 629 bp and 71.1% of GC content. The plasmid 2 was found to carry one IS6-composite transposon containing IS6100 carrying the sul1 gene, one tellurite resistance gene TerC, and several transcriptional regulators. Inverse PCR analyses showed its circular form. All 10 SXT-susceptible isolates do not contain sul1. In addition, mutations with strong associations to SXT resistance were not conclusive.This is the first study to elucidate the transposon-mediated sulfamethoxazole resistance in N. farcinica. Our results provide insights on acquired drug resistance of N. farcinica and further suggest that the prevalence and correlation of this resistance's determinants in clinical isolates should be continuously monitored to provide effective clinical management of its resultant diseases.

Nocardiosis is a rare opportunistic infection that is frequently associated with dissemination (i.e. involvement of several body sites). Identifying the factors associated with Nocardia spp. dissemination may help improving the management of patients with nocardiosis.This 10-year (2010-2020) retrospective multicenter cohort study included adult patients with Nocardia-confirmed infections. The first objective was to determine the factors associated with disseminated nocardiosis. The secondary endpoints were to determine and compare the management and the 12-month overall mortality in patients with localized and disseminated nocardiosis. Univariate and multivariate logistic regression analyses were used.Nocardia spp. infection was confirmed in 110 patients, of whom 38 (34.5%) had disseminated nocardiosis. In univariate analysis, the factors associated with dissemination were immunosuppressive conditions: having an auto-immune disease and receiving high-dose corticosteroid (31.5% vs 8.3%, P = 0.003 and 52.6% vs 26.3%, P = 0.007, respectively). Absolute lymphocyte count1 G/L at diagnosis was the only biomarker associated with dissemination (57.2% vs 26.3%, P = 0.007). Nocardia farcinica was not only the most frequent species identified in patient specimens (n = 22, 20%) but was also associated with a higher rate of dissemination (36.8% vs 11.1%, P = 0.002). Multivariate analysis confirmed the association between auto-immune diseases, lymphopenia, N. farcinica species and the higher rate of dissemination. Even though patients with disseminated nocardiosis were treated longer and more often with an antibiotic combination therapy, their 12-month overall mortality was significantly higher than that of patients with localized nocardiosis (36.8% vs 18%).Dissemination of Nocardia spp. is favoured by auto-immune diseases, lymphopenia, and infection with N. farcinica.

Nocardia is an uncommon cause of septic arthritis. We found only 37 cases reported in the literature thus far. Amongst these, only five involved prosthetic joints. Three cases were caused by N. nova and one each by N. farcinica and asteroides. Septic arthritis due to Nocardia has a favorable outcome with a combination of surgical debridement and prolonged antimicrobial therapy of three to six months. For prosthetic joint infections, removal of hardware seems to carry a better prognosis. Trimethoprim-sulfamethoxazole continues to remain the drug of choice.

Nocardiosis is a clinical and diagnostic challenge. This was a retrospective study carried out on cases of pulmonary nocardiosis presenting over 15 years. Clinical data was retrieved using the electronic patient records. Vitek MS 3.2 (MALDI TOF MS) was carried out on 22 isolates and sequencing on another 9 isolates. Of 71 patients presenting with pulmonary nocardiosis, 58 (81.6%) were on immunosuppressant therapy, 26 (46%) had a previous lung pathology, 11 (8%) were HIV associated. Disseminated disease was seen in 6 (8.4%). There were 8 (11.26%) deaths in this cohort of patients. Of 31/71 identified to species, the most common were Nocardia cyriacigeorgica (n ​= ​11) followed by Nocardia farcinica (n ​= ​9).

Interleukin-8 (IL-8 or C-X-C motif chemokine ligand 8, CXCL8) is a cytokine secreted by numerous cell types and is best known for its functional roles in inflammatory response by binding to specific receptors (the interleukin-8 receptors, IL-8Rs). From the transcriptomic data of largemouth bass (Micropterus salmoides), we identified an IL-8R that is highly homologous to the functionally validated teleost IL-8Rs. The M. salmoides IL-8 receptor (MsCXCR2) was further compared with the C-X-C motif chemokine receptor 2 subfamily by phylogenetic analysis. Briefly, the full-length CDS sequence of MsCXCR2 was cloned into the pEGFP-N1 plasmid, and the membrane localization of fusion expressing MsCXCR2-EGFP was revealed in HEK293 cells. To determine the functional interaction between IL-8 and MsCXCR2, secretory expressed Larimichthys crocea IL-8 (LcIL-8) was used to stimulate MsCXCR2 expressing cells. MsCXCR2 was demonstrated to be activated by LcIL-8, leading to receptor internalization, which was further revealed by the detection of extracellular regulated protein kinase (ERK) phosphorylation. Quantitative real-time PCR was used to evaluate the expressional distribution and variation of MsCXCR2 in healthy and Nocardia seriolae infected fish. Based on our findings, MsCXCR2 was constitutively expressed in all examined tissues, despite at different levels. Furthermore, gene expression was found to be significantly upregulated in the liver and head kidney of diseased fish. Collectively, our findings reveal the molecular activity of MsCXCR2 and indicate the functional involvement of this IL-8R in the immune response induced by N. seriolae in M. salmoides.

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.

MALDI-TOF mass spectrometry has become a reference method for the routine identification of bacterial isolates in clinical microbiology laboratories around the world. Its high specificity, user-friendliness and cost-efficiency, together with its ability to provide reliable results in less than 5min have favoured its implementation and further development. The amount of microbial species that can be identified by MALDI-TOF routinely has increased in the last few years and now it is possible to reliably identify non-tuberculous mycobacteria or closely-related species of Nocardia spp. Yeasts, both belonging to Candida and non-Candida genera can also be identified by MALDI-TOF, as well as filamentous fungi. In the latter case, both sample preparation methods and the available databases have been important factors in achieving accurate identifications at the species level. The expertise acquired over time has allowed researchers to identify microorganisms directly from clinical samples, facilitating improved management of infected patients. This expertise has also been applied to the development of a MALDI-TOF-based methodology for the detection of different antimicrobial resistance mechanisms. Therefore, future applications such as bacterial strain typing, or the detection of virulence markers seems feasible to perform with this technology. Furthermore, other emerging mass spectrometry and spectroscopy technologies may assist MALDI-TOF in the near future to carry out important tasks that nowadays are performed by time-consuming and labour-intensive methods.

Interferon (IFN)γ is a pivotal cytokine that promotes and orchestrates innate cellular and adaptive cell-mediated immunity against intracellular pathogens. The capacity of T cells in mammals to produce IFNγ has been measured using specific antibodies in order to analyze cell-mediated immune responses against infection or immuno-stimulants. In fish, however, measurement of IFNγ protein levels has not been possible due to a lack of research tools. In the present study, therefore, we established antibodies that react with endogenous amberjack IFNγ. An enzyme-linked immunosorbent assay (ELISA) for IFNγ in amberjack species was developed using these antibodies. The ELISA could detect endogenous IFNγ at concentrations less than 100 pg/mL in PMA/ionomycin-stimulated leukocytes culture supernatant. IFNγ production was enhanced and lasted a long time following intracellular bacterial infection with Nocardia seriolae, which is thought to be targeted by cell-mediated immunity. These results demonstrate that quantification of IFNγ using the reported ELISA can be used to estimate the status of cell-mediated immunity in amberjack species.

Fish nocardiosis is a widespread chronic granulomatous disease in aquatic environment, which was particularly caused by Nocardia seriolae. The phage shock protein A (PspA) and tellurium resistance protein D (TerD) were identified to be the immunodominant antigens of the wild-type N. seriolae strain ZJ0503 in our previous study. In an attempt to develop effective DNA vaccines against this pathogen, PspA and TerD were used as candidates to ligate with pcDNA3.1-Flag plasmids, respectively. In addition, the abilities of these two DNA vaccines to elicit various immune responses in hybrid snakehead and supply protective efficacy against artificial challenge with N. seriolae were determined in the present study. The results showed that intramuscular injection with pcDNA-PspA and pcDNA-TerD did not exhibit cytotoxic activities in hybrid snakehead via histopathological examination. Besides, hybrid snakehead immunization with pcDNA-PspA and pcDNA-TerD could increase several non-specific immune paraments in serum, including LYZ, POD, ACP, AKP and SOD activities. Meanwhile, the pcDNA-TerD DNA vaccine could induce strongly specific antibody (IgM) titer in hybrid snakehead with a relative percent of survival (RPS) value of 83.14% against N. seriolae, while that of pcDNA-PspA DNA vaccine was displayed comparably low IgM titer with RPS value of 57.83%. Furthermore, quantitative real-time PCR assays presented that the expression of immune-related genes (MHCIα, MHCIIα, CD4, CD8α, IL-1β and TNFα) were up-regulated to various degrees after vaccination with pcDNA-PspA or pcDNA-TerD, indicating that these two DNA vaccines were able to boost humoral and cell-mediated immune responses in hybrid snakehead. Taken together, both the pcDNA-PspA and pcDNA-TerD DNA vaccines were proved to be safe, immunogenic and effective in protecting hybrid snakehead against N. seriolae infection, which can promote the development and application of DNA vaccines to control fish nocardiosis in aquaculture.

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.

Atypical microbial keratitis refers to corneal infections caused by micro-organisms not commonly encountered in clinical practice. Unlike infections caused by common bacteria, cases of atypical microbial keratitis are often associated with worse clinical outcomes and visual prognosis. This is due to the challenges in the identification of causative organisms with standard diagnostic techniques, resulting in delays in the initiation of appropriate therapies. Furthermore, due to the comparatively lower incidence of atypical microbial keratitis, there is limited literature on effective management strategies for some of these difficult to manage corneal infections. This review highlights the current management and available evidence of atypical microbial keratitis, focusing on atypical mycobacteria keratitis, nocardia keratitis, achromobacter keratitis, and pythium keratitis. It will also describe the management of two uncommonly encountered conditions, infectious crystalline keratopathy and post-refractive infectious keratitis. This review can be used as a guide for clinicians managing patients with such challenging corneal infections.

Purpose of the study Nocardia affects immunocompromised human host exhibiting an altered cell-mediated immunity. Infectious risk after allogeneic hematopoietic cell transplantation (AHCT) is significantly correlated to the recovery status of donor-derived immune system, especially CD4+ T-cells reconstitution and thymopoiesis. The purpose of this paper is to highlight a lack of cell-mediated immunity recovery for patients presenting a nocardiosis compared to a control cohort. Patients and methods This is a case control retrospective monocentric study. We retrospectively analyzed a monocentric cohort of 15 cases of nocardiosis after AHCT and we explored the degree of patients’ immunosuppression by phenotyping circulating lymphoid subpopulations, including NK cells, CD8+ T-cells, CD4+ T-cells and CD19+ B-cells. We focused on CD4+ T-cell subsets to appreciate thymic output, especially on naive CD4+ T-cells (NTE, CD45RA+/RO− CD4+ T-cells) and recent thymic emigrants (RTE, CD4+CD45RA+/RO−/CD31+). Infected patients were paired with a control cohort of patients with identical transplantation characteristics screened on hematological disease, AHCT conditioning, primary graft-versus-host disease (GHVD) prophylaxis, graft type, sex, age, and season at the AHCT and data concerning immunological reconstitution were compared. Results At onset of nocardiosis, circulating lymphocytes and CD4+ T-cells means count were respectively 730/μL and 162/μL. CD8+ T-cells, CD56+ NK cells and CD19+ B-cells means count were respectively 362/μL, 160/μL, 112/μL. CD4+ T-cells subpopulations, naive CD4+ T-cells production was impaired with NTE and RTE means count at 26/μL and 11/μL respectively. Comparison between nocardiosis cohort and control cohort over time highlight significant lower cellular count for lymphocytes, CD4+ T-cells, NTE and RTE with p = 0.001, p Conclusion Immune recovery monitoring follow-up after AHCT is of particular importance to identify patients susceptible to develop Nocardiosis. Efficient microbiological investigations toward Nocardia such PCR should be used in case of compatible clinical presentation.

Actinomycetes from unexplored habitats are considered as a promising source for novel bioactive compounds with a broad range of biological activities. A study was carried out to isolate and identify rare actinomycetes producing antimicrobial from a natural wetland. Water samples from Fetzara Lake (North eastern-Algeria) were collected and subjected to rare actinomycetes isolation using different rich media. Eight selected actinomycetes were screened in vitro for hydrolytic enzymes, antibacterial and anticandidal activities. Based on the 16S rRNA sequencing, the eight actinomycetes isolates were categorized into four different rare genera Actinomadura, Nocardia, Nonomuraea and Micromonospora. Interestingly, significant anticandidal and antibacterial activities against both Gram-positive and Gram-negative bacteria were observed. Furthermore, the actinomycetes isolates were able to produce different hydrolytic enzymes with potential industrial and food processing applications such as amylase, cellulase, protease, and lipase. Overall, the study revealed that the selected aquatic rare actinomycetes recovered from Fetzara Lake presented good candidates to be explored as new sources of bioactive compounds.

Nocardia spp. is a pathogen responsible for a variety of clinical infections, ranging from skin and soft tissue infections, to the respiratory tract and central nervous system infections. Its epidemiological characteristics, including species distribution, clinical features, and antimicrobial susceptibility profiles, should be under surveillance for the prevention and treatment of nocardiosis. In the present study, over a 9-year period (from 2009 to 2017), 53 non-repetitive Nocardia isolates were collected from 8 tertiary general hospitals of 7 cities in China. These isolates were identified to species level by multilocus sequence analysis(MLSA). The clinical data were also reviewed. The susceptibilities to 10 commonly-used antibiotics for Nocardia were determined by E-test stripes, and the resistance rates, MIC50 and MIC90 to each antibiotic by different species were analyzed. Of 53 Nocardia isolates, N. farcinica was the most common species (24.5%, 13/53), followed by N. cyriacigeorgica (20.8%, 11/53), N. terpenica (15.1%, 8/53), N. abscessus (9.43%, 5/53), N. otitidiscaviarum (7.55%, 4/53), respectively. Furthermore, 31 Nocardia (58.5%) isolates were recovered from lower respiratory tract (sputum and BALF), 15 (28.3%) from superficial Infection, 3 (5.7%) from pleural effusion, 2 (3.8%) from CSF, and 1 from bone marrow and 1 from synovial fluid, respectively. The antibiotic resistance profiles varied between different Nocardia species. All Nocardia isolates were susceptible to linezolid, followed by imipenem and amikacin (both 92.5% susceptibility rate). N. terpenica, rarely documented elsewhere, showed a different antimicrobial susceptibility profile. In summary, herein, the clinical and antibiotic resistance features of Nocardia species reported would be helpful for understanding the diversity of Nocardia species circulating in China and for decision making in the context of empiric therapy.

The present study was designed to identify the potential bioactive compound from endophytic actinomycetes (EA) Nocardiopsis sp. GRG 2 (KT 235641) against selected extended spectrum beta lactamase (ESBL) producing Pseudomonas aeruginosa (P. aeruginosa) and Klebsiella pneumoniae (K. pneumoniae). Initially, the multi drug resistance (MDR) effect of selected uropathogens was confirmed by respective UTI panel of Hexa antibiotics disc methods. The zone of inhibition ≤22 mm for ceftazidime, ≤ 27 mm for cefotaxime and ≤8 mm zone of MIC stripe against both the uropathogens of phenotypic methods confirmed, the selected strains were ESBL producer. Among the various EA extracts, GRG 2 extract showed excellent antibacterial activity against both ESBL producing P. aeruginosa and K. pneumonia by agar well diffution method. The molecular identification of selected GRG 2 strain was named as Nocardiopsis sp. GRG 2 (KT235641). The antibacterial metabolites present in the TLC elution was exhibited at 274 nm by UV visible spectrometer. The partial purification of preparative HPLC fraction 3 showed 14, 16 mm against P. aeruginosa and K. pneumoniae, respectively. Based on the antibacterial effect, the FT-IR, GC-MS and LC-MS analysis of fraction 3 was confirmed as 1, 4-diaza-2, 5-dioxo-3-isobutyl bicyclo[4.3.0]nonane (DDIBN). Further, the dose dependent inhibition of DDIBN against both ESBL producing pathogens was observed at 75 μg/mL by minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC). The increased cell death and disrupted cell membrane integrity were observed at MIC of DDIBN by confocal laser scanning electron microscope (CLSM) and scanning electron microscope (SEM). The results were proved that the DDIBN has potential antibacterial metabolites against ESBL producing pathogens and it can be applied for various other biomedical fields.

Objectives To describe the epidemiological, clinical, microbiological, and therapeutic characteristics of Nocardiosis patients treated in a general hospital. Patients and methods Monocentric retrospective analysis of patients presenting with Nocardia-positive biological sample from January 1, 1998 to May 1, 2017. Results We identified nine cases of Nocardia infections. Risk factors were oral corticosteroid therapy (n = 3), solid cancer (n = 2), hematological cancer (n = 1), COPD (n = 1). No risk factor was identified in patients with isolated cutaneous presentation (n = 2). Disseminated presentations (n = 3) were observed in patients receiving corticosteroid therapy (n = 2) and presenting with ENT cancer (n = 1). Identified Nocardia species were Nocardia nova (n = 4), Nocardia cyriacigeorgica (n = 2), Nocardia abscessus (n = 1), Nocardia brasiliensis (n = 1), and Nocardia asteroides (n = 1). The median diagnostic time was 17 days. Antibiotic therapy was prolonged and included trimethoprim-sulfamethoxazole in 6/9 cases. The overall one-year case fatality was high (3/8). No recurrence was observed. We identified two cases of respiratory colonization with N. abscessus and N. cyriacigeorgica in COPD patients. Conclusion Nocardiosis can occur both in immunocompetent and immunocompromised patients. It is a severe infection, with a miscellaneous clinical spectrum and complex treatments. Greater knowledge of nocardiosis is required from physicians for optimal medical care.

Objective:Nocardia is an opportunistic organism that usually infects immunocompromised patients. However, suppurative thyroiditis is a rare complication of nocardiosis.Methods: We report a case of Nocardia thyroiditis in an immunosuppressed patient following renal transplant.Results: A 45-year-old man presented with worsening diffuse muscle pain, weakness, and subjective fever. He had a significant history of recent renal transplant with immunosuppression at the time of presentation. Mild swelling was noted in the right submandibular area, and multiple papules were noted on the skin. Although pulmonary exam revealed no abnormalities, computed tomography revealed numerous bilateral small pulmonary nodules and multiple hypodense thyroid nodules. A positron emission tomography scan showed hypermetabolic activity in the mediastinum, lungs, thyroid, and skeletal muscles. During a right-thyroid lobectomy to rule out post-transplant lymphoproliferative disease, purulent discharge from a ruptured cyst was identified. Histopathology revealed granulomatous, focally suppurative thyroiditis and filamentous microorganisms morphologically resembling Nocardia. The pathological and clinical findings in the thyroid, lungs, skin, and nervous system correlated with disseminated nocardiosis.Conclusion:Nocardia thyroiditis is a rare presentation of disseminated nocardiosis. Diagnosis in our case was achieved upon analysis of unusual purulent drainage during thyroid lobectomy for suspicion of post-transplant lymphoma. Thyroidectomy may be considered in resistant and recurrent Nocardia thyroiditis following surgical drainage and antibiotic management. Although most cases of suppurative thyroiditis are of bacterial origin, this case suggests the importance of considering Nocardia as a possible etiological agent of suppurative thyroiditis, particularly in an immunocompromised patient with additional pulmonary, cutaneous, and nervous system manifestations.

Bacterial pathogens are the most frequent cause of pneumonia after transplantation. Early after transplantation, recipients are at higher risk for nosocomial infections. The most commonly encountered pathogens during this period are gram-negative bacilli (Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa …), but gram-positive coccus such as Staphylococcus aureus or Streptococcus pneumoniae and anaerobic bacteria can also be found. Empirical antibiotic therapy should be guided by previous colonisation of the recipient and bacterial resistance pattern in the hospital. Six months after transplantation, pneumonias are mostly due to community-acquired bacteria (S. pneumonia, H. influenza, Mycoplasma, Chlamydia and others). Opportunistic pathogens take advantage of the state of immunosuppression which is usually highest from one to six months after transplantation. During this period, but also occurring many years later in the setting of a chronically depressed immune system, bacterial pathogens with low intrinsic virulence can cause pneumonia. The diagnosis of pneumonia caused by opportunistic pathogens can be challenging. The delay in diagnosis preventing the early instauration of adequate treatment in kidney transplant recipients with a depressed immune system, frequently coupled with co-morbid conditions and a state of frailty, will affect prognosis and outcome, increasing morbidity and mortality. This review will focus on the most common opportunistic bacterial pathogens causing pneumonia in kidney transplant recipients: Legionella, Nocardia, Mycobacterium tuberculosis/nontuberculous, and Rhodococcus. Recognition of their specificities in the setting of immunosuppression will allow early diagnosis, crucial for initiation of effective therapy and successful outcome. Interactions with immunosuppressive therapy should be considered as well as reducing immunosuppression if necessary.

A case of granulomatous hepatitis due to Nocardia is reported here. The case patient was a 63-year-old immunocompetent man who presented with persistent fever, weight loss, and malaise. Radiology suggested an enlarged liver with dense diffuse to multiple tiny micronodular areas of parenchymal involvement, possibly granulomatous. Liver biopsy showed necrotizing granulomas and anti-tuberculosis therapy was initiated, but the patient showed no improvement. A repeat liver biopsy showed similar histopathology; however PCR for Mycobacterium tuberculosis was negative, while MGIT 960 culture grew filamentous Gram-positive bacilli, acid-fast by 1% H2SO4, identified biochemically as Nocardia spp. 16S rRNA sequencing confirmed Nocardia spp. A diagnosis of granulomatous hepatitis due to Nocardia spp. was made. Treatment based on drug sensitivity testing was initiated, resulting in a resolution of symptoms. The patient’s history revealed that stray dogs adopted by his family had skin lesions, likely canine distemper (two newborn puppies had died recently). Nocardia is known to co-infect animals with distemper. This could have been the possible source of a zoonotic infection to the case patient. Nocardia spp. are seldom reported from sites other than the lungs, skin, or brain; the current case highlights the involvement of the liver. Due to the granulomatous tissue response, it could represent a differential diagnosis of tuberculosis in such cases. Keywords: Pyrexia of unknown origin (PUO), Actinomycete, Immunocompetent, Disseminated nocardiosis

Despite advances in treatment, human immunodeficiency virus/tuberculosis (HIV/TB) coinfection remains highly prevalent in selected low- and middle income countries. The diagnosis of tuberculosis frequently proves challenging in the setting of advanced HIV, as patients may present with atypical features. A high index of suspicion must be maintained for TB in this setting, but it is critical that alternative diagnoses are considered. A myriad of opportunistic infections may mimic TB and a definitive microbiological diagnosis prior to TB treatment should always be sought. We report on a case of a young, HIV positive male who presented with a delayed diagnosis of nocardiosis that was thought to be TB of the spine. Despite extensive laboratory and radiological investigations, the diagnosis was only made after tissue was cultured. Earlier diagnosis of this mimic would have led to appropriate therapy and may have improved the outcome for this patient.

Mycetoma is a chronic granulomatous inflammatory disease that is caused either by bacteria or fungi. Bacterial mycetoma (actinomycetoma) can be caused by various causative agents of the genera Nocardia, Streptomyces and Actinomadura. On the other hand, fungal mycetoma (eumycetoma) is most commonly caused by causative agents belonging to the genera Madurella, Scedosporium and Falciformispora. Early and accurate diagnosis of the causative organisms can guide proper patient management and treatment. To allow rapid and accurate species identification, different molecular techniques were developed over the past decades. These techniques can be protein based (MALDI-TOF MS) as well as DNA based (Sequencing, PCR and isothermal amplification methods). In this review, we provide an overview of the different molecular techniques currently in use and identify knowledge gaps, which need to be addressed before we can implement molecular diagnostics for mycetoma in different clinical settings.

Evolution of genome sequencing technology, on the one hand, and advancement of computational genome mining tools, on the other hand, paves way for improvement in predicting secondary metabolites. In past, numerous efforts were made concerning genome mining for recognizing secondary metabolites within the genus, but only a negligible quantity of comparative genomic reports had carried out among species of different genera. In this study, we explored potential of 24 actinobacteria species belonging to the genera, including Streptomyces, Nocardia, Micromonospora, and Saccharomonospora, to traverse diversity and distribution of Biosynthetic Gene Clusters (BGCs). Investigating results obtained from antiSMASH (Antibiotics and Secondary Metabolites Analysis Shell), NaPDoS (Natural Product Domain Seeker), and NP.searcher revealed conservation of genus-specific gene clusters among various species. E.g., NAGGN (n-acetyl glutaminyl glutamine amide) is present in Micromonospora, furan in Nocardia, melanin, and lassopeptide occur in Streptomyces. Bioactive compounds like alkyl-O-dihydro geranyl methoxy hydroquinone, SapB, desferrioxamine E, 2-Methylisoborneol, mayamycin, cyclodipeptide synthase, diisonitrile, salinichelin, hopene, ectoine and isorenieratene are highly conserved among diverse genera. Furthermore, pharmacological activity of actinobacterial derived metabolites against bacterial and fungal pathogens were illustrated. We need to accomplish large-scale analysis of natural products, including various genera of actinobacteria to deliver comprehensive intuition to overcome antibiotic resistance.

Resume Introduction Nocardia est un germe opportuniste chez les patients presentant une immunodepression cellulaire ou une pathologie pulmonaire chronique. Les portes d’entree les plus frequentes sont l’appareil respiratoire par inhalation ou l’inoculation directe par une effraction cutanee. Les nocardioses peuvent etre localisees ou disseminees. Observation Nous rapportons une observation rare de nocardiose disseminee a Nocardia nova avec atteinte pulmonaire, cutanee, cerebrale et osteomyelite femorale. Le diagnostic etait fait grâce aux cultures prolongees du liquide broncho-alveolaire et du pus issu d’une lesion cutanee. L’evolution etait favorable sous antibiotherapie adaptee prolongee par imipenem et amikacine puis cotrimoxazole. Conclusion Cette observation est originale car elle atteint un sujet immunocompetent avec une association de deux atteintes exceptionnelles pour N. nova : l’atteinte cerebrale et osseuse. La recherche de formes cerebrales doit etre systematique, meme en l’absence de signes neurologiques patents. Une antibiotherapie adaptee et prolongee doit etre la regle.

The genus Nocardia is an aerobic bacterium, Gram-positive and catalase positive that is in Nocardiaceae family. This bacterium first described by Edmond Nocard in 1888 and is not in human commensal bacteria. To date, nocardiosis incidence is increasing due to increase population growth rate, increase in patients with immune disorder diseases and immunocompromised patients. We surveyed taxonomic position, isolation methods, phenotypic and molecular identification at the genus and species levels, antibiogram, treatment and epidemiology in the world from 1888 to 2017.

TOPIC: Chest Infections TYPE: Medical Student/Resident Case Reports INTRODUCTION: The novel coronavirus disease (COVID-19) has been associated with diffuse lung injury. Corticosteroids have been shown to suppress inflammation-mediated lung injury and as a result, decrease progression to respiratory failure. Based on the RECOVERY trial, the use of dexamethasone in patients hospitalized with COVID-19 resulted in lower 28-day mortality among those who were receiving either invasive mechanical ventilation or supplemental oxygen at randomization [1]. Per IDSA treatment guidelines dexamethasone use in hospitalized patients is strongly recommended, thereby prompting most intuitions in the United States and worldwide to initiate its use. We present a unique case of Nocardia farcinica brain abscess in the setting of prolonged dexamethasone use in a patient with COVID-19 infection. CASE PRESENTATION: 80-year-old female from Pakistan with a past medical history of hypertension, who while in Pakistan was diagnosed with COVID-19 and treated with Xarelto and dexamethasone (dose and duration unknown). Her course was complicated by the development of left elbow and hand Zoster and over the 10 days prior to presentation, she was noted to develop increasing left-sided weakness and aphasia. Patient was transferred to the United States where a CT scan revealed a left frontal mass, prompting transfer to a tertiary care facility. MRI brain revealed a left frontal cystic rim-enhancing lesion that was concerning for a brain abscess. The patient subsequently underwent left frontal stereotactic brain biopsy with recovery of 3 mL of purulent fluid. Gram staining revealed beaded branching gram-positive rods. She was initially placed on vancomycin/cefepime/metronidazole/dexamethasone and was changed to IV Bactrim/ceftriaxone/doxycycline to cover for Nocardia and Actinomyces. Modified acid-fast stain returned positive with beaded, branching, filamentous rods, consistent with Nocardia. Cultures returned with Nocardia farcinica. DISCUSSION: Nocardia infection primarily occurs via inhalation or direct skin inoculation and subsequently disseminates hematogenously to end organs, which include the brain [2]. Nocardia typically presents as a respiratory or skin infection;brain abscesses are rare and primarily found in immunocompromised patients. As outlined in this case, an immunocompromised state was induced by high dose steroid use. Corticosteroids modulate inflammatory mediators and thereby cause immunosuppression. New symptoms should be monitored closely in patients undergoing steroid therapy, as seen in our patient who presented with new onset aphasia and left sided weakness. This is especially true during the COVID-19 pandemic that has prompted widespread use of dexamethasone in order to prevent respiratory failure and death. CONCLUSIONS: Physicians should be vigilant of superimposed infections in patients with COVID-19 receiving high dose steroids. REFERENCE #1: RECOVERY Collaborative Group. Dexamethasone in Hospitalized Patients with Covid-19. N Engl J Med. 2021;384(8):693-704. doi:10.1056/NEJMoa2021436. REFERENCE #2: Lin YJ, Yang KY, Ho JT, Lee TC, Wang HC, Su FW. Nocardial brain abscess. J Clin Neurosci. 2010;17(2):250-253. doi:10.1016/j.jocn.2009.01.032 DISCLOSURES: No relevant relationships by Waqas Bhatti, source=Web Response No relevant relationships by Tanisha Kaur, source=Web Response

TOPIC: Chest Infections TYPE: Medical Student/Resident Case Reports INTRODUCTION: Nocardia is an opportunistic aerobic actinomycete that most frequently affects the lungs, brain, and skin in 0.04% to 3.5%2 patients after solid organ transplant. Natural and synthetic glucocorticoids are at the forefront of anti-inflammatory and immunosuppressive therapies in transplant patients who often succumb to Nocardia infections. Out of the eight species, N. farcinica is potentially more lethal because of its tendency to disseminate and its resistance to antibiotics1. We present a unique patient who developed N. farcinica at the end of a 10-day course of dexamethasone for COVID-19. CASE PRESENTATION: A 61-year-old female with past medical history of non- insulin dependent type II diabetes (hgbA1c 6.3), hypertension, CHF on GDMT, and COVID-19 pneumonia presented with chest pain on the 10th and last day of per oral 4mg dexamethasone course. On admission patient's vitals were stable and labs were notable for leukocytosis, elevated glucose, BNP, and D-dimer prompting a CTA which showed subsegmental PE and a thrombus in SVC extending to the IVC. She was also found to have a right upper lobe 3.3 x 3.2 cm subpleural mass and a left upper lobe 1.9 x 1.5 cm nodule (figure 2). Percutaneous CT-guided coaxial core needle biopsy of right lung mass was done with pathology results notable for branching filamentous organisms consistent with Nocardia further refined by cultures growing Nocardia farcinica. The MRI brain did not show any abscess. She was started on IV Bactrim and meropenem. Eventually, the patient was discharged home on Bactrim and linezolid due to N. farcinica's high resistance rates to Bactrim alone. DISCUSSION: Nocardiosis usually occurs in immunosuppressed states, such as lymphomas, HIV, diabetics, transplant recipients or patients on long term immunosuppressants. Glucocorticoids are widely used as an effective treatment to control inflammatory and autoimmune diseases with more recent prevalent use for covid-19 infections to control immune-mediated damage of lung tissue. We are presenting the first case of N. farcinica infection in a COVID-19 patient after a brief steroid course. The case also highlights N. farcinica infection mimicking a lung mass and demonstrates that pulmonary Nocardia infections can easily be misdiagnosed, highlighting the importance of keeping a broad differential. CONCLUSIONS: steroid use in the management of COVID-19 infection can result in opportunistic infections, including N. farcinica. REFERENCE #1: Margalit I, Goldberg E, Ben Ari Y, Ben-Zvi H, Shostak Y, Krause I, Muhsen K. Clinical correlates of nocardiosis. Sci Rep. 2020 Aug 31;10(1):14272. doi: 10.1038/s41598-020-71214-4. PMID: 32868850;PMCID: PMC7459281 REFERENCE #2: Coussement J, Lebeaux D, van Delden C, Guillot H, Freund R, Marbus S, Melica G, Van Wijngaerden E, Douvry B, Van Laecke S, Vuotto F, Tricot L, Fernandez-Ruiz M, Dantal J, Hirzel C, Jais JP, Rodriguez-Nava V, Lortholary O, Jacobs F;European Study Group for Nocardia in Solid Organ Transplantation. Nocardia Infection in Solid Organ Transplant Recipients: A Multicenter European Case-control Study. Clin Infect Dis. 2016 Aug 1;63(3):338-45. doi: 10.1093/cid/ciw241. Epub 2016 Apr 18. PMID: 27090987. DISCLOSURES: No relevant relationships by Muhammad Arif, source=Web Response No relevant relationships by Ericka Charley, source=Web Response No relevant relationships by Jonathan Munoz, source=Web Response No relevant relationships by Hursh Sarma, source=Web Response No relevant relationships by Andrew Talon, source=Web Response

Mitogen-activated protein kinase/extracellular signal-regulated kinase kinase kinase 3 (MEKK3) is a serine/threonine protein kinase that acts as a key regulator and is widely involved in various innate and acquired immune signaling pathways. In this study, we first cloned the complete open reading frame (ORF) of the MEKK3 gene (named CcMEKK3) in a hybrid snakehead (Channa maculate ♀ × Channa argus ♂). The full-length ORF of CcMEKK3 is 1851 bp, and encodes a putative protein of 616 amino acids containing a serine/threonine kinase catalytic (S-TKc) domain and a Phox and Bem1p (PB1) domain. A sequence alignment and phylogenetic tree analysis showed that CcMEKK3 is highly conserved relative to the MEKK3 proteins of other teleost species. CcMEKK3 was constitutively expressed in all the healthy hybrid snakehead tissues tested, with greatest expression in the immune tissues, such as the head kidney and spleen. The expression of CcMEKK3 was usually upregulated in the head kidney, spleen, and liver at different time points after infection with Nocardia seriolae or Aeromonas schubertii. Similarly, the dynamic expression levels of CcMEKK3 in head kidney leukocytes after stimulation revealed that CcMEKK3 was induced by LTA, LPS, and poly(I:C). In the subcellular localization analysis, CcMEKK3 was evenly distributed in the cytoplasm of HEK293T cells, and its overexpression significantly promoted the activities of NF-κB and AP-1. These results suggest that CcMEKK3 is involved in the immune defense against these two pathogens, and plays a crucial role in activating the NF-κB and MAPK signaling pathways.

F420-dependent glucose-6-phosphate dehydrogenase (FGD1) catalyzes the conversion of glucose-6-phosphate (G6P) to 6-phosphogluconolactone. During the course of this reaction, the oxidized cofactor F420 is converted to its reduced form (F420H2). FGD was initially identified and studied extensively within mycobacteria prior to the more recent discovery of FGDs from Rhodococcus jostii RHA1. Another group of FGDs that utilize a variety of sugar-6-phosphates from Nocardia and Cryptosporangium arvum is also known as the FSDs. Crystal structures of FGD from the pathogens Mycobacterium tuberculosis and Rhodococcus jostii RHA1 have provided significant insight into the structural and mechanistic properties of the enzymes and have been the basis for mutagenesis, kinetic and mechanistic studies in recent years. This review discusses the role of FGD within M. tuberculosis, followed by our current understanding of the FGD catalytic mechanism. This will also be discussed with reference to the relationship between FGD and the structurally unrelated NADP+-dependent glucose-6-phosphate enzymes.

Antimicrobial susceptibility testing (AST) of fastidious bacteria is an essential yet challenging exercise for the clinical microbiology laboratory. An understanding of bacterial growth requirements is essential to ensure optimal recovery of pathogens. A working knowledge of reference methods for antimicrobial susceptibility testing, such as agar and broth microdilution, as well as knowledge of modifications to these systems, will aid the laboratory in the selection of the appropriate AST method to meet regulatory requirements and ensure quality results for patient care. The establishment of AST breakpoints and interpretive criteria is dependent upon the AST methodology used and the regulatory standard applied by the laboratory. AST should be performed when clinically relevant, as testing of isolates not implicated in true infection may result in inappropriate antimicrobial therapy. This review discusses methods for AST, medium requirements, quality control, and site-specific AST result reporting, as well as testing and reporting recommendations for both common and uncommon fastidious bacteria implicated in human infection. AST testing methods for mycobacteria and Nocardia spp. are not reviewed in this manuscript.

Background Infection by Nocardia species is an uncommon cause of severe clinical syndromes, particularly in immunocompromised patients, and solid-organ transplantation is the most common underlying condition. The syndrome of inappropriate antidiuretic hormone secretion (SIADH) has been described thus far in lung and stem cell transplants with systemic nocardiosis. Case Report We report the first case of SIADH in a female elderly renal transplant recipient diagnosed with systemic nocardiosis 2 years after transplantation. The SIADH was managed appropriately, and her immunosuppressive regimen remained unchanged but was adjusted at a lower level. The systemic Nocardia infection was successfully treated with intravenous administration of trimethoprim-sulfamethoxazole and imipenem for 2 weeks followed by oral trimethoprim-sulfamethoxazole for a total of 12 months. Conclusions The SIADH syndrome is a recognizable complication of Nocardia infection in renal transplant recipients. Prompt identification along with proper management and prolonged antimicrobial treatment are essential to improve patients' outcome.

Nocardia and Actinomyces are Gram-positive bacteria of the order Actinomycetales. These ubiquitous organisms exhibit filamentous branching structures, which sometimes coalesce and develop into bundles known as mycelia. They are the cause of rare, but clinically important, infections and are often termed ‘the great masqueraders'. Affected individuals tend to present with chronic debilitating suppurative infections, and there can be a significant delay before a definitive diagnosis is made. Microbiological diagnosis is challenging, but advances in molecular techniques are improving the identification of these organisms. Despite the relative rarity of these conditions, an awareness of the disease manifestations caused by these organisms is beneficial; outcomes are more favourable if they are diagnosed early and effective treatment is initiated.

Nocardiosis afflicts multiple species of cultured fish, resulting in substantial economic losses to the aquaculture industry, however, lack of detailed knowledge on disease pathogenesis has hampered the development of effective prevention and control strategies. In this study, we injected a green fluorescent protein (GFP)-labeled Nocardia seriolae strain into a transparent mutant strain of Tiger barb (Puntius tetrazona) to monitor tissue pathogen accumulation and tissue damage in vivo, and to clarify the relationship between pathogenic processes and overt symptoms. GFP-labeled bacteria were phagocytized by leukocytes and could proliferate within these cells, which in turn led to leukocyte aggregation, leukocyte death, and granuloma formation. In addition, intracellular bacteria could permanently colonize various tissues via leukocyte circulation, causing multi-organ infection as revealed by changes of tissue transparency. Histology revealed granulomatous lesions in organs such as muscle, kidney, and spleen that was corresponded to the tissue opacities in vivo. Confocal microscopy confirmed massive accumulations of GFP-labeled bacteria within these granulomas, which often contained a necrotic core. Tiger barb transparency allows for real-time observation of in vivo pathological changes within the same animal, and the pathogenic process can be evaluated based on the shape and size of body opacities. Thus, transparent Tiger barb is a promising model to study the pathogenesis of nocardiosis.

Nocardia species are the most commonly isolated aerobic actinomycetes from human clinical specimens. Our objective was to assess the identification of clinically relevant actinomycetes using the Bruker Biotyper MALDI-TOF system, including comparison of extraction methods, Biotyper library versions, score cutoffs, and media. Banked Streptomyces (n=10), Tsukamurella (n=2), and Nocardia isolates (n=60) were cultured and extracted using three methods: mycobacterial extraction, ethanol formic acid extraction, or direct on-target extraction. Following MALDI-TOF analysis, spectra were analyzed using versions 5 and 6 of the BDAL Biotyper library. Optimal species-level identifications for Nocardia were achieved using BDAL v6 at a score cutoff of ≥1.8 after direct extraction (49/60, 82%). Overall, the Biotyper platform with BDAL v6 accurately identified 12/16 species of Nocardia, demonstrating the utility of MALDI-TOF for identification of clinically relevant actinomycetes without the need for supplementation of the database.

Resume Introduction Les pneumonies causees par des bacteries a croissance lente sont rares mais sont parfois severes et delabrantes. Etat des connaissances Ces infections partagent plusieurs points communs comme de nombreux diagnostics differentiels, la difficulte a mettre en evidence l’agent pathogene, l’importance d’impliquer le microbiologiste dans l’exploration diagnostique et la necessite d’un traitement antibiotique prolonge. Par contre, des differences majeures permettent de les distinguer : Nocardia et Rhodococcus touchent principalement des immunodeprimes alors que l’actinomycose concerne egalement les patients immunocompetents ; la gravite des nocardioses est liee a leur dissemination hematogene alors que l’extension locoregionale par contiguite fait toute la gravite des actinomycoses. Perspectives Pour ces pathologies, les outils de diagnostic moleculaire sont fondamentaux, soit pour obtenir un diagnostic d’espece et guider le traitement dans le cas des nocardioses, soit pour affirmer le diagnostic a partir d’un prelevement biologique. Le traitement de ces infections est complexe du fait : (1) du peu de donnees dans la litterature ; (2) de la necessite d’un traitement prolonge de plusieurs mois ; (3) de la gestion des toxicites et interactions medicamenteuses pour le traitement de Nocardia et Rhodococcus. Conclusion Une collaboration etroite entre pneumologues, infectiologues et microbiologistes est indispensable a la prise en charge de ces patients.

A rubber-degrading bacterial consortium named H2DA was obtained from an enrichment culture with natural rubber latex and rubber-processing factory waste in Vietnam. Gel permeation chromatography analysis revealed that only the strain NVL3 degraded synthetic poly(cis-1,4-isoprene) into low-molecular-weight intermediates among the three strains found in the H2DA. The 16S-rRNA gene sequence of NVL3 showed the highest identity with that of Nocardia farcinica DSM 43665T. NVL3 accumulated aldehyde intermediates from synthetic poly(cis-1,4-isoprene) on a rubber-overlay plate as indicated by Schiff's staining. NVL3 also degraded deproteinized natural rubber into low-molecular-weight aldehyde intermediates. A latex-clearing protein (lcp) gene ortholog was identified within the genome sequence of NVL3, and it showed a moderate amino-acid identity (54–75%) with the lcp genes from previously reported rubber degraders. The heterologous expression of the NVL3 lcp in Escherichia coli BL21(DE3) allowed us to purify the 46.8-kDa His-tagged lcp gene product (His-Lcp). His-Lcp degraded synthetic poly(cis-1,4-isoprene) and accumulated aldehyde intermediates from deproteinized natural rubber suggesting the functional expression of the lcp gene from a Nocardia degrader in E. coli. Quantitative reverse transcription PCR analysis indicated the strong transcriptional induction of the lcp gene in NVL3 in the presence of synthetic poly(cis-1,4-isoprene). These results suggest the involvement of the lcp gene in rubber degradation in NVL3.