Determination of antimicrobial susceptibility patterns of Nocardia spp. from clinical specimens by Etest

Atypical microbial keratitis

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.

Nocardia keratitis presenting as an anterior chamber ball of exudates and its management

A man in late 40s presented with corneal ulcer of the right eye of 1 month duration. He had a central corneal epithelial defect measuring 4.6×4.2 mm with an underlying 3.6×3.5 mm anterior to mid stromal patchy infiltrate and 1.4 mm hypopyon. Gram stain of the colonies on chocolate agar showed presence of confluent thin branching, gram-positive beaded filaments, which were positive after 1% acid fast stain. This confirmed our organism to be Nocardia sp. Topical amikacin was started but continued worsening of the infiltrate and presence of a ball of exudates in the anterior chamber, prompted the use of systemic trimethoprim-sulfamethoxazole. There was a dramatic improvement in the signs and symptoms, with complete resolution of infection over a period of 1 month.

Identification of a novel drug-resistant community-acquired Nocardia spp. in a patient with bronchiectasis

A previously unknown Nocardia species was isolated from the lung tissue and bronchoalveolar lavage fluid (BALF) of a 58-year-old woman with bronchiectasis and recurrent pneumonia. This Nocardia (GZ2020^T), which grew readily in Columbia blood agar and could induce pneumonia in a mouse model, represents a novel Nocardia species, and its closest known relatives are Nocardia anaemiae NBRC 100462^T, Nocardia pseudovaccinii NBRC 100343^T and Nocardia vinacea NBRC 16497^T. However, unlike all previously known species, GZ2020^T is the first genus of Nocardia spp. that is not susceptible to multiple drugs but does show susceptibility to linezolid and moxifloxacin, and thus, GZ2020^T potentially represents a substantial health threat to patients with bronchiectasis and immunocompromised individuals. Although the original pathogen source and method of spreading remain uncertain, a mode of transmission from the environment to humans could exist. Vigilance with respect to its spread in the population and the transmission of antibiotic resistance genes in the environment should be maintained.

MLSA phylogeny and antimicrobial susceptibility of clinical Nocardia isolates: a multicenter retrospective study in China

Background

With the increase of detection rate and long treatment period, nocardiosis has become a noticeable problem in China. However, there are limited large-scale studies on the epidemiology and antimicrobial susceptibility profiles of clinical Nocardia spp. in China. The present study aimed to explore the species distribution and drug susceptibility pattern of 82 clinical Nocardia isolates from three tertiary hospitals in China by multilocus sequence analysis (MLSA) and broth microdilution (BMD) method.

Results

Pulmonary nocardiosis (90.2%) was the most common clinical presentation of infection. N. cyriacigeorgica (n = 33; 40.2%) and N. farcinica (n = 20; 24.4%) were the most frequently encountered Nocardia species, followed by N. otitidiscaviarum (n = 7; 8.5%), N. abscessus (n = 5; 6.1%), N. asiatica (n = 4; 4.9%), and N. wallacei (n = 4; 4.9%). Trimethoprim/sulfamethoxazole (SXT) remained high activity against all Nocardia isolates (susceptibility rate: 98.8%). Linezolid and amikacin were also highly active; 100 and 95.1% of all isolates demonstrated susceptibility, respectively. Except for N. otitidiscaviarum, all the Nocardia isolates exhibited high susceptibility rates to imipenem. The resistance rates of all isolates to clarithromycin and ciprofloxacin were 92.7 and 73.2%, respectively, but the resistance rate of N. farcinica to ciprofloxacin was only 25%.

Conclusions

The clinically isolated Nocardia spp. had diverse antimicrobial susceptibility patterns, which were similar to the reports by other groups elsewhere, but some differences were also observed, mainly including imipenem and ciprofloxacin. According to this study, SXT still can be the first choice for empirical therapy due to the low resistance rate. Linezolid can be chosen when a patient is allergic to SXT, and amikacin and imipenem can be the choice in a combination regimen.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02412-x.

Nocardia huaxiensis sp. nov., an actinomycete isolated from human skin

A novel actinomycete, designated as strain WCH-YHL-001^T, was isolated from skin biopsy specimens of a patient at West China Hospital, Chengdu, Sichuan Province, PR China. The cells were Gram-positive, aerobic, heterotrophic and non-motile. They formed an extensive substrate with short aerial mycelia, whose branches fragmented into rod-shaped elements. Growth occurred at 10-40 °C, pH 5.0-12.0 and with NaCl concentrations of 0-4.0 % (w/v). The major cellular fatty acids of strain WCH-YHL-001^T were C_16 : 0, C_18 : 1  ω9c, C_18 : 0 10-methyl and summed feature 3. The predominant respiratory quinone was MK-8 (H4ω-cycl). The major polar lipids were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylinositol mannoside, unknown phospholipids and unidentified glycolipids. The diagnostic diamino acid of peptidoglycan was meso-diaminopimelic acid. The whole-cell sugar pattern consisted of arabinose and glucose. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain WCH-YHL-001^T belonged to the genus Nocardia. The average nucleotide identity (ANI) and in silico DNA-DNA hybridization (isDDH) values between strain WCH-YHL-001^T and type strains of Nocardia species were lower than the cut-offs (≥95-96 % for ANI and ≥70 % for isDDH) required to define a bacterial species. The genomic DNA G+C content was 67.8 mol%. Phylogenetic, physiological and chemotaxonomic data suggested that strain WCH-YHL-001^T represented a novel species of the genus Nocardia, for which the name Nocardia huaxiensis sp. nov. is proposed, with the type strain WCH-YHL-001^T (=GDMCC 4.181^T=JCM 34475 ^T=NBRC 114973^T).

Molecular identification and antibiotic resistance pattern of actinomycetes isolates among immunocompromised patients in Iran, emerging of new infections

Recent advancements in DNA-based approaches have led to the identification of uncommon and rare bacterial pathogens. In this study, by utilizing a DNA-based approach, a total of 1043 clinical specimens were processed for the identification of actinobacteria targeting the 16S rRNA and gyrB genes. Drug susceptibility testing was also conducted using micro-broth dilution and PCR. Two isolates of Nocardia flavorosea and Rhodococcus erythropolis were reported for the first time in Iran. Also, Nocardiopsis dassonvillei, Streptomyces olivaceus, and Streptomyces griseus were reported for the first time in Asia. Infections caused by Nocardia caishijiensis and Prauserella muralis have also been reported in this study. The first Asian case of pulmonary infection caused by Nocardia ignorata and the first global case of brain abscess caused by Nocardia ninae and Nocardia neocaledoniensis have been reported in this study. Overall 30 isolates belonging to 6 genera (Nocardia, Streptomyces, Rodoccoccus, Nocardiopsis, Rothia, and Prauserella) were detected in 30 patients. All 30 isolates were susceptible to amikacin and linezolid. Three isolates including Nocardia otitidiscaviarum (n = 2) and Nocardia flavorosea (n = 1) were resistant to trimethoprim-sulfamethoxazole which were the first trimethoprim-sulfamethoxazole resistant clinical actinomycetes in Iran. Isolation of rare species of actinomycetes particularly Nocardia spp. requires urgent action before they spread clinically particularly among immunocompromised patients.

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.

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.

Peritonite piogranulomatosa por Nocardia concava em cão - relato de caso

RESUMO Nocardiose é causada por bactérias do gênero Nocardia do subgrupo Actinomycetos, que são Gram-positivas aeróbicas, filamentosas e podem apresentar ramificações. O diagnóstico baseia-se na presença de lesão inflamatória, com o microrganismo morfologicamente compatível, associada ao isolamento e à identificação microbiológica e molecular. Este trabalho tem por objetivo relatar um caso de nocardiose em canino, que desenvolveu inflamação piogranulomatosa peritoneal seis meses após ovariossalpingo-histerectomia. O animal apresentava hipertermia, distensão abdominal, taquipneia, polidipsia, hiporexia, mucosas hipocoradas e fezes pastosas. Os achados laboratoriais evidenciaram anemia leve e leucocitose por neutrofilia com desvio à esquerda e hipoalbuminemia. Uma massa na região mesogástrica e efusão peritoneal foram evidenciadas por meio da ultrassonografia abdominal. O líquido foi classificado como exsudato piogranulomatoso, e o animal submetido à laparotomia exploratória para lavagem abdominal e remoção da massa. Após procedimentos terapêuticos, ocorreu piora clínica e óbito. Peritonite piogranulomatosa foi a principal alteração anatomopatológica a qual foi associada à Nocardia spp. Molecularmente, a espécie isolada se aproxima da N. concava, por meio da análise filogenética. Essa espécie já foi descrita como causa de infecção em humanos na Ásia, no entanto não há registros na literatura na espécie canina, sendo este o primeiro relato.

Molecular identification and phylogenetic relationships of clinical Nocardia isolates

Species identification of Nocardia is difficult because of a complex and rapidly evolving taxonomy. In this study, gene sequencing (16S rRNA, gyrB, secA1, hsp65, rpoB), single 16S rRNA gene sequence phylogenetic analysis, and MALDI-TOF analysis were used to accurately identify 46 clinical Nocardia isolates to the species level. This provided a basis for establishing a routine method of multi-locus sequence analysis (MLSA) for molecular identification of Nocardia species. Genetic polymorphism analysis showed that MLSA was a powerfully discriminating method compared with the 16S rRNA gene to identify clinical Nocardia isolates. However, five-locus (gyrB-16S rRNA-secA1-hsp65-rpoB) MLSA led to misidentifications of all of the five Nocardia abscessus, which were confirmed by digital DNA-DNA hybridization (DDH) analysis. Interestingly, four strains identified as Nocardia beijingensis by a 16S rRNA gene phylogenetic tree may be novel species as suggested by DDH studies. For the purpose of achieving both accuracy and discrimination, the data of MLSA were reanalyzed. A three-locus MLSA with concatenated gyrB-16S rRNA-secA1 sequences was used to construct the phylogenetic tree with high accuracy and powerful discrimination. Therefore, a routine method of MLSA was developed to identify clinical Nocardia species.

Nocardial endocarditis in native aortic valve with nocardial sepsis in a case of breast cancer

Central venous catheter-associated bacteraemia caused by Nocardia species is very rare; the diagnosis of nocardiosis in patients with cancer is challenging because its clinical presentation is varied, sometimes mimicking metastases, and the high index of clinical suspicion is required for prompt institution of therapy. Herein, we report a case of nocardial sepsis with native aortic valve endocarditis in a patient with breast cancer in whom multidisciplinary team involvement and prompt initiation of therapy have led to successful outcome.

ENDOGENOUS NOCARDIA ENDOPHTHALMITIS PRESENTING AS A MASS LESION IN A PATIENT WITH METATSTATIC NONSMALL CELL CARCINOMA OF THE LUNG

PURPOSE

To report a case of Nocardia cyriacigeorgica endophthalmitis.

METHODS

Case report.

RESULTS

A 71-year-old man on long-term steroid therapy for poor respiratory function from lung carcinoma and presumed recent liver metastases presented with a four week history of blurry vision in the left eye. Ophthalmic examination revealed a white elevated mass in the macula with hemorrhage, concerning for metastasis. The patient was treated for presumed ocular metastases but had poor response to radiotherapy and was diagnosed four weeks later with N. cyriacigeorgica by retinal biopsy. Despite intravitreal and systemic antibiotics, the patient had progression of disease and died of respiratory involvement.

CONCLUSION

Nocardia endogenous endophthalmitis can present as a mass retinal lesion in immunosuppressed patients with metastatic disease. Early vitreous and retinal biopsy may be required for definitive diagnosis and treatment. A pulmonary source of infection should be suspected and monitored closely.

Nocardia infections in solid organ transplantation: Guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of Nocardia infections after solid organ transplantation (SOT). Nocardia infections have increased in the last two decades, likely due to improved detection and identification methods and an expanding immunocompromised population. The risk of developing nocardiosis after transplantation varies with the type of organ transplanted and the immunosuppression regimen used. Nocardia infection most commonly involves the lung. Disseminated infection can occur, with spread to the bloodstream, skin, or central nervous system. Early recognition of the infection and initial appropriate treatment is important to achieve good outcomes. Species identification and antimicrobial susceptibility testing are strongly recommended, as inter- and intraspecies susceptibility patterns can vary. Sulfonamide is the first-line treatment of Nocardia infections, and combination therapy with at least two antimicrobial agents should be used initially for disseminated or severe nocardiosis. Trimethoprim-sulfamethoxazole (TMP-SMX) prophylaxis may be helpful in preventing Nocardia infection after SOT.

Clinical features, identification, antimicrobial resistance patterns of Nocardia species in China: 2009-2017

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.

Clinical Assessment of a Nocardia PCR-Based Assay for Diagnosis of Nocardiosis

The diagnosis of nocardiosis, a severe opportunistic infection, is challenging. We assessed the specificity and sensitivity of a 16S rRNA Nocardia PCR-based assay performed on clinical samples. In this multicenter study (January 2014 to April 2015), patients who were admitted to three hospitals and had an underlying condition favoring nocardiosis, clinical and radiological signs consistent with nocardiosis, and a Nocardia PCR assay result for a clinical sample were included. Patients were classified as negative control (NC) (negative Nocardia culture results and proven alternative diagnosis or improvement at 6 months without anti-Nocardia treatment), positive control (PC) (positive Nocardia culture results), or probable nocardiosis (positive Nocardia PCR results, negative Nocardia culture results, and no alternative diagnosis). Sixty-eight patients were included; 47 were classified as NC, 8 as PC, and 13 as probable nocardiosis. PCR results were negative for 35/47 NC patients (74%). For the 12 NC patients with positive PCR results, the PCR assay had been performed with respiratory samples. These NC patients had chronic bronchopulmonary disease more frequently than did the NC patients with negative PCR results (8/12 patients [67%] versus 11/35 patients [31%]; P = 0.044). PCR results were positive for 7/8 PC patients (88%). There were 13 cases of probable nocardiosis, diagnosed solely using the PCR results; 9 of those patients (69%) had lung involvement (consolidation or nodule). Nocardia PCR testing had a specificity of 74% and a sensitivity of 88% for the diagnosis of nocardiosis. Nocardia PCR testing may be helpful for the diagnosis of nocardiosis in immunocompromised patients but interpretation of PCR results from respiratory samples is difficult, because the PCR assay may also detect colonization.

Epidemiology and susceptibility to antimicrobial agents of the main Nocardia species in Spain

Objectives

The aims of this study were to explore the clinical distribution, by species, of the genus Nocardia and to assess the antimicrobial susceptibilities of the 10 most prevalent species identified in Spain.

Methods

Over a 10 year period (2005-14), 1119 Nocardia strains were molecularly identified and subjected to the Etest. The distribution and resistance trends over the sub-periods 2005-09 and 2010-14 were also examined.

Results

Of the strains examined, 82.9% belonged to the following species: Nocardia cyriacigeorgica (25.3%), Nocardia nova (15.0%), Nocardia abscessus (12.7%), Nocardia farcinica (11.4%), Nocardia carnea (4.3%), Nocardia brasiliensis (3.5%), Nocardia otitidiscaviarum (3.1%), Nocardia flavorosea (2.6%), Nocardia rhamnosiphila (2.6%) and Nocardia transvalensis (2.4%). Their prevalence values were similar during 2005-09 and 2010-14, except for those of N. abscessus , N. farcinica and N. transvalensis , which fell significantly in the second sub-period ( P ≤  0.05). The major location of isolation was the respiratory tract (∼86%). Half (13/27) of all strains from the CNS were N. farcinica . Significant differences in MIC results were recorded for some species between the two sub-periods. According to the CLSI's breakpoints, low resistance rates (≤15%) were recorded for seven species with respect to cefotaxime, imipenem and tobramycin; five species showed similar rates with respect to trimethoprim/sulfamethoxazole. Linezolid and amikacin were the most frequently active agents.

Conclusion

The accurate identification of the infecting species and the determination of its susceptibility to antimicrobial agents, given the large number of strains with atypical patterns, are crucial if patients with nocardiosis are to be successfully treated.

Identification and antimicrobial susceptibility of clinical Nocardia species in a tertiary hospital in China

OBJECTIVES

There is a lack of information on the activities of antimicrobial agents against Nocardia clinical isolates of specific species in China. The aim of this study was to determine the antibiotic susceptibility of 28 clinical isolates of Nocardia spp. isolated from Beijing Chao-Yang Hospital (Beijing, China).

METHODS

Molecular diagnosis of Nocardia spp. was performed using partial 16S rRNA and rpoB gene sequences. Antimicrobial susceptibility testing was performed by broth microdilution according to Clinical and Laboratory Standards Institute (CLSI) recommendations.

RESULTS

The species distribution was as follows: Nocardia cyriacigeorgica (n=13); Nocardia farcinica (n=6); Nocardia beijingensis (n=3); Nocardia abscessus (n=2); Nocardia wallacei (n=2); Nocardia otitidiscaviarum (n=1); and Nocardia nova (n=1). The susceptibility rates to trimethoprim/sulfamethoxazole (SXT), linezolid, amikacin, imipenem, tobramycin, ceftriaxone and cefotaxime were 100.0%, 100.0%, 92.9%, 75.0%, 67.9%, 67.9% and 64.3%, respectively, whilst the resistance rate both to ciprofloxacin and clarithromycin was 71.4%.

CONCLUSIONS

N. cyriacigeorgica was the most frequently isolated Nocardia spp. All clinical isolates showed low susceptibility to ciprofloxacin and clarithromycin and complete susceptibility both to SXT and linezolid, which can be considered the primary choice for the treatment of Nocardia infections in China.

Outcome and Treatment of Nocardiosis After Solid Organ Transplantation: New Insights From a European Study

BACKGROUND

Solid organ transplant (SOT) recipients are at risk of nocardiosis, a rare opportunistic bacterial infection, but prognosis and outcome of these patients are poorly defined. Our objectives were to identify factors associated with 1-year mortality after nocardiosis and describe the outcome of patients receiving short-course antibiotics (≤120 days).

METHODS

We analyzed data from a multicenter European case-control study that included 117 SOT recipients with nocardiosis diagnosed between 2000 and 2014. Factors associated with 1-year all-cause mortality were identified using multivariable conditional logistic regression.

RESULTS

One-year mortality was 10-fold higher in patients with nocardiosis (16.2%, 19/117) than in control transplant recipients (1.3%, 3/233, P < .001). A history of tumor (odds ratio [OR], 1.4; 95% confidence interval [CI], 1.1-1.8), invasive fungal infection (OR, 1.3; 95% CI, 1.1-1.5), and donor age (OR, 1.0046; 95% CI, 1.0007-1.0083) were independently associated with 1-year mortality. Acute rejection in the year before nocardiosis was associated with improved survival (OR, 0.85; 95% CI, 0.73-0.98). Seventeen patients received short-course antibiotics (median duration 56 [24-120] days) with a 1-year success rate (cured and surviving) of 88% and a 5.9% risk of relapse (median follow-up 49 [6-136] months).

CONCLUSIONS

One-year mortality was 10-fold higher in SOT patients with nocardiosis than in those without. Four factors, largely reflecting general medical condition rather than severity and/or management of nocardiosis, were independently associated with 1-year mortality. Patients who received short-course antibiotic treatment had good outcomes, suggesting that this may be a strategy for further study.

Susceptibility profiles of Nocardia spp. to antimicrobial and antituberculotic agents detected by a microplate Alamar Blue assay

Nocardia species are ubiquitous in natural environments and can cause nocardiosis. Trimethoprim-sulfamethoxazole has long been the monotherapy treatment of choice, but resistance to this treatment has recently emerged. In this study, we used microplate Alamar Blue assays to determine the antimicrobial susceptibility patterns of 65 standard Nocardia isolates, including 28 type strains and 20 clinical Nocardia isolates, to 32 antimicrobial agents, including 13 little studied drugs. Susceptibility to the most commonly used drug, trimethoprim-sulfamethoxazole, was observed in 98% of the isolates. Linezolid, meropenem, and amikacin were also highly effective, with 98%, 95%, and 90% susceptibility, respectively, among the isolates. The isolates showed a high percentage of resistance or nonsusceptibility to isoniazid, rifampicin, and ethambutol. For the remaining antimicrobials, resistance was species-specific among isolates and was observed in traditional drug pattern types. In addition, the antimicrobial susceptibility profiles of a variety of rarely encountered standard Nocardia species are reported, as are the results for rarely reported clinical antibiotics. We also provide a timely update of antimicrobial susceptibility patterns that includes three new drug pattern types. The data from this study provide information on antimicrobial activity against specific Nocardia species and yield important clues for the optimization of species-specific Nocardia therapies.

The role of oral co-trimoxazole in treating Nocardia farcinica keratitis-a case report

BACKGROUND

Nocardia farcinica is one of the more recently identified species of the Nocardia genus. Nocardia farcinica keratitis is a rare occurrence, with only eight previously reported cases. Semi-permeable rigid contact lens use was associated with one of these reported cases. We report the first case of extended wear soft contact-lens-related Nocardia farcinica keratitis and recommend a new treatment regime.

FINDINGS

A 47-year-old lady presented with a right eye keratitis after wearing her extended wear soft contact lenses for five continuous weeks. There was no history of trauma or swimming with contact lenses in. Empirical ciprofloxacin and tobramycin eye drops were not tolerated due to ocular surface irritation on application; and instead, empirical treatment was with chloramphenicol and fortified gentamicin 1.5 % eye drops. Corneal scrapings grew Nocardia farcinica after 3 weeks-sensitive to amikacin and co-trimoxazole. Treatment was changed to amikacin 2.5 % eye drops, resulting in partial resolution of the corneal infiltrates. Oral co-trimoxazole 160/800 mg BD was added, due to cultured drug sensitivity and its high ocular penetration, with good results and a final right eye best-corrected visual acuity of 6/5.

CONCLUSION

Nocardia farcinica keratitis should be considered in the differential diagnosis of contact-lens-related keratitis. We report the first case occurring in association with extended wear soft contact lenses. Nocardia species can mimic fungal and Acanthamoeba keratitis. Treatment with oral co-trimoxazole has not been previously reported. This case demonstrates a role for co-trimoxazole in treating Nocardia farcinica keratitis based on cultured drug sensitivities.

The role of oral co-trimoxazole in treating Nocardia farcinica keratitis: a case report

Nocardia farcinica is one of the more recently identified species of the Nocardia genus. Nocardia farcinica keratitis is a rare occurrence, with only eight previously reported cases. Semi-permeable rigid contact lens use was associated with one of these reported cases. We report the first case of an extended wear soft contact lens-related Nocardia farcinica keratitis and recommend a new treatment regime. A 47-year-old lady presented with a right eye keratitis after wearing her extended wear soft contact lenses for five continuous weeks. There was no history of trauma or swimming with contact lenses in. Empirical ciprofloxacin and tobramycin eye drops were not tolerated due to ocular surface irritation on application, and instead, empirical treatment was with chloramphenicol and fortified gentamicin 1.5 % eye drops. Corneal scrapings grew Nocardia farcinica after 3 weeks-sensitive to amikacin and co-trimoxazole. Treatment was changed to amikacin 2.5 % eye drops, resulting in partial resolution of the corneal infiltrates. Oral co-trimoxazole 160 mg/800 mg BD was added, due to cultured drug sensitivity and its high ocular penetration, with good results and a final right eye best-corrected visual acuity of 6/5. Nocardia farcinica keratitis should be considered in the differential diagnosis of contact lens-related keratitis. We report the first case occurring in association with extended wear soft contact lenses. Nocardia species can mimic fungal and acanthamoeba keratitis. Treatment with oral co-trimoxazole has not been previously reported. This case demonstrates the role of co-trimoxazole in treating Nocardia farcinica keratitis based on cultured drug sensitivities.

LInezolid for the Treatment of Nocardia spp. Infections

Objective:

To review the available evidence regarding the use of linezolid for the treatment of Nocardia spp. infections.

Data Sources:

Data were identified through a search of MEDLINE (1966-May 2007), American Search Premier (1975-May 2007), International Pharmaceutical Abstracts (1960-2007), Science Citation Index Expanded (1996-2007), and Cochrane Databases (publications archived until May 2007) using the terms linezolid and Nocardia.

Study Selection and Data Extraction:

Prospective and retrospective studies, case reports, case series, and in vitro studies were eligible for inclusion if they used linezolid for nocardiosis regardless of site of infection and outcome.

Data Synthesis:

We identified 11 published cases of linezolid use for Nocardia spp. infections. The predominant species isolated were N. asteroides (n=4; 36%) and N. farcinica (n= 3; 27%). Nocardiosis with central nervous system involvement (n= 7; 64%) or disseminated disease (n= 4; 36%) were most common. The main reason for discontinuation of previous antimicrobials was most often related to adverse effects (n= 5; 45%), followed by clinical failure (n = 3; 27%). Linezolid was associated with cure or improvement in all cases (n =11; 100%). However, the majority of patients developed serious complications that may have led to premature discontinuation of therapy with linezolid, including myelosuppression (n = 5; 45%) or possible/confirmed peripheral neuropathy (n = 2; 18%).

Conclusions:

The limited published data suggest that linezolid appears to be an effective alternative to trimethoprim/sulfamethoxazole for the treatment of nocardiosis. Unfortunately, the high cost and potentially serious long-term toxicities of linezolid appear to limit its use and relegate it to salvage therapy alone or in combination with other antimicrobials.

Different faces of Nocardia infection in renal transplant recipients

AIM

Nocardia infections are an uncommon but important cause of morbidity and mortality in renal transplant recipients. The present study was carried out to determine the spectrum of Nocardia infections in a renal transplant centre in Australia.

METHODS

A retrospective chart analysis of all renal transplants performed from 2008 to 2014 was conducted to identify cases of culture proven Nocardia infection. The clinical course for each patient with nocardiosis was examined.

RESULTS

Four of the 543 renal transplants patients developed Nocardia infection within 2 to 13 months post-transplant. All patients were judged at high immunological risk of rejection pre-transplant and had received multiple sessions of plasmaphoeresis and intravenous immunoglobulin before the onset of the infection. Two patients presented with pulmonary nocardiosis and two with cerebral abscesses. One case of pulmonary nocardiosis was complicated by pulmonary aspergillosis and the other by cytomegalovirus pneumonia. All four patients improved with combination antibiotic therapy guided by drug susceptibility testing. At the time of Nocardia infection all four patients were receiving primary prophylaxis with trimethoprim/sulphamethoxazole (TMP/SMX) 160/800 mg, twice weekly.

CONCLUSION

Plasmaphoeresis may be risk factor for Nocardia infection and need further study. Nocardia infection may coexist with other opportunistic infections. Identification of the Nocardia species and drug susceptibility testing is essential in guiding the effective management of patients with Nocardia. Intermittent TMP-SMX (one double strength tablet, twice a week) appears insufficient to prevent Nocardia infection in renal transplant recipients.

Unusual presentation of disseminated Nocardia abscessus infection in a patient with AIDS

A 40-year-old man with AIDS presented with symptoms of a chronic cough, subacute headache, generalised weakness with falls, urinary and faecal incontinence, and acute onset subcutaneous nodules. A chest CT scan showed multiple cavitary and nodular pulmonary infiltrates. MRI of his brain and spinal cord revealed innumerable ring-enhancing lesions. Pathological examination of the purulent material obtained from his subcutaneous lesions, as well as transbronchial tissue specimens obtained by biopsy, revealed beaded and branching Gram-positive rods, subsequently identified by 16S RNA sequencing to be Nocardia abscessus species. We observed an excellent therapeutic response to a combination antimicrobial therapy with resolution of the subcutaneous, pulmonary and central nervous system (CNS) lesions. Infections caused by N. abscessus are rare and typically occur in immunocompromised patients. In this article, we will review the presentation, diagnosis and treatment of N. abscessus infection.

Pulmonary nocardiosis in Chronic Obstructive Pulmonary Disease: A new clinical challenge

Pulmonary nocardiosis (PN) is a rare but severe disease caused by Nocardia spp. Despite the traditional description as opportunistic infection, case reports and case series of pulmonary nocardiosis have recently been reported in immunocompetent patients too, in particular among people with chronic pulmonary diseases such as advanced Chronic Obstructive Pulmonary Disease (COPD). PN is characterized by non-specific symptoms and radiological findings; bacteriological culture can be difficult. For the reasons above, diagnosis of PN is challenging, sometimes resulting in a misdiagnosis of tuberculosis. We report an interesting case of PN in a 75-year-old male with COPD. He complained a 3-months history of fatigue, evening rise in body temperature, night sweats, unexplained weight loss of 5 kg, worsening dyspnea, cough and mucopurulent sputum. The chest X-ray showed multiple nodules with cavitations bilaterally in the apical and subclavian regions. Nocardia cyriacigeorgica with 100% identity was identified in three sputum samples. Since the patient has never undergone a systemic and/or inhaled steroid therapy, and has no respiratory failure and comorbidities entailing immunodepression, it is conceivable that, in this immunocompetent patient, the COPD could represent an isolated risk factor for PN. Risk factors, clinical presentations, radiographic findings, differential diagnosis and review of the literature of PN cases in COPD, pointing out the similarities and differences, are also described.

Genetic diversity and antimicrobial susceptibility of Nocardia species among patients with nocardiosis

The aim of this multicenter study was to determine the genetic diversity and antibiotic susceptibility of clinically isolated Nocardia species. One hundred twenty-seven patients with nocardiosis were randomly selected from 5 provinces of Iran. Molecular diagnosis of Nocardia species was performed using multilocus sequence analysis of gyrase B of the β subunit of DNA topoisomerase (gyrB), and 16S rRNA and subunit A of SecA preproteintranslocase (secA1). Antimicrobial susceptibility testing was performed following the Clinical and Laboratory Standards Institute recommendations. Thirty-five N. cyriacigeorgica, 30 N. asteroides, 26 N. farcinica, 12 N. otitidiscaviarum, and 10 N. abscessus cultures were studied. All isolates were susceptible to linezolid. All isolates of N. cyriacigeorgica, N. asteroides, N. abscessus, and N. otitidiscaviarum were susceptible to trimethoprim-sulfamethoxazole, while 8% of N. farcinica isolates were resistant to this drug. All N. otitidiscaviarum isolates were highly resistant to imipenem, but N. cyriacigeorgica, N. asteroides, N. farcinica, and N. abscessus were only moderate resistant. The susceptibility patterns vary with different species of Nocardia. Resistance to trimethoprim-sulfamethoxazole in Iran is low and this drug should be first line therapy, unless drug susceptibility testing shows resistance. Linezolid also covers Nocardia well and could be a second line agent.

Pulmonary Nocardiosis in the Immunocompetent Host: Case Series

Pulmonary nocardiosis is commonly recognized as an opportunistic infection in patients with predisposing immunosuppressive conditions. However, reports of pulmonary nocardiosis in the immunocompetent host are rare. Here, we report a case series of four patients with pulmonary nocardiosis without a predisposing condition.

Nocardia prosthetic knee infection successfully treated by one-stage exchange: case report and review

A 64-year-old man with a history of sarcoidosis on corticosteroids and azathioprine was admitted to our hospital with complaints of worsening left knee pain and swelling for the past 3 weeks. His past medical history is also significant for severe osteoarthritis requiring a cemented total left knee arthroplasty 1 year ago. Diagnostic investigation during his hospital admission eventually led to the diagnosis of Nocardia nova knee prosthetic joint infection in the setting of a disseminated nocardiosis. He was successful treated by one-stage complete hardware exchange in conjunction with an adapted antibiotic therapy regimen (meropenem and doxycycline followed by ceftriaxone and doxycycline). Two years later, his recovery was deemed excellent.

Nocardia infections among immunomodulated inflammatory bowel disease patients: A review

Human nocardiosis, caused by Nocardia spp., an ubiquitous soil-borne bacteria, is a rare granulomatous disease close related to immune dysfunctions. Clinically can occur as an acute life-threatening disease, with lung, brain and skin being commonly affected. The infection was classically diagnosed in HIV infected persons, organ transplanted recipients and long term corticosteroid treated patients. Currently the widespread use of immunomodulators and immunossupressors in the treatment of inflammatory diseases changed this scenario. Our purpose is to review all published cases of nocardiosis in immunomodulated patients due to inflammatory diseases and describe clinical and laboratory findings. We reviewed the literature concerning human cases of nocardiosis published between 1980 and 2014 in peer reviewed journals. Eleven cases of nocardiosis associated with anti-tumor necrosis factor (TNF) prescription (9 related with infliximab and 2 with adalimumab) were identified; 7 patients had inflammatory bowel disease (IBD), 4 had rheumatological conditions; nocardia infection presented as cutaneous involvement in 3 patients, lung disease in 4 patients, hepatic in one and disseminated disease in 3 patients. From the 10 cases described in IBD patients 7 were associated with anti-TNF and 3 with steroids and azathioprine. In conclusion, nocardiosis requires high levels of clinical suspicion and experience of laboratory staff, in order to establish a timely diagnosis and by doing so avoid worst outcomes. Treatment for long periods tailored by the susceptibility of the isolated species whenever possible is essential. The safety of restarting immunomodulators or anti-TNF after the disease or the value of prophylaxis with cotrimoxazole is still debated.

MOLECULAR IDENTIFICATION AND ANTIMICROBIAL RESISTANCE PATTERN OF SEVEN CLINICAL ISOLATES OF Nocardia spp. IN BRAZIL

Nocardia is a ubiquitous microorganism related to pyogranulomatous infection, which is difficult to treat in humans and animals. The occurrence of the disease is on the rise in many countries due to an increase in immunosuppressive diseases and treatments. This report of cases from Brazil presents the genotypic characterization and the antimicrobial susceptibility pattern using the disk-diffusion method and inhibitory minimal concentration with E-test® strips. In summary, this report focuses on infections in young adult men, of which three cases were cutaneous, two pulmonary, one neurological and one systemic. The pulmonary, neurological and systemic cases were attributed to immunosuppressive diseases or treatments. Sequencing analysis of the 16S rRNA segments (1491 bp) identified four isolates of Nocardia farcinica, two isolates of Nocardia nova and one isolate of Nocardia asiatica. N. farcinica was involved in two cutaneous, one systemic and other pulmonary cases; N. nova was involved in one neurological and one pulmonary case; and Nocardia asiatica in one cutaneous case. The disk-diffusion antimicrobial susceptibility test showed that the most effective antimicrobials were amikacin (100%), amoxicillin/clavulanate (100%), cephalexin (100%) and ceftiofur (100%), while isolates had presented most resistance to gentamicin (43%), sulfamethoxazole/trimethoprim (43%) and ampicillin (29%). However, on the inhibitory minimal concentration test (MIC test), only one of the four isolates of Nocardia farcinica was resistant to sulfamethoxazole/trimethoprim.

Resistance gene pool to co-trimoxazole in non-susceptible Nocardia strains

The soil-borne pathogen Nocardia sp. causes severe cutaneous, pulmonary, and central nervous system infections. Against them, co-trimoxazole (SXT) constitutes the mainstay of antimicrobial therapy. However, some Nocardia strains show resistance to SXT, but the underlying genetic basis is unknown. We investigated the presence of genetic resistance determinants and class 1–3 integrons in 76 SXT-resistant Nocardia strains by PCR and sequencing. By E test, these clinical strains showed SXT minimum inhibitory concentrations of ≥32:608 mg/L (ratio of 1:19 for trimethoprim: sulfamethoxazole). They belonged to 12 species, being the main representatives Nocardia farcinica (32%), followed by N. flavorosea (6.5%), N. nova (11.8%), N. carnea (10.5%), N. transvalensis (10.5%), and Nocardia sp. (6.5%). The prevalence of resistance genes in the SXT-resistant strains was as follows: sul1 and sul2 93.4 and 78.9%, respectively, dfrA(S1) 14.7%, blaTEM-1 and blaZ 2.6 and 2.6%, respectively, VIM-2 1.3%, aph(3′)-IIIa 40.8%, ermA, ermB, mefA, and msrD 2.6, 77.6, 14.4, and 5.2%, respectively, and tet(O), tet(M), and tet(L) 48.6, 25.0, and 3.9%, respectively. Detected amino acid changes in GyrA were not related to fluoroquinolone resistance, but probably linked to species polymorphism. Class 1 and 3 integrons were found in 93.42 and 56.57% strains, respectively. Class 2 integrons and sul3 genes were not detected. Other mechanisms, different than dfrA(S1), dfrD, dfrF, dfrG, and dfrK, could explain the strong trimethoprim resistance shown by the other 64 strains. For first time, resistance determinants commonly found in clinically important bacteria were detected in Nocardia sp. sul1, sul2, erm(B), and tet(O) were the most prevalent in the SXT-resistant strains. The similarity in their resistome could be due to a common genetic platform, in which these determinants are co-transferred.

Identification of Nocardia species using matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry

BACKGROUND

The MALDI (matrix-assisted laser desorption/ionization) Biotyper system for bacterial identification has already been utilized in clinical microbiology laboratories as a successful clinical application of protoemics. However, in cases of Nocardia, mass spectra suitable for MALDI Biotyper identification are often not obtained if such specimens are processed like general bacteria. This problem is related to the insufficiencies in bacterial spectrum databases that preclude accurate specimen identification. Here, we developed a bacterial processing method to improve mass spectra from specimens of the genus Nocardia. In addition, with the new processing method, we constructed a novel in-house bacterial database that combines a commercial database and mass spectra of Nocardia strains from the Department of Clinical Laboratory at Chiba University Hospital (DCLC) and the Medical Mycology Research Center at Chiba University (MMRC).

RESULTS

The newly developed method (Nocardia Extraction Method at DCLC [NECLC]) based on ethanol-formic acid extraction (EFAE) improved mass spectra obtained from Nocardia specimens. The Nocardia in-house database at Chiba University Hospital (NDCUH) was then successfully validated. In brief, prior to introduction of the NECLC and NDCUH, 10 of 64 (15.6%) clinical isolates were identified at the species level and 16 isolates (25.0%) could only be identified at the genus level. In contrast, after the introduction, 58 isolates (90.6%) were identified at the species level and 6 isolates (9.4%) were identified at the genus level.

CONCLUSIONS

The results of this study suggest that MALDI-TOF (time-of-flight) Biotyper system can identify Nocardia accurately in a short time in combination with a simple processing method and an in-house database.

Nocardiosis in 132 patients with cancer: microbiological and clinical analyses

OBJECTIVES

To correlate the microbiological and clinical features of infections caused by Nocardia species.

METHODS

We determined the species and drug susceptibility of 138 Nocardia strains isolated from 132 patients at the University of Texas M. D. Anderson Cancer Center (Houston, TX) from 2002 through 2012 and analyzed the clinical features.

RESULTS

The 132 patients included 82 men and 50 women with a mean age of 59.1 years. All except two had underlying cancer, and 47 (35.6%) also received a stem cell transplant. These patients experienced 136 episodes of Nocardia infection, including pulmonary infection, abscess of deep skin and soft tissue, bacteremia and dissemination, and brain abscess. The 138 Nocardia strains involved 27 species, of which 20 species have been described since 2000. Common species included Nocardia nova, Nocardia cyriacigeorgica, Nocardia farcinica, and Nocardia abscessus, together accounting for 59.4%. N nova caused most bacteremia cases, whereas N farcinica caused most of the skin and brain infections. Infections with a few recent species likely represented first confirmation or report of human infections. Antimicrobial susceptibility tests of 117 strains showed that they were all susceptible to trimethoprim-sulfamethoxazole and linezolid but variably susceptible to other drugs depending on species. Most patients who were treated for the infection showed improvement or resolution.

CONCLUSIONS

Diverse Nocardia species can cause secondary infections in patients with cancer. Timely species identification and antimicrobial susceptibility tests may guide treatment.

Antimicrobial susceptibility among clinical Nocardia species identified by multilocus sequence analysis

Antimicrobial susceptibility patterns of 112 clinical isolates, 28 type strains, and 9 reference strains of Nocardia were determined using the Sensititre Rapmyco microdilution panel (Thermo Fisher, Inc.). Isolates were identified by highly discriminatory multilocus sequence analysis and were chosen to represent the diversity of species recovered from clinical specimens in Ontario, Canada. Susceptibility to the most commonly used drug, trimethoprim-sulfamethoxazole, was observed in 97% of isolates. Linezolid and amikacin were also highly effective; 100% and 99% of all isolates demonstrated a susceptible phenotype. For the remaining antimicrobials, resistance was species specific with isolates of Nocardia otitidiscaviarum, N. brasiliensis, N. abscessus complex, N. nova complex, N. transvalensis complex, N. farcinica, and N. cyriacigeorgica displaying the traditional characteristic drug pattern types. In addition, the antimicrobial susceptibility profiles of a variety of rarely encountered species isolated from clinical specimens are reported for the first time and were categorized into four additional drug pattern types. Finally, MICs for the control strains N. nova ATCC BAA-2227, N. asteroides ATCC 19247(T), and N. farcinica ATCC 23826 were robustly determined to demonstrate method reproducibility and suitability of the commercial Sensititre Rapmyco panel for antimicrobial susceptibility testing of Nocardia spp. isolated from clinical specimens. The reported values will facilitate quality control and standardization among laboratories.

Soil-acquired cutaneous nocardiosis on the forearm of a healthy male contracted in a swamp in rural eastern Virginia

A 45-year-old man complained of pain and swelling on his right wrist after receiving a scratch while playing paintball in a swampy area of eastern Virginia. Two weeks later, he noticed a pimple-like lesion developing, which quickly grew in size and then ulcerated. Because of the severity of his condition, the patient was taken to the emergency room where surgical drainage of the abscess was carried out and the pus was sent for culture and sensitivity testing. Enlarged and tender lymph nodes were palpable going up the arm and surrounding the right axillary area. Three days following culture of pus from his lesion, colonies of Nocardia brasiliensis were isolated. He was successfully treated with an extended regimen of trimethoprim-sulfamethoxazole. Because of its low incidence, nocardiosis is usually not considered in the initial diagnosis. The rapidity with which his infection developed from a pimple-like lesion into an extensive ulcerated area, the involvement of his lymphatic system, the extended time needed to successfully treat his infection, and the potential for infection to rapidly disseminate, reinforces the necessity for laboratory identification and immediate treatment of severe pyogenic cutaneous lesions.

Nocardiosis of the central nervous system: experience from a general hospital and review of 84 cases from the literature

Central nervous system (CNS) nocardiosis is a rare disease entity caused by the filamentous bacteria Nocardia species. We present a case series of 5 patients from our hospital and a review of the cases of CNS nocardiosis reported in the literature from January 2000 to December 2011. Our results indicate that CNS nocardiosis can occur in both immunocompromised and immunocompetent individuals and can be the result of prior pulmonary infection or can exist on its own. The most common predisposing factors are corticosteroid use (54% of patients) and organ transplantation (25%). Presentation of the disease is widely variable, and available diagnostic tests are far from perfect, often leading to delayed detection and initiation of treatment. The optimal therapeutic approach is still undetermined and depends on speciation, but lower mortality and relapse rates have been reported with a combination of targeted antimicrobial treatment including trimethoprim/sulfomethoxazole (TMP-SMX) for more than 6 months and neurosurgical intervention.

Nocardiosis in transplant recipients

Nocardiosis is a rare opportunistic infection caused by Nocardia spp., an aerobic actinomycete, that mainly affects patients with cell-mediated immunity defects, such as transplant recipients. Despite recent progress regarding Nocardia identification and changes in taxonomic assignment, many challenges remain for the diagnosis or management of nocardiosis. This opportunistic infection affects 0.04 to 3.5 % of patients with solid organ or hematopoietic stem cell transplantation, depending on the organ transplanted, cytomegalovirus (CMV) infection, corticosteroids dose and calcineurin inhibitors level. Nocardiosis diagnosis relies on appropriate clinical, radiological and microbiological workup that includes the sampling of an accessible involved site and molecular microbiology tools. In parallel, extensive clinical and radiological evaluations are mandatory, including brain imaging, even in the absence of neurological signs. In transplanted patients, differential diagnosis is challenging, with co-infections reported in 20 to 64 % of cases. As the antibiotic susceptibility pattern varies among species, the antimicrobial regimen before species identification should rely on the association of antibiotics active on all species of Nocardia. Bactericidal antibiotics are required in cases of severe or disseminated disease. Furthermore, in transplant recipients, combination therapy is difficult to manage because of cumulative toxicity and interactions with immunosuppressive agents. Because of a high recurrence rate, antibiotic therapy should be prescribed for 6 to 12 months.

Identification, typing, and phylogenetic relationships of the main clinical Nocardia species in spain according to their gyrB and rpoB genes

This study compares the identification, typing, and phylogenetic relationships of the most prevalent clinical Nocardia species in Spain, as determined via sequence analysis of their housekeeping genes gyrB and rpoB, with the results returned by the gold standard 16S rRNA method. gyrB and rpoB analyses identified Nocardia abscessus, N. cyriacigeorgica, N. farcinica, and the N. nova complex, species that together account for more than half of the human nocardiosis cases recorded in Spain. The individual discriminatory power of gyrB and rpoB with respect to intraspecies typing, calculated using the Hunter-Gaston discriminatory index (HGDI), was generally high (HGDI, 0.85 to 1), except for rpoB with respect to N. farcinica (HGDI, 0.71). Phylogenetically, different degrees of intra- and interspecies microheterogeneity were observed for gyrB and rpoB in a group of 119 clinical strains. A single 16S haplotype was obtained for each species, except for the N. nova complex (8 types), while gyrB and rpoB were more polymorphic: N. abscessus had 14 and 18 haplotypes, N. cyriacigeorgica had 17 and 12, N. farcinica had 11 and 5, and the N. nova complex had 26 and 29 haplotypes, respectively. A diversity gradient was therefore seen, with N. farcinica at the bottom followed by N. abscessus and N. cyriacigeorgica in the middle and N. nova complex at the top. The complexity of the N. nova complex is highlighted by its six variations in the GyrB (126)AAAPEH motif. gyrB sequencing (with or without rpoB sequencing) offers a simple means for identifying the most prevalent Nocardia species in Spanish medical laboratories and for determining the intraspecific diversity among their strains.

Cutaneous nocardiosis in two dogs receiving ciclosporin therapy for the management of canine atopic dermatitis

BACKGROUND

Ciclosporin is a calcineurin inhibitor that is currently registered for the treatment of canine atopic dermatitis. The most common adverse effects include mild, transient gastrointestinal disturbances. Single case reports of opportunistic infections due to Nocardia spp., Neospora spp. and papillomaviruses have also been reported.

HYPOTHESIS/OBJECTIVES

Clinicians should be aware of the potential risk of systemic immunosuppression and subsequent infection with Nocardia spp. in dogs receiving ciclosporin.

ANIMALS

Cutaneous nocardiosis in two dogs receiving ciclosporin therapy for management of canine atopic dermatitis.

METHODS

Histopathology, PCR for Nocardia spp. and computed tomography.

RESULTS

One dog developed disseminated nocardiosis due to Nocardia brasiliensis and a second dog developed localized cutaneous nocardiosis due to a novel Nocardia species subsequent to ciclosporin administration at the recommended dose rate for the management of canine atopic dermatitis. The second case was receiving a combination of ciclosporin and ketoconazole, and serum trough ciclosporin levels were elevated.

CONCLUSIONS AND CLINICAL IMPORTANCE

Clinicians should be aware of the potential risk of systemic immunosuppression and subsequent infection with Nocardia spp. in dogs receiving ciclosporin. Measurement of serum ciclosporin levels may be useful in identifying those individuals which are at risk of opportunistic infections.

First report of Nocardia asiatica olecranon bursitis in an immunocompetent traveler returning to Austria

Nocardia spp. are rarely isolated in extrapulmonary clinical specimens. We describe the first case of olecranon bursitis caused by Nocardia asiatica. The patient, a traveler returning from Thailand, was successfully treated with linezolid.

Molecular identification and susceptibility pattern of clinical Nocardia species: Emergence of Nocardia crassostreae as an agent of invasive nocardiosis

BACKGROUND

Nocardia species are rare, opportunistic organisms that cause disease in both immunocompetent and immunocompromised individuals.

OBJECTIVE

To investigate the clinical presentations of various Nocardia infections based on the 16S ribosomal RNA gene of the isolate, as well as related risk factors and susceptibility patterns to antimicrobial agents.

METHODS

Thirteen patients with a diagnosis of nocardiosis were included in the present study. Seven Nocardia species were identified by 16S ribosomal RNA. Susceptibility testing was performed using six antimicrobial agents.

RESULTS

Five patients were immunocompromised, and eight were immunocompetent with predisposing factors including cystic fibrosis, tuberculosis and ophthalmic infections. Nocardia caused pulmonary infections in eight patients (61.5%), invasive systemic infections in three patients (23%) and local (ophthalmic) infections in two patients (15.4%). In the patients with pulmonary disease, nocardiosis was caused by six species (Nocardia cyriacigeorgica, Nocardia otitidiscaviarum, Nocardia farcinica, Nocardia carnea, Nocardia testacea and Nocardia asiatica). The seventh species identified in the present study was Nocardia crassostreae.

DISCUSSION

N crassostreae is a multidrug-resistant organism that was reported to be an emerging human pathogen causing invasive nocardiosis in a patient with non-Hodgkin's lymphoma. N farcinica was isolated from blood in a patient with breast cancer. None of the Nocardia isolates were resistant to linezolid. One N otitidiscaviarum isolate was a multidrug-resistant organism. All patients in the present study were treated with the appropriate antibiotics and their condition resolved without further sequelae.

CONCLUSIONS

The present study is the first report on N crassostreae as a human pathogen. The detection of multidrug-resistant species necessitate molecular identification and susceptibility testing, and should be performed for all Nocardia infections. Nocardiosis manifests various clinical features depending on the Nocardia species and underlying conditions.

First Report of Nocardia asiatica Presenting as an Anterior Mediastinal Mass in a Patient with Myasthenia Gravis: A Case Report and Review of the Literature

The spectrum of infections with Nocardia spp. is heterogeneous. It has classically been associated with lung, brain, or skin involvement. We describe an unusual presentation of Nocardia asiatica (N. asiatica) in an Iraqi patient with myasthenia gravis suffering from a disseminated infection and presenting with an anterior mediastinal cystic mass. N. asiatica has only been three times described outside Japan and Thailand, and the rarity of this entity deserves this communication.

Nocardiosis: updates and clinical overview

Nocardia, a gram-positive bacillus with the microscopic appearance of branching hyphae, can produce considerable disease in the appropriate host. The taxonomy of Nocardia continues to evolve; more than 50 species have been described. Early recognition and effective therapy are imperative to achieve successful outcomes. Although nocardiosis typically occurs in patients with cell-mediated immunosuppressive conditions, infection may occasionally develop in immunocompetent patients as well. This review addresses the microbiology of Nocardia, risk factors for infection, clinical presentations, and management strategies.