Ocular nocardiosis: HSP65 gene sequencing for species identification of Nocardia spp

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 arthritidis scleritis: A case report

Purpose

This report describes a case and management of a 69-year-old female with infectious scleritis found to be caused by Nocardia arthritidis species.

Observations

Our patient presented with severe constant pain in the left eye (OS) following cataract surgery. She had a pertinent past medical history significant for renal transplantation (on oral tacrolimus, mycophenolate, and prednisone). Slit lamp examination OS (1 month after cataract surgery) demonstrated 3+ injection temporally accompanied by scleral thickening and multiloculated abscesses with purulent drainage from small conjunctival erosions. The abscesses were debrided and sent for gram stain and culture. The patient was treated with repeated subconjunctival injections of antibiotics and an antifungal; topical amphotericin, vancomycin, and amikacin; and oral trimethoprim-sulfamethoxazole (double strength). Two separate gram stains with cultures confirmed the diagnosis and species identification. The patient responded well to repeat subconjunctival injections early on in addition to the prescribed regimen, remaining free of disease at the last follow-up (12 months following presentation).

Conclusions and Importance

This unique case demonstrates infectious scleritis caused by an uncommon Nocardia species (N. arthritidis) that was successfully treated with similar strategies used for other reported Nocardia species. As Nocardia scleritis can lead to adverse outcomes if not treated promptly and properly, it should be considered on the differential diagnoses in an immunocompromised patient who presents with acute ocular symptoms after any recent ocular surgery.

Updated Review on Nocardia Species: 2006-2021

This review serves as an update to the previous Nocardia review by Brown-Elliott et al. published in 2006 (B. A. Brown-Elliott, J. M. Brown, P. S. Conville, and R. J. Wallace. Jr., Clin Microbiol Rev 19:259-282, 2006, https://doi.org/10.1128/CMR.19.2.259-282.2006). Included is a discussion on the taxonomic expansion of the genus, current identification methods, and the impact of new technology (including matrix-assisted laser desorption ionization-time of flight [MALDI-TOF] and whole genome sequencing) on diagnosis and treatment. Clinical manifestations, the epidemiology, and geographic distribution are briefly discussed. An additional section on actinomycotic mycetoma is added to address this often-neglected disease.

Multidrug-resistant novel Nocardia neocaledoniensis brain abscess in sarcoidosis

Central nervous system nocardiosis is a rare, life-threatening infection seen commonly in immunocompromised individuals. Nocardia neocaledoniensis is a novel species seldom causing infections in humans. We describe a patient of sarcoidosis on immunosuppression, who presented with altered sensorium due to a frontal lobe abscess secondary to N. neocaledoniensis infection. Despite appropriate and adequate antibiotic coverage, and timely surgical intervention, the patient succumbed to her illness on day 6 of hospitalisation. This case warrants the consideration of novel infections in patients on immunosuppression and the need for aggressive management.

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.

First case of fatal bacteremia due to Nocardia neocaledoniensis

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First case of bacteremia due to N.neocaledoniensis in an immunocompromised patient.

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Mass spectrometry is a discriminant technique to identify rapidly N.neocaledoniensis.

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Incubating culture media for a longer time helps to obtain definitive diagnosis and adapt antibiotics.

Nocardia neocaledoniensis is an uncommon cause of human-infections. Few cases are reported in the literature. We describe the first case of bacteremia caused by N. neocaledoniensis. This article underlines the importance of mass spectrometry for easy and rapid identification of such bacterium.

Characteristics of nocardiosis patients with different immune status from a Chinese tertiary general hospital during 8-year period: A STROBE-compliment observational study

Nocardia is an opportunistic pathogen from environment, which is generally thought to infect immunosuppressed patients (ISPs), but recent studies showed it could also cause infections in immunocompetent patients (ICPs).The aim of this study was to compare the clinical characteristics, patients' outcome, Nocardia species' identification, and antibiotic susceptibility profiles of nocardiosis between ICPs and ISPs.The detailed clinical data were collected from all the nonrepetitive nocardiosis patients during 2011 and 2018, from a tertiary general hospital in Beijing, China. Then each Nocardia isolate was identified to species level by DNA sequencing. The antibiotic susceptibility testing was performed by E test method, and interpreted following CLSI M24 document. The clinical and microbiological characteristics between ICPs and ISPs were compared statistically.A total of 23 nonrepetitive nocardiosis patients with detailed clinical data were enrolled in this study. Among them, 9 were ICPs and 14 were ISPs. All the skin and soft tissue infections occurred in ICPs (33.3% vs 0%, P < .05). Bronchiectasis occurred more frequently in ICPs (44.4% vs 21.4%), whereas chronic kidney diseases and coinfection with aspergillosis occurred more frequently in ISPs (35.7% vs 0%, 35.7% vs 0%, respectively), although they did not reach the statistical significance. There were no significant differences in other clinical characteristics, Nocardia species' identification, and antibiotic susceptibility between ISPs and ICPs (P > .05).Nocardiosis could occur in both ISPs and ICPs. Skin and soft tissue infection and bronchiectasis occurred more frequently in ICPs. Chronic kidney diseases and co-infection with aspergillosis occurred more frequently in ISPs. These characteristics should be noticed by physicians in diagnosis of nocardiosis.

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.

Nocardiosis from 1888 to 2017

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.

Accurate Identification of Common Pathogenic Nocardia Species: Evaluation of a Multilocus Sequence Analysis Platform and Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry

Species identification of Nocardia is not straightforward due to rapidly evolving taxonomy, insufficient discriminatory power of conventional phenotypic methods and also of single gene locus analysis including 16S rRNA gene sequencing. Here we evaluated the ability of a 5-locus (16S rRNA, gyrB, secA1, hsp65 and rpoB) multilocus sequence analysis (MLSA) approach as well as that of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) in comparison with sequencing of the 5'-end 606 bp partial 16S rRNA gene to provide identification of 25 clinical isolates of Nocardia. The 5'-end 606 bp 16S rRNA gene sequencing successfully assigned 24 of 25 (96%) clinical isolates to species level, namely Nocardia cyriacigeorgica (n = 12, 48%), N. farcinica (n = 9, 36%), N. abscessus (n = 2, 8%) and N. otitidiscaviarum (n = 1, 4%). MLSA showed concordance with 16S rRNA gene sequencing results for the same 24 isolates. However, MLSA was able to identify the remaining isolate as N. wallacei, and clustered N. cyriacigeorgica into three subgroups. None of the clinical isolates were correctly identified to the species level by MALDI-TOF MS analysis using the manufacturer-provided database. A small "in-house" spectral database was established incorporating spectra of five clinical isolates representing the five species identified in this study. After complementation with the "in-house" database, of the remaining 20 isolates, 19 (95%) were correctly identified to species level (score ≥ 2.00) and one (an N. abscessus strain) to genus level (score ≥ 1.70 and < 2.00). In summary, MLSA showed superior discriminatory power compared with the 5'-end 606 bp partial 16S rRNA gene sequencing for species identification of Nocardia. MALDI-TOF MS can provide rapid and accurate identification but is reliant on a robust mass spectra database.

Sternal Osteomyelitis Caused by Gordonia bronchialis after Open-Heart Surgery

We report the case of a deep sternal wound infection with sternal osteomyelitis caused by Gordonia bronchialis after open-heart surgery. The isolate was identified as a G. bronchialis by 16S rRNA and hsp65 gene sequencing, having initially been misidentified as a Rhodococcus by a commercial phenotypic identification system.

Molecular identification of nocardia isolates from clinical samples and an overview of human nocardiosis in Brazil

BACKGROUND

Nocardia sp. causes a variety of clinical presentations. The incidence of nocardiosis varies geographically according to several factors, such as the prevalence of HIV infections, transplants, neoplastic and rheumatic diseases, as well as climate, socio-economic conditions and laboratory procedures for Nocardia detection and identification. In Brazil the paucity of clinical reports of Nocardia infections suggests that this genus may be underestimated as a cause of human diseases and/or either neglected or misidentified in laboratory specimens. Accurate identification of Nocardia species has become increasingly important for clinical and epidemiological investigations. In this study, seven clinical Nocardia isolates were identified by multilocus sequence analysis (MLSA) and their antimicrobial susceptibility was also determined. Most Nocardia isolates were associated to pulmonary disease.

METHODOLOGY/PRINCIPAL FINDINGS

The majority of Brazilian human isolates in cases reported in literature were identified as Nocardia sp. Molecular characterization was used for species identification of Nocardia nova, Nocardia cyriacigeorgica, Nocardia asiatica and Nocardia exalbida/gamkensis. Data indicated that molecular analysis provided a different Nocardia speciation than the initial biochemical identification for most Brazilian isolates. All Nocardia isolates showed susceptibility to trimethoprim-sulfamethoxazole, the antimicrobial of choice in the treatment nocardiosis. N. nova isolated from different clinical specimens from one patient showed identical antimicrobial susceptibility patterns and two distinct clones.

CONCLUSIONS/SIGNIFICANCE

Although Brazil is the world's fifth-largest country in terms of land mass and population, pulmonary, extrapulmonary and systemic forms of nocardiosis were reported in only 6 of the 26 Brazilian states from 1970 to 2013. A least 33.8% of these 46 cases of nocardiosis proved fatal. Interestingly, coinfection by two clones may occur in patients presenting nocardiosis. Nocardia infection may be more common throughout the Brazilian territory and in other developing tropical countries than is currently recognized and MLSA should be used more extensively as an effective method for Nocardia identification.

The first Korean case of disseminated mycetoma caused by Nocardia pseudobrasiliensis in a patient on long-term corticosteroid therapy for the treatment of microscopic polyangiitis

Nocardia pseudobrasiliensis is predominantly associated with invasive infections in immunocompromised patients. We report a case of disseminated mycetoma caused by N. pseudobrasiliensis in a 57-yr-old woman with microscopic polyangiitis, who was treated for 3 months with corticosteroids. The same organism was isolated from mycetoma cultures on the patient's scalp, right arm, and right leg. The phenotypic characteristics of the isolate were consistent with both Nocardia brasiliensis and N. pseudobrasiliensis, i.e., catalase and urease positivity, hydrolysis of esculin, gelatin, casein, hypoxanthine, and tyrosine, but no hydrolysis of xanthine. The isolate was identified as N. pseudobrasiliensis based on 16S rRNA and hsp65 gene sequencing. The patient was treated for 5 days with intravenous ampicillin/sulbactam, at which time both the mycetomas and fever had subsided and discharged on amoxicillin/clavulanate. This case highlights a very rare presentation of mainly cutaneous mycetoma caused by N. pseudobrasiliensis. This is the first reported case of N. pseudobrasiliensis infection in Korea.

Nocardia neocaledoniensis [corrected] as a cause of skin and soft tissue infection

Nocardia neocaledoniensis was introduced as a new environmental species of Nocardia in 2004. We present the first case of human skin and soft tissue infection caused by this species in a patient with rheumatoid arthritis receiving prednisone and methotrexate therapy.

Nocardiosis: updated clinical review and experience at a tertiary center

Nocardiosis is a rare opportunistic disease that affects mainly patients with deficient cell-mediated immunity, such as those with acquired immunodeficiency syndrome (AIDS) or transplant recipients. Pulmonary disease is the most common presentation in immunosuppressed patients and approximately one-third have a disseminated disease. Primary cutaneous nocardiosis is more frequently observed in immunocompetent patients with direct inoculation of the organism through professional exposure. The diagnosis can be challenging, as signs and symptoms are not specific and a high index of clinical of suspicion is necessary. Although gram stain, modified acid-fast stain, and cultures remain as the standard diagnostic tools, novel molecular techniques have changed the taxonomy of these organisms and, in some instances, have facilitated their identification. The disease has a marked tendency to recur and a high morbidity and mortality rate in immunosuppressed patients. Treatment is usually prolonged and an associated antibiotic treatment is preferred for severe disease. Although sulfonamides in combination with other antibiotics are still the treatment of choice, other associations such as imipenem plus amikacin are preferred in some centers. Linezolid is a useful alternative therapeutic agent due to its oral availability and activity against most of the isolates studied. Twenty-eight cases of nocardiosis were diagnosed at our center between January 1989 and April 2009. We report the epidemiologic characteristics of Nocardia spp. observed in our institution and discuss the risk factors, clinical features, diagnosis, and management of the disease.

Nocardia keratitis

PURPOSE OF REVIEW

Nocardia keratitis is a rarity in most parts of the world. If the diagnosis is timely, and appropriate treatment started, then the visual outcome is good. The purpose of this review is to discuss the recently published literature in relation to the epidemiology, cause, diagnosis, and therapy of Nocardia keratitis.

RECENT FINDINGS

The incidence of Nocardia keratitis, although not well established, appears to be increasing with new species identified with newer molecular methods. The different species causing keratitis are Nocardia. arthritidis, N. neocaledoniensis, N. asiatica, N. asteroids type IV, N. brasiliensis, N. pseudobrasiliensis, N. cyriacigeorgica, N. farcinica, N. otitidiscaviarum, and N. transvalensis. Current therapies with fortified amikacin and newer fluoroquinolones are effective, provided the diagnosis has been made in good time. Ongoing research toward rapid diagnosis using various molecular techniques seems to be promising. Diagnostic microbiology laboratories need to be familiar with these organisms especially in endemic areas, and it is important for the clinician to notify the suspicion of such cases.

SUMMARY

The current recommended treatment is amikacin, and with appropriate therapy, Nocardia keratitis resolves with scarring, with or without vascularization, resulting in good visual outcome.