In vitro and in vivo activities of antimicrobials against Nocardia brasiliensis

Development and validation of a resazurin assay for in vitro susceptibility testing of Actinomadura madurae: a common causative agent of actinomycetoma

OBJECTIVES

Actinomycetoma is a chronic granulomatous disease affecting skin, subcutaneous tissue, fascia, muscle and bones. With increasing resistance against commonly used treatment regimens, susceptibility testing is urgently needed.

METHODS

We developed an in vitro susceptibility assay for Actinomadura madurae, one of the common causative agents of actinomycetoma, employing resazurin for endpoint reading. Using this assay, reproducible MICs were determined for the most commonly used antibacterial agents for actinomycetoma treatment. The tested antibacterial agents included trimethoprim/sulfamethoxazole, amikacin, streptomycin, amoxicillin, ceftriaxone, gentamicin, ciprofloxacin, doxycycline, imipenem, linezolid, penicillin G and rifampicin.

RESULTS

Following the clinical breakpoints as stated by CLSI, 100% of the tested strains were susceptible to trimethoprim/sulfamethoxazole (MIC 0.03/0.59-1/19 mg/L), amikacin (MIC 0.0078-0.25 mg/L), doxycycline (MIC <0.25-1 mg/L) and linezolid (MIC <0.25-2 mg/L), 90% to ciprofloxacin (MIC <0.25-2 mg/L), 80% to ceftriaxone (MIC <0.5 to >64 mg/L) and imipenem (MIC <0.25-32 mg/L) and only 20% to amoxicillin (MIC <0.5 to >64 mg/L) and rifampicin (MIC 0.5 to >32 mg/L).

CONCLUSIONS

Determinations of MICs by visual readings of colour changes versus spectrophotometric readings were comparable. This convenient visual reading has the advantage of feasible implementation in endemic settings.

Clinical Characteristics and Treatment Outcome of Central Nervous System Nocardiosis: A Systematic Review of Reported Cases

BACKGROUND

The clinical spectrum of systemic nocardiosis encompasses pulmonary and disseminated disease. Central nervous system (CNS) involvement is an important feature of disseminated disease with significant mortality and high relapse rate, especially in those with suppressed cell-mediated immunity. This systematic review aimed to evaluate the epidemiology, clinical features, diagnosis, therapeutic interventions, and outcome in patients with CNS nocardiosis.

METHODS

A literature search was performed in major databases (PubMed, Google Scholar, and Scopus) by using distinct keywords: "CNS disease," "Nocardia," "meningitis," "brain abscess," "disseminated disease," and "Cotrimoxazole." We included all patients ≥18 years with CNS nocardiosis reported between January 2000 and December 2020.

RESULTS

A total of 129 papers were included in the final analysis. The mean age of patients was 55 ± 16 years, and the majority were male (70.8%). Nocardia farcinica was the commonest species (39.6%), followed by Nocardia nova (5.9%). Thirty-four percent of the patients were found to be immunocompetent. Corticosteroid use was the most common predisposing factor (55.8%). Among neuroimaging findings, brain abscess was most common (86.9%), followed by leptomeningeal enhancement (12.1%). The overall case-fatality rate in CNS disease was 22.8%. On multivariate analysis, patients who underwent surgery (OR 2.4, 95% CI 0.99-4.11, p value 0.046) had better survival than those treated with antimicrobial therapy alone. Immunodeficient state (OR 0.32, 95% CI 0.15-0.90, p value 0.019) was independently associated with poor outcome.

CONCLUSION

CNS nocardiosis carries significant mortality, especially in immunodeficient patients. We advocate the use of surgery combined with antimicrobials to improve clinical outcome.

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

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

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

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

Clinical characteristics and treatment of actinomycetoma in northeast Mexico: A case series

Background

Mycetoma is a neglected tropical disease characterized by nodules, scars, abscesses, and fistulae that drain serous or purulent material containing the etiological agent. Mycetoma may be caused by true fungi (eumycetoma) or filamentous aerobic bacteria (actinomycetoma). Mycetoma is more frequent in the so-called mycetoma belt (latitude 15° south and 30° north around the Tropic of Cancer), especially in Sudan, Nigeria, Somalia, India, Mexico, and Venezuela. The introduction of new antibiotics with fewer side effects, broader susceptibility profiles, and different administration routes has made information on actinomycetoma treatment and outcomes necessary. The objective of this report was to provide an update on clinical, therapeutic, and outcome data for patients with actinomycetoma attending a reference center in northeast Mexico.

Methodology/principal findings

This was a retrospective, cross-sectional, descriptive study of 31 patients (male to female ratio 3.4:1) diagnosed with actinomycetoma by direct grain examination, histopathology, culture, or serology from January 2009 to September 2018. Most lesions were caused by Nocardia brasiliensis (83.9%) followed by Actinomadura madurae (12.9%) and Actinomadura pelletieri (3.2%). About 50% of patients had bone involvement, and the right leg was the most commonly affected region in 38.7% of cases. Farmers/agriculture workers were most commonly affected, representing 41.9% of patients. The most commonly used treatment regimen was the Welsh regimen (35.5% of cases), a combination of trimethoprim/sulfamethoxazole (TMP/SMX) plus amikacin, which had a 90% cure rate, followed by TMP/SMX plus amoxicillin/clavulanic acid in 19.4% of cases with a cure rate of 100%. In our setting, 28 (90.3%) patients were completely cured and three (9.7%) were lost to follow-up. Four patients required multiple antibiotic regimens due to recurrences and adverse effects.

Conclusions/significance

In our sample, actinomycetoma was predominantly caused by N. brasiliensis. Most cases responded well to therapy with a combination of TMP/SMX with amikacin or TMP/SMX and amoxicillin/clavulanic acid. Four patients required multiple antibiotics and intrahospital care.

Mycetoma is a chronic skin disease that can invade bone or underlying organs. Inadequate treatment may lead to long-lasting disability. Information about treatment is scarce. We report the outcomes of 31 patients with a diagnosis of bacterial actinomycetoma attending a tertiary care hospital in northeast Mexico. Most cases were treated with a combination of antibiotics including TMP/SMX plus amikacin or TMP/SMX plus amoxicillin/clavulanic acid. Cure was achieved in 90% of patients and only one required surgery.

Pedal Fungal Mass in the Midwest

Mycetoma cases are predominantly found in tropical regions and are a rare finding in the United States. These masses that are fungal or bacterial in origin can result in significant destruction of soft tissue and bone. We present a case of a patient who emigrated from Mexico to Indianapolis. He presented with a soft-tissue mass that was excised and ultimately found to be a eumycetoma of the hallux of his left foot. Successful treatment included surgical resection in combination with postoperative terbinafine, which was pulse dosed to decrease its impact on hepatic function.

Review of 21 cases of mycetoma from 1991 to 2014 in Rio de Janeiro, Brazil

Mycetoma is caused by the subcutaneous inoculation of filamentous fungi or aerobic filamentous bacteria that form grains in the tissue. The purpose of this study is to describe the epidemiologic, clinic, laboratory, and therapeutic characteristics of patients with mycetoma at the Oswaldo Cruz Foundation in Rio de Janeiro, Brazil, between 1991 and 2014. Twenty-one cases of mycetoma were included in the study. There was a predominance of male patients (1.3:1) and the average patient age was 46 years. The majority of the cases were from the Southeast region of Brazil and the feet were the most affected anatomical region (80.95%). Eumycetoma prevailed over actinomycetoma (61.9% and 38.1% respectively). Eumycetoma patients had positive cultures in 8 of 13 cases, with isolation of Scedosporium apiospermum species complex (n = 3), Madurella mycetomatis (n = 2) and Acremonium spp. (n = 1). Two cases presented sterile mycelium and five were negative. Six of 8 actinomycetoma cases had cultures that were identified as Nocardia spp. (n = 3), Nocardia brasiliensis (n = 2), and Nocardia asteroides (n = 1). Imaging tests were performed on all but one patients, and bone destruction was identified in 9 cases (42.68%). All eumycetoma cases were treated with itraconazole monotherapy or combined with fluconazole, terbinafine, or amphotericin B. Actinomycetoma cases were treated with sulfamethoxazole plus trimethoprim or combined with cycles of amikacin sulphate. Surgical procedures were performed in 9 (69.2%) eumycetoma and in 3 (37.5%) actinomycetoma cases, with one amputation case in each group. Clinical cure occurred in 11 cases (7 for eumycetoma and 4 for actinomycetoma), and recurrence was documented in 4 of 21 cases. No deaths were recorded during the study. Despite of the scarcity of mycetoma in our institution the cases presented reflect the wide clinical spectrum and difficulties to take care of this neglected disease.

Nocardiosis in the south of France over a 10-years period, 2004-2014

BACKGROUND

Nocardiosis is a rare disease with polymorphic presentations. The epidemiology and clinical presentation could change with the increasing number of immunocompromised patients.

METHODS

The medical records and microbiological data of patients affected by nocardiosis and treated at the university hospitals of Marseille between 2004 and 2014 were analyzed retrospectively.

RESULTS

The cases of 34 patients infected by Nocardia spp during this period were analyzed. The main underlying conditions were transplantation (n=15), malignancy (n=9), cystic fibrosis (n=4), and immune disease (n=3); no immunodeficiency condition was observed for three patients. No case of AIDS was observed. At diagnosis, 61.8% had received steroids for over 3 months. Four clinical presentations were identified, depending on the underlying condition: the disseminated form (50.0%) and the visceral isolated form (26.5%) in severely immunocompromised patients, the bronchial form (14.7%) in patients with chronic lung disease, and the cutaneous isolated form (8.8%) in immunocompetent patients. Nocardia farcinica was the main species identified (26.5%). Trimethoprim-sulfamethoxazole was prescribed in 68.0% of patients, and 38.0% underwent surgery. Mortality was 11.7%, and the patients who died had disseminated or visceral nocardiosis.

CONCLUSIONS

The clinical presentation and outcome of nocardiosis depend on the patient's initial immune status and underlying pulmonary condition. Severe forms were all iatrogenic, occurring after treatments altering the immune system.

Disseminated nocardiosis caused by Nocardia otitidiscaviarum in an immunocompetent host: A case report and literature review

The aim of the present study was to summarize the clinical characteristics of nocardiosis caused by Nocardia otitidiscaviarum in order to improve the knowledge of nocardiosis. A case of dissemination nocardiosis caused by N. otitidiscaviarum in an immunocompetent host is reported and the associated literature reviewed. Informed consent for publication of this case report was provided by the patient. The present patient was a young immunocompetent man suffering from disseminated nocardiosis induced by infection with N. otitidiscaviarum. Following a poor response to β-lactam antibiotic, a combination of sulfonamide with minocycline was administered, which successfully ameliorated the symptoms. Previous studies published in English were retrieved from PubMed with 'Nocardia otitidiscaviarum' used as the search keyword. A total of 23 articles were retrieved from the PubMed database, supporting the assertion that N. otitidiscaviarum is a rare Nocardia species. Among these 23 cases, there were 11 cases of lymphocutaneous (48%), 5 of pulmonary (22%), 2 of brain (9%) and 1 of pyothorax (4%) infection, and 4 cases of disseminated infections (17%). Analysis of the immune state of these patients demonstrated that 9 were immunocompetent (39%), 7 of whom had cutaneous infections (30%) with a predominant history of trauma (6/7), and 14 were immunosuppressed, 9 of whom were treated with prednisolone. Microbiology and histopathology were necessary in all cases for definite diagnosis. Among the 13 cases who underwent drug susceptibility testing, 10 cases were sensitive to trimethoprim-sulfamethoxazole (TMP-SMX) and 12 cases were sensitive to aminoglycoside. In conclusion, although N. otitidiscaviarum is one of the less commonly isolated species of Nocardia, it is capable of inducing localized or disseminated infection, even in an immunocompetent host. The majority of cases respond well to TMP-SMX and aminoglycoside, but the therapeutic action of cephalosporin is weak. Identification of bacteria and drug sensitivity tests for Nocardia is critical for guiding clinical treatment.

In Vivo Activity of the Benzothiazinones PBTZ169 and BTZ043 against Nocardia brasiliensis

Background

Mycetoma is a neglected, chronic, and deforming infectious disease caused by fungi and actinomycetes. In Mexico, N. brasiliensis is the predominant etiologic agent. Therapeutic alternatives are necessary because the current drug regimens have several disadvantages. Benzothiazinones (BTZ) are a new class of candidate drugs that inhibit decaprenyl-phosphoribose-epimerase (DprE1), an essential enzyme involved in the cell wall biosynthesis of Corynebacterineae.

Methodology/Principal findings

In this study, the in vitro activity of the next generation BTZ, PBTZ169, was tested against thirty Nocardia brasiliensis isolates. The MIC₅₀ and MIC₉₀ values for PBTZ169 were 0.0075 and 0.03 μg/mL, respectively. Because Nocardia is a potential intracellular bacterium, a THP-1 macrophage monolayer was infected with N. brasiliensis HUJEG-1 and then treated with PBTZ169, resulting in a decrease in the number of colony-forming units (CFUs) at a concentration of 0.25X the in vitro value. The in vivo activity was evaluated after infecting female BALB/c mice in the right hind food-pad. After 6 weeks, treatment was initiated with PBTZ169 and its activity was compared with the first generation compound, BTZ043. Both BTZ compounds were administered at 100 mg/kg twice daily by gavage, and sulfamethoxazole/trimethoprim (SXT), at 100 mg/kg sulfamethoxazole, was used as a positive control. After 22 weeks of therapy, only PBTZ169 and SXT displayed statistically significant activity.

Conclusion

These results indicate that DprE1 inhibitors may be useful for treating infections of Nocardia and may therefore be active against other actinomycetoma agents. We must test combinations of these compounds with other antimicrobial agents, such as linezolid, tedizolid or SXT, that have good to excellent in vivo activity, as well as new DprE1 inhibitors that can achieve higher plasma levels.

Mycetoma is a neglected tropical disease caused by many etiological agents, including actinobacteria and true fungi. In Mexico, Nocardia brasiliensis and Actinomadura madurae account for more than 90% of the total cases. This subcutaneous infectious disease can affect skin and subcutaneous tissue; actinomycetomas are particularly osteolytic. The presence of abundant scar tissue, pus, and the intracellular growth of Nocardia make treatment very difficult. Current N. brasiliensis actinomycetoma therapy includes the use of trimethoprim-sulamethozaxole, diamino-diphenyl-sulphone (DDS), amikacin, and amoxicillin-clavulanate. N. brasiliensis is resistant to many other antimicrobials due in part to its richness in copies of genes related to pharmacoresistance, for instance rpoB, gyrase, beta-lactams, P450 cytochromes, etc. DprE1 inhibitors are new types of compounds that target a completely different gene, dprE1, encoding the decaprenylphosphoryl-d-ribose oxidase. Assays evaluating these experimental or other new drugs are necessary to develop a better therapeutic scheme for actinomycetoma, with more potent, less toxic antimicrobials.

Mycetoma medical therapy

Medical treatment of mycetoma depends on its fungal or bacterial etiology. Clinically, these entities share similar features that can confuse diagnosis, causing a lack of therapeutic response due to inappropriate treatment. This review evaluates the response to available antimicrobial agents in actinomycetoma and the current status of antifungal drugs for treatment of eumycetoma.

Long-term treatment of persistent disseminated Nocardia cyriacigeorgica infection

In this paper a disseminated persistent Nocardia cyriacigeorgica infection in an immunocompetent patient is described. The patient's long-term treatment, as well as its implications for managing similar cases in the future, is emphasized. Presenting with high fever, multiple nodules, and ulcerative cutaneous lesions of body sites, the patient was treated with various antimicrobials. Under combined therapy, empyema and arthritis, leading to disseminated nocardiosis, were seen. The overall treatment course was 28 months. It can be concluded that the choice of the antibiotics and optimal duration of treatment are uncertain; therefore the treatment of nocardiosis requires expertise.

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.

Complete genome sequence analysis of Nocardia brasiliensis HUJEG-1 reveals a saprobic lifestyle and the genes needed for human pathogenesis

Nocardia brasiliensis is an important etiologic agent of mycetoma. These bacteria live as a saprobe in soil or organic material and enter the tissue via minor trauma. Mycetoma is characterized by tumefaction and the production of fistula and abscesses, with no spontaneous cure. By using mass sequencing, we determined the complete genomic nucleotide sequence of the bacteria. According to our data, the genome is a circular chromosome 9,436,348-bp long with 68% G+C content that encodes 8,414 proteins. We observed orthologs for virulence factors, a higher number of genes involved in lipid biosynthesis and catabolism, and gene clusters for the synthesis of bioactive compounds, such as antibiotics, terpenes, and polyketides. An in silico analysis of the sequence supports the conclusion that the bacteria acquired diverse genes by horizontal transfer from other soil bacteria, even from eukaryotic organisms. The genome composition reflects the evolution of bacteria via the acquisition of a large amount of DNA, which allows it to survive in new ecological niches, including humans.

Multisite reproducibility of the broth microdilution method for susceptibility testing of Nocardia species

Antimicrobial susceptibility testing (AST) of clinical isolates of Nocardia is recommended to detect resistance to commonly used antimicrobial agents; such testing is complicated by difficulties in inoculum preparation and test interpretation. In this study, six laboratories performed repetitive broth microdilution testing on single strains of Nocardia brasiliensis, Nocardia cyriacigeorgica, Nocardia farcinica, Nocardia nova, and Nocardia wallacei. For each isolate, a total of 30 microdilution panels from three different lots were tested at most sites. The goal of the study was to determine the inter- and intralaboratory reproducibility of susceptibility testing of this group of isolates. Acceptable agreement (>90% agreement at ±1 dilution of the MIC mode) was found for amikacin, ciprofloxacin, clarithromycin, and moxifloxacin. After eliminating MIC values from single laboratories whose results showed the greatest deviation from those of the remaining laboratories, acceptable agreement was also found for amoxicillin-clavulanic acid, linezolid, minocycline, and tobramycin. Results showed unsatisfactory reproducibility of broth microdilution testing of ceftriaxone with N. cyriacigeorgica and N. wallacei, tigecycline with N. brasiliensis and N. cyriacigeorgica, and sulfonamides with N. farcinica and N. wallacei. N. nova ATCC BAA-2227 is proposed as a quality control organism for AST of Nocardia sp., and the use of a disk diffusion test for sulfisoxazole is proposed as a check of the adequacy of the inoculum and to confirm sulfonamide MIC results.

Central venous catheter-associated Nocardia bacteremia in cancer patients

TOC Summary: Heavy biofilm growth can be reduced through use of antimicrobial lock solutions.

Central venous catheters, often needed by cancer patients, can be the source of Nocardia bacteremia. We evaluated the clinical characteristics and outcomes of 17 cancer patients with Nocardia bacteremia. For 10 patients, the bacteremia was associated with the catheter; for the other 7, it was a disseminated infection. N. nova complex was the leading cause of bacteremia. Nocardia promoted heavy biofilm formation on the surface of central venous catheter segments tested in an in vitro biofilm model. Trimethoprim- and minocycline-based lock solutions had potent in vitro activity against biofilm growth. Patients with Nocardia central venous catheter–associated bloodstream infections responded well to catheter removal and antimicrobial drug therapy, whereas those with disseminated bacteremia had poor prognoses.

Efficacy of imipenem therapy for Nocardia actinomycetomas refractory to sulfonamides

BACKGROUND

Actinomycetomas are chronic, granulomatous, subcutaneous infections caused by actinomycetes bacteria. Despite prolonged high-dose and combination antibiotic therapies, some cases remain resistant with risks of bone and visceral involvement.

OBJECTIVES

We sought to evaluate the efficacy and safety of imipenem monotherapy, and in combination with amikacin for the treatment of severe and refractory disease, and to identify the disease characteristics that might predict therapy failure with first-line sulfonamides.

METHODS

A retrospective study was performed of all microbiologically confirmed cases of actinomycetomas treated since 1995 at a tertiary center for mycology. Eleven patients (Nocardia, n = 10) were treated with sulfonamide combinations (trimethoprim/sulfamethoxazole and dapsone). Eight patients (Nocardia, n = 7) refractory to previous therapies including sulfonamides received a 3-week course of either parenteral imipenem monotherapy (1.5 g daily, n = 3) or combination therapy with amikacin (1 g daily, n = 5), which was repeated at 6-month intervals.

RESULTS

Eleven patients with limited disease and mean disease duration of 1.7 years responded successfully to sulfonamides after a mean treatment period of 15 months (range 6-48 months). Patients receiving imipenem had mean disease duration of 10 years, with visceral and bone involvement in 4 patients. Imipenem treatment was well tolerated, and 4 patients achieved clinical and microbiological cure after one to two courses of treatment, the others demonstrating greater than 75% clinical improvement and negative culture results.

LIMITATIONS

Patient cohorts in this study were small because strict criteria for inclusion included species identification and adequate follow-up periods. The efficacy data for imipenem +/- amikacin therapy cannot be extrapolated to all Nocardia mycetomas, as the cohort treated in this study had particularly refractory infection.

CONCLUSIONS

Sulfonamides are effective for limited disease of relatively short duration. Imipenem monotherapy or in combination with amikacin is well tolerated and demonstrates efficacy in severe disease refractory to sulfonamides.

Comparative in vitro activities of nemonoxacin, doripenem, tigecycline and 16 other antimicrobials against Nocardia brasiliensis, Nocardia asteroides and unusual Nocardia species

OBJECTIVES

The aim of this study was to assess the in vitro activities of nemonoxacin (a novel non-fluorinated quinolone), doripenem, tigecycline and 16 other antimicrobial agents against the Nocardia species.

METHODS

MICs of 19 antimicrobial agents for 125 clinical isolates of the Nocardia species were determined by the broth microdilution method.

RESULTS

Nocardia brasiliensis (n = 61), Nocardia asteroides (n = 45), Nocardia flavorosea (n = 5), Nocardia otitidiscaviarum (n = 4), Nocardia farcinica (n = 3), Nocardia beijingensis (n = 2), Nocardia puris (n = 2) and one each of Nocardia nova, Nocardia jinanensis and Nocardia takedensis were identified based on a 16S rRNA gene sequencing analysis. For N. brasiliensis isolates, the MIC(90)s of the tested quinolones were in the order nemonoxacin < gemifloxacin = moxifloxacin < levofloxacin = ciprofloxacin, and the MIC(90)s of the tested carbapenems were in the order doripenem = meropenem < ertapenem < imipenem. Tigecycline had a lower MIC(90) (1 mg/L) than linezolid (8 mg/L). For N. asteroides isolates, the MIC(90)s of the tested quinolones were in the order nemonoxacin < gemifloxacin = moxifloxacin < levofloxacin < ciprofloxacin, and the MIC(90)s of the tested carbapenems were in the order doripenem = meropenem = imipenem < ertapenem. For the other 19 Nocardia species isolates, nemonoxacin showed good activity with the lowest MIC(90) of the tested quinolones. Among the four tested carbapenems, doripenem and meropenem had comparatively lower MIC(90)s.

CONCLUSIONS

The results of this in vitro study suggest that nemonoxacin, linezolid and tigecycline show promise as treatment options for nocardiosis. Further investigation of their clinical role is warranted.

Antimicrobial activity screening of some sulfonamide derivatives on some Nocardia species and isolates

Nocardia are aerobic, catalase-positive, Gram-positive microorganisms and typically acid-alcohol fast at some stage of the growth cycle. The genus Nocardia, a member of Mycolata group, is clinically important because it is an opportunistic pathogen. The sulfonamide derivative medicines are prefered to cure infection caused by Nocardia, such as nocardiaosis and mycetoma. Antimicrobial activities of seven sulfonamide derivatives have been investigated against some Nocardia species and isolates using the disk diffusion method on Sensitest agar medium (Oxoid). Thirty-six organisms, which consisted of 10 soil isolates selected from different clusters of Aymen study (2003), six clinical isolates provided by Ege University, Medical School, Microbiology and Clinical Microbiology Department, four reference strains, 15 type strains and a control strain of Staphylococcus aureus ATCC 43300 were tested. The strongest inhibition was observed in the cases of IV [N-(2-hydroxy-4-nitro-phenyl)-4-methyl-benzensulfonamid], V [N-(2-hydroxy-5-nitro-phenyl)-4-methyl-benzensulfonamid] and III [N-(2-Hydroxy-phenyl)-4-methyl-benzenesulfonamide] against Nocardia. Introducing a hydroxyl group into the ortho position on the ring increased the antimicrobial activity. Substitution of the electron withdrawing groups such as a nitro group increased the antimicrobial activity remarkably.

Plasmid-borne armA methylase gene, together with blaCTX-M-15 and blaTEM-1, in a Klebsiella oxytoca isolate from China

An armA-producing Klebsiella oxytoca isolate, strain 157, was detected after screening of 447 extended-spectrum beta-lactamase-producing Enterobacteriaceae isolates in China. K. oxytoca 157 was resistant to aminoglycosides, ciprofloxacin and most beta-lactams. Resistance to aminoglycosides and beta-lactams could be transferred to recipient Escherichia coli by conjugation. armA, blaCTX-M-15 and blaTEM-1 genes were detected in K. oxytoca 157 and transconjugant E. coli strain 600(pEC157). Mutation of aa 87 in GyrA was found in K. oxytoca 157. A plasmid of approximately 55 kb was extracted from K. oxytoca 157(pKO157) and E. coli 600(pEC157). Southern blot hybridization confirmed that the armA, blaCTX-M-15 and blaTEM-1 genes were all located on this conjugative plasmid (pEC157). PCR mapping was also performed to investigate the genetic environment of armA. The armA gene was found to be flanked by the same putative transposable elements as reported previously in E. coli, Klebsiella pneumoniae and Citrobacter freundii isolates from different countries.

Therapeutic effect of a novel oxazolidinone, DA-7867, in BALB/c mice infected with Nocardia brasiliensis

Background

Mycetoma is a chronic infectious disease of tropical and subtropical countries. It is produced by true fungi and actinobacteria. In México, Nocardia brasiliensis is the main causative agent of mycetoma, producing about 86% of the cases; the gold standard for the therapy of mycetoma by N. brasiliensis is the use of sulfonamides which give a 70% cure rate. The addition of amikacin to this regime increases to 95% the cure rate; however, the patients have to be monitored for creatinine clearance and audiometry studies because of the potential development of side effects. Because of that it is important to search for new active compounds. In the present work, we evaluated the in vivo effect of DA-7867, an experimental oxazolidinone, on the development of experimental mycetomas by N. brasiliensis in BALB/c mice.

Methodology/Principal Findings

In order to determine the optimal dose utilized to apply to the animals, we first determined by HPLC the plasma levels using several concentrations of the compounds. Based on these results, we used 10 and 25 mg/kg subcutaneously every 24 hr; DA-7867 was also supplied in the drinking water at a calculated dose of 25 mg/kg. As a control we utilized linezolid at 25 mg/kg, a compound active in murine and human infections, three times a day. The mice were infected in the right footpad with a young culture of N. brasiliensis HUJEG-1, and one week later we started the application of the antimicrobials for six more weeks. After that we compared the development of lesions in the groups injected with saline solution or with the antimicrobials; the results were analyzed by the variance ANOVA test. DA-7867 was able to reduce the production of lesions at 25 mg/kg, when given either subcutaneously or in the drinking water.

Conclusions/Significance

The experimental oxazolidinone DA-7867 is active in vivo against N. brasiliensis, which opens the possibility of using this drug once it is accepted for human application. Since oxazolidinones seem to be active against a wide spectrum of actinobacteria, it is possible they could be used in human cases of mycetoma by other actinomycetales, such as Streptomyces somaliensis, highly prevalent in Sudan, or Actinomadura madurae and A. pelletieri, which are commonly observed in Africa and India.

Actinomycetoma is an infectious disease of tropical and subtropical regions produced by actinobacteria of the genera Nocardia, Streptomyces, and Actinomadura. Therapeutic alternatives are scarce and include trimethoprim-sulfamethoxazole, diaminodiphenylsulfone, amoxicillin-clavulanate, imipenem, and amikacin. Oxazolidinones are a new class of antimicrobials with a completely different cellular target; the first compound in the market, linezolid, was introduced in the year 2000. It is active against many species of Nocardia and other aerobic actinomycetes; however, the long-term application in human subjects produces side effects including peripheral neuropathy and mielossupression. Therefore, it is important to screen other oxazolidinones with higher activity and less toxicity. In the present work, we tested DA-7867, a new oxazolidinone, in an experimental mouse model. The drug is active in vivo and decreases the production of lesions using only one dose a day in contrast to linezolid, which needs to be injected three times a day. Although it was tested on N. brasiliensis, it can possibly be active (once it is accepted for its use in humans) against Actinomadura spp and Streptomyces spp, which are frequently found in places of Africa and India where actinomycetoma is also an important consult in dermatology.

In vivo therapeutic effect of gatifloxacin on BALB/c mice infected with Nocardia brasiliensis

In the present work, we evaluated the effect of gatifloxacin on the evolution of experimental murine infection with Nocardia brasiliensis using linezolid as a control. Gatifloxacin was injected subcutaneously at 100 mg/kg body weight every 8 h for 4 weeks. This compound was equally as efficient as linezolid in reducing the production of lesions.

Efficacy of DA-7218, a new oxazolidinone prodrug, in the treatment of experimental actinomycetoma produced by Nocardia brasiliensis

Two recently synthesized oxazolidinones: (R)-3-(4-(2-(2-methyltetrazol-5-yl)-pyridin-5-yl)-3-fluorophenyl)-5-hydroxymethyloxazolidin-2-one (DA-7157) and its corresponding pro-drug (R)-3-(4-(2-(2-methyltetrazol-5-yl)-pyridin-5-yl)-3-fluorophenyl)-2-oxo-5-oxazolidinyl) methyl disodium phosphate (DA-7218), have shown very good activity against several Gram positive bacteria, including Nocardia and Mycobacterium. In the present work we evaluated the therapeutic in vivo effects of DA-7218 on Nocardia brasiliensis. We first determined the plasma concentration of the prodrug in BALB/c mice using several doses and then tested its activity in an in vivo experimental actinomycetoma murine model. At the end of treatment, there was a statistically significant difference between the three drug receiving groups (25, 12.5 and 5 mg/kg) and the control group(saline solution) (p=0.001), proving that DA-7218 is effective for the treatment of experimental murine actinomycetoma. This compound could be a potential option for patients affected with mycetoma by Nocardia brasiliensis.

Prodrugs for the treatment of neglected diseases

Recently, World Health Organization (WHO) and Medicins San Frontieres (MSF) proposed a classification of diseases as global, neglected and extremely neglected. Global diseases, such as cancer, cardiovascular and mental (CNS) diseases represent the targets of the majority of the R&D efforts of pharmaceutical companies. Neglected diseases affect millions of people in the world yet existing drug therapy is limited and often inappropriate. Furthermore, extremely neglected diseases affect people living under miserable conditions who barely have access to the bare necessities for survival. Most of these diseases are excluded from the goals of the R&D programs in the pharmaceutical industry and therefore fall outside the pharmaceutical market. About 14 million people,mainly in developing countries, die each year from infectious diseases. From 1975 to 1999,1393 new drugs were approved yet only 1% were for the treatment of neglected diseases[3]. These numbers have not changed until now, so in those countries there is an urgent need for the design and synthesis of new drugs and in this area the prodrug approach is a very interesting field. It provides, among other effects, activity improvements and toxicity decreases for current and new drugs, improving market availability. It is worth noting that it is essential in drug design to save time and money, and prodrug approaches can be considered of high interest in this respect. The present review covers 20 years of research on the design of prodrugs for the treatment of neglected and extremely neglected diseases such as Chagas' disease (American trypanosomiasis), sleeping sickness (African trypanosomiasis), malaria, sickle cell disease, tuberculosis, leishmaniasis and schistosomiasis.

Mycetoma

Mycetoma is a granulomatous infection affecting mainly the feet and lower extremities. It can be caused either by aerobic, branched actinomycetes or by eumycetes. Most cases are found in tropical and subtropical regions. The infection is usually produced by the introduction of the etiologic agents through minor wounds caused by thorns and wood splinters. Clinically the disease begins as small, firm nodules that can enlarge to form extensive lesions with fistulae and abscesses with pus containing granules of the causative microorganisms. Antimicrobials and surgery are used in the management of mycetoma. The actinomycetomas generally respond well to antimicrobials. For eumycetomas, surgery may be required. New therapeutic options for drug-resistant cases are discussed.

Treatment of actinomycetoma due to Nocardia spp. with amoxicillin?clavulanate

BACKGROUND

Actinomycetoma is a chronic occupational condition that occurs frequently in tropical regions. In Mexico 85% of cases are caused by Nocardia brasiliensis. There are two treatments of choice for these cases: a regimen of dapsone plus trimethoprim-sulfamethoxazole (co-trimoxazole) and, recently, amikacin, either alone or combined. However, not all cases respond properly to these therapies.

OBJECTIVES

To report a retrospective, 11-year study of cases of actinomycetomas caused by Nocardia spp., treated with amoxicillin-clavulanate (co-amoxiclav).

METHODS

All cases were identified clinically and microbiologically and had previously failed standard therapies. Oral co-amoxiclav 875/125 mg was administered every 12 h. Clinical, microbiological and laboratory follow up was performed every 2 months during the treatment period.

RESULTS

Twenty-one cases of actinomycetoma were included, 19 caused by N. brasiliensis and one each by N. asteroides and N. otitidiscaviarum. Clinical and microbiological cure occurred in 15 of 21 cases (71%); two cases improved (10%) and four failed (19%). Mean treatment period was 9.6 months, during which neither side-effects nor laboratory test alterations were reported.

CONCLUSIONS

Treatment with co-amoxiclav represents an alternative or rescue treatment for cases that have previously failed standard therapies.

Simultaneous determination and validation of antimicrobials in plasma and tissue of actinomycetoma by high-performance liquid chromatography with diode array and fluorescence detection

A simple, precise, and reliable chromatographic method was developed for the simultaneous determination in plasma and infected tissue of five antimicrobials proposed for the treatment of actinomycotic mycetoma: amoxicillin, trimethoprim, linezolid, sulfamethoxazole and garenoxacin. Separation of the analytes was achieved on an Atlantis dC18 column (150 mm x 4.6 mm, ID 5 microm) with a mobile phase composed of acetonitrile and trifluoroacetic acid (ATF) 0.1% (v/v) using a gradient program. The detection was carried out using a diode array detector at 254 nm and in a fluorescence detector at wavelengths of excitation and emission of 292 nm and 392 nm for linezolid and sulfamethoxazole, and 292 nm and 408 nm for garenoxacin, respectively. The intraday precision was in the range of 0.7-15% of relative standard deviations (%R.S.D.) for plasma and 1-18% for tissue. Linearity range was from 2.4 to 20 microg/ml for amoxicillin, 0.3 to 20 microg/ml for trimethoprim, sulfamethoxazole and linezolid, and 0.3 to 10 microg/ml for garenoxacin. Acetonitrile was used to precipitate proteins from plasma. Recoveries in plasma ranged from 71% to 118% and in infected tissue from 78% to 122%. Limits of detection (LODs) were 1.2 and 0.5 microg/ml for amoxicillin in plasma and tissue, respectively and 0.15 and 1.2 microg/ml in plasma and tissue, respectively for the other antimicrobials. The method can be applied for individual or simultaneous determination of the antimicrobials in plasma and tissue of mouse infected with actinomycetoma.

In vitro activities of tigecycline and eight other antimicrobials against different Nocardia species identified by molecular methods

The in vitro activities of tigecycline and other antimicrobials against 51 isolates of Nocardia spp. were evaluated. MIC(90)s and MIC ranges were as follows: tigecycline, 4 and < or =0.06 to 8 mg/liter, respectively; minocycline, 2 and < or =0.06 to 2 mg/liter, respectively; linezolid, 1 and < or =0.06 to 2 mg/liter, respectively; moxifloxacin, 2 and < or =0.06 to >64 mg/liter, respectively; ertapenem, 32 and < or =0.06->64 mg/liter, respectively; imipenem, 2 and < or =0.06 to >64 mg/liter, respectively; meropenem, 8 and < or =0.06 to >64 mg/liter, respectively; amikacin, 1 and < or =0.06 to 32 mg/liter, respectively; and trimethoprim-sulfamethoxazole, 1/19 and < or =0.5/9.5 to >2/38 mg/liter, respectively.

In vitro activities of DA-7157 and DA-7218 against Mycobacterium tuberculosis and Nocardia brasiliensis

The in vitro activities of DA-7157, a novel oxazolidinone, against clinical isolates of Nocardia brasiliensis and Mycobacterium tuberculosis were determined. Equal MIC(50)s and MIC(90)s (0.25 and 0.5 microg/ml, respectively) were found for susceptible and multidrug-resistant isolates of M. tuberculosis. The N. brasiliensis isolates showed an MIC(90) of 1 microg/ml and an MIC(50) of 1 microg/ml. The DA-7157 prodrug, DA-7218, exhibited similar MICs for M. tuberculosis but fivefold-higher MICs for N. brasiliensis.

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

Susceptibilities to 11 antimicrobial agents were determined by Etest for 93 Nocardia isolates from clinical specimens and 15 type strains belonging to different Nocardia spp. All isolates were susceptible to trimethoprim-sulphamethoxazole, amikacin and linezolid, but susceptibilities of the various Nocardia spp. to beta-lactams, aminoglycosides, ciprofloxacin and clarithromycin varied markedly. Overall, there was a good correlation between the drug resistance patterns and the species identification established by conventional phenotypic tests and 16S rDNA sequencing. Among the different species encountered, Nocardia farcinica and Nocardia brasiliensis displayed the most multiresistant profiles, with resistance to imipenem occurring mainly among isolates of N. brasiliensis and Nocardia abscessus. The species variability in susceptibility profiles and the numerous recent taxonomic changes means that in-vitro susceptibility tests may be a complementary tool for the identification of Nocardia isolates from human clinical specimens. Further studies on a larger number of species from more diverse geographical sources, including species that are found less commonly among clinical isolates, are required to validate and extend the results.

A successfully treated case of mycetoma due to Nocardia veterana

We report a successfully treated case of mycetoma from which an unusual Nocardia species was isolated. The isolate was identified as N. veterana by biochemical characterization and 16S ribosomal RNA gene sequencing, and it has not been previously reported as a causative agent of human mycetomas. Treatment with various antibiotics over 6 years and surgical resection failed to cure the disease. However, the combination of intravenous imipenem/cilastatin and amikacin along with oral clarithromycin and minocycline proved very effective in this case. This is the first case report of mycetoma due to N. veterana in a clinical setting.