Severe progressive subcutaneous abscesses and necrotizing tenosynovitis caused by Rhodococcus aurantiacus

Aerobic Actinomycetes of Clinical Significance

The group of Gram-positive bacillary organisms broadly known as "aerobic actinomycetes" consists of heterogeneous and taxonomically divergent genera. They are found in a wide variety of natural and man-made environments but are rarely considered a part of the normal human flora, with infections normally originating from exogenous sources. An extensive number of genera have been described, but only a minority of these has been associated with human or veterinary health. The association with human disease is usually of an opportunistic nature, either through accidental means of inoculation or through involvement with immunocompromising conditions in the host. They cause a wide spectrum of diseases in humans, which may differ greatly between the genera and even between species, but which also may have a great amount of overlap. The occurrence of such infections is probably greater than appreciated, since many may go unrecognized. Etiologic prevalence of specific genera and species varies geographically within the United States and worldwide. Traditional phenotypic identification methods for separation of the many genera and species of aerobic actinomycetes have found great difficulties. Recent use of chemotaxonomic analyses and emerging technologies such as molecular analysis of nucleic acids, and more recently proteomics for identification to the genus/species level, has provided a far more robust technique to understand the organisms' relatedness, distribution, epidemiology, and pathogenicity in humans.

Community-acquired Tsukamurella pneumonia in a young immunocompetent adult: a case misdiagnosed as pulmonary tuberculosis and literature review

This report describes a case of Tsukamurella pneumonia in a 24-year-old immunocompetent woman. The patient was diagnosed as having pulmonary tuberculosis and was treated for nearly 9 months. The correct diagnosis was suspected only when the results of mycobacteria nucleic acid amplification tests on cultural colonies were negative. Tsukamurella was identified from the patient's sputum and bronchoalveolar lavage fluid by using 16S rRNA sequence analysis. Here, the clinical presentation, diagnosis, and treatment strategies of Tsukamurella pneumonia are discussed, along with a literature review. Tsukamurella pneumonia may be highly underdiagnosed owing to its similarity with pulmonary tuberculosis and the habitual thinking of doctors in countries with a high tuberculosis burden. Tsukamurella should be carefully considered in the etiology of tuberculosis-like lung diseases.

First report of Tsukamurella keratitis: association between T. tyrosinosolvens and T. pulmonis and ophthalmologic infections

We describe the first two cases of Tsukamurella keratitis, presented as eye pain with or without blurring of vision. One case was associated with trichiasis and the other with contact lens wear. The two isolates were identified as T. tyrosinosolvens and T. pulmonis, respectively, by phenotypic characterization and 16S rRNA sequencing.

Temperature resistant Nocardia biovarieties in Tucumán, Argentina?

Eighty-six regional strains of the pathogenic Nocardia species isolated from soil and human mycetoma were tested for their response to different incubation temperatures and for their tolerance to different temperatures. The aim was to assess whether growth temperature and tolerance to elevated temperatures are valuable criteria for the differentiation of pathogenic species of local strains based on the results obtained from a large number of strains. The results showed that 75.34% of all N. brasiliensis isolates from both sources grew at a temperature higher than 37 degrees C. 20% of the mycetoma strains and 11.32% of those from soil grew at 45 degrees C. 98.1% of N. brasiliensis from soil and 55.0% of the mycetoma strains tolerated 50 degrees C for 8 h and many isolates from both sources endured this temperature for an even longer time and tolerated yet higher temperatures. Both properties (growth temperature and temperature tolerance) are used to identify N. asteroides complex (N. farcinica) and N. otitidiscaviarum, and according to our results they are not suitable to differentiate regional strains of this species. The N. asteroides strains assayed showed an ability to grow at and tolerate elevated temperatures superior to those belonging to the other species. Although adaptation of local N. asteroides and N. otitidiscaviarum strains to temperature is important, it is more significant for N. brasiliensis, because this species is predominant in the Tucumán soil and responsible for the major number of diseases in the area.

Central venous catheter-related bacteremia due to Tsukamurella species in the immunocompromised host: a case series and review of the literature

We report 6 cases of bacteremia due to Tsukamurella species, all of which were in immunosuppressed patients with indwelling central venous catheters (CVCs). Fewer than 20 cases of serious illness due to these gram-positive bacilli have been reported in the medical literature; these cases have mostly been ascribed to the species Tsukamurella paurometabola. Tsukamurella species are frequently misidentified as Rhodococcus or Corynebacterium species. We used high-performance liquid chromatography to identify these organisms to the genus level and 16S ribosomal RNA gene sequencing and DNA-DNA dot blots for species identification. Three of our isolates were identified as Tsukamurella pulmonis, 1 was identified as Tsukamurella tyrosinosolvans, and 1 was identified as a unique species. One isolate was not maintained long enough for species identification. All patients were successfully treated with antimicrobial therapy and CVC removal. Infection with this organism should be considered in the immunosuppressed patient with an indwelling CVC and gram-positive bacilli in the blood.

Tsukamurella strandjordae sp. nov., a proposed new species causing sepsis

We have isolated a gram-positive, weakly acid-alcohol-fast, irregular rod-shaped bacterium from cultures of blood from a 5-year-old girl with acute myelogenous leukemia. This isolate was compared with 14 other strains including reference strains of Tsukamurella species by a polyphasic approach based on physiological and biochemical properties, whole-cell short-chain fatty acid and mycolic acid analyses, DNA-DNA hybridization, and sequencing of the 16S rRNA gene. This isolate represents a new taxon within the genus Tsukamurella for which we propose the name Tsukamurella strandjordae sp. nov. Our study also revealed that Tsukamurella paurometabola ATCC 25938 represents a misnamed Tsukamurella inchonensis isolate and confirms that Tsukamurella wratislaviensis belongs to the genus Rhodococcus.

Reciprocal action of interferon-gamma and interleukin-4 promotes granulomatous inflammation induced by Rhodococcus aurantiacus in mice

An intravenous injection of Rhodococcus aurantiacus to mice causes granulomatous inflammation dependent on endogenous interferon-gamma (IFN-gamma). The present study examined the role of endogenous interleukin-4 (IL-4) on granulomatous inflammation. Endogenous IL-4 in the spleen extracts was not detected during the phase of granuloma formation by enzyme-linked immunosorbent assay (ELISA). However, IL-4 protein level was elevated during the phase of granuloma regression. IL-4 mRNA expression in the livers and spleens was also elevated during the phase of granuloma regression. In addition, IL-4 levels during the phase of granuloma formation were increased by treatment with anti-IFN-gamma monoclonal antibody (mAb), suggesting that endogenous IFN-gamma might inhibit IL-4 production during the phase of granuloma formation. Administration of anti-IL-4 mAb on weeks 3 and 4 after the inoculation inhibited the regression of granulomas and augumented IFN-gamma level at 5 weeks. Endogenous IFN-gamma was produced by CD4+ T cells during the phase of granuloma regression and endogenous IL-4 was produced by both CD4+ and CD8+ T cells. These findings suggest that during the phase of granuloma formation endogenous IL-4 might be inhibited by IFN-gamma, while during the phase of granuloma regression endogenous IL-4 might play a crucial role in the reduction of granulomas and IFN-gamma production.

The medically important aerobic actinomycetes: epidemiology and microbiology

The aerobic actinomycetes are soil-inhabiting microorganisms that occur worldwide. In 1888, Nocard first recognized the pathogenic potential of this group of microorganisms. Since then, several aerobic actinomycetes have been a major source of interest for the commercial drug industry and have proved to be extremely useful microorganisms for producing novel antimicrobial agents. They have also been well known as potential veterinary pathogens affecting many different animal species. The medically important aerobic actinomycetes may cause significant morbidity and mortality, in particular in highly susceptible severely immunocompromised patients, including transplant recipients and patients infected with human immunodeficiency virus. However, the diagnosis of these infections may be difficult, and effective antimicrobial therapy may be complicated by antimicrobial resistance. The taxonomy of these microorganisms has been problematic. In recent revisions of their classification, new pathogenic species have been recognized. The development of additional and more reliable diagnostic tests and of a standardized method for antimicrobial susceptibility testing and the application of molecular techniques for the diagnosis and subtyping of these microorganisms are needed to better diagnose and treat infected patients and to identify effective control measures for these unusual pathogens. We review the epidemiology and microbiology of the major medically important aerobic actinomycetes.

Polyphasic taxonomic study of the genera Gordona and Tsukamurella including the description of Tsukamurella wratislaviensis sp. nov

Representatives of the genera Gordona and Tsukamurella together with related actinomycetes were the subject of chemotaxonomic, numerical taxonomic and DNA homology studies. In the numerical analysis the organisms were examined for 116 unit characters and the data sorted using the simple matching, Jaccard and pattern coefficients; clustering was achieved using the unweighted pair group method with arithmetic averages algorithm. The numerical groupings were not affected by the statistics used or by test error, estimated at 1.9%. The numerical taxonomic data supported the integrity of the four validly described species of Gordona but indicated that the genus Tsukamurella might encompass a species in addition to Tsukamurella paurometabola. The putative new strains had chemical, enzymic, nutritional and tolerance properties consistent with their assignment to the genus Tsukamurella and formed a DNA homology group corresponding to the one formed by the Tsukamurella paurometabola strains. It is proposed that the new taxon be assigned to the genus Tsukamurella as Tsukamurella wratislaviensis.

Rhodococcus infection of the skin with lymphadenitis in a nonimmunocompromised girl

A 7-year-old girl had a 4 X 3 X 3 cm nodule on the left wrist with axillary lymphadenopathy. Acid-fast bacilli were seen on a smear from a biopsy specimen of this granulomatous skin lesion. A Rhodococcus species grew on culture. Skin infections caused by Rhodococcus may be more common than the few prior case reports suggest.

Characterization of Nocardia, Rhodococcus and Gordona species by in vitro susceptibility testing

Representative strains of Gordona, Nocardia and Rhodococcus were tested against 26 antimicrobial agents using the disc diffusion method. A distinct susceptibility profile was noted for most species. Nocardia asteroides, N. brasiliensis, N. otitidiscaviarum, N. transvalensis and N. vaccinii were rarely susceptible to the antibiotics tested; N. brevicatena and N. farcinica varied in their susceptibility depending on the strain tested. Only the antibiotic amikacin was active against all nocardiae. In contrast, the Gordona and Rhodococcus strains showed considerable susceptibility, in particular to the beta-lactam antibiotics. Amoxicillin + clavulanic acid and gentamicin were active against all of the gordonae and rhodococci. The differences in susceptibility patterns may prove useful in characterizing the genera Gordona, Nocardia and Rhodococcus and in separating species within these taxa.

Rhodococcus peritonitis in a patient treated with peritoneal dialysis

This report is of a patient treated with continuous ambulatory peritoneal dialysis who developed peritonitis attributed to a Rhodococcus species. The rhodococci are rarely pathogenic to humans, and there are no previous reports of peritonitis associated with these organisms. It is important for clinicians to be aware of these bacteria because they can be acid-fast and can be confused with mycobacteria. They are often reported as "diphtheroids" but should not be considered contaminants.