Nonmycetomic Actinomadura madurae infection in a patient with AIDS

Actinomadura soli sp. nov., isolated from the top soil layer on basaltic material in Turkey

An actinobacterium, designated 14C53^T, was isolated from a soil sample on basaltic material from Samsun, Turkey. The growth ranges for NaCl concentration and pH of strain 14C53^T were quite limited and the growth temperature range of the strain was 20-37 °C, with an optimum at 28 °C. Phylogenetic analysis of 16S rRNA gene sequences revealed that strain 14C53^T was most closely related to Actinomadura geliboluensis A8036^T (98.5 % similarity value), but in the phylogenetic tree, it formed a clade with Actinomadura alkaliterrae D310A^T. The genome tree revealed a close relationship between the strain and Actinomadura pelletieri DSM 43383^T. However, the digital DNA-DNA hybridization and average nucleotide identity values between strain 14C53^T with Actinomadura geliboluensis A8036^T and Actinomadura pelletieri DSM 43383^T were 28.6-30.2 % and 84.3-85.5 %, respectively, and comparative analyses based on the genome sequences demonstrated that it represents a novel species of the genus Actinomadura. The genome size of strain 14C53^T was approximately 9.0 Mb and the genomic DNA G+C content of the strain was 71.3 mol%. The major cellular fatty acids of strain 14C53^T were C_16 : 0 and iso-C_16 : 0. Strain 14C53^T contained meso-diaminopimelic acid as the diamino acid in the cell-wall peptidoglycan. The predominant menaquinones were MK-9(H₈) and MK-9(H₆). Based on evidence collected from the phenotypic, genotypic and phylogenetic analyses, a novel species Actinomadura soli sp. nov. is proposed, with 14C53^T (=DSM 104447^T=KCTC 39878^T) as the type strain.

Tuning the Mycobacterium tuberculosis Alternative Sigma Factor SigF through the Multidomain Regulator Rv1364c and Osmosensory Kinase Protein Kinase D

Bacterial alternative sigma factors are mostly regulated by a partner-switching mechanism. Regulation of the virulence-associated alternative sigma factor SigF of Mycobacterium tuberculosis has been an area of intrigue, with SigF having more predicted regulators than other sigma factors in this organism. Rv1364c is one such predicted regulator, the mechanism of which is confounded by the presence of both anti-sigma factor and anti-sigma factor antagonist functions in a single polypeptide. Using protein binding and phosphorylation assays, we demonstrate that the anti-sigma factor domain of Rv1364c mediates autophosphorylation of its antagonist domain and binds efficiently to SigF. Furthermore, we identified a direct role for the osmosensor serine/threonine kinase PknD in regulating the SigF-Rv1364c interaction, adding to the current understanding about the intersection of these discrete signaling networks. Phosphorylation of SigF also showed functional implications in its DNA binding ability, which may help in activation of the regulon. In M. tuberculosis, osmotic stress-dependent induction of espA, a SigF target involved in maintaining cell wall integrity, is curtailed upon overexpression of Rv1364c, showing its role as an anti-SigF factor. Overexpression of Rv1364c led to induction of another target, pks6, involved in lipid metabolism. This induction was, however, curtailed in the presence of osmotic stress conditions, suggesting modulation of SigF target gene expression via Rv1364c. These data provide evidence that Rv1364c acts an independent SigF regulator that is sensitive to the osmosensory signal, mediating the cross talk of PknD with the SigF regulon.IMPORTANCE Mycobacterium tuberculosis, capable of latently infecting the host and causing aggressive tissue damage during active tuberculosis, is endowed with a complex regulatory capacity built of several sigma factors, protein kinases, and phosphatases. These proteins regulate expression of genes that allow the bacteria to adapt to various host-derived stresses, like nutrient starvation, acidic pH, and hypoxia. The cross talk between these systems is not well understood. SigF is one such regulator of gene expression that helps M. tuberculosis to adapt to stresses and imparts virulence. This work provides evidence for its inhibition by the multidomain regulator Rv1364c and activation by the kinase PknD. The coexistence of negative and positive regulators of SigF in pathogenic bacteria reveals an underlying requirement for tight control of virulence factor expression.

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.

Molecular diagnosis of Actinomadura madurae infection by 16S rRNA deep sequencing

Next-generation DNA sequencing can be used to catalog individual organisms within complex, polymicrobial specimens. Here, we utilized deep sequencing of 16S rRNA to implicate Actinomadura madurae as the cause of mycetoma in a diabetic patient when culture and conventional molecular methods were overwhelmed by overgrowth of other organisms.

Majority of Actinomadura clinical isolates from sputa or bronchoalveolar lavage fluid in Japan belongs to the cluster of Actinomadura cremea and Actinomadura nitritigenes, and the description of Actinomadura chibensis sp. nov

In Japan during 1996-2004, 21 actinomycete strains that have madurose as the diagnostic cell-wall sugar and show true branching in their substrate and aerial mycelia were isolated from sputa or bronchoalveolar lavage (BAL) fluid of patients with pulmonary infections or who were suspected of having related infections. Chemotaxonomic studies showed that all the isolates belong to the genus Actinomadura. Among them, six and seven strains were classified respectively into clusters of Actinomadura nitritigenes and Actinomadura cremea based on 16S rDNA analyses because their 16S rDNA similarities to those respective species were greater than 99.5%. To our knowledge, this is first report that strains of above two species were isolated from clinical specimens. Neither Actinomadura madurae nor Actinomadura pelletieri strain was isolated, and one new species, Actinomadura chibensis, was proposed; the remaining seven strains were not assigned into any known species, suggesting the presence of another new Actinomadura species.

Polyphasic taxonomic study of clinically significant actinomadurae including the description of Actinomadura latina sp.nov

Thirty-one strains received either as Actinomadura madurae or Actinomadura pelletieri were assigned to four phena, clusters 1 to 4, in a numerical phenetic survey of the genus Actinomadura. Clusters 2 and 4 corresponded to the validly described species A. madurae and A. pelletieri whereas clusters 1 and 3 encompassed strains received as A. madurae and A. pelletieri, respectively. The two clusters that contained A. madurae strains formed a single taxon when a dataset lacking the antibiotic sensitivity entries was examined. Results from pyrolysis mass spectrometric and DNA amplification fingerprinting analyses underpinned the taxonomic status of clusters 2, 3 and 4 and suggested that the A. madurae strains accounted for a relatively wide range of variation. It is proposed that the cluster 3 strains be given species status within the genus Actinomadura given the congruence found between the chemical, molecular and numerical phenetic data. The name Actinomadura latina is proposed for the new taxon. The type strain is DSM 43382.

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.