Call number: LD2668 .T4 1960 A23

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A dissertation submitted to the Faculty of Science, University of' the Witwatersrand, in partial fulfilment of the requirements of the Degree of Master of Science in the field ·of Biotechnology. February 1991. / Nocardioform bacteria were studied for their ability to interconvert bile acids. From the studies of utilisation and resistance curves, the most suitable donor and recipient strains for complementary gene cloning, were Arthrobacter oxydans strain C1 and Rhodococcus erythropolis strain ATCC 4217-1 respectively. [Abbreviated Abstract. Open document to view full version] / MT2016

Rifampicin is one of the major antibiotics used in the treatment of Mycobacterium tuberculosis. This organism causes tuberculosis. Other related nocardioform bacteria which include the Rhodococci are opportunistic pathogens in AIDS patients. These organisms cause tuberculosis-like disease and are currently treated with rifampicin and other drugs. The presence of a low level rifampicin resistance mechanism was identified in seven rhodococcal strains and five other related and unrelated bacteria. Abbreviated Abstract. Open document to view full version] / GR2017

Nitrilases are enzymes which catalyze the hydrolysis of nitriles to corresponding carboxylic acids. These enzymes have a great potential in biocatalysis, for example in the synthesis of mandelic acid and mandelamide, because of their chemo- and enantioselectivity. As bioremediation agents they are also applicable to sites contaminated with organic nitriles. In this work, activities of recombinant strains of E. coli expressing hypothetical nitrilases from fungi Giberella moniliformis and Nectria haematococca mpVI 77-13-4 were studied, as well as the biodegradation potential of bacteria from Rhodococcus and Nocardia genera towards benzonitrile herbicides dichlobenil (2,6-dichlorobenzonitrile), ioxynil (3,5-diiodo-4- hydroxybenzonitrile) and bromoxynil (3,5-dibromo-4-hydroxybenzonitrile). The hypothetical fungal nitrilases were expressed as functional enzymes. Nitrilase from G. moniliformis showed highest activity towards benzonitrile (30.9 U/mg protein), total activity yield was 2,560 U/l cell culture. The preferred substrate of the nitrilase from N. haematococca was phenylacetonitrile (12.3 U/mg prot.), total activity yield was 28,050 U/l cell culture. Nitrilase from N. haematococca was also able to hydrolyze mandelonitrile (5.9 U/mg prot.). Soil bacteria Rhodococcus rhodochrous PA-34, Nocardia globerula...

Les bactéries du genre Nocardia sont des Actinobactéries filamenteuses. Ces microorganismes sont saprophytes du sol. Les infections à Nocardia ou nocardioses se manifestent dans la majorité des cas (60%) par des infections pulmonaires et plus rarement par des infections cérébrales. La souche Nocardia cyriacigeorgica GUH-2 à causé la mort d’un patient dans les années 70. Des études sur cette souche ont montré qu’elle avait un haut pouvoir pathogène et qu’elle était capable dans certaines conditions de déclencher chez la souris et les primates le développement de troubles moteurs similaires à ceux observés dans la maladie de Parkinson. Afin d’appréhender l’implication de l’espèce pathogène opportuniste N. cyriacigeorgica dans l’une des plus importantes maladies neurodégénératives du 21ème siècle, le séquençage du génome de la souche N. cyriacigeorgica GUH-2 à été entrepris. Il a permis l’identification d’un grand nombre de gènes liés à la virulence et à la résistance aux antibiotiques ainsi que l’identification d’ilots génomiques et de séquences d’insertions reflétant une plasticité plus grande que celle qui était décrite pour ce genre bactérien. L’étude de groupements de gènes impliqués dans la production de métabolites secondaire a montré que ces molécules pourraient être responsables des propriétés neurodégénératives de la souche. L’espèce de N. cyriacigeorgica étant retrouvée fréquemment en clinique sans que son réservoir naturel n’ai été mis en évidence à ce jour, la mise au point de marqueurs de détection génétique a été réalisé afin de permettre la recherche de la niche écologique de cette espèce mais également de faciliter le diagnostic des nocardioses. / Nocardia are filamentous-growing Gram-positive soil saprophytes that belong to Actinobacteria. Nocardial infections or nocardiosis are lung infections in most of the cases (60%) and more rarely brain infections. Nocardia cyriacigeorgica strain GUH-2 had cause the death of a patient in the 70's. Studies have shown that its strain had a high pathogenicity and the ability to trigger the development of motor disorders in mice and primates similar to those seen in Parkinson's disease.In order to understand the involvement of this opportunistic pathogen in one of the major neurodegenerative diseases of the 21st century, the genome of the strain N. cyriacigeorgica GUH-2 was sequenced. It allowed the identification of a large number of genes related to virulence, antibiotic resistance and the identification of genomic islands and insertion sequences reflecting a greater plasticity that it was previously described for this bacterial genus. The study of clusters of genes involved in the production of secondary metabolites showed that these molecules could be responsible for the neurodegenerative properties of the strain. N. cyriacigeorgica species is frequently encountered in the clinic without its natural reservoir has been identified to date. The development of genetic markers for detection was carried out to allow the search for the habitat of this species but also to facilitate the diagnosis of nocardiosis.

by Chung Wai Ki. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1992. / Includes bibliographical references (leaves 110-120). / Acknowledgments --- p.i / Abstract --- p.ii / Table of Content --- p.iii / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Sewage Treatment --- p.1 / Chapter 1.1.1 --- Overview --- p.1 / Chapter 1.1.2 --- Types of Treatment --- p.2 / Chapter 1.2 --- Activated Sludge Process --- p.3 / Chapter 1.2.1 --- Overview --- p.3 / Chapter 1.2.2 --- Biology of Activated Sludge --- p.3 / Chapter 1.2.3 --- Operation of the Activated Sludge Process --- p.4 / Chapter 1.2.4 --- Floe Formation in Activated Sludge Process --- p.10 / Chapter 1.2.5 --- Operational Problems Associated with the Activated Sludge Process --- p.12 / Chapter 1.2.5.1 --- Bulking --- p.12 / Chapter 1.2.5.2 --- Foaming --- p.14 / Chapter 1.3 --- Foaming in Activated Sludge Process --- p.15 / Chapter 1.3.1 --- Overview --- p.15 / Chapter 1.3.2 --- Causes of Foaming --- p.16 / Chapter 1.3.2.1 --- Biology of Nocardia --- p.18 / Chapter 1.3.2.2 --- Growth Strategy of Nocardia --- p.18 / Chapter 1.3.2.3 --- Metabolic Specialization of Nocardia amarae --- p.19 / Chapter 1.3.3 --- Controls of Foaming --- p.20 / Chapter 1.4 --- Microbial Lipid and Bacterial Foaming --- p.23 / Chapter 1.4.1 --- Overview --- p.23 / Chapter 1.4.2 --- Fatty Acids in Bacteria --- p.24 / Chapter 1.4.3 --- Analytical Techniques --- p.25 / Chapter 1.4.3.1 --- Chromatography --- p.25 / Chapter 1.4.3.2 --- Gas Chromatography - Mass Spectrometry (GC-MS) --- p.26 / Chapter 1.4.4 --- Significance of Fatty Acids to Foaming --- p.27 / Chapter 1.5 --- Disinfection --- p.29 / Chapter 1.5.1 --- Overview --- p.29 / Chapter 1.5.2 --- Types of Disinfectants --- p.30 / Chapter 1.5.3 --- Mechanism of Disinfection --- p.31 / Chapter 1.5.4 --- Disinfection with Chlorine and Hypochlorite --- p.31 / Chapter 1.5.5 --- Chemistry of Chlorine Disinfection --- p.32 / Chapter 2. --- Objectives of Study --- p.35 / Chapter 3. --- Materials and Methods --- p.37 / Chapter 3.1 --- Sample Collection: --- p.37 / Chapter 3.2 --- Biological Studies of Activated Sludge Samples --- p.37 / Chapter 3.2.1 --- Microscopic Examination --- p.37 / Chapter 3.2.2 --- Isolation of Foam-Causing Filamentous Bacteria --- p.38 / Chapter 3.3 --- Physiology Studies of Nocardia amarae --- p.39 / Chapter 3.3.1 --- Growth Kinetics --- p.40 / Chapter 3.3.2 --- Effects of Fatty Acids on Nocardia amarae --- p.40 / Chapter 3.3.2.1 --- Fatty Acids as Sole Carbon Source --- p.41 / Chapter 3.3.2.2 --- Growth Stimulation --- p.42 / Chapter 3.3.2.3 --- Foam Test --- p.43 / Chapter 3.4 --- Fatty Acids Analysis --- p.43 / Chapter 3.4.1 --- Fatty Acid Extraction --- p.43 / Chapter 3.4.2 --- GC Analysis --- p.45 / Chapter 3.4.3 --- GC-MS Analysis --- p.46 / Chapter 3.5 --- Laboratory-Scale Activated Sludge Unit --- p.46 / Chapter 3.5.1 --- Set Up --- p.46 / Chapter 3.5.2 --- Performance Assessment of Laboratory-Scale Unit --- p.52 / Chapter 3.5.2.1 --- Physical Parameters --- p.52 / Chapter 3.5.2.2 --- Chemical Parameters --- p.54 / Chapter 3.5.2.3 --- Biological Parameters --- p.55 / Chapter 3.5.3 --- Anoxic Condition --- p.56 / Chapter 3.6 --- Toxicity Studies --- p.56 / Chapter 3.6.1 --- Comparative Toxicity Studies in Pure Culture --- p.56 / Chapter 3.6.2 --- Chlorination Studies of the Laboratory-Scale Unit --- p.58 / Chapter 3.6.3 --- Residual Chlorine Measurement --- p.58 / Chapter 3.7 --- Scanning Electron Microscopy --- p.60 / Chapter 4. --- Results --- p.61 / Chapter 4.1 --- Biological Studies of Activated Sludge --- p.61 / Chapter 4.1.1 --- Microscopic Examination --- p.61 / Chapter 4.1.2 --- Isolation of Foam-Causing Filamentous Bacteria --- p.61 / Chapter 4.2 --- Physiological Studies of Nocardia amarae --- p.65 / Chapter 4.2.1 --- Growth Kinetics --- p.65 / Chapter 4.2.2 --- Effects of Fatty Acids on Nocardia amarae --- p.69 / Chapter 4.2.2.1 --- Fatty Acids as Sole Carbon Source --- p.69 / Chapter 4.2.2.2 --- Growth Stimulation --- p.69 / Chapter 4.2.2.3 --- Foam Test --- p.69 / Chapter 4.3 --- Fatty Acids Analysis --- p.75 / Chapter 4.4 --- Laboratory-Scale Activated Sludge Unit --- p.80 / Chapter 4.4.1 --- Assessment of Performance of the Laboratory-Scale Unit --- p.80 / Chapter 4.4.2 --- Under Anoxic Condition --- p.80 / Chapter 4.5 --- Toxicity Studies --- p.85 / Chapter 4.5.1 --- Comparative Toxicity Studies in Pure Culture --- p.85 / Chapter 4.5.2 --- Chlorination Studies of Laboratory-Scale Unit --- p.85 / Chapter 4.5.3 --- Residual Chlorine Measurement --- p.91 / Chapter 5. --- Discussion --- p.94 / Chapter 5.1 --- Biological Studies of Activated Sludge Samples --- p.94 / Chapter 5.1.1 --- Microscopic Examination --- p.94 / Chapter 5.1.2 --- Isolation of Foam-Causing Filamentous Bacteria --- p.95 / Chapter 5.2 --- Physiological Studies of Nocardia amarae --- p.96 / Chapter 5.2.1 --- Growth Kinetics --- p.96 / Chapter 5.2.2 --- Effects of Fatty Acids on Nocardia amarae --- p.96 / Chapter 5.2.2.1 --- Fatty Acids as Sole Carbon Source --- p.96 / Chapter 5.2.2.2 --- Growth Stimulation --- p.97 / Chapter 5.2.2.3 --- Foam Test --- p.98 / Chapter 5.3 --- Fatty Acids Analysis --- p.99 / Chapter 5.4 --- Laboratory-Scale Activated Sludge Unit --- p.101 / Chapter 5.4.1 --- Assessment of Performance of the Laboratory-Scale Unit --- p.102 / Chapter 5.4.2 --- Under Anoxic Condition --- p.103 / Chapter 5.5 --- Toxicity Studies --- p.103 / Chapter 5.5.1 --- Comparative Toxicity Studies in Pure Culture --- p.103 / Chapter 5.5.2 --- Chlorination Studies of the Laboratory-Scale Unit --- p.105 / Chapter 6. --- Conclusion --- p.107 / Chapter 7. --- Summary --- p.108 / Chapter 8. --- References --- p.110

by Sonia, Tze Yan Lo. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 132-147). / Abstracts in English and Chinese. / Acknowledgments --- p.i / Abstract --- p.ii / Table of Content --- p.iii / List of Figures --- p.ix / List of Tables --- p.xiii / List of Abbreviations --- p.xv / Terminology --- p.xvii / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Objectives of sewage treatment process --- p.1 / Chapter 1.1.1 --- Types of treatment --- p.1 / Chapter 1.1.2 --- Activated sludge process --- p.2 / Chapter 1.1.3 --- Functioning of activated sludge process --- p.2 / Chapter 1.2 --- Common microbially mediated solid separation problems --- p.4 / Chapter 1.3 --- Bacterial foaming --- p.4 / Chapter 1.4 --- Factors enhancing foam production --- p.5 / Chapter 1.4.1 --- Substrates present in sewage --- p.6 / Chapter 1.4.2 --- Operating conditions --- p.8 / Chapter 1.4.3 --- Overpopulation of foaming bacteria --- p.8 / Chapter 1.5 --- Bacteria reported for foaming --- p.9 / Chapter 1.5.1 --- Foaming bacteria reported in different countries --- p.9 / Chapter 1.5.2 --- Nocardia Biology --- p.10 / Chapter 1.6 --- Metaboilsm of hydrophobic substances in sewage --- p.11 / Chapter 1.6.1 --- Metabolism of alkanes --- p.11 / Chapter 1.6.2 --- Metabolism of grease and oils --- p.11 / Chapter 1.6.3 --- Functions of lipids in the formation of bacterial foam --- p.11 / Chapter 1.7 --- Competition between floc-formers and foam-formers --- p.12 / Chapter 1.7.1 --- Interactions between microbial populations in activated sludge process --- p.12 / Chapter 1.7.2 --- Monod relationship and kinetic selection --- p.15 / Chapter 1.7.3 --- Effects of grease and oils in dominance of foaming bacteria --- p.17 / Chapter 1.8 --- Suggested mechanisms for bacterial foaming --- p.18 / Chapter 1.8.1 --- Mechanism suggested in early stage --- p.18 / Chapter 1.8.2 --- Froth flotation theory --- p.18 / Chapter 1.9 --- Problems from foaming --- p.21 / Chapter 1.10 --- Control of filamentous bacterial foaming --- p.22 / Chapter 2. --- Objectives of the study --- p.26 / Chapter 3. --- Materials and Methods --- p.27 / Chapter 3.1 --- Sample collection --- p.27 / Chapter 3.2 --- Isolation of major foaming and non-foaming bacteria --- p.27 / Chapter 3.2.1 --- Isolation of foaming bacteria --- p.27 / Chapter 3.2.2 --- Isolation of non-foaming bacteria --- p.30 / Chapter 3.3 --- "Physiological studies on type strain Nocardia amarae ATCC 27810, isolated major foaming bacterium, Nocardia sp. CU-2 and non- foaming bacterium, Aeromonas sp. CU-1" --- p.31 / Chapter 3.4 --- Effects of fatty acids on growth kinetics of Nocardia sp. CU-2 and Aeromonas sp. CU-1 in pure culture --- p.32 / Chapter 3.5 --- Effects of fatty acids on growth yields of Nocardia sp. CU-2 and Aeromonas sp. CU-1 in pure culture --- p.34 / Chapter 3.6 --- Effects of fatty acids on growth yields of Nocardia sp. CU-2 and Aeromonas sp. CU-1 in mixed culture --- p.37 / Chapter 3.7 --- Effect of fatty acids on the propensity of foam formation of Nocardia sp. CU-2 growing with different fatty acids --- p.38 / Chapter 3.8 --- Effects of fatty acids on hydrocarbon affinity (HA) of Nocardia sp CU-2 --- p.39 / Chapter 3.9 --- "Effects of fatty acids on the filamentous growth, nocardial growth, foaming abilities and settling abilities of activated sludge in batch cultures of foaming and non-foaming samples" --- p.43 / Chapter 4. --- Results --- p.48 / Chapter 4.1 --- Isolation of foaming and non-foaming bacteria --- p.48 / Chapter 4.1.1 --- Isolation of foaming bacteria --- p.48 / Chapter 4.1.2 --- Isolation of non-foaming bacteria --- p.48 / Chapter 4.2 --- "Physiological studies on type strain Nocardia amarae ATCC 27810, isolated major foaming bacterium, Nocardia sp. CU-2 and non- foaming bacterium, Aeromonas sp. CU-1" --- p.56 / Chapter 4.3 --- Effects of fatty acids on growth kinetics of Nocardia sp. CU-2 and Aeromonas sp. CU-1 in pure culture --- p.56 / Chapter 4.4 --- Effects of fatty acids on growth yields of Nocardia sp. CU-2 and Aeromonas sp. CU-1 in pure culture --- p.60 / Chapter 4.4.1 --- Effects of fatty acids on Nocardia sp. CU-2 --- p.77 / Chapter 4.4.2 --- Effects of fatty acids on Aeromonas sp. CU-1 --- p.77 / Chapter 4.5 --- Effects of fatty acids on growth yields of Nocardia sp. CU-2 and Aeromonas sp. CU-1 in mixed culture --- p.78 / Chapter 4.6 --- Effect of fatty acids on the propensity of foam formation of Nocardia sp. CU-2 growing with different fatty acids --- p.78 / Chapter 4.7 --- Effects of fatty acids on hydrocarbon affinity (HA) of Nocardia sp CU-2 --- p.83 / Chapter 4.8 --- "Effects of fatty acids on the filamentous growth, nocardial growth, foaming abilities and settling abilities of activated sludge in batch cultures of foaming and non-foaming samples" --- p.103 / Chapter 4.8.1 --- The filamentous growth of activated sludge --- p.103 / Chapter 4.8.2 --- Nocardial count --- p.103 / Chapter 4.8.3 --- Foam ratings --- p.107 / Chapter 4.8.4 --- Sludge settling ability --- p.107 / Chapter 5. --- Discussion --- p.114 / Chapter 5.1 --- "Physiological studies on type strain Nocardia amarae ATCC 27810, isolated major foaming bacterium, Nocardia sp. CU-2 and non- foaming bacterium, Aeromonas sp. CU-1" --- p.114 / Chapter 5.2 --- Effects of fatty acids on growth kinetics of Nocardia sp. CU-2 and Aeromonas sp. CU-1 in pure culture --- p.114 / Chapter 5.2.1 --- Inhibition effects of MC fatty acids on growth of Nocardia sp. CU-2 --- p.115 / Chapter 5.2.2 --- Effects of fatty acids on specific growth rates --- p.115 / Chapter 5.2.3 --- Length of lag phase --- p.115 / Chapter 5.2.4 --- Kinetic selection of Nocardia sp. CU-2 and Aeromonas sp. CU-1 --- p.116 / Chapter 5.3 --- Effects of fatty acids on growth yields of Nocardia sp. CU-2 and Aeromonas sp. CU-1 in pure culture --- p.117 / Chapter 5.3.1 --- Growth of Nocardia sp. CU-2 and Aeromonas sp. CU-1 in different media --- p.117 / Chapter 5.3.2 --- "Effects of fatty acids on Nocardia sp, CU-2" --- p.118 / Chapter 5.3.3 --- Effects of fatty acids on Aeromonas sp. CU-1 --- p.119 / Chapter 5.4 --- Effects of fatty acids on growth yields of Nocardia sp. CU-2 and Aeromonas sp. CU-1 in mixed culture --- p.119 / Chapter 5.4.1 --- Effects of fatty acids in NB --- p.119 / Chapter 5.4.2 --- Effects of fatty acids in MM --- p.120 / Chapter 5.4.3 --- Effects of fatty acids in SS --- p.121 / Chapter 5.5 --- Effect of fatty acids on the propensity of foam formation of Nocardia sp. CU-2 growing with different fatty acids --- p.122 / Chapter 5.6 --- Effects of fatty acids on hydrocarbon affinity (HA) of Nocardia sp CU-2 --- p.122 / Chapter 5.6.1 --- Differences in HA of Nocardia sp. CU-2 among three hydrocarbons --- p.122 / Chapter 5.6.2 --- Differences in HA of Nocardia sp. CU-2 among three different media --- p.123 / Chapter 5.6.3 --- Effects of fatty acids on HA of Nocardia sp. CU-2 --- p.123 / Chapter 5.7 --- "Effects of fatty acids on the filamentous growth, nocardial growth, foaming and settling abilities of activated sludge in batch cultures" --- p.124 / Chapter 5.7.1 --- Abundance of filamentous microorganisms in activated sludge --- p.124 / Chapter 5.7.2 --- Nocardial count --- p.124 / Chapter 5.7.3 --- Foam ratings --- p.125 / Chapter 5.7.4 --- Sludge settling ability --- p.126 / Chapter 6. --- Conclusion --- p.127 / Chapter 7. --- Summary --- p.129 / Chapter 8. --- References --- p.132

Les bactéries du genre Nocardia sont des Actinobactéries filamenteuses. Ces microorganismes sont saprophytes du sol. Les infections à Nocardia ou nocardioses se manifestent dans la majorité des cas (60%) par des infections pulmonaires et plus rarement par des infections cérébrales. La souche Nocardia cyriacigeorgica GUH-2 à causé la mort d'un patient dans les années 70. Des études sur cette souche ont montré qu'elle avait un haut pouvoir pathogène et qu'elle était capable dans certaines conditions de déclencher chez la souris et les primates le développement de troubles moteurs similaires à ceux observés dans la maladie de Parkinson. Afin d'appréhender l'implication de l'espèce pathogène opportuniste N. cyriacigeorgica dans l'une des plus importantes maladies neurodégénératives du 21ème siècle, le séquençage du génome de la souche N. cyriacigeorgica GUH-2 à été entrepris. Il a permis l'identification d'un grand nombre de gènes liés à la virulence et à la résistance aux antibiotiques ainsi que l'identification d'ilots génomiques et de séquences d'insertions reflétant une plasticité plus grande que celle qui était décrite pour ce genre bactérien. L'étude de groupements de gènes impliqués dans la production de métabolites secondaire a montré que ces molécules pourraient être responsables des propriétés neurodégénératives de la souche. L'espèce de N. cyriacigeorgica étant retrouvée fréquemment en clinique sans que son réservoir naturel n'ai été mis en évidence à ce jour, la mise au point de marqueurs de détection génétique a été réalisé afin de permettre la recherche de la niche écologique de cette espèce mais également de faciliter le diagnostic des nocardioses.

Descrição: As doenças causadas por actinomicetos patógenos, aeróbios e anaeróbios facultativos, diferem consideravelmente no que diz respeito à sua etiologia, patogênese, apresentação clínica e epidemiologia. Objetivos: Analisar a distribuição etária, manifestações clínicas, doenças de base e condições associadas, achados radiológicos, microbiológicos, tratamento e evolução, nos pacientes com actinomicetoses (actinomicose, nocardiose, rodococose). Delineamento: Foram analisados, retrospectivamente, prontuários de pacientes com achados microbiológicos positivos para infecções por actinomicetos. Local do estudo: Um hospital universitário de atendimento terciário em Porto Alegre, Rio Grande do Sul, Brasil. Pacientes e métodos: Foram incluídos neste estudo, pacientes com diagnóstico de actinomicose, nocardiose e rodococose, num período de 1978 a 2009. Os critérios microscópicos para o diagnóstico de actinomicetose foram os seguintes: actinomicose - composto por grânulos actinomicóticos, filamentos Gram-positivos, não ácido-resistentes; nocardiose - bactérias filamentosas ramificadas, Gram-positivas, e ácido-resistentes; rodococose - cocobacilos Gram-positivos, ácido resistentes. Resultados: Foram incluídos 59 pacientes com actinomicetose. Actinomicose foi obervada em 27 pacientes entre 8 e 65 anos (idade média de 39,9 anos), 22 do sexo masculino (81,5%). Doença oral (cárie dentária, a doença periodontal) esteve frequentemente associada, sendo procedimento odontológico o fator de risco mais importante. A apresentação clínica foi actinomicose torácica em 24 casos, em dois facial e em um cérvico-facial e mediastinal. O diagnóstico microscópico foi positivo em 25, com o isolamento do organismo em cultivo anaeróbico em um, e, pelo teste de imunofluorescência direta em um. Estes dois últimos casos foi identificado como A. israelii. O tratamento mais utilizado consiste na administração prolongada de penicilina e esteve associado a boa evolução na maioria dos casos. Nocardiose foi observada em 27 pacientes, a idade variou entre 21 e 84 anos, idade média de 51,8 anos. A manifestação mais comum foi pneumonia cavitária, apresentado no paciente imunossuprimido, especialmente recebendo altas doses de corticoterapia. Todos os casos foram positivos para filamentos bacterianos ramificados Gram-positivos, ácido resistentes, sugestivos de espécies de Nocardia. Nocardia sp foi isolada em 14 casos, ―N. asteroides” em 7, N. farcinica em 2, N. brasiliensis em 1, N. pseudobrasiliensis em 1, N. abscessus em 1 e N. cyriacigeorgica em 1. Doze pacientes foram a óbito e os restantes tiveram melhora clínica. A rodococose foi diagnosticada em 5 pacientes, com idade, no momento do diagnóstico, de 22-69 anos (média de 45,6). Rhodococcus foi isolado em todos os 5 casos, três pacientes imunodeprimidos apresentaram infecção pulmonar pelo R. equi. O caso do paciente com HIV/AIDS foi fatal. Conclusões: Esta experiência, indica que a informação clínica associada ao Gram e a ácido-resistência em amostras clínicas é útil no reconhecimento da infecção por actinomicetos. A actinomicetose deve ser sempre considerada em pacientes apresentando doença febril supurativa ou radiografia de tórax anormal, em paciente com estado imune alterado causado por determinadas drogas (corticoterapia) e condições associadas (HIV/AIDS). / Background: Diseases caused by pathogenic aerobic and facultative anaerobic actinomycetes differ considerably with respect to their etiology, pathogenesis, clinical appearence and epidemiology. Objectives: To analyse the age distribution, clinical manifestations, underlying diseases and associated medical conditions, radiographic findings, microbiology, treatment and outcome, in patients with actinomycetosis (actinomycosis, nocardiosis, rhodococcosis). Design: The medical records of patients with positive microbiology findings to actinomycetes infections were retrospectively analysed. Settings: A university-based tertiary care hospital in Porto Alegre, Rio Grande do Sul, Brazil. Patients and methods: From 1978 through 2009 patients diagnosed with actinomycosis, nocardiosis, and rhodococcosis were included in this study. The microscopic criteria for diagnosis of actinomycetosis were as follow: actinomycosis –granules composed by branching Gram-positive organisms non acid-fast stained; nocardiosis - branched filamentous, Gram-positive, and acid-fast bacteria; rhodococcosis - coccobacilli Gram-positive, and acid-fast organism. Results: Sixty-five patients with actinomycetosis were included. Actinomycosis was oberved in 27 patients between 8 and 65 years old (mean age, 39,9 years), 22 were male (81,5%). Oral disease (poor dentition, periodontal disease) frequently associated with dental procedure was the most important risk factor. The clinical presentation was thoracic actinomycosis in 24 cases, facial in two, and cervico-facial and mediastinal one. Microcopic diagnosis were positive in 25, recovery of organism in anaerobic culture in one, and by fluorescent antibody test in one. These last two cases was identified as A. israelii. Treatment most commonly consisted of prolonged administration of penicillin and was associated with good outcome in the majority of cases. Nocardiosis was observed in 27 patients, aged 21 to 84 years old, with a mean age of 51,8 years. Cavitary pneumonia was the most common manifestation, presented in immunosuppresed patient, especially receiving high-dose corticotherapy. All cases were positive for branching Gram-positive, acid-fast bacterial filaments, suggestive of a Nocardia species. Nocardia sp was isolated in 14 cases, ―N. asteroides” in 7, N. farcinica in 2, N. brasiliensis in 1, N. pseudobrasiliensis in 1, N. abscessus in 1 and N. cyriacigeorgica in 1. Twelve patients died and the remaining cases were well improved. The diagnosis of rhodococcosis was made in five patients, ranged in age at time of diagnosis from 22 to 69 years, with a mean age of 45,6 years. Rhodococcus was isolated in all 5 cases, three immunocompromised patients showed pulmonary infection by R. equi. The case with HIV/AIDS was fatal. Conclusions: This experience, indicates that clinical information with Gram and acid-fast stains on clinical specimens is helpful in recognizing the possibility os actinomycetes should always be considered as a cause os suppurative febrile illness or abnormal chest roentgenograms in patient who may have an altered immune status caused by certain drugs (corticotherapy) and underlying conditions (HIV/AIDS).