Actinomycetes and Nocardia


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ACTINOMYCETES ( Includes Nocardia)

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Actinomycetes and Nocardia

  1. 1. ACTINOMYCETES( Includes Nocardia)Dr.T.V.Rao MDDr.T.V.Rao MD 1
  2. 2. ACTINOMYCETES MORPHOLOGY• Have filamentous growth, like fungi• On substrate, grow on and in it• Thallus -- tissuelike mass, grown inculture• Mycelium -- tangled mass of hyphae,found in natureDr.T.V.Rao MD 2
  3. 3. Actinomyctes.• Actinomyctes are branching Gram-positive bacilli. They are facultativeanaerobes, but often fail to growaerobically on primary culture. Theygrow best under anaerobic or micro-aerophilic conditions with theaddition of 5-10% carbon dioxideDr.T.V.Rao MD 3
  4. 4. Morphology of ActinomycetesDr.T.V.Rao MD 4
  6. 6. ACTINOMYCETES ECOLOGY• Predominantly soil bacteria• Good at degrading recalcitrantcompounds such as chitin & cellulose• Often active at higher pH (contrast tofungi who may dominate at lower pH)• Give soil the “earthy” smellDr.T.V.Rao MD 6
  7. 7. Commensals in the Mouth• Almost all species arecommensals of the mouth andhave a narrow temperature rangeof growth of around 35-37°C.They are responsible for thedisease known as actinomycosis.Dr.T.V.Rao MD 7
  8. 8. Species of Actinomyctes• Three-quarters of human cases arecaused by Actinomyces israelii. Lesscommon causes include A.gerencseriae, A. naeslundii, A.odontolyticus, A. viscosus, A. meyeri,Arachnia propionica and members ofthe genus Bifidobacterium.Dr.T.V.Rao MD 8
  9. 9. Actinomycetes• Classification– Order – Actinomycetales• Show fungus-like characteristics such as branching intissues or in culture (look like mycelia).– The filaments frequently segment during growth to producepleomorphic, diphtheroidal, or club shaped cells.• The cell wall and the internal structures are typical ofbacteria rather than fungi.• Some are aerobic and others are anaerobic.• All are slow growingDr.T.V.Rao MD 9
  10. 10. Clinical PresentationDr.T.V.Rao MD 10
  11. 11. Clinical presentation• Cervicofacial infection, whichaccounts for more than half ofreported cases; the jaw is ofteninvolved. The disease is endogenousin origin; dental caries is apredisposing factor, and infectionmay follow tooth extractions orother dental procedures.Dr.T.V.Rao MD 11
  12. 12. Who Get Infected• Men are affected morefrequently than women,and in some regions thedisease is morecommon in ruralagricultural workersthan in town dwellers,probably owing tolower standards ofdental care in theformer.Dr.T.V.Rao MD 12
  13. 13. Thoracic actinomycosis• Thoracic actinomycosis commences inthe lung, probably as a result ofaspiration of actinomyces from themouth. Sinuses often appear on thechest wall, and the ribs and spine maybe eroded. Primary endobronchialactinomycosis is an uncommoncomplication of an inhaled foreign body.Dr.T.V.Rao MD 13
  14. 14. Abdominal Actinomyctes• Abdominal cases commence in the appendixor, less frequently, in colonic diverticulae.• Pelvic actinomycosis occurs occasionally inwomen fitted with plastic intra-uterinecontraceptive devices.• Actinomyces have been isolated from cases ofchronic granulomatous disease and should bevigorously sought in this rare condition.Dr.T.V.Rao MD 14
  15. 15. Actinomycetes• Clinical significance– Are part of the NF found in the cavities of humans andother animals.– All may cause actinomycosis or “lumpy jaw” which is acervicofacial infection that used to occur followingtooth extractions or dental surgery which providedtraumatized tissue for growth of the microorganismwhich may also invade the bone.» This is rare today because of prophylactic antibiotictherapy.– May cause thoracic or abdominal infections– May cause meningitis, endocarditis, or genital infectionsDr.T.V.Rao MD 15
  16. 16. Actinomycetes–Every kind of infection ischaracterized by draining sinuses,usually containing characteristicgranules which are colonies ofbacteria that look like denserosettes of club-shaped filamentsin radial arrangement•Treatment–Penicillin Dr.T.V.Rao MD 16
  17. 17. Diagnosis• Specimens should be obtained directly fromlesions by open biopsy, needle aspiration or, inthe case of pulmonary lesions, by fibreopticbronchoscopy. Examination of sputum is of novalue as it frequently contains oralactinomycetes. Material from suspected casesis shaken with sterile water in a tube. Sulphurgranules settle to the bottom and may beremoved with a Pasteur pipette.Dr.T.V.Rao MD 17
  18. 18. Diagnosis• Granules crushed between two glassslides are stained by the Gram andZiehl-Neelsen (modified by using 1%sulphuric acid for decolorization)methods, which reveal the Gram-positive mycelia and the zone ofradiating acid-fast clubs.Dr.T.V.Rao MD 18
  19. 19. Identification• Sulphur granules andmycelia in tissuesections areidentifiable by use offluorescein-conjugated specificantisera. In-situ PCRhas been used todetect A. israelii intissue biopsies. Dr.T.V.Rao MD 19
  20. 20. Actinomyctes sppObtained from the CDC Public Health Image LibraryDr.T.V.Rao MD 20
  21. 21. Culturing• For culture, suitablemedia, such as bloodor brain-heartinfusion agar,glucose broth andenrichedthioglycollate broth,are inoculated withwashed and crushedgranules. Dr.T.V.Rao MD 21
  22. 22. Culturing• Cultures are incubated aerobically andanaerobically for up to 14 days. After severaldays on agar medium, A. israelii may form so-called spider colonies that resemble molarteeth. The identity may be confirmed bybiochemical tests, by staining with specificfluorescent antisera or by gas chromatographyof metabolic products of carbohydratefermentation.Dr.T.V.Rao MD 22
  23. 23. Antibiotics in Actinomyctes• Actinomyces are sensitive to many antibiotics,but the penetration of drugs into the denselyfibrotic diseased tissue is poor. Thus, largedoses are required for prolonged periods, andrecurrence of disease is not uncommon.Surgical debridement reduces scarring anddeformity, hastens healing and lowers theincidence of recurrences..Dr.T.V.Rao MD 23
  24. 24. Antibiotics in Actinomyctes• Prolonged penicillin-based regimens areincreasingly being replaced by shorterregimens based on amoxicillin withclavulanic acid (the clavulanic acid isrequired because lesions are oftenconcomitantly infected with β-lactamase-producing bacteria) or cephalosporins,especially ceftriaxone.Dr.T.V.Rao MD 24
  25. 25. Antibiotics in Actinomyctes• Alternative agents include tetracyclines,macrolides, fluoroquinolones andimipenem but in-vitro sensitivity testingis unreliable. Additional drugs, includingaminoglycosides and metronidazole, maybe required when concomitantorganisms are present.Dr.T.V.Rao MD 25
  26. 26. NOCARDIADr.T.V.Rao MD 26
  27. 27. Nocardiosis• Nocardiosis primarily presents as a pulmonarydisease or brain abscess in the U.S. In LatinAmerica, it is more frequently seen as thecause of a subcutaneous infection, with orwithout draining abscesses. It can evenpresent as a lesion in the chest wall thatdrains onto the surface of the body similar toactinomycosis. Brain abscesses are frequentsecondary lesions.Dr.T.V.Rao MD 27
  28. 28. Morphology of Nocardia–The Nocardia are branched, strictlyaerobic, Gram-positive bacteria thatare closely related to the rapidlygrowing mycobacteria. Like the latter,but unlike Actinomyctes, they areenvironmental saprophytes with abroad temperature range of growth. .Most isolates are acid-fast whendecolorized with 1% sulphuric acid.Dr.T.V.Rao MD 28
  29. 29. Epidemiology• Many species of Nocardia are found in theenvironment, notably in soil, and a range ofspecies cause human opportunist disease,notably Nocardia asteroids, so named becauseof its star-shaped colonies, N, abscessus, N.farcinica, N. brasiliensis, N. brevicatena, N.otitidiscaviarum, N. nova and N. transvalensis.A wider range of species is encountered inprofoundly immunosuppressed patients.Dr.T.V.Rao MD 29
  30. 30. Other Species Infective• Nocardiae, principally N. asteroides, areuncommon causes of opportunist pulmonarydisease, which usually, but not always, occursin immunocompromised individuals, includingthose receiving post-transplantimmunosuppressive therapy or chemotherapyfor cancer and those with acquired immunedeficiency syndrome (AIDS).Dr.T.V.Rao MD 30
  31. 31. Nocardia and Corticosteroid Therapy• Corticosteroid therapy is a strong risk factor.As a result, the frequency and diversity ofclinical manifestations of Nocardia disease hasincreased over the past few decades. Pre-existing lung disease, notably alveolarproteinosis, also predisposes to nocardialdisease. The infection is exogenous, resultingfrom inhalation of the bacilli. The clinical andradiological features are very variable andnon-specific, and diagnosis is not easyDr.T.V.Rao MD 31
  32. 32. Clinical presentation• Most cases there are multiple confluentabscesses with little or no surroundingfibrous reaction, and local spread mayresult in pleural effusions, empyema andinvasion of bones. In some cases thedisease is chronic, whereas in others itspreads rapidly through the lungs.Dr.T.V.Rao MD 32
  33. 33. Other Complications• Secondary abscesses in the brain and, lessfrequently, in other organs occur in about one-third of patients with pulmonary nocardiosis.Acute dissemination with involvement ofmany organs occurs in profoundlyimmunosuppressed persons, notably thosewith AIDS. Recurrence is common inimmunosuppressed patients and mortality ishigh.Dr.T.V.Rao MD 33
  34. 34. Other Complications• Nocardiae also cause primary post-traumatic,postoperative or post-inoculation cutaneousinfections (primary cuteneous nocardiasis).The most frequent cause is N. brasiliensis butsome cases are caused by N. asteroides orother species. In the USA and the southernhemisphere, but rarely in Europe, cutaneousinfections may result in fungating tumour-likemasses termed mycetomas.Dr.T.V.Rao MD 34
  35. 35. Diagnosis of Nocardia Infections• A presumptive diagnosis of pulmonarynocardiasis may be made by a microscopicalexamination of sputum. In many cases thesputum contains numerous lymphocytes andmacrophages, some of which containpleomorphic Gram-positive and weakly acid-fast bacilli, and occasional extracellularbranching filaments.Dr.T.V.Rao MD 35
  36. 36. Modified Z N Staining• Nocardia are not soeasily seen in tissuebiopsies stained by theGram or modified Ziehl-Neelsen methods, butmay be seen inpreparations stained bythe Gram-Weigert orGomori methenaminesilver methods.Dr.T.V.Rao MD 36
  37. 37. Culturing Nocardia• Nocardiae grow on blood agar,although growth is better onenriched media includingLöwenstein-Jensen medium, brain-heart infusion agar and Sabouraudsdextrose agar containingchloramphenicol as a selective agent.Dr.T.V.Rao MD 37
  38. 38. Culture on Media• Growth is visible afterincubation for between2 days and 1 month;selective growth isfavoured by incubationat 45°C. Colonies arecream, orange or pinkcoloured; their surfacesmay develop a dry,chalky appearance, andthey adhere firmly tothe mediumDr.T.V.Rao MD 38
  39. 39. Treating Nocardia• Widely used regimen issulfamethoxazole with trimethoprim(co-trimoxazole) for 3-6 months,although this prolonged course oftencauses adverse drug reactions. Inaddition, some strains, especially ofN. farcinica, are resistant tosulphonamides.Dr.T.V.Rao MD 39
  40. 40. Other drugs in Use• An alternative regimen, particularlyin severe disease, is high-doseimipenem with amikacin for 4-6weeks. Minocycline, third generationcephalosporins, amoxicillin-clavulanate combinations andlinezolid, an oxazolidinone, are alsoeffective. Dr.T.V.Rao MD 40
  41. 41. • Programme Created by Dr.T.V.Rao MDfor Medical and Paramedical Students• Email• doctortvrao@gmail.comDr.T.V.Rao MD 41