This document discusses the aerobic actinomycete Nocardia. It begins by classifying Nocardia taxonomically and noting it is an opportunistic pathogen found in soil. The document then covers the epidemiology, pathogenesis, clinical manifestations including pulmonary, skin and disseminated infections, diagnosis through microscopy, culture and molecular methods, and treatment with antimicrobials. In summary, Nocardia is an environmental actinomycete that can cause infection in immunocompromised individuals, with pulmonary disease being most common and diagnosis relying on microscopy, culture and molecular identification methods.

1. AEROBIC
ACTINOMYCETES
PRESENTED BY:DR.AAMIR

2. ACTINOMYCETES
 Better known for the production of a wide range of
 Antibiotics
 Anticancer drugs
 Industrial enzymes
 Only a few species of this order are human pathogens
 Mostly oppurtunistic

3. ACTINOMYCETES
 Thin, Gram +ve, non-motile, non-sporing, non- capsulated filaments
containing muramic acid.
 Morphological resemblance to fungi, cellular organization typical of
bacteria
 Related to Mycobacteria and Corynebacteria
 Mostly free living, mainly soil
 Slow growers

5. AEROBIC ACTINOMYCETES

6. CLASSIFICATION

7. NOCARDIA

8. History
 Named after Edmond Nocard
 Described & isolated the organism in
cattle with bovine farcy(1888).
 In 1889 given the name Nocardia
farcinica by Trevisan
 First human case of Nocardiosis was
reported in 1890 by Eppinger.
 From brain abscess
 Cladothrix asteroides
 Later renamed Nocardia asteroides
Edmond Nocard

9. TAXONOMY
Kingdom: Bacteria
Phylum: Actinobacteria
Class: Actinobacteria
Order: Actinomycetales
Suborder: Corynebacterineae
Family: Nocardiaceae
Genus: Nocardia

10. INTRODUCTION
 Most important genus among aerobic
actinomycetes.
 Saprophytic
 Nearly 100 species isolated
 Reside in soil
 Contribute to decay of organic matter
 Responsible for localized or
disseminated infections in animals
and humans

11. Characteristics
 Gram-positive bacilli showing a
branching, beaded, and filamentous
form.
 Stain poorly with Gram stain
 Appear to be Gram negative with
intracellular Gram-positive granules
 Usually weakly acid fast
 Acid fastness differentiates it from
other similar bacteria, such as
Actinomyces.

12.  Catalase positive
 CELL WALL COMPOSITION:
 Short chain mycolic acids
 Peptidoglycan
 Meso-DAP
 Arabinose
 Galactose

13. Nocardia species
 Of 100 species , 40 species are known to be human
pathogens.
 Most commonly reported species from clinical sources:
 Nocardia asteroides complex
 Nocardia nova (most commonly isolated)
 Nocardia farcinica (most resistant & likely to disseminate)
 Nocardia cyriacigeorgica
 Nocardia abscessus
 Nocardia brasiliensis (skin,sub-cutenous,lymphocutaneous)

14. Nocardia vs Fungi
Characteristic Nocardia Fungi
Filament/hyphae 0.5–1.0μm in diameter 1.5 to ≥15μm
Reproduction Binary Fission, Hyphae
Fragmentation
Sexually/Asexually
Cell wall composition Mycolic acid Chitins+glucans+mannans+
other fungal specific
proteins
Treatment Anti-bacterials Anti-fungals

15. Epidemiology
 Nocardia is everywhere in the environment:
 Soil,
 Organic matter, and
 Water.
 Common animal infection
 Outbreaks in oncology and transplant wards and surgical wounds have
occured from :
 Fomites,
 Hospital construction with resultant contaminated dust,
 Health care worker hands.

16.  United States: 500-1,000 new cases of Nocardiosis occur every
year.
 60% of Nocardiosis cases are associated with pre-existing immune
compromise.
 Men greater risk than women; 3:1

17. Transmission
 HABITAT: Soil rich in organic matter.
 Nocardia spp. that colonize the normal
humans usually do not cause any
infection in the same host.
 Inhalation of infective aerosols.
 Penetration through the skin.

18. People at risk
 Pathogenic bacteria have low virulence in Immuno-competent
 Nocardiosis is increasingly found in the immunocompromised
individuals.
 More common in patients with HIV
 Received organ, bone marrow, or stem cell transplantation
 Cirrhosis, lymphoreticular malignancies, and SLE.
 Chronic pulmonary disease, such as emphysema, bronchitis,
bronchiectasis, etc.
 Small children
 Elderly

19. PATHOGENESIS
 Disease manifestations of Nocardiosis are determined by
 Strain characteristics
 Inoculation site
 Tissue tropism
 Ability to survive initial neutrophilic leukocyte phagocytic attack
 Nature of the immune response.
 T-cell–mediated immunity is the principal protective immune
response to Nocardiosis
 Most problematic in individuals with impaired T-cell–mediated immunity.
 Chronic granulomatous disease patients-more vulnerable to this
infection

20. Pathogenesis(contd.)
Outer lipids-cytokines IL-1β & IL-6(MACROPHAGES)
=>powerful granulomatous reaction
Catalase & Superoxide Dismutase inactivate reactive
oxygen species that would otherwise prove toxic to the bacteria
Cord Factor-
interferes with phagocytosis by macrophages by preventing the
fusion of phagosome with lysosome.
Gives rise to cell wall–deficient forms (L-forms) that
can be isolated from within macrophages many days later

21. CLINICAL MANIFESTATIONS
Pulmonary
Manifestation
Pneumonia
Disseminated
Disease
Brain
abscess
Skin
Manifestations
Superficial
infection
Lympho-
cutaneous
syndrome
Actino-
mycetoma
Eye Infection
Keratitis
Endopthalmatitis

22. Pulmonary Manifestations
 Most common spp –
 N. cyriaci-georgica,
 N. nova,
 N. farcinica.
 Suppurative in nature, but
granulomatous or mixed responses
occur
 Endobronchial inflammatory
masses,
 Pneumonia,
 Lung abscess,
 Cavitary disease

23. Skin Manifestations
Cellulitis,
Lympho-
cutaneous
syndrome,
Actino-
mycetoma .

24. Cellulitis
 N. brasiliensis and N. otitidis caviarum complex
 Begins 1–3 weeks after a recognized breach of the skin, (often with soil
contamination)
 Sub-acute cellulitis, with pain, swelling, erythema, and warmth, develops
over days to weeks
 Lesions are usually firm and not fluctuant.
 May progress to involve underlying muscles, tendons, bones, or joints
 Dissemination is rare.

25. Lympho-Cutaneous Syndrome
(Sporotrichoid Nocardiosis)
 Associated with N. brasiliensis
 Similar disease occurs with other pathogens, most notably Sporothrix
schenckii and Mycobacterium marinum
 Begins as a pyodermatous nodule at the site of inoculation with
 Central ulceration
 Purulent or honey-colored drainage
 appear along lymphatics that drain the primary lesion.

26. ACTINOMYCETOMA(Madura Foot)
 Nocardia asteroides causes infections
worldwide,
 N. brasiliensis is limited to the southern United
States and Central and South America
 Organism enters the body through breaks in the
skin
 Causes a localized infection involving skin ,
cutaneous , and subcutaneous tissue
 Chronic, indurated, granulomatous masses,
mostly found on the lower extremities

27.  Characteristic features in Mycetoma
 Swelling (tumifaction)
 Draining sinuses
 Granules
 Tends to invade underlying connective tissue,
muscle, bone

 Also caused by fungi (eumycetoma)

28. Disseminated Disease
 Disseminated infection- characterized by
widespread abscess formation.
 Most common site - brain.
 Eye (particularly the retina), skin and
subcutaneous tissues, kidneys, joints, bone,
and heart
 Brain abscesses are usually supra-tentorial ,
multiloculated , single or multiple

29. Nocardial keratitis
 Most commonly identified agents -“N.
asteroides complex” and N. brasiliensis
 Well described in Asia and has been reported in
travelers returning from Asia
 Aggressive ocular infection, typically following
corneal trauma or minor surgical procedures to
the eye
 Appropriate therapy - keratitis resolves with
good visual outcomes
 Nocardial endophthalmitis can develop :
 after eye surgery.
 during disseminated disease.

30. DIAGNOSIS
 IMAGING STUDIES
 Plain chest radiography
 CT chest scanning
 CT or MRI Brain
 CSF analysis(meningitis)
 Skin ,lung or brain biopsies

31. LAB DIAGNOSIS
 SPECIMEN:
 Sputum is a frequently received specimen.
 Other specimen:
 Respiratory secretions(BAL, bronchial washings)
 Biopsies-skin ,lung
 Pus from abscesses.

32. MICROSCOPY
GRAM
STAIN
ACID
FAST
STAIN
SILVER
STAIN

33. GRAM STAIN
 Routine Gram staining
 Examination of sputum or pus
for crooked, branching,
beaded, gram-positive
filaments 1 μm wide and up to
50 μm long

34. ACID FAST STAIN
 Most Nocardiae are acid-fast in
direct smears if a weak acid is used
for de-colorization
 Modified Kinyoun,
 Ziehl-Neelsen,
 Fite-Faraco methods

35. Modified Acid Fast stain

36. SILVER STAIN
 Gomori methanemine
silver stain of tissue
specimen-biopsy

37. CULTURE
 Grow on most non-selective media
used routinely for culture of bacteria
e.g
 Sheep’s blood agar,
 Brain–heart infusion agar,
 SAB without antibiotics
 LJ medium
 Middlebrook 7H10 agar
 Specimen containing mixed flora
(e.g., respiratory secretions) use of
selective media e.g
 Thayer-Martin agar with antibiotics
 Paraffin agar.
 Buffered charcoal-yeast
extract(BCYE) medium

38. CULTURE
 N. asteroides grows well at 25°C,
35°C to 37°C, and at 42°C to 45°C
 Growth is enhanced by incubation
in 10% CO2.
 Growth of Nocardia species may
take 48 hours to 7 to 14 days,
 But typical colonies are usually
seen after 3 to 5 days
 Nocardia colonies vary from white,
to tan, orange and red in color.

39. CULTURE
 Appear either buff or pigmented,
 Waxy cerebriform colonies
 Dry, chalky-white appearance if aerial
hyphae are produced.
 Characteristic earthy odor

40. CULTURE
 Lowenstein–Jensen media:
 Whitesh chalky adherent colonies
of Nocardia species
 Tap-water agar:
 Growth shows aerIal hyphae

42. Orange colony of Nocardia

43. Aerial hyphae of Nocardia

44. Other etiologies

46. Molecular Methods
 Nocardia isolates were previously classified on the basis of
phenotypic tests( hydrolysis of casein, tyrosine, xanthine, hypoxanthine, and
testosterone and by sugar utilization tests.)
 Phenotypic methods are relatively expensive, slow, and limited by
their inability to differentiate between members :largely replaced by
molecular identification tests.
 Gene targets
 65-kda heat shock protein (hsp) gene
 16S rRNA gene
 secA1 gene

47. Methods
 PCR-RFLP analysis:
 Nocardia 16S rRNA gene and the hsp65 gene (441 bp)
 Good, although incomplete, agreement for species identification
 Cant identify the more uncommon Nocardia species
 RIBOTYPING:
 identify a small number of Nocardia species
 differentiate between N. asteroides sensu stricto and N. farcinica
 limited by the need for multiple probes to identify different species
 GENE SEQUENCING
 Rapid and identifies most isolates reliably
 Sequencing of the first 500 to 606 base pairs (bp) of the 5′ end of the 16S rRNA gene
is currently the most informative approach
 Accuracy of identification is dependent on the quality of the gene repositories

48. MALDI-TOF
 Recent studies- analysis of bacterial cell wall proteins by MALDI-
TOF MS is a reliable, cheap, and rapid method for identification of
Nocardia
 Has become the method of choice in many laboratories.

49. SPECIATION ALGORITHM

50. TREATMENT
Mild/Moderate disease TMP-SMX in Two Divided doses
Severe disease TMP-SMX, Amikacin , and Ceftriaxone or
Imipenem.
Keratitis Topical sulfonamide or Amikacin drops plus a
sulfonamide or an alternative oral drug
Nocardial infections tend to relapse (particularly in patients with
chronic granulomatous disease), and long courses of antimicrobial
therapy are necessary

51. Treatment Duration
 N

52. Surgical treatment
 Brain abscesses should be aspirated, drained, or excised if:
 the diagnosis is unclear
 abscess is large and accessible,
 abscess fails to respond to chemotherapy
 In deep or extensive mycetoma cases, drainage or excision
of heavily involved tissue may facilitate healing

53. Prophylaxis
 Use of SMX and TMP in high-risk populations to prevent
Pneumocystis disease or urinary tract infections appears to reduce
but not eliminate the risk of Nocardiosis.
 Incidence of Nocardiosis is low enough and prophylaxis solely to
prevent this disease is not recommended.

54. Clinical Outcomes
 Dependent on the site and extent of disease and underlying
host factors.
 Cure rates:
 almost 100% - skin or soft tissue involvement,
 90% in - pleuropulmonary disease,
 63% in disseminated infection, and
 50% in brain abscess.

55. PREVENTION
 No specific ways to prevent infection.
 People(weakened immune systems )should
wear shoes as well as clothing covering the
skin, open wounds, and cuts when they are
working with the soil.
 Hospitals should maintain strong infection
control practices to avoid outbreaks of
Nocardiosis.
 Organ transplant recepients might be given
antibiotics to prevent bacterial infections.

56. OTHER AEROBIC ACTINOMYCETES

57. RHODOCOCCUS SPP.
 Closely related to the Nocardia
 Lack aerial “hyphae”
 Gram-positive , partially acid-fast.
 Non-motile , non-sporulating
 Coccoid or rod-like
 Rhodococcus equi -most important human
pathogen in the genus.

58. Rhodococcosis
 Zoonotic disease, presumably by a
respiratory route
 Immunocompromised individuals(defects in
cell-mediated immunity)
 Primarily pulmonary disease-clinically mimic
tuberculosis
 Also causes bacteremia, endophthalmitis,
osteomyelitis, pleurisy with effusion and
wound infections
 Mortality
 Immunocompetent = 11%
 Immunocompromised (HIV)= 50 to 55%
 Non hiv = 20 to 25 %

59. ACTINOMADURA SPP.
 Actinomadura spp. are soil organisms that are introduced
through the skin by trauma.
 primarily in tropical and subtropical countries
 India and Tunisia (A. madurae) or
 Senegal, Chad, and Somalia (A. pelletieri)
 Etilogic agent of Actinomycetoma (Madura foot)
 A. madurae infections are superficial, and can be found on
any part of the host ; Most commonly the foot

60. STREPTOMYCES SPP.
 Soil organisms- Saprophytes
 Production of two-thirds of the world’s naturally occurring
antibiotics
 S. somaliensis causes actinomycetoma
 worldwide distribution
 Recovered from patients with mycetoma in Saudi Arabia,
Nigeria, Niger, Sudan, Somalia, South Africa, Venezuela, India,
and Mexico
 Madura skull-infections involving head & neck