Page 206 - Review of Medical Microbiology and Immunology ( PDFDrive )

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mebooksfree.com mebooksfree.com mebooksfree.com Growth in Diagnosis CHAPTER 22 Actinomycetes 195 mebooksfree.com
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TABLE 22–1 Actinomycetes

Species
Disease
Habitat
Treatment
Media
Actinomycosis (abscess with
Gram-positive branching
Strictly
Oral cavity
Penicillin G
A. israelii
draining sinus tract and “sulfur
anaerobic
filamentous rods; culture
granules” in pus)
(anaerobic)
N. asteroides
Nocardiosis (abscesses in brain
sulfamethoxazole
filamentous rods; often
and kidneys in immunodeficient
acid-fast; culture (aerobic)
patients, pneumonia) Environment Aerobic Gram-positive branching Trimethoprim-
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mebooksfree.com mebooksfree.com mebooksfree.com Nocardia species are aerobes and are found in the environ- mebooksfree.com
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Treatment & Prevention
Important Properties & Pathogenesis
Treatment consists of prolonged administration of penicil-
ment, particularly in the soil. In immunocompromised
lin G, coupled with surgical drainage. There is no signifi-
cant resistance to penicillin G. No vaccine or prophylactic
individuals, they can produce lung infection and may dis-
seminate. In tissues, Nocardia species are thin, branching
drug is available.
filaments that are gram-positive on Gram stain. Many iso-
lates of N. asteroides are weakly acid-fast (i.e., the staining
NOCARDIA ASTEROIDES
decolorize than that used in the stain for mycobacteria). If
Disease
the regular-strength acid is used, N. asteroides will
Nocardia asteroides causes nocardiosis. process uses a weaker solution of hydrochloric acid to
decolorize.
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mebooksfree.com mebooksfree.com mebooksfree.com Nocardia asteroides typically causes either pneumonia, lung mebooksfree.com
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Clinical Findings
abscess with cavity formation, lung nodules, or empyema.
From the lung, the organism can spread to various organs,
notably the brain, where it causes brain abscess. Disease
occurs most often in immunocompromised individuals,
especially those with reduced cell-mediated immunity.
Nocardia brasiliensis, a different species of Nocardia, causes
skin infections in the southern regions of the United States
and mycetoma, usually in tropical regions.
Laboratory Diagnosis
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mebooksfree.com mebooksfree.com mebooksfree.com or weakly acid-fast in an acid-fast stain and (2) seeing aero- mebooksfree.com
Diagnosis in the laboratory involves (1) seeing branching
rods or filaments that are gram-positive (see Figure 22–1)
bic growth on bacteriologic media in a few days.
Treatment & Prevention
Treatment is with trimethoprim-sulfamethoxazole. Surgical
drainage may also be needed. Occasional drug resistance
occurs. No vaccine or prophylactic drug is available.
SELF-ASSESSMENT QUESTIONS
mebooksfree.com mebooksfree.com mebooksfree.com says is worse than her usual smoking-related cough. She is taking mebooksfree.com
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1. Your patient is a 75-year-old woman with fever and a painful nod-
ule on her forearm. She also has a nonproductive cough that she
FIGURE 22–2
Actinomycosis. Note inflamed lesion with small
high-dose corticosteroids (prednisone) for an autoimmune dis-
sinus tract opening anterior to right ear. Yellowish “sulfur granule” can
ease. Chest X-ray reveals a nodular lesion in the right upper lobe.
be seen at the opening. (Source: Dr. Thomas F. Sellers, Public Health Image
A biopsy of the nodule on her arm was obtained. Gram stain of the
Library, Centers for Disease Control and Prevention.)

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