Authentic NEET PG / AIIMS PG Question with Complete ExplanationNocardia
Morphology
- Gram positive
- Rod-shaped bacteria
- Show true branching both in culture and in stains from clinical lesions.
METABOLIC PROPERTIES
- Aerobic and mesophilic.
- Chemoorganotrophic, having an oxidative type metabolism.
KEY BIOCHEMICAL REACTIONS
- Catalase-positive.
- Urease-positive.
- Oxidase-positive.
Staining
- Nocardia is an acid fast organism
- Acid fast stains commonly used for staining of Nocardia are:
- Ziehl – Neelson stain
- Differentiated from Actinomyces by Ziehl Neelsen (Z.N.) stain
- Kinyon acid fast stain
- Fite faraco stain
- Mucin stains can also stain Nocardia.
- Examples of mucin stain are ?
- Mucicarmine stain
- Alcian blue stain
HABITAT
- Widely distributed in soil, water, air, sewage, insects and plants
- Maybe present in clinical specimens as opportunistic pathogens.
PATHOGENICITY
- Pathogenic opportunists in humans and animals whose host defenses are compromised.
- Exception is N. brasiliensis an obligatory pathogen.
Culture
- Use paraffin as carbon source so paraffin baiting is used for isolation.
- Time
- 3-10 days
- Temp.
- 35 degrees C.
- Aerobic atmosphere
- Select media
- Colistin-nalidixic acid agar
- Modified Thayer-Martin Agar
- Buffered charcoal yeast agar
Clinical Manifestations
- MC species associated with invasive disease N. asteroids
- MC manifestation is pneumonia and disseminated disease which follows inhalation of bacteria.
- Manifestation divided into:
Respiratory tract disease
MC is pneumonia.
- Prominent cough small amount of thick purulent sputum that is odorless.
Extrapulmonary dissemination
- MC site brain
- Usually supratentorial
- Subacute abscess
- Typical manifestation is subacute abscess usually supratentorial.
Disease following transcutaneous inoculation –
- Cellulitis, lymphocutaneous syndrome (most cases associated with N.brasiliensis)
- Actinomycetoma
- Disease begins as a papule or a nodule
- Slowly progress into multiple abcesses and sinus tracts ramifying deep into the tissue
- X-ray of the foot shows destructive changes in the underlying bone
Treatment
- Trimethoprim-Sulfamethoxazole-
- DOC
- Minocycline
- Best alternative oral drug
- Amikacin
- Best parenteral drug
Exam Question
Morphology
- Gram positive
- Show true branching both in culture and in stains from clinical lesions.
- Aerobic
Staining
- Nocardia is an acid fast organism
- Acid fast stains commonly used for staining of Nocardia are:
- Ziehl – Neelson stain
- Differentiated from Actinomyces by Ziehl Neelsen (Z.N.) stain
- Kinyon acid fast stain
- Fite faraco stain
- Mucin stains can also stain Nocardia.
- Examples of mucin stain are ?
- Mucicarmine stain
- Alcian blue stain
Culture
- Use paraffin as carbon source so paraffin baiting is used for isolation.
Clinical Manifestations
- MC species associated with invasive disease N. asteroids
- Manifestation divided into:
Respiratory tract disease
- MC is pneumonia.
Extrapulmonary dissemination
- MC site brain
- Usually supratentorial
- Subacute abscess
- Typical manifestation is subacute abscess usually supratentorial.
Actinomycetoma
- Disease begins as a papule or a nodule
- Slowly progress into multiple abcesses and sinus tracts ramifying deep into the tissue
- X-ray of the foot shows destructive changes in the underlying bone
Treatment
- Trimethoprim-Sulfamethoxazole-
- DOC
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