Aspergillosis

Aspergillosis is the most common infection caused by the common fungi growing on damp bread. The two fungi of this group are aspergillus niger and aspergillus fumigatus, of which the later is more potent.The fungi cause opportunistic infections of which otomycosis is a common occurence.

Morphology

They have septate hyphae and are charcterised by dichotomous branching and an irregular outline.

Types of aspergillosis

Pulmonary aspergillosis

It can present as
  • aspergillus asthma
  • bronchopulmonary aspergillosis or
  • colonising aspergillosis (aspergilloma)
Aspergillus asthma is mostly seen in atopic individuals folllowing sensitisation to inhaled aspergillus spores.
Bronchopulmonary aspergillosis is characterised by fungal growth within the lumen of bronchioles which may be occluded by fungus plugs.
Colonising aspergillosis or aspergilloma usually develops in pre-existing pulmonary cavity or cavity of tuberculosis, sarcoidosis, bronchiectasis or histoplasmosis. Often the person will present with hemoptysis. The treatment of aspergilloma is surgical removal.

Superficial infection

They can cause superficial infections such as sinusitis and otomycosis.Otomycosis refers to the fungal infection of the external ear and is characterised by itching, pain and deafness. This can be complicated by secondary bacterial infection caused by proteus and pseudomonas bacteria. The daignosis is made by demonstration of fungi by scrapings and culture.

Disseminated aspergillosis

Also known as invasive aspergillosis. Disdisseminated aspergillosis is seen exclusily in immunosuppresd individuals of whom d granulocyte counts are less than 500/ml..ie mostly in patients suffering from AIDS,acute leukaemiasand receptors of tissue transplantation.involved hypheal invasion of bloodvessels ;characteised by thrombosis,necrosis and hemmorhagic infarction.later invades mainly brain ,kidney and other organs.

Investigations

CT scan findings

  • Halo sign: It is the presence of a hazy rim around the infarcted tissue.
  • Crescent sign: This sign appears in CT when bone marrow function recovers.

Diagnosis

1.KOH
Isolate of aspergillus in KOH mount of sputum of neutropenic patients. They can be identified by the presence of septate hyphae and asexual conidia arranged in chains on elongated cells called sterigmata, borne on vesicles of the conidiophore.
2.Culture
Velvety to powdery surface of colony.
The ability to grow at 45 degree celsius helps differentiate aspergillus fumigatus from other species of aspergillus.

Treatment

If fungus ball has formed lobectomy is the preferred treatment. ABPA can be treated with a short course of glucocorticoids. Patients with invasive variety of aspergillosis can be treated with drugs like voriconazole and amphoteroicin.



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