Aspergillus flavus

cultures grown from BAL fluid showing formation of sclerotia.

<p>These colonies were isolated from a BAL, (also with bacterial qrowth of S.aureus and S.maltophilia) from a patient with a VAP (undergoing corticosteroid treatment). The growth medium used is sabouraud dextrose agar , incubated at 37° C The identification is made by microscopic/macroscopic observation criteria.</p>

<p style="font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12px; line-height: 1.5; color: rgb(0, 0, 0);">Colonies on&nbsp;CYA&nbsp;60-70 mm&nbsp;diam, plane, sparse to moderately dense,&nbsp;velutinous&nbsp;in marginal areas at least, often&nbsp;floccose&nbsp;centrally, sometimes deeply so; mycelium only conspicuous in&nbsp;floccose&nbsp;areas, white;&nbsp;conidial&nbsp;heads usually borne uniformly over the whole colony, but sparse or absent in areas of&nbsp;floccose&nbsp;growth or&nbsp;sclerotial&nbsp;production, characteristically&nbsp;Greyish&nbsp;Green to Olive Yellow (1-2B-E5-7), but sometimes pure Yellow (2-3A7-8), becoming greenish in age;&nbsp;sclerotia&nbsp;produced by about 50% of isolates, at first white, becoming deep reddish brown, density varying from inconspicuous to dominating colony appearance and almost entirely suppressing&nbsp;conidial&nbsp;production;&nbsp;exudate&nbsp;sometimes produced, clear, or reddish brown near&nbsp;sclerotia; reverse&nbsp;uncoloured&nbsp;or brown to reddish brown beneath&nbsp;sclerotia. Colonies on MEA 50-70 mm&nbsp;diam, similar to those on&nbsp;CYA&nbsp;although usually less dense. Colonies on&nbsp;G25N&nbsp;25-40 mm&nbsp;diam, similar to those on&nbsp;CYA&nbsp;or more deeply&nbsp;floccose&nbsp;and with little&nbsp;conidial&nbsp;production, reverse pale to orange or salmon. No growth at 5°C. At 37°C, colonies usually 55-65 mm&nbsp;diam, similar to those on&nbsp;CYA&nbsp;at 25°C, but more&nbsp;velutinous, with olive&nbsp;conidia, and sometimes with more abundant&nbsp;sclerotia.</p>

<p style="font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12px; line-height: 1.5; color: rgb(0, 0, 0);">Sclerotia&nbsp;produced by some isolates, at first white, rapidly becoming hard and reddish brown to black, spherical, usually 400- 800 µm&nbsp;diam.&nbsp;Teleomorph&nbsp;not known.&nbsp;Conidiophores&nbsp;borne from subsurface or surface&nbsp;hyphae,&nbsp;stipes&nbsp;400 µm to 1 mm or more long,&nbsp;colourless&nbsp;or pale brown, rough walled; vesicles spherical, 20-45 µm&nbsp;diam, fertile over three quarters of the surface, typically bearing both&nbsp;metulae&nbsp;and&nbsp;phialides, but in some isolates a proportion or even a majority of heads with&nbsp;phialides&nbsp;alone;&nbsp;metulae&nbsp;and&nbsp;phialides&nbsp;of similar size, 7-10 µm long;&nbsp;conidia&nbsp;spherical to&nbsp;subspheroidal, usually 3.5-5.0 µm&nbsp;diam, with relatively thin walls, finely roughened or, rarely, smooth.</p>

<h4 style="line-height: normal; font-family: Verdana, Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">Distinctive features</h4>

<p style="font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12px; line-height: 1.5; color: rgb(0, 0, 0);"><i>Aspergillus&nbsp;flavus</i>&nbsp;is distinguished by rapid growth at both 25°C and 37°C, and a bright yellow green (or less commonly yellow)&nbsp;conidial&nbsp;colour.&nbsp;<i>A.&nbsp;flavus</i>&nbsp;produces conidia which are rather variable in shape and size, have relatively thin walls, and range from smooth to moderately rough, the majority being finely rough.</p>