Volume 6, Spring 2008 - Saddleback College

Fall 2007 Biology 3A Abstracts
onto Agar plates, prepared with bromcresol green (pH
6.1 ± 0.1; at 25 °C) according to a Bacto Candida BCG
agar formula (Difco, NJ). Urine not plated within 1
hour was refrigerated at 10°C until plating.
Inoculated plates were incubated at 37 °C.
Examination for Candida albicans growth on the
plates, was performed after 24 hours and after 72 hours
of incubation. Difco Manual was used as a reference
for morphology and pH indications to identify various
Candida species.
The morphology of the fungal colonies present was
interpreted as Candida albicans, Candida stellatoidea
and/or Candida guilliermondii (Difco reference
manual). An unpaired, t-test and A-Nova test was
performed in MS Excel (Microsoft Corporation,
Sylmar, Ca) to assess the statistical differences
between the quantity of specimens positive for
Candida fungus in children diagnosed with Autism
compared to children not diagnosed with Autism.
Results
After three days of incubation, inoculated agar plates
were observed for growth and morphological
identification. Twelve of the twenty-one plates had
positive Candida growth (table 1). Fifty percent of the
plates with specimen from children diagnosed with
autism and sixty seven percent of the plates with
specimen from non-autistic children were positive for
Candida growth.
Table 1. Results of urine samples plated on pH
indicated agar, to indicate intestinal Candida growth in
children with and without autism and food allergies.
+Growth
+ Food
allergies
-Growth
+ Food
allergies
+ Growth
-Food
allergies
-Growth
-Food
allergies
Autistic
children 4 2 2 4
Non-autistic
children 2 0 4 3
Plates that were positive for Candida growth varied in
morphology most commonly found configuration was
round with raised margin, smooth margins, and
convexed elevation. Few of the colonies showed
variations in morphology including one concentric
configuration, undulate or irregular margins, and
elevations ranging from raised to drop-like. All
growths were characteristically deep green to blue with
margins fading to a pale yellow (figure 1). A decrease
in pH was also observed as the blue in the agar change
d to green or yellow around colonial growths.
Figure 1. Candida growth showing characteristic
morphology round configuration with smooth (some
undulated in this figure), raised margin, and convexed
elevation. Deep green to blue coloring, with
diminishing color to pale yellow toward margins.
Interpretation of identification was ambiguous, due
to less than 100% agreement between defined
morphological characteristics and morphology
characteristics observed on the plates. However, each
colony was deduced to be one of two types of Candida.
Eight of twelve growths were identified as either
Candida albicans or Candida stelloidea. Three were
identified as Candida albicans or Candida
guilliermondi. One was deduced to be Candida
albicans.
There was not a significant difference in the number
of positive plates of Candida growth between autistic
and non-autistic children (p= 0.234, one-tailed t-test;
n=21).
Sixty-seven percent of the plates from children
having food allergies were positive for Candida
growth. There was not a significant difference in the
number of plates positive for Candida growth between
children with and without food allergies (p= 0.267,
one-tailed t-test; n=6).
Discussion
This study did not support a significant difference in
Candida growth between autistic children and any
other group including autistic children without food
allergies, non-autistic children with and without food
allergies.
The small number of participants yielded a limited
result with narrow statistics in this study.
False positives may be a variable, as independent
collection of specimens may have been exposed to
non-aseptic environments. Additionally, females are
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Saddleback Journal of Biology
Spring 2008